E mail:yugandhargarlapati@yahoo.com

Dr.Venkat ramana Irukulla
Associate professor of orthodontics
Government dental college & hospital
Vijayawada

Dr.Srinivasa Rao Kolasani
Associate professor of orthodontics
Government dental college & hospital
Vijayawada

Dr.Bhaskar Mummudi
Professor of orthodontics
Vishnu dental college
Bhimavaram

Abstract: The time at which orthodontic treatment should be started remains a matter of conjecture. Anomalies of dental development and functional problems tend to be addressed in the mixed dentition, while definitive treatment tends to be delayed until the late mixed dentition to maximize growth potential and patient compliance. However, some clinicians advocate starting treatment earlier in certain types of malocclusion. In this article, the current concepts of early treatment, both physiological and psychological, will be explored and the relevant indications are discussed with a case report .

 Clinical Relevance: General dental practitioners need to have an understanding of the timing of orthodontic treatment in different types of malocclusion to maximize the effectiveness of patient referrals.

key words:  Rapid palatal expansion, Niti expander, Proclination.

Introduction:

Within the practice environment, dentists are the first to examine and screen children for developing malocclusions. They are often faced with the dilemma of deciding at what age to refer for further opinion and possibly treatment. This of course depends on the problem that has been diagnosed and the dental development of the child, but is there an ‘ideal’ time for orthodontic treatment, if the clinician wants to maximize the benefits of growth and co- operation without subjecting every child to four or more years of treatment? From the eruption of the first primary tooth until the development and eruption of the wisdom teeth, the developing dentition should be monitored and interceptive treatment prescribed as necessary. There is a difference, however, between treatment decisions that are thrust upon us due to aberrations of dental development and types of malocclusion that we may choose to treat early by use of appliance therapy or elective extraction of teeth. It is obvious from these lists that the management of certain problems such as skeletal discrepancies or crowding can be undertaken at differing times during the dental development. When early treatment is contemplated, especially if it involves the use of active appliances, the following questions should be asked.

Will early treatment correct the problem or eliminate the need for comprehensive treatment at a later date? Will it reduce the treatment time and also avoid radical extraction line of treatment?

 Following are few check list in early treatment point of view :

Early mixed dentition:

• Delayed eruption of permanent incisors
• Supplemental incisors
• Early loss of deciduous teeth
• Congenital absence of incisors
• One or more incisors in crossbite
•  Impaction of first permanent molars
• Severe crowding
• Severe skeletal discrepancy
• Posterior crossbites.

Late mixed dentition:

• Severe skeletal problems
• Unfavourably positioned canines or other teeth
• Congenitally absent permanent teeth
• Poor-quality first permanent molars
• Traumatic overbites.

Early permanent dentition:

• Severe skeletal problems
• Impacted teeth
• Crowding
• Hypodontia

Crowding is  very common and thought to be related to the dimension of the dental arches in that the greatest crowding exists in the narrower arches. This has led some clinicians to advocate active expansion of the arches in the mixed dentition in an attempt to create space to accommodate the complete dentition. Unfortunately, it appears that lower arch width, particularly in the intercanine region, typically decreases after treatment, regardless of whether a case was expanded during treatment or not. This results in higher degrees of relapse in cases where there has been enlargement of the mandibular arch. But many clinicians observed stable results with prolonged retention and early intervention could obtain stable results.

Crossbites with displacement are generally thought to be a functional indication for early orthodontic treatment. The aim is to stop the crossbite becoming established in the permanent dentition, as crossbites with displacement are one of the few occlusal traits that have a slight association with the development of temporomandibular joint dysfunction later in life. There is evidence of asymmetric muscle activity and altered bite force in children with a posterior crossbite with displacement. Treatment in the primary or early mixed dentition by selective grinding and active expansion with a removable plate is thought to decrease the risk of the crossbite being perpetuated to the permanent dentition. The correction of anterior crossbites in the mixed dentition may prevent loss of periodontal attachment of the lower incisors.

By starting treatment in the mixed dentition, there will inevitably be a period when the clinician is awaiting further dental development before further treatment decisions can be made. This will mean either that treatment will have to be discontinued during this period or that some form of retention regime will have to be implemented.

However there are no hard rules or regime to follow the timing of treatment initiation, individual case selection and the  optimum treatment planning can be well done when patient reports at the late mixed dentition or early permanent dentition at the pre pubertal maximum growth status.

CASE REPORT:

A 13-year-old male patient reported to the department of orthodontics with Complaints of irregular teeth and pain in the lower anterior region. The patient’s mother reported that her son had been treatment planned for extraction of 4 teeth and fixed braces.  The patient and mother were apprehensive regarding extractions. Past dental history revealed trauma to the deciduous anterior teeth.

Extra-orally he is mesofacial, straight divergence and straight profile, asymmetry in his face mild anterior depression in the right maxillary canine region.

Intr-orally he is a Class I molar relation and right unilateral cross bite from 11 to 17 and 13 is buccally blocked out, lower 41 presented with signs of traumatic bite with gingival recession and grade 1 mobility. Maxillary mid line is shifted to right side. Maxillary arch is “V” shaped and mandibular arch is “U” shaped with crowding. Carey’s arch perimeter analysis revealed 8mm of space requirement, Ashley Howe analysis revealed requirement of arch expansion.

Treatment objectives:

Requires correction of cross bite, correction of crowding, obtain good functional intercuspation, obtain balance symmetrical facial features.

TREATMENT:

Taking the pre-pubertal growth status into consideration it was planned non-extraction line of treatment by Hyrax screw rapid palatal expander initially.

The expansion was done such that the maxillary palatal cusps are in contact with mandibular buccal cusps. Followed by 0.22 slots MBT pre adjusted appliance with maintenance of expansion with Niti expander.

The series of wires are 0.16 Niti, 0.18 S.S wire with Niti open coil spring to procline the anteriors, correct the midline and gain space for canine. After the space is achieved, 0.16 Niti for further level aligning and followed by 0.17×0.25 Niti and finishing with 0.19×0.25 S.S wire with reverse curve to Spee to maintain torque.

Cross elastics are given to detail the mid line and finish the case with optimum treatment objectives.  The treatment lasted for 10 months. All the parameters listed in the treatment objectives are achieved.

Discussion:

If the same patient had reported in early mixed dentition period the initial treatment would be to correct the crossbite and utilize the leeway space to correct the crowding and the treatment would have been prolonged due to waiting and planning for the un erupted permanent teeth. Patient co-operation for prolonged treatment may affect the treatment outcome.

If patient had reported with the same problem post pubertal or adolescent period the treatment would be extraction of 4 first premolars and the treatment time would be comparatively more than non extraction line ,with compromised stability.

This case was completed satisfactorily and patient was happy to receive non-extraction line of treatment. However prolonged retention is demanded with removable Hawley’s retainer was given as expansion has high tendency of relapse. Periodic check up for 9 months with retainer and after discontinuation of retainer follows up presented with stable results. The key to this treatment outcome was the growth potential and the thick soft tissue drape, which permitted proclination of maxillary and mandibular anteriors to gain space for leveling and aligning.

 Cephalometric:

Ricketts four-step superimposition presented with clockwise rotation of mandible due to extrusion of posterior due to rapid palatal expansion and orthodontic mechanics, proclination of anterior teeth both maxillary and mandibular anteriors. Supra eruption of maxillary and mandibular posteriors, acceptable forward placement of upper and lower lips.

REFERENCES

1.  James RD. Early protrusion reduction – two phase malocclusion correction: a case report. Am J Orthod Dentofacial Orthop 1997; 112: 523–537.

2. Stephens CD.The use of natural spontaneous tooth movement in the treatment of malocclusion. Dent Update 1989; 16: 337–342.

3. Haruki T, Little RM. Early versus late treatment of crowded first premolar extraction cases: postretention evaluation of stability and relapse. Angle Orthod 1998; 68: 61–68.

4. Brennan MB, Gianelly AA.The use of the lingual arch in the mixed dentition to resolve incisor crowding. Am J Orthod Dentofacial Orthop 2000; 117: 81–85.

5. Howe RP, McNamara JA, O’Connor KA. An examination of dental crowding and its relationship to tooth size and arch dimensions. Am J Orthod 1983; 83: 363–373.

6. Little RM, Riedel RA, Stein A. Mandibular arch length during the mixed dentition: postretention evaluation of stability and relapse treatment. Am J Orthod Dentofacial Orthop 1990; 97: 393–404.

7. Mohli B,Thilander B. The importance of the relationship between malocclusion and mandibular dysfunction and some clinical applications in adults. Eur J Orthod 1984; 6: 192–204.

8. Ingervall B,Thilander B. Activity of temporalis and masseter muscles in children with a lateral forced bite. Angle Orthod 1975; 45: 249–258.

9. Sonnesen L, Bakke M, Solow B. Bite force in pre- orthodontic children with unilateral crossbite. Eur J Orthod 2001; 23: 741–749.

10. Harrison JE, Ashby D. Orthodontic treatment for posterior crossbites (Cochrane Review). In: The Cochrane Library, 4. Oxford: Update Software, 2001.

11. Bell RA, LeCompte EJ.The effects of maxillary expansion using a quad-helix appliance during the deciduous and mixed dentition. Am J Orthod 1981; 79: 152–161.

12. Herold JC. Maxillary expansion: a retrospective study of three methods of expansion and their long term sequelae. Br J Orthod 1989; 16: 195– 200.

13. Erinc AE, Ugur T, Erbay E. A comparison of different treatment techniques for posterior crossbite in the mixed dentition. Am J Orthod Dentofacial Orthop 1999; 116: 287–300.

14. Littlewood SJ, Tait AG, Mandall NA, Lewis DH. The role of removable appliances in contemporary orthodontics. Br Dent J 2001; 161: 304–310.

15. McKeown HF, Sandler J.The two by four appliance: a versatile appliance. Dent Update 2001; 28: 496–500.

16. Loh MK, Kerr WJS. The Functional Regulator III – effects and indications for use. Br J Orthod 1985; 12: 153–157.

17. Kidner G, DiBiase A, Ball J, DiBiase D. Reverse twin blocks for early treatment of class III. Eur J Orthod 1999; 21: 631 (Abstr. 189).

18.Da Silva Filho OM, Magro AC, Filho LC. Early treatment of class III malocclusion with rapid maxillary expansion and maxillary protraction. Am J Orthod Dentofacial Orthop 1998; 113: 196–203.

19. Kapust AJ,            Sinclair PM, Turley PK. Cephalometric effects of facemask/expansion therapy in class III children: a comparison of three age groups. Am J Orthod Dentofacial Orthop 1998; 113: 204–212.

20. Sugawara J, Asano T, Endo N, Mitani H. Long-term effects of chincap therapy on skeletal profile in mandibular prognathism. Am J Orthod Dentofacial Orthop 1990; 98: 127–133.

21. Battagel JM, Orton HS.A comparative study of the effects of customized facemask therapy or headgear to the lower arch on the developing Class III face. Eur J Orthod 1995; 17: 467–482.

22. Dugoni SA. Comprehensive mixed dentition treatment. Am J Orthod Dentofacial Orthop 1998; 113: 75–84.

23. Baccetti TB, Franchi L,Toth LR, McNamara JA. Treatment timing for twin-block therapy. Am J Orthod Dentofacial Orthop 2000; 118: 159–170.

24. Malmgren O, Omblus J, Hagg U, Pancherz H. Treatment with an appliance system in relation to treatment intensity and growth periods. Am J Orthod Dentofacial Orthop 1987; 91: 143–151.

25. Hagg U, Pancherz H. Dentofacial orthopaedics in relation to chronological age, growth period and skeletal development: an analysis of 72 male patients with Class II Division 1 malocclusion treated with the Herbst appliance. Eur J Orthod 1988; 10: 169–176.

26. McNamara JA, Brookstein FL, Shaughnessy TG. Skeletal and dental changes following functional regulator therapy on Class II patients. Am J Orthod 1985; 87: 1–20.

27. Liveratos FA, Johnson LE. A comparison of one- stage and two-stage nonextraction alternatives in matched Class II samples. Am J Orthod Dentofacial Orthop 1995; 108: 118–131.

28. Tulloch JFC, Philips C, Proffit WR. Benefit of early Class II treatment: Progress report of a two-phase randomized control trial. Am J Orthod Dentofacial Orthop 1998; 113: 62–72.

29. ShawWC.Theinfluenceofchildren’sdental appearance on their social attractiveness as judged by peers and lay adults. Am J Orthod 1981; 79: 399–415.

30. ShawWC,MeekSC,JonesDS.Nicknames, harassment and the salience of dental features among school children. Br J Orthod 1980; 7: 75– 80.

31. HelmS,KreiborgS,SolowB.Psychosocial implications of malocclusion: a 15-year follow-up study on 30-year-old Danes. Am J Orthod Dentofacial Orthop 1985; 87: 110–118.

Dr. Arundhati P. Tandur
Senior consultant and private practitioner
Bangalore

Dr. Karunakara
Professor
Department of Orthodontics and Dentofacial Orthopedics
K.L.E.S Institute of Dental Sciences, Bangalore

Dr. Sumitra
Professor
Department of Orthodontics and Dentofacial Orthopedics
K.L.E.S Institute of Dental Sciences, Bangalore

Dr. Shweta
Reader
Department of Orthodontics and Dentofacial Orthopedics
K.L.E.S Institute of Dental Sciences, Bangalore

Corresponding address –

Dr. Amit Prakash
Department of Orthodontics and Dentofacial Orthopedics
Darshan dental college and hospital, Loyara, Udaipur

   E-mail address- drprakash24@yahoo.co.in

amitprakash30@gmail.com

The MBT bracket system is based on a more balanced mix of science, tradition and experience. Good diagnosis and treatment planning, correct positioning of brackets, effective aligning technique, ability to level the dental arches, persistence in finishing and good retention protocol are the features which makes it best available bracket system. The system’s full name is MBT™ Versatile+ and as the name implies, it is designed to be versatile, in order to deal with most treatment challenges.

The MBT prescription have lower incisor brackets with 0 degree tip, which was used to make less demand on lower arch anchorage. 0 degree tip allows all the lower incisor brackets to be interchangeable, thereby assisting inventory control.  But in some cases where lower incisors are severely malaligned and placed lingually we can modify bracket placement by placing lower first premolar bracket on incisors to have better torque correction without tedious wire bending.  Lower first premolars have 2 degree tip and -12 degree torque value which is higher than -6 degree value of lower incisors. It helps in placing lower incisor roots labially (desirable in such situations). This modification is useful in achieving good results without additional wire bending for torque correction.

In the case shown here lower lateral incisors were out of arch and lingually placed. (Fig 1) After creations of space incisors were bonded and in left quadrant on lateral incisor, first premolar bracket was placed. Alignment was carried out with the 0.014 NiTi wire followed by 0.016 NiTi. (Fig 2) After initial alignment, leveling was done with 0.019”×0.025” NiTi wire. (Fig 3)  To achieve complete torque expression ‘’0.019”×0.025” stainless steel was placed in lower arch. (Fig 4) Post treatment occlusal photographs shows good and stable result. (Fig 5)  

Fig 1- Pre-treatment

Fig 2- Alignment with 0.014 NiTi wire

Fig 3- Leveling with 0.019x0, 025 NiTi wire

Fig 4 - With 0.019x0.025 Stainless Steel wire

Fig 5 – Post-treatment

1. McLaughlin R P, Bennett J C. The transition from standard edgewise to preadjusted appliance systems. J. Clin. Orthod 1989; 23:142-153.

^a Postgraduate  student
Department of Orthodontics,
KLE V.K Institute of dental sciences,
JNMC campus,Nehru nagar,
Belgaum 590010, Karanataka.
Email address: prankymahajan@gmail.com
Tel no:  09620846359

^b Professor
Department of Orthodontics,
KLE V.K Institute of dental sciences,
JNMC campus, Nehru nagar,
Belgaum 590010, Karanataka.
Email address : rupa_md9@rediffmail.com
Tel No:  09341463124

^c Professor and Head of the department
Department of Orthodontics,
KLE V.K Institute of dental sciences,
JNMC campus, Nehru nagar,
Belgaum 590010, Karanataka.
Email address: keluskar@yahoo.com
Tel no:  09448136832

Abstract:

The growth and development of the maxilla and the mandible is being considered as an important part in orthodontics. So, normal growth of the maxilla and the mandible is considered in this study with the help of the C- axis and G- axis. Also, an angle between the C-axis and G- axis (CG angle) is introduced after setting the normal standards for 300 patients, 150 males and 150 females in 3 growth patterns.

Annual serial lateral cephalograms of Karnataka population, 30 males and 30 female subjects from 11 to 16 years were selected.

Group 1 :  15 males and 15 females treated with removable twinblock.

Group 2 :  15 males and 15 females treated with fixed twinblock.

Lateral cephalograms (T1) were taken of all patients at the onset and at the completion (T2) of each functional-appliance treatment regimen. No other appliances were used during functional therapy. The cephalometric measurements descriptive of the growth axis of the dento-maxillary complex, and growth axis of the mandible, were recorded at T1 and T2. One investigator made all the T1 and T2 cephalometric measurements of the Removable Twin block-treated group, and another investigator made all the T1 and T2 cephalometric measurements of the patients treated with the fixed Twin Block appliance.

Introduction:

The ‘ANB’ angle. Introduced in 1953, it still holds good in the world of  communication among orthodontists. But the gnawing questions are, is it reliable? Is it the best? Or is it the only one to relate the skeletal bases. Dr. Alex Jacobson did an evaluation study in 1975 and observed that the stability of point N was found to vary with the growth. It moved either sagitally or vertically with growth and this movement in turn would alter the ANB angle.¹

To overcome these setbacks, many investigators came forward with different cephalometric parameters like the Beta angle which is formed between a  line extending from the centre of condyle to B point and the another line from A to B and a perpendicular from the centre of condyle – B line through point A.  C- axis, is a growth vector of the maxilla and G- axis, is a growth vector of the mandible. ²

Materials and Methods:

Lateral cephalograms of Karnataka population, 30 males and 30 female subjects from 11 to 16 years were selected.

Two groups of patients were treated.

Group 1:  15 males and 15 females treated with removable twinblock.

Group 2:  15 males and 15 females treated with fixed twinblock.

One group with 30 patients were treated by removable twinblock. The ages of females at the onset of treatment ranged from 11.0 to 14.0 years (mean, 12.5 years). The ages of males at the onset of treatment ranged from 11 to 16 years (mean, 13.5 years). The length of removable twinblock therapy extended from a minimum of 0.5 to a maximum of 1.2 years (mean, 0.85 years) in females and 0.7 to 1.8 years in males (mean, 1.25 years).

The second group, treated with the fixed Twin Block appliance, comprised 15 females and 15 males. The ages of females at the onset of treatment ranged from 11.0 to 15.0 years (mean, 13 years). The ages of males at the onset of treatment ranged from 11.2 to 16.1 years (mean, 13.6 years). The length of modified Twin Block therapy extended from 0.5 to 1.1 years (mean, 0.8 years) in females and 0.7 to 1.3 years in males (mean, 1 years)

Lateral cephalograms (T1) were taken of all patients at the onset and at the completion (T2) of each functional-appliance treatment regimens. No other appliances were used during functional therapy. The cephalometric measurements descriptive of the growth axis of the dento-maxillary complex, and growth axis of the mandible, were recorded at T1 and T2.

C- axis linear (S-M point) and angular( SN-SM point) and the mean G-Axis linear measurements (S-G point) and mean angular values ({S-N}–{S-G point}) and ({M plane}–{S-G point) were measured for each group. (Fig: 01)

Fig:01 – Landmarks, planes and angles measured. i) M point; ii) G point; iii) C axis; iv) G axis; v) CG angle.

One investigator made all the T1 and T2 cephalometric measurements of the removable twinblock-treated group, and another investigator made all the T1 and T2 cephalometric measurements of the patients treated with the fixed twinblock appliance.

300 Lateral cepahlograms of patients from age 11 years to 16 years were taken and were divided into three groups;

Group A: 100 -  Average growth pattern group.

Group B:  100 -  Horizontal growth pattern group.

Group C:  100 -  Vertical growth pattern group.

An angle between C- axis and G- axis was measured and values were obtained for each group of different growth patterns. The values obtained for each group were tabulated. ( TABLE: 01, 02, 03)

Table: 1  Values of the angle formed between c axis and g axis in vertically growing individuals in growing stages.

Table: 2  Values of the angle formed between c axis and g axis in horizontally growing individuals in growing stages.

Table: 3  Values of the angle formed between c axis and g axis in average growing individuals in growing stages.

Results:

Changes in the ‘C’-axis (growth vector) linear measurements (Sella-M point), and in the angular measurements ([Sella-Nasion]–[Sella-M point]), and palatal plane–(Sella- M point) were obtained and compared between both the groups. This is based on the slope of regression formula where

C axis length in mm =  1.142    (age in years) + 63.157 with a correlation (R)   of 0.699

while C- axis length in females is characterized by a second order regression formula where

C- axis length in milimeters =  -0.099 (age in years)²  + 3.454 (age in years) + 48.519, having a correlation coefficient (R) of 0.618.

In removable twinblock group, C axis linear measurements increased by 3 – 4mm (Graph: 01)  ; C axis angular was increased by 1 degree ± 2 degrees in the T2 cephalometric measurements.(Graph: 02)  Also the palatal plane to C axis relationship is achieved by a formula:

ANS – PNS  =         C axis    angle  -    ANS – PNS   angle

C axis angle               SN                              SN

The palatal plane to C axis relationship showed increase in the angle  by an average of 2° in the T2 cephalometric readings.

In the fixed twinblock group very few changes in linear measurements were seen of 1 – 2 mm ( Graph: 01) ; C axis angular also showed no change ( Graph: 02). The palatal plane relation to the C axis showed an increase in the angle by an average of 1.5 degrees in the cephalometric readings.

Graph: 01 – Changes in C axis linear in removable and fixed twinblock.

Graph 02 – Changes in C axis angular in removable and fixed twinblock.

Changes in the ‘G’ axis (growth vector) linear measurements (S-G point) and mean angular values ({S-N}–{S-G point}) and ({M plane}–{S-G point}) obtained for each group and compared.

In the Removable Twinblock group, G axis linear showed significant increase  ( Graph: 03) by and the angle was also decreased by 2 degrees – 4 degrees, thus confirming the definite closure of the mandibular angle. There was no significant increase in G axis linear but there is a definite closure of the mandible by 1 degrees – 2 degrees, observed in the Fixed Twinblock group. ( Graph: 04)

Graph: 03 – Changes in G axis linear in removable and fixed twinblock.

Grpah 04 – Changes in G axis angular in removable and fixed twinblock.

Angle between C- axis and G- axis is measured for each group. Also CG angle was measured in both the groups to check for the skeletal effects.

In Group I, the CG angle decreased by 2 degrees ± 2 degrees , when comparison between T1 and T2 stages were done. (Graph: 05)

Graph 5: Changes in CG angle in removable and fixed twinblock.

Discussion:

In the normal growing individuals, with no functional treatment C axis linear increases continually at the mean rate of 1.14 mm per year from ages 7.4 to 18.75. The regression formula shows that the growth along the growth axis ceases at the age of 16 for females. The total mean angular increase for males and females is relatively small: 3.98 degrees and 2.25 degrees, respectively. The increase in C- axis up to the age of 14 years in males and females display average growth of 1.14mm and  1.31 mm per year.

The G axis length (S-G point) in female subjects increases linearly at a rate of 1.6 mm per year and linearly in male subjects at a rate of 2.3 mm per year from 6 to 19.25. The growth velocities of the G-Axis length are determined by the slope of the mean linear regression formulas for each gender seen. At six years, the mean G-Axis lengths of the female and male subjects are 97.8 and 97.6 mm, respectively, representing no significant difference. At 6.28 years, the mean G-Axis lengths are equal for both genders. At 19.25 years, the mean male subject G-Axis length exceeds that of the female subjects by 9.8 mm.

The mean growth axis vector angle   decreases 0.02 degrees/ year in female subjects and increases 0.14 degrees/year in male subjects. At six years, the female subject mean growth vector angle exceeds that of the males’ by only 1degree (67.16 degrees– 66.12 degrees), and at 19.25 years the male subject mean growth vector angle exceeds that of the female subjects by only 1degree (67.93 degrees–66.87 degrees). The small angular differences between genders are not clinically significant. The low correlation coefficients (R 0.022 for female subjects, R 0.103 for male subjects) between the growth axis vector angle and age for the age range studied imply little change of the magnitude of the mean growth axis angle related to age.

The mean  mandibular  plane angle relative to the G-Axis increases at a rate of 0.4 degree per year and 0.3 degrees per year in the female and male subject groups, respectively, in the age range studied (Figure 6). Thus, from age six to 19.25 years, increases 5.3 degrees (39.0 degrees–33.7 degrees) in female subjects and 3.7 degrees (36.2 degrees–32.5 degrees) in male subjects.

The CG angle is been introduced in this study to check the relationship between the maxillary and mandibular skeletal bases during growth in different growth patterns. It is observed that the CG angle in average growth pattern for male, is  20 degrees ± 2 degrees and increases up to 26 degrees ± 1 degree from the age of 11 to 16 respectively. For females, CG angle  is 22 degrees ± 2 degrees and increases up to 25 degrees ± 1 degree.

The CG angle in horizontal growth patterns for male, is 20 degrees  ± 2 degrees and 23 degrees ± 2 degrees at 11 years and 16 years respectively. In females, CG angle increases from 19 degrees ± 1.5 degrees to 24 degrees ±  2 degrees from  the age of 11 to 16 years respectively.

Similarly in vertical growing individuals, the CG angle at 11 years of age is   24 degrees ± 1 degree for males and 25 degrees ±  2 degrees for females  and by the age of 16 years the CG angle increases upto 30 degrees ± 2 degrees  in males and     29 degrees ± 1 degree in females.

Removable and fixed  twinblocks were given in this study to check for the skeletal changes seen in both the groups on the C and G axis. Mills and McCulloch in 1998 concluded that the removable twinblock provided mandibular growth increments greater in magnitude than other removable functional appliances. The mandibular unit length (Co to Gn) increses by 6.5 mm in Twin block patients and this was the probable cause of increase in the SNB angle by 1.9 degrees.

Carlos and Paul Major in 2006 stated that evidence supporting the claim for an improvement of the facial convexity with twin block treatment of Class II division I malocclusion was not found. Changes produced by the twinblock appliance in the upper lip seem to be controversial, although the study with sounder methodological quality did not report significant changes. No change in the anteroposterior position of the lower lip and soft tissue menton was found.

In our study we have concluded that, Removable twinblock has significant skeletal changes as compared to the fixed twinblock in the individuals. Removable twinblock showed downward tipping of the maxilla and hence significant decrease in the CG angle. The mandibular anterior rotation is justified by decrease in the CG angle by 2 degrees ± 2 degrees and also the mandibular length is increased.

G axis linear showed significant increase and the angle was also decreased by 1degrees ± 2 degrees, thus confirming the definite closure of the mandibular angle.

Fixed twinblock on the other hand showed decrease in the CG angle by 1 degree  ± 2 degrees without any downward tipping of the maxilla. There is no significant increase in G axis linear but there is a definite closure of the mandible observed. It does not have as much skeletal changes like removable twinblock but it also shows decrease in the CG angle which is slightly less as compared to the removable twinblock.

Conclusion:

• C axis and G axis (linear and angular) are the reliable cephalometric measurements to check for the growth of the  maxilla and the mandible respectively.
• Both removable and fixed twinblock shows skeletal changes.
• Removable twinblock shows downward tipping of the maxilla; whereas fixed twinblock shows no such changes.
• The newly introduced CG angle is a reliable angle in analyzing the skeletal changes during the growth phases and also to check for the skeletal changes seen after any treatment modality done for skeletal changes.

 References

1)      Charles .M. Taylor ;Changes in relationship of Nasion, point A and point B, and the effect upon ANB. AJO 1969, 56: 143 – 163.

2)      Chong Yol Baik, Maria Ververidou: A new approach of assessing sagittal discrepancies: The Beta angle. AJO 2004; 126: 100-105.

3)      Stanley Braun, Shaun Hicken; C – axis: A growth vector for the maxilla. AO Vol. 69 No. 6, 1999; 539- 542.

4)      Stanley Braun, Russell Kittleson, Kyonghwan Kim; The G-Axis: A Growth Vector for the Mandible; Angle Orthod 2004;74:328–331.

Dr. Pushpa V. Hararey
Professor and Head,
Department of Orthodontics,
Sharad Pawar Dental College,
Sawangi (Meghe), Wardha.

Dr. Ram D. Mundada
Post Graduate student,
Department of Orthodontics,
Sharad Pawar Dental College,
Sawangi (Meghe), Wardha
Abstract:

Laser etching has been tried as an alternative method to acid etching.  An ultra pulse and a continuous pulse CO₂ laser were used to carry out enamel etching in vitro. The shear bond strength of brackets bonded to extracted premolars after etching with conventional acid etching technique, laser etching and laser etching followed by conventional acid etching technique was evaluated.

Both continuous pulse(10.26±1.44 MPa) and ultra pulse(7.33±0.93 MPa) resulted in lower shear bond strength which is more than optimal bond strength, than that of chemical etching technique(14.52±2.31 MPa), but the combination of laser etching followed by acid etching resulted in more bond strength than acid etching alone(14.80±1.18 MPa). While etching directly irradiating the enamel surface with ultra pulse laser resulted in minimum temperature rise in pulp chamber (4.73±1.78˚C) as compared to continuous pulse laser.

Thus from the findings of the study it can be concluded that etching of enamel surface with ultra pulse laser is more advantageous than etching of enamel surface with continuous pulse laser and conventional etching technique.

Key words:  Pulsed lasers, Continuous wave lasers, Dental bonding, Shear strength,   Premolar, Enamel

INTRODUCTION:

Silverstone¹ described the role and importance of acid etching in the direct bonding process as initially a shallow layer of enamel is removed by etching thereby effectively removing subsurface particles from the site to be bonded. In addition, chemically inert crystallites on surface enamel are also removed thus favoring chemical union between hard tissue and resin. Secondly after removal of surface layer by etching, the remaining underlying enamel surface is rendered porous as a result of selective decalcification of enamel which increases wetability of the enamel surface and hence facilitates penetration of polymerizing resin into the etched surface to a depth of 15µ to 25µ achieving mechanical bonding between enamel surface and the material.

In recent years there has been a growing interest in the application of Lasers in medical and dental therapies. A number of studies have been done to see the effects lasers had on dental hard tissues, but not much research has been done to analyze the etching produced by lasers and its effect on orthodontic bonding. The application of Co₂ started with industrial application of cutting and welding after Q. Patel et.al² published it in 1964. Taking into account that the wavelength of the Co₂ laser is absorbed much better in collagen than in water, it seems evident that the interaction cannot avoid direct heating of the tissues. In laser etching, adjustment of Laser power output permits localized melting and ablation of the enamel surface, which in turn results in etching through a process of continuous vaporization and micro explosions due to vaporization of water trapped within hydroxyappatite matrix. The surface changes of the enamel is dependent on the wavelength of Laser, emission mode of Laser  (pulsed or continuous), energy density achieved at surface, duration of exposure and nature of substance absorbing the Laser energy. Therefore different Lasers have produced different results. Studies on enamel etching with different laser systems e.g. Argon, Nd-YaG, Er-YaG, but there is no study on CO₂ lasers with continuous pulse and ultra pulse mode and in combination with conventional acid etching technique. Hence, in the present study, Co₂ laser was used in continuous and ultra pulsed mode, as ultra pulse Co₂ lasers provide short duration pulses separated by sufficient time to allow the tissues to cool between the pulses and as a result it limit’s thermal damage.

MATERIALS AND METHODS:

120 freshly extracted young healthy non carious human maxillary and mandibular premolars extracted for orthodontic purpose. The criteria for tooth selection included intact enamel surface with no carious or hypoplastic lesions, no history of any pretreatment with chemical agent like hydrogen peroxide and no cracks due to use of extraction forceps. 100 aluminum blocks of size 10 x 10 mm dimension and 1 inch in length, 100 curved base beggs brackets (T.P Orthodontics), 37% phosphoric acid (3M SPE, Scotch Bond USA), Ultra CO₂ surgical VISCO Laser System USA, Transbond XT light cure bonding adhesive paste and primer (3M Unitek Monrovia, CA, USA), Light emitting diode, Autopolymerizing resin (DPI-RR Cold Cure), K-type Chromel-Alumel thermocouple (NABL Chennai), Barbed broaches (WAVE Broach Micro Mega), K-files 15-80 number (Dentsply Maillfer, Tulsa, Okla), Instron Machine (Universal testing machine 467 H, 1978 ENGLAND), Scanning electron microscope (JEOL, JSM, 6380 A JAPAN)

FOR STUDYING SHEAR BOND STRENGTH

Group I consisted of extracted 100 premolars. The roots of these teeth were embedded in cold cure resin encased in square aluminum blocks (10Χ10mm, 1 inch length) to which acrylic tail (10Χ5mm, 2½ inch length) were attached.

It was further divided into Sub group A, B and C

• SUB GROUP A consisted of 20 samples. 37% orthophosphoric acid gel was applied on the buccal surface of the premolars in the area of 4 Χ4 mm² for 15 seconds, and then the specimen were washed in free running water for 30 seconds and dried for 15 seconds with compressed air without oil or moisture.  A white frosty surface indicated etched enamel.
• SUB GROUP B consisted of 40 samples, enamels of which were subjected to two modes of laser etching. 20 samples were subjected to continuous pulse mode (B1) and remaining 20 samples which were subjected to ultra pulse mode (B2).

For better surface absorption of CO₂ laser beam by enamel surface, the surface was covered with a light absorbing material. For this purpose oil based black ink was used as an initiator. It was thinly coated on the buccal surface of the teeth to be etched covering an area of 4 X 4 mm²

• SUB GROUP C consisted of 40 samples, enamel of which were subjected to two modes of laser for etching i.e. continuous mode (C1) and ultra pulse mode (C2) after which they were acid etched with 37% of orthophosphoric acid for 15 seconds .

After the completion of laser etching procedure, samples were subjected to 37% orthophosphoric acid etching for 15 seconds. The samples were dried with dry air without oil contamination and bonding of orthodontic brackets was done.

After bonding all the samples in all the groups, they were stored in water at room temperature for approximately 24 hours. The bond strength testing was carried out on an Instron testing machine (model number 4467).

The acrylic blocks that held the samples were secured to the base of machine with series of set screws. Chisel-shaped blade of machine was placed as close to tooth bracket as possible to simulate a pure shearing force. A crosshead speed of 1mm/min was used to shear the bracket from teeth and force required to debond the brackets was recorded to a 0.1KN resolution. Force at which bond failure occurred was taken. Debonding tests were conducted in air at ambient laboratory temperature. The breaking load obtained in KN was converted to KgF (KN x 100= KgF). The surface area of bracket was approximately 9mm².

The following formula was used to obtain shearing strength.

Shearing bond strength in MPa = Breaking load in Kg F/Cross section area in mm² x 9.81.

GROUP II

FOR CALCULATING INTRAPULPAL TEMPERATURE RISE IN LASER ETCHED ENAMEL

Sample comprised of 20 premolars to evaluate the temperature changes in pulp chamber after CO₂ laser etching. For this purpose the cervical to middle 1/3 level of roots of these specimens were sectioned and removed to gain an access in to pulp chamber for insertion of thermocouple.

A K-type Chromel-Alumel thermocouples was used to measure the temperature rise. Pulp tissue was removed using barbed broach, canal and pulp chamber were enlarged from apex towards the pulp chamber using K-files from number 15-80. Canals were thoroughly cleaned with saline. The thermocouple was .005” wire insulated to the full length except the tip which acts as a sensor for measuring temperature. The thermocouple wire was inserted into the root canal stabilized using cold cure resin and their position was rectified radiographically and then the specimen was etched with two modes of laser (continuous and ultra pulse) to record temperature rise in the pulp chamber.

The other end of the thermocouple was attached to a multipoint digital temperature indicator calibrated to record the temperature in the range of 0-60⁰ C accurately and the temperature rise was recorded for continuous pulse and ultra pulse mode respectively.

STATISTICAL ANALYSIS

Student’s independent “t” test was used to compare the difference among the samples in the same subgroup. The results of this comparison are reported as degree of freedom and p value. If the p value was less than point 0.05 it was considered that the difference is significant.

Results:

• There was a highly significant difference observed in shear bond strength between samples etched with continuous pulse 2 watt (B1₁) and 3 watt (B1₂) respectively. The mean value was highest in continuous pulse 3 watt laser group (Table 1).
• Similarly there was highly significant difference in shear bond strength between control group and continuous pulse laser group (B1₁, B1₂). The highest mean shear bond strength was observed in control group (Table 1).
• There was highly significant difference in shear bond strength between control group and ultra pulse laser group (B2₁, B2₂) i.e. acid etch group resulted in more shear bond strength than the ultra pulse laser group (Table 1).
• There was a highly significant difference in temperature rise in pulp canal between continuous pulse 2 watt laser group and continuous pulse 3 watt laser group. The mean value for temperature rise in the pulp canal was highest in the continuous pulse 3 watt laser group (Table 1).
• There was a highly significant difference in intrapulpal temperature rise between continuous pulse laser group and ultra pulse laser group, with continuous pulse laser group resulted in highest mean value among the two groups (Table 1).
• Highest shear bond strength was observed in samples of continuous pulse laser 3 watt followed by acid etching group and lowest shear bond strength was observed in samples of 2 watt ultra pulse laser group (Table 1).
• Maximum intrapulpal temperature rise was observed in samples of continuous pulse 3 watt laser group and minimum intrapulpal temperature rise was observed in samples of ultra pulse 2 watt laser group (Table 1).

Table I: Mean, median and ranges of all groups are summarized in this table

Baseline Temperature = 29⁰ C

Discussion:

Lasers, with its bioefficiency and utility, have been reported in various studies on caries prevention³, also its ability to enhance acid resistance of the lased enamel surface^4,5 and their soft tissue applications. Studies have shown that lasing of enamel can produce increase dissolution resistance and reduction in rate of subsurface demineralization⁶. Similarly ultra structural changes such as variation in crystal size and crystallinity, inorganic phase changes and loss of prismatic structure occurs within laser treated regions of enamel. Additionally there are many other studies performed in vitro describing significant structural alterations of sound enamel and dentin caused by the ablative and thermal effects of laser irradiation⁷.The CO₂ laser used in the present study is an infrared laser which causes a photo thermal reaction on the enamel surface.This surface of enamel surface melts and reforms with numerous bubble like inclusions with minimal enamel loss which makes it resistant to caries^8.9.

Powell and Morton¹⁰ 1989 reported that continuous wave CO₂ laser with low power did not cause any damage to the pulpal tissue. Obata eta⁸ in their study on comparison of intrapulpal temperature changes with lasers, concluded that pulsed mode laser has short duration pulses separated by sufficient time to allow the tissue to cool between the pulses and as a result limits thermal damage.

There was significant difference in temperature in pulp chamber between 2 and 3 watt continuous pulse irradiated group. Temperature rise with 3 watt laser was 6.5⁰ C and 2 watt irradiated group was 3.16⁰ C. J A Fraunhahoffer¹¹ reported that heating effects at dentinal pulpal on both buccal and lingual surfaces showed an increase in heat as a function of the increase in power output from laser unit. The temperature measured at power level 3 watt appeared to be of sufficient magnitude to cause pulpal inflammation and possible irreversible damage to pulp tissue immediately opposite to the site of laser radiation. With 2 watt laser irradiation group, the temperature rise was in acceptable limits to cause any irreversible pulpal tissue damage but very near to the limit of reversible damage to the dental pulp¹².

Photo thermal ablation cause pulpal heating¹³ in 1989 suggested that the temperature change was directly proportional to level of exposure. In order to reduce heating on enamel by laser exposure, surface treatment water spray and controlled absorption of laser by isolating the area with dyes was used¹⁴. Cohen Leozech and Garsen¹⁵ had reported that around 5⁰ C pulps fail to recover.

The time taken for Laser exposure was also a critical factor becausem prolonged etching might be hazardous to the pulp. The exposure time was limited to 15 sec to obtain an optimum bond strength required clinically i.e. 6-8 Mpa¹⁸. This has proved advantageous over acid etching procedure. The minimum time required for acid etching was 15 seconds followed by 15–30 seconds for isolation of field, whereas laser etching was computed within 12-15 sec enabling immediate placement of brackets. Hence there was a minimal time loss in isolation, washing and drying procedures which on the other hand are essential protocols followed during acid etching technique.

Conclusion:

The etching of enamel surface with laser is more advantageous than etching of enamel surface with phosphoric acid as there is less enamel loss during etching, debonding and clean up procedures with less technique sensitivity, controlled depth, reduced time of etching and resistance against caries producing acids.

Ultra pulse 3 watt laser can be used in routine orthodontic practice as it gives optimal bond strength with acceptable temperature rise in the pulp chamber. However continuous mode of CO₂ laser gives better results in terms of shear bond strength than ultra pulse laser etching. But the temperature rise in the pulp chamber was more in continuous mode as compared to the ultra pulse mode of laser which should be given consideration while using it in clinical practice.

Since this was an in vitro study, it had its limitations pertaining to in-vitro situations. The complex oral environment with variations in temperature, stresses, humidity, acidity, and plaque is difficult to reproduce in the laboratory, which may affect the bond strength.

Acknowledgements:

We are thankful to Mrs. Varsha Patankar, Dept. of metallurgy, VNIT, Nagpur for her help during study.

References:

1. Silverstone LM. Variation in pattern of acid etching of human dental enamel examined by SEM. Caries Res, 1975; 9:373-387
2. Neumann G.V. Epoxy resin for orthodontic attachments; A progress report – AJO, 1965:901-912.
3. J.D.B. Featherstone, N.A. Barrett-Vespone, D. Fried, Z. Kantorowitz and W. Seka. CO2 Laser Inhibition of Artificial Caries-like Lesion Progression in Dental Enamel. J Dent Res, 1998; 77: 1397
4. Hajime Tamamato and Katsuhiko Sato. Prevention of dental caries by Nd:YAG Laser irradiation – J. Dent. Res, 1980; 59: 2171-2173
5. Tagomori S and Iwase. Ultra structural change of enamel exposed to normal pulsed Nd:YAG Laser-Caries Research, 1995; 29(6): 513-520
6. Akira Yamamoto, Takeshi Yoshida, Keishi Tsubota, Toshiki Takamizawa, Hiroyasu Kurokawa, and Masashi Miyazakid. Orthodontic bracket bonding: Enamel bond strength vs. time Am J Orthod Dentofacial Orthop, 2006;130:435.e1-435.e6
7. 7.     M.D. McKee. Effects of CO2 Laser Irradiation in vivo on Rat Alveolar Bone and Incisor Enamel, Dentin, and pulp .J Dent Res, 1993; 72: 1406
8. Akihiko Obata, Toshnobu Tsumura,Ken Niwa, Yuji Ashizawa, Toshio Deguchi and Michio Ito. Super pulse CO₂  laser for bracket bonding and debonding :European Journal Of Orthodontics, 1999 ; 21: 193-198
9. Bor-Shiunn Lee, Tseng-Ting Hsieh, Yuan-Ling Lee, Wan-Hong Lan,  Yao-Jeng Hsu, Ping-Han Wen & Chun-Pin Lin. Bond Strengths of Orthodontic Bracket After Acid-Etched, Er:YAG Laser-Irradiated and Combined Treatment on Enamel Surface; Angle Orthod, 2003;73:565–570
10. Powell G L; Morton T H; Larsen A E.  Pulpal response to irradiation of enamel with continuous wave CO2 laser. Journal of endodontics, 1989;15(12):581
11. Von Fraunhofer J.A.,  G.M. Orbell and Allen D.J. Thermal effects associated with Nd:YAG Dental Laser – Angle. Orthod, 1993; 63: 299-304
12. J.D.B. Featherstone, N.A. Barrett-Vespone, D. Fried, Z. Kantorowitz and W. Seka. CO2 Laser Inhibition of Artificial Caries-like Lesion Progression in Dental Enamel. J Dent Res, 1998; 77: 1397
13. Leo Zack, Garsen, Cohen. Pulp response to externally applied heat. AJO, 1965; 19: 515
14. Walsh L.J., Abod D. et al. Bonding of Resin composite to Carbon di Oxide Laser modified human enamel – Dent. Material, 1994;10(3): 162-166
15. Paul Surmount, Luc Dermaut et al. Comparison is shear bond strength of orthodontic brackets between five bonding systems related to different etching times; An in-vitro study – Am. J. Ortho. Dentofac. Orthop, 1992; 101:414 – 419
16. Wayne A. Labart, Barkmeler W. et al. Bracket retention after 15 second acid conditioning – JCO, 1988; 254-255
17. Wayne Barkmeier, Gwinnett J, Shaffer S. Effects of enamel etching time on bond strength and morphology. J Clin Orthod, 1985;19:36-38.
18. Reynolds, IR. A review of direct orthodontic bonding : Br J  Orthod, 1997; 2 : 171-178.

Why does it matter whether you are considered Totally or Partially Disabled by your Disability Insurance Carrier?  Most disability insurance policies provide that an individual with a partial disability will be paid only through the age of 65, while many individuals on Total Disability Benefits will be paid for the duration of their life.  Moreover, partial disability benefits are based on the percentage of earned income lost.  Thus, unlike Total Disability benefits, if the individual does not suffer a loss of earned income, benefits are not paid and in many cases, the contract ends after a few months.

Finally, in the event of a Buy-Out of the contract by the disability insurance carrier, resulting in a lump-sum settlement in lieu of periodic payments, an individual would be more apt to surrender the contract for less money than if the individual were deemed Partially rather than Totally Disabled.  Insurance companies save themselves hundreds of millions of dollars each year by paying out Partial rather than Total Disability Benefits to their claimants.

This is exactly what almost happened to my client, Dr. Brown.  Fourteen years ago, shortly after starting his dental practice, Dr. Brown bought an insurance policy to protect his income in case of an illness or injury that prevented him from completely or partially working in his chosen profession.  Over the years, Dr. Brown’s practice grew substantially and so did his annual income.  As such, Dr. Brown’s insurance carrier made several offers to increase his monthly disability benefit in case of total disability.  Each time, Dr. Brown gladly accepted the increase in premium payments for the added protection.

Dr. Brown’s practice consisted mainly of crown and bridge work, endodontics, extractions, and general dentistry.  Unfortunately, four years ago, Dr. Brown began to experience stiffness and pain that radiated through his right arm and shoulder.  At first, he dismissed the pain as overuse and applied home remedies.  However, over time the pain became more severe, more frequent, and lingered longer.  Dr. Brown sought treatment from a rheumatologist and was subsequently diagnosed with osteoarthritis.  Nevertheless, Dr. Brown continued to treat patients.  However, his pain, now excruciating after only two hours of use, forced him to change his practice significantly.  He had to forego crown and bridge work, endodontics and more difficult extractions.

After almost a year of cutting back, Dr. Brown read the disability income policy he bought so many years earlier.  The policy provided for the following:

Total Disability:

“You are considered Totally Disabled, if due to injury or illness, you are unable to perform the Substantial and Material Duties of your Regular Occupation and are under the Regular care of a Physician. . . .

Residual (Partial) Disability:

You are considered Residually (Partially) Disabled if, due to injury or illness, you are unable to perform one of the material and substantial duties of your regular occupation, have at least a 20% loss of earned income, and are under the regular care of a physician.” 

Dr. Brown decided to apply for disability income benefits.

Shortly after he mailed his application for benefits to his disability insurance carrier, Dr. Brown received a telephone call from his carrier.  The claims analyst asked him many questions regarding his condition and his continued treatment of patients.  The claims analyst requested additional documentation and indicated that the carrier’s investigation might take several weeks.  However, after only two and a half weeks, the insurance carrier sent Dr. Brown a correspondence that read:

“We conducted a thorough investigation into your claim for disability income benefits and we are pleased to inform you that you are eligible to receive benefits under the terms of your disability income contract.  As you are still working in your profession, you will receive partial disability benefits as long as you remain disabled and continue to suffer at least a 20% loss of earned monthly income.”

Dr. Brown was also pleased by this news.  Many of his colleagues had had very different experiences with their insurance carriers when attempting to collect under their disability income policies.

Dr. Brown was required to provide his carrier with monthly profit and loss statements.  In many months he received no benefit, as in those months he did not sustain at least a 20% loss of earned income.  Dr. Brown subsequently hired another dentist to perform procedures that he could no longer safely perform.  Dr. Brown was able to retain his patient load, as he no longer had to refer his patients to other dentists.  This resulted in fewer and fewer months in which Dr. Brown was “eligible” to collect his disability income benefit.  After two years, Dr. Brown’s carrier approached him to request a buy-out of his disability income contract.  The carrier offered him $100,000.00 for the surrender of his contract.  Dr. Brown found this fair because, in most months, he was collecting little or nothing in partial disability benefits.  However, before signing the agreement, Dr. Brown wanted an attorney to review the buyout agreement and advise him of his rights.  That is when I began to represent Dr. Brown.

After speaking with Dr. Brown and reading his contract it became clear to me that, not only was the offer unreasonably low, but that Dr. Brown was actually Totally Disabled under the terms of his contract and had been eligible to receive Total Disability Benefits for the two years prior and possibly for the rest of his life.  When I explained my concerns to Dr. Brown he was hesitant at first, explaining, “I am still working.  I’m not totally disabled.”  Like so many others, Dr. Brown was convinced that total disability meant the complete inability to engage in his occupation. This erroneous assumption was bolstered by the insurance carrier’s simple statement, “As you are still working in your profession you will receive partial disability benefits.”  It was perpetuated by two years of similar statements by the carrier and, eventually, a seemingly gracious offer to buy out an all-but-useless policy for the sum of $100,000.00.

Inasmuch as many disability policies provide that the inability to perform one substantial and material duty renders a claimant partially disabled, many claimants infer that total disability must be the inability to perform every single duty of the claimant’s occupation. Many claimants do not realize that often a claimant’s disability may render him both totally and partially disabled under the terms of the disability insurance contract. In most states, ambiguous contract language is decided in favor of the insured. If there are two reasonable interpretations of the same provision, it is considered an ambiguous term. Many claims analysts continue to misread these provisions and determine that the claimant is partially rather than totally disabled, as he is still working in his dental practice. Claimants who are not knowledgeable about contract interpretation will often look to the writer of the contract, in this case, their insurance carrier, for clarification. When they are informed that, because they continue to work in some capacity, they are partially rather than totally disabled, this interpretation seems reasonable to many claimants. The conflict is obvious.

As I explained to Dr. Brown, under the terms of his contract, total disability means the inability to perform the “substantial and material” duties of his occupation as they existed just prior to his illness. Dr. Brown’s substantial and material duties prior to his disability consisted of crown and bridge work, endodontics, extractions, consultations, and many cosmetic procedures. Dr. Brown’s post-disability duties consisted mainly of some simple procedures and consultations. He was unable to perform the substantial and material duties of his occupation and, thus, was totally disabled under the terms of his contract. Most significantly, Dr. Brown had been paying premiums for more than a decade for this protection.

After our initial consultation, Dr. Brown turned down his carrier’s offer to buy out his contract and retained me to assert his rights to recover Total Disability Income Benefits under the terms of his contract.  I was able to secure Dr. Brown’s Total Disability Income Benefits, his back benefits totaling almost $200,000.00, interest on his back benefits, and attorneys’ fees.  Ultimately, we negotiated a buy-out of Dr. Brown’s contract, one well in excess of the meager $100,000.00 for which the carrier once attempted to settle his claim.

Attorney Alicia Paulino-Grisham is a partner with Disability Insurance Law Group (DI Law Group) which focuses on individual and group Disability Insurance Claims at all stages of the claims process.  DI Law Group represents clients who are preparing to file a disability insurance claim, have filed and payment has been delayed, or whose claims have been denied.  Many claim denials can be overturned without filing a lawsuit; however, if an insurance company refuses to overturn its unreasonable denial of disability insurance benefits, DI Law Group will file a lawsuit and litigate on behalf of our clients.  Alicia Paulino-Grisham can be reached at alicia@dilawgroup.com.

Dr Sujala G. Durgekar, MDS (Corresponding author)
Assistant professor,
Department of Orthodontics and dentofacial orthopaedics
KLE Vishwanath Katti institute of Dental Sciences,
KLE University, JNMC Campus
Nehru Nagar, Belgaum, Karnataka,
Pin-590010, India

Dr K. Nagaraj, MDS
Reader
Department of Orthodontics and dentofacial orthopaedics
KLE Vishwanath Katti institute of Dental Sciences,
KLE University, JNMC Campus
Nehru Nagar, Belgaum, Karnataka,
Pin-590010, India

Abstract:

Congenital absence of teeth (hypodontia) is the most common developmental dental anomaly in human. Certain adult patients with unique orthodontic problems contralateral tooth size differences, and maxillary/ mandibular tooth size disharmonies demand asymmetric extraction. This report describes management of class I malocclusion with congenital bilateral agenesis of maxillary lateral incisors and mandibular anterior crowding with asymmetric extraction in mandibular dental arch.

INTRODUCTION:

An essential goal of orthodontic treatment is to attain a normal relationship of the teeth and their surrounding soft tissue structures. The dentition should be placed in a healthy and stable position to promote symbiosis between all parts of the masticatory mechanism. Dr Edward H Angle determined that each dental unit was required to achieve this goal. Hindsight has enabled orthodontists to understand that the maintenance of all dental units to achieve the goals of harmony and stability is not always possible, nor it is always desirable. Times have changed and many treatment planning rules that were once considered sacrosanct cannot be applied to non-growing, adults patients. Certain adult patients with unique orthodontic problems like jaw size/tooth size discrepancies, contralateral tooth size differences, and maxillary/mandibular tooth size disharmonies demand asymmetric extraction^1-3.

Congenital absence of teeth (hypodontia) is the most common developmental dental anomaly in human⁴. Congenitally absent teeth are more common in the permanent dentition and have a prevalence ranging from 3.7 to 9 % (excluding the third molars). The most frequently occurring congenitally missing permanent teeth, excluding third molars are the mandibular second premolar (3.4%) and maxillary lateral incisor (2.2%)^5-7.There are various treatment alternatives to deal with the missing teeth which includes^8-17: space closure by spontaneous drift of teeth, orthodontic space closure, auto-transplantation of other developing teeth,  a prosthetic appliance and an implant.

This report describes management of class I malocclusion with congenital bilateral agenesis of maxillary lateral incisors and mandibular anterior crowding.

HISTORY:

A 20 years old male patient came to the department of orthodontics at KLES Academy of higher education and research, Belgaum, India with the chief complaint of spacing between upper front teeth and irregularly placed lower front teeth. He was physically healthy and had no history of medical trauma. He gave history of an accident 2 years ago in which he lost an upper primary tooth. No signs or symptoms of temporomandibular joint dysfunction were noted at the initial examination.

DIAGNOSIS:

The extraoral clinical examination showed a slight concave profile, normal lip competence at rest and low smile line^18-19. There were no gross asymmetries (Fig 1a-d). The maxillary midline was shifted to left by 3 mm relative to the facial midline. The mandibular dental midline was shifted to right by 3mm relative to facial midline. The intraoral examination showed an Angle Class I malocclusion with severe crowding of 9 mm in the mandibular arch (Fig 2a-e). Maxillary lateral incisors were missing in the arch. The mandibular right canine was in labial crossbite. The overjet was 1mm and overbite was 3mm. The curve of Spee was 1.5mm.

Fig 1a-d: Pre-treatment facial photographs

Fig 2a-e: Pre-treatment intraoral photographs

Cephalometrically (Fig 3 and Table 1), the patient had a Class III skeletal relationship with a retropositioned maxilla (Ba-PNS: 39mm, Ba-ANS: 90 mm), slightly prognathic mandible (ANB: -2 degrees) and a prominent chin (Pog-NB: 5 mm). The maxillary incisors were proclined while the mandibular incisors were retroclined (IMPA: 76 degrees). The panoramic radiograph revealed congenital agenesis of both maxillary lateral incisors (Fig 4). The overall alveolar bone was within normal limits.

Fig 3: Pre-treatment lateral cephalogram

Table 1: Cephalometric data

Fig 4: Pre-treatment panoramic radiograph

As the patient didn’t report a significant medical history, the etiology of the malocclusion was considered developmental especially because of reduced maxillary growth, and congenital bilateral agenesis of maxillary lateral incisors. As the patient had a prognathic mandible with horizontal growth pattern that is anterior rotation of mandible, this might have caused mandibular anterior crowding.

TREATMENT OBJECTIVES:

The treatment objectives based on the results of cephalometrics and model analyses were:

1. To create adequate arch length in the lower arch to relieve crowding and align the teeth.
2. To correct crossbite involving the mandibular right canine.
3. To close the maxillary anterior spacing.
4. To substitute the maxillary canines as lateral incisors.
5.  To obtain ideal overjet and overbite and normal interincisal angulation.
6. To accept patient’s profile.

TREATMENT ALTERNATIVES:

• The ideal treatment plan for this patient could have been combined comprehensive orthodontic treatment with orthognathic surgery. Maxillary surgery (Lefort I) combined with genioplasty could help to achieve straight profile. However, such an approach appeared to be aggressive and invasive. Besides, the risks and treatment expenses involved would be high.
• The second option would have been extraction of a lower right lateral incisor. This would help to uncrowd the lower anteriors. But the deviated mandibular midline could not be corrected. Extraction treatment plan was not considered in the maxillary arch as there was already excessive space in it.
• The third treatment option would be extraction of lower first premolars to get lower right lateral incisor in the dental arch. But this treatment option would leave us with excess of space in the lower arch.
• The fourth treatment option would be extraction of lower right canine and mandibular left first premolar. The extraction of lower right canine could have been planned on the basis that it is in labial crossbite. But since canine tooth is the corner stone of an arch this option was omitted.

Finally, it was decided to extract the right mandibular lateral incisor and left mandibular first premolar.

TREATMENT PROGESS:

After oral hygiene instructions, the mandibular right lateral incisor and left first premolar were extracted. The remaining teeth were banded and bonded with a 0.022 inch slot preadjusted edgewise appliance (Roth prescription, Gemini brackets, 3M Unitek). Since maxillary lateral incisors were congenitally missing, lateral incisor brackets were bonded on maxillary canines. This was done in order to achieve adequate lingual root torque and enough angulation to avoid the long roots of the canines from coming in contact and damaging the central incisor roots. The excessive labial root torque in canine brackets could damage the apical ends of these long rooted teeth by forcing them against cortical bone in the nasal area of the maxilla⁸. In order to hide the palatal cusp of the first premolar and to have the same appearance of the canine cusp the first premolar should be rotated mesiopalatally. This was done by bonding the canine bracket on the first premolar tooth distally to enable rotation of this tooth and avoid occlusal prematurities.

Initial levelling and aligning of dental arches was accomplished by sequential use of 0.016 inch, 0.018 inch, 0.017X 0.025 inch and 0.019X0.025 inch NiTi archwires. The patient’s posterior bite was raised with the help of GIC block until the mandibular right canine cross bite was corrected. After 5 months of levelling and aligning, 0.019X 0.025 stainless steel archwires were placed in both the arches. The open coil spring was placed on the maxillary archwire between the left central incisor and left canine; and continuous elastomeric chain was stretched from maxillary right first molar to right central incisor. This was done in order to shift the maxillary dental midline to right side so that the maxillary midline coincides with the facial midline. In the mandibular arch, crimpable hook was placed between left lateral incisor and canine. The elastomeric chain was stretched from mandibular left molar hook to the anterior crimpable hook. The premolar extraction space was utilised to shift the mandibular dental midline to left side to facilitate coinciding mandibular dental and facial midlines.

After 11 months of treatment the space closure was achieved with midline correction. Finishing of the case was done by certain bracket repositioning. The final occlusal adjustment in both the arches was made with settling elastics on braided 0.017 inch X 0.025 inch stainless steel archwires. Fixed appliance was removed after 14 month of treatment. After debonding, a lingual retainer made from 0.017- in multistranded wire ( Coaxial , 3M Unitek, Monrovia, Calif) were placed in the maxillary and mandibular arches from right to left first premolar.

TREAMENT RESULTS:

There was marked improvement in the facial esthetics and smile of the patient. The facial balance was maintained (Fig 5a-d). The patient’s dental appearance was improved, and the molar relationship was preserved. The teeth were well aligned. An ideal Class I buccal occlusion was obtained (Fig 6a-e). The mandibular right canine showed mild labial gingival recession. Since oral hygiene of the patient throughout the treatment period was good, labial and rotated position of the tooth could have been the sole reason for the recession. In spite of the uniarch extraction, treatment concluded with a correct overjet and overbite; the maxillary and mandibular midlines coincided with the facial midline.

Fig 5a-d: Post treatment facial photographs

Fig 6a-e: Post treatment intraoral photographs

Post treatment panoramic radiograph at the completion of treatment revealed good root parallelism with minimal apical blunting of the central incisor roots (Fig 7). Supporting tissues appeared healthy.

Fig 7: Post treatment panoramic radiograph

Cephalometric superimpositions revealed limited late mandibular growth (Fig 8 and Fig 9). The skeletal relationship (angle ANB) was maintained. The interincisal angle was dramatically reduced by 23 degrees due to mainly proclination of lower incisors. The pre and post treatment cephalometric changes are summarised in Table 1.

Fig 8: Post treatment lateral cephalogram

Fig 9: Pre treatment (black) and post treatment (red) cephalometric tracings superimposed on sella nasion plane at sella

As the maxillary lateral incisor should be two thirds of the width of the upper central incisor^18-21, after debonding, the patient was referred to an endodontist for recontouring maxillary canines into maxillary lateral incisor.

Records collected after 2 years of retention show the normal gingival topography around mesially relocated canines with no signs of gingival recession around mandibular right canine.(Fig 10).

Fig 10: Intraoral photograph after 2 years of retention showing normal gingival topography around mesially relocated cuspid.

DISCUSSION: 

Congenital absence of maxillary lateral incisors is common in orthodontic patients. This condition causes several problems, including spacing between the anterior teeth, drifting and rotation of the central incisors and the canines. Treatment depends on a number of factors including patient’s motivation, attitude toward orthodontic treatment, type of malocclusion, overjet and the shape and colour of the canines^{15, 17}. Management can be broadly divided into space closure, space opening or redistribution and prosthetic replacement. Orthodontic space reopening and replacement with prosthesis inherently commit the patient to lifelong artificial restoration in the most visible area of the mouth¹⁴. A study¹³ has demonstrated that subjects treated with orthodontic space closure are more satisfied with the appearance of their teeth than those who had prosthesis with no significant difference in prevalence of temporomandibular dysfunction. Early loss of retained primary teeth results in alveolar atrophy and complete space closure is not possible^{15, 22}. As our patient had lost deciduous tooth 2 years back; alveolar bone was healthy and the space closure was treatment of chose. The space present in the right side of maxillary arch was utilized for achieving coincident maxillary dental and facial midlines.

However, having the canines mesially next to the central incisor might not be esthetically pleasing, because of discrepancy in the gingival margins of central incisors and canines. The cusps of canine teeth are more prominent and are naturally darker than the lateral incisor. The low smile line of patient made the gingival margin discrepancies unapparent. Moreover, the gingival tissue and interdental papillae would change in synchrony with the patient’s own teeth over his lifetime^{17, 23}. A restorative camouflage consisting of careful grinding and composite build up was an integral part of the treatment plan. Because only a minimal amount of enamel is removed during esthetic recontouring of canine, there was no risk of pulp damage¹⁴. The patient was satisfied with the outcome without the need for bleaching of canines.

The marked difference in the crown torque difference between canine and lateral incisor was taken into consideration. The lingual root torque was obtained on the canine by placing lateral incisor bracket on it. Additional palatal root torque was given in the maxillary 0.019 X 0.025 stainless steel archwire to reduce the canine eminence. Buccal root torque was incorporated in the archwire in the first premolar region in order to produce some root eminence^{8, 14}.

Though it is said to be potential disadvantage to have first premolar in the position of previously occupied canines (since lack of canine protected occlusion and heavy lateral occlusal forces on smaller and thinner roots of the first premolars) long term study²⁴ failed to demonstrate this effect. Some studies^{8, 13, 17} indicate that an adequate group function occlusion can be obtained with the first premolars substituting canines. The risk of reopening of closed space was handled by placing a fixed retainer made of braided stainless steel wire from first premolar to first premolar.

This case demonstrates the importance of identifying the specific area of arch asymmetry. Because the dental asymmetry for the patient was in the mandibular arch, it was appropriate to unilaterally extract right lateral incisor. The tooth was completely blocked in lingually. The extraction of this tooth helped to relieve mandibular anterior crowding as well as the labial canine crossbite was corrected. On left side of the mandibular arch, first premolar extraction was done to shift the midline .If the mandibular arch had been treated with non extraction or with bilateral extraction of first premolar, it was unlikely that the mandibular arch asymmetry would have been corrected thereby resulting in a failure to centre the dental midlines facially.

CONCLUSION:

                    Atypical treatment planning is necessary to correct specific and unusual malocclusion. Traditional extraction considerations must be modified to satisfy the treatment needs. In maxillary arch the Prosthodontic option of space opening for prosthesis was less attractive than purely orthodontic solution. Mandibular arch demanded asymmetrical extraction to achieve the desired treatment results.

REFERENCES:

1. Tayer B. H. The asymmetric extraction decision. Angle Orthod 1992;62 :291-297
2. Shelley A, Beam W., Merger J, Parks C.T., Casko J. Asymmetric extraction treatment of an Angle Class II Division 2 subdivision left malocclusion with anterior and posterior crossbites. Am J Orthod Dentofacial Orthop 2000;118:462-466
3. Todd M, Hosier M, Sheehan T, Kinser D. Asymmetric extraction treatment of a Class II Division 1 subdivision left malocclusion with anterior and posterior crossbites. Am J Orthod Dentofacial Orthop 1999;115:410-417
4. Shapiro SD, Farrington FH.A potpourri of syndromes with anomalies of the dentition .Birth Defects. 1983;19:129-40
5. Winter GB. Hereditary and idiopathic anomalies of tooth number, structure and form. Dent Clin North Am 1969;13: 355-373
6.  Zhu J F, Crevoisier R, Henry R J .Congenitally missing permanent lateral incisors in conjunction with a supernumerary tooth: case report. Pediatric Dentistry- 1996;18:64-66
7. Backman B and Wahlin YB. Variations in number and morphology of permanent teeth in 7 year old Swedish children. Int J Paediatr Dent. 2001;11:11-17
8. Tuverson DL. Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod Dentofacial Orthop 1970;58:109-127
9. McNeil, R.W. and Joondeph, D.R.: Congenitally absent maxillary lateral incisors: Treatment planning considerations, Angle. Orthod. 1973;43:24-29
10. Senty, E.L.: The maxillary cuspid and missing lateral incisors: Esthetics and occlusion, Angle orthod. 1976;73:274-289
11. Thordason A, Zachrisson BC, Mjor IA. Remodelling of canines to the shape of lateral incisors by grinding a long term clinical and radiographic evaluation Am J Orthod Dentofacial Orthop 1991; 100:123-132.
12. Sabri R. Management of missing lateral incisors. J Am. Dent. Ass. 1999; 130:80-84.
13. Robertsson S, Mohlin B. The congenitally missing upper lateral incisor. A retrospective study of orthodontic space closure versus restorative treatment. Eur J Orthod. 2000; 22: 697-7100.
14. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin. Orthod.2001; 35:221-234.
15. Carter NE, Gillgrass TJ, Hobson RS, Jepson N, Meechan JG, Nohl FS ,etal. The interdisciplinary management of hypodontia: orthodontics. Br Dent J. 2003; 194:361-36
16.  Umashankara K.V., Nagaveni N.B. Congenital bilateral agenesis of permanent mandibular incisors: case reports and literature review. Archives of Orofacial Sciences 2009, 4: 41-46.
17. Al Anezi S. A. Orthodontic treatment for a patient with hypodontia involving the maxillary lateral incisors. Am J Orthod Dentofacial Orthop 2011;139:690-697
18. Zachrisson, B.U.: Esthetic factors involved in anterior tooth display and the smile: Vertical dimension, J Clin. Orthod.1998; 32:432-445.
19. Durgekar SG, K. Nagaraj, Naik V. The ideal smile and its orthodontic implications World J Orthod 2010;11:211-220
20. Brezniak N, Wasserstein A. Root resorption after orthodontic treatment: Part 2.Literature review. Am J Orthod Dentofac Orthop 1993;103:138-146
21. Levin H I. Dental aesthetic and the golden proportion. J Pros Dent 1978; 40: 244-252.Bergendal B, Bergendal T,
22. Hallonsten A-L, Koch G, Kurol J, Kvint S. A multidisciplinary approach to oral rehabilitation with osseointegrated implants in children and adolescents with multiple aplasia. Eur J Orthod 1996;18:119-129
23. Issacson KG, Thom AR, Horner K, Whaites E. Orthodontic radiographs: guidelines. London, United Kingdom: British Orthodontic Society;2008.
24. Nordquist, G.G. and McNeill, R.W.: Orthodontic Vs. restorative treatment of the congenitally absent lateral incisor; Long- term periodontal and occlusal evaluation, J. Periodontal.1975;46:139-143.

Reader, Dept of Orthodontics and Dentofacial Orthopaedics,

Kothiwal Dental College and Research Centre,

Moradabad. (U.P) India.

Email id:  prety.dr@gmail.com

Dr. Shveta Duggal (B.D.S)

P.G student (II ^nd year)

Dept of Orthodontics and Dentofacial Orthopaedics

Kothiwal Dental College and Research Centre

Moradabad. (U.P) .India

Email id : shvet61185@yahoo.com

Abstract

Osteoporosis has been shown to affect periodontium and orthodontic tooth movement. There are also reports of Osteonecrosis related to oral bisphosphonate therapy during treatment for Osteoporosis. Hence an Orthodontist should be aware of the possible risks involved in osteoporotic patients undergoing Orthodontic treatment. Hence, certain recommendations are being suggested while doing Orthodontic treatment of an Osteoporotic patient.

Key words: Osteoporosis, Orthodontics, Osteonecrosis, Bisphosphonates.

Introduction

There is an increase in demand of the adult patients undergoing orthodontic tooth movement. Females are most common who are aware of their esthetics and undergo orthodontic treatment. Among these patients the postmenopausal females are more prone to Osteoporosis. Osteoporosis is defined as bone density of 2.5 S.D below the mean of a presence of a fragility fracture. ⁷ .Osteoporosis has been shown to affect tooth movement, it can be senile postmenopausal or corticosteroid induced. It has an effect on bone remodeling and thus can affect the speed of tooth movement. In addition, patients who are on long-term medication of corticosteroids are at risk of developing Osteoporosis. It may lead to increased bone fragility or susceptibility to fracture. ⁸ The earliest suggestion of an association between the osteoporosis and oral bone loss was made n 1960¹⁶

Classification

Miyajima et al ¹⁴ classified osteoporosis into:-

1-         Postmenopausal osteoporosis with accelerated bone formation but even more accelerated bone resorption

2-         Senile osteoporosis with depressed and imbalanced bone resorption and formation

Osteoporosis, an age related condition, is classified into primary and secondary types. Primary osteoporosis encompasses the post-menopausal and senile types, secondary osteoporosis occurs secondary to endocrine and renal diseases¹⁸.

Prevalence and Incidence

The prevalence of osteoporosis among post-menopausal women associated with femoral neck is 20 %, 12 % in other men and women associated with vertical deformities and this percentage increases with age ⁸

The incidence of bisphosphonates associated Osteonecrosis is approx. 68 % in the mandible and 28 % in the maxilla and 4 % in both jaws. Jaw necrosis occurs predominately in the posterior alveolar region⁷

According to a study by Hildebolt CF by the year 2050, people over 65 years of age will constitute 22% of the total population, and people over 85 years will compromise 5% of the population.

Risk factors

Female sex, advanced age, low body weight (<58kg), dementia, estrogen deficiency, early menopause (<45 years), Calcium /vitamin deficiency, low calcium intake are the most common factors that have encountered in causing osteoporosis in women¹⁷.

Higher bone resorption was detected in the women with a higher number of pregnancies ¹⁶ Women with history of backaches had more bone resorption compared to those who did not have it. ¹⁹

Prevention

Calcium intake of 1200 to1500 mg per day, cessation of smoking, regular exercise, average daily sun exposure of approximately 30 minutes & optimized medications²⁰

Diagnosis

The diagnosis of Osteoporosis is based on low BMD T- score at lumbar spine, total hip or femoral length BMD T –score of -1 or higher is considered normal for healthy adult. A t-score between -1 to -2.5 is considered Osteopenia, a T- score of -2.5 or less is considered Osteoporosis. ²¹ Mandible like other bones of the body has a series of anatomical landmarks that can serve as radiographic indicators .It was found that the thickness of the mandibular, angular cortex can be used as an index for bone resorption¹⁶.  Studies suggest that findings on the dental panoramic radiograph may be used to detect individuals with low BMD¹⁹.

Drugs used in Osteoporosis

Bisphosphonates are the drugs used to treat the bone metabolic disorders such as Osteoporosis and bone diseases. Although the exact mechanism of bisphosphonates induced osteonecrosis has not been determined but several hypotheses have been proposed .In most cases the pathogenesis of this process is consistent with the defect in jaw bone physiologic remodelling are wound healing. The profound inhibition of osteoclast function can also inhibit normal bone turnover to an extent that local microdamage from normal mechanical loading or injury like tooth extraction cannot be repaired. This ultimately leads to bone necrosis. They have side effects in dental treatment, They may inhibit tooth movement, may impair bone healing and even induce osteonecrosis in the maxilla and the mandible. Due to administration of bisphosphonates in patients with osteoporosis there can be interference with the orthodontic tooth movement, possibly due to higher affinity of bisphosphonates to osteoclast and its anti-angiogenic effect¹¹

Zolendronic acid has been demonstrated to exert an inhibitory effect on circulating levels of vascular endothelial growth factors^22,23 (a potent stimulator of angiogenesis),this may affect the local blood supply of the bone leading to apparent ischemic changes noted in patients’ jaw bones .Since only a minority of bisphosphonate users ,develop bone necrosis , there may be individual genetic variations in drug metabolism or skeletal hemostasis that may confer susceptibility or resistance to developing BRONZ , these theories need to be validated by evidence based research.

Uniquely, bisphosphonates induced Osteonecrosis is only seen in jaws and not seen in long bones or encountered with orthopedic related surgery of bones other than that of maxilla ⁹ In patients taking bisphosphonates, Osteonecrosis symptoms can mimic dental or periodontal disease .

While, doing orthodontic treatment, an Orthodontist should be aware of the pharmacology of the drugs which can change the bone physiology, which in turn hinder the tooth movement and increase morbidity. Hence, a detailed medical history should be taken along with the patient’s informed consent and patient counselling and proper treatment planning should be done. Bisphosphonates are unique in having a long life of 10 years or longer. Hence, their effects on bone turnover and repair may be for an extended period of time ^10. Therefore, Bisphosphonates may still affect the patient, even after the patients have discontinued the drug. Hence, an orthodontist should ask patients not only about current drug usage but about previous medications, too.⁹

.

Orthodontic considerations in Osteoporosis¹¹

Osteoporotic patients are at high risk in developing periodontal disease .Alveolar bone height plays an important role in determining the effect of the orthodontic forces. Myjiama¹⁴ et al concluded that when there is a decrease in the alveolar bone height, the center of resistance moves apically resulting in a decrease in the moment of force. Hence, force systems must be controlled during orthodontic treatment in osteoporotic patient ^12,13. Osteoporotic patient should be thoroughly examined before and during the orthodontic treatment. If the patients are receiving medications such as Corticosteroids or Estrogen, the medications need to be temporarily ceased during space closure and after consultation with the patient’s physician. The individual orthodontic treatment should be planned which is least invasive, especially as far as extractions are concerned, since orthodontic tooth uprighting is problematic.

Post-menopausal females receiving estrogens’ therapy also had greater bone loss as compared to post-menopausal females¹¹.

Hildbolt¹⁵ reviewed the literature on association between osteoporosis and oral bone loss. He concluded that there was a marked increase in the cortical porosity of the mandible, with an increased porosity in the alveolar bone than the mandibular body. The loss of bone mineral content was 1.5 % per year in females and 0.9 % in males. But, it was observed that in women there had been lower mandibular bone mineral content (BMC) as compared to men of the same age group. It was also suggested that the systemic factors responsible for osteoporotic bone loss may combine with local factors (periodontal disease) to increase the rates of periodontal alveolar bone loss that would affect the orthodontic tooth movement¹⁶

Patients who have undergone bisphosphonate therapy should avoid with dental implants.  Impacted teeth that are completely covered by bone and soft tissue should be left undisturbed .Small lingual mandibular tori or midline palatal tori should not be removed. Extractions, surgeries, laser therapy, orthognathic surgeries, root canals should be avoided and non-invasive procedures like proximal stripping should be favored which reduces the amount of necessary tooth movement.

The tooth movements may be slowed or even stopped during the first three years of oral bisphosphonates exposure because of the anti-resorptive affect. Primary space closure should be attempted if extraction is unavoidable. Since bodily tooth movement is difficult, so in extraction the space is closed by the tipping tooth movement. Because of the concomitant incorrect angulation there is an increased tendency for relapse. Frequent oral prophylaxis and fluoride treatment should be considered. If the tooth is not restorable by treatment, then amputation of the crown is a better option than extraction treatment. Teeth having grade II or III mobility must be splinted. If mobility is greater than grade III or there is an associated periodontal abscess, there is the strong possibility that Osteonecrosis is present and the granulation tissue is covering the exposed bone. In such instances, removing the tooth and providing antibiotic treatment is the only option ⁹.

Estrogen and Orthodontic tooth movement

Estrogen substitutes used for the treatment of Osteoporosis help to reduce the alveolar bone loss. This effect is due to decrease in the rate of bone resorption by inhibiting the production of various cytokines, mainly Interleukin -1, tissue necrosis factor- alpha, and interleukin -6 which enhances osteoclast formation and osteoclastic bone resorption. Miyajima et al ¹⁴ concluded that the tooth movement is slowed in women taking estrogen therapy. Younger women taking oral contraceptives also have been found to have inhibited tooth movements.

Corticosteroid induced osteoporosis and orthodontic tooth movement

The main side effect of corticosteroid administration is Osteoporosis, it involves the uncoupling of bone formation and bone resorption leading to a net decrease in the bone formation. Osteoporosis induced by corticosteroids affect the speed of the tooth movement. Ashcraft ²⁴et al found that the corticosteroids administered in rabbits elevated osteoclastic activity. There was an increase in alveolar bone resorption and decrease in bone deposition. There was an acceleration of the tooth movement with subsequent greater relapse. Kailia²⁵ et al supported this finding in their pathological studies and found that in both chronic and acute corticosteroid tooth movement, tooth movement increases. Verna²⁶ et al found more root resorption in an acute corticosteroid treatment group as compared to controlled and chronic group. In chronic corticosteroid treatment, the orthodontic forces must be controlled and reduced. In acute corticosteroid treatment bone turnover is reduced, but there is an increase in bone resorption thus, orthodontic treatment should be postponed until the patient is taken off the medication.

Orthodontic Recommendations for Osteoporotic patients

• Patient’s detailed medical history must be taken. If there is a history of osteoporosis, then a history of bisphosphonates must be taken into consideration, as the risk of bone necrosis increases in patients taking bisphosphonates therapy.
• Patient’s physician must be consulted prior to starting any orthodontic treatment.
• Patient’s informed consent form must be taken and patient must be informed about the risks and the benefits that outweigh each other.
•  Educate patients on oral hygiene and signs and symptoms of BRONZ.
• Assess PDL status. Refer for PDL evaluation and ensure regular orthodontic recalls
• Invasive procedures like surgeries, RCT, extractions and laser therapy must be avoided including orthognathic surgeries.
• Non-invasive treatment is a wise option to opt for after weighing the risk vs. benefits. Non- invasive treatments like interproximal enamel reduction is preferred over extractions.
• Light and Controlled forces must be applied according to the alveolar bone height.
• Bodily tooth movements are difficult to achieve, only tipping movements are possible and this increases the chances of relapse.
• Prolonged retention and tooth borne retainers should be preferred. In case the removable retainers are used, they should not exert pressure on the soft tissue covering bone.
• Increased chances of root resorption in patients taking corticosteroids
• The treatment should be either deferred or postponed until the physician’s consent.

Conclusion

It has been found that Osteoporosis and their medications affect orthodontic tooth movement and the stability of orthodontic treatment. Even a spontaneous Osteonecrosis has been reported among patients undergoing oral bisphosphonates therapy. Hence, Orthodontic patients may be at a risk of osteonecrosis of the maxilla or mandible. Orthodontic treatment should be carried out with caution! Orthodontists should avoid any invasive procedures. Periodontal conditions must be assessed and post regular patient recalls during orthodontic treatment. Light and continuous forces should be applied. Prolonged retention should be advised due to poor stability.

Ongoing research may lead to alternative therapeutic regimens in future that could induce apotopsis of osteoclast and to place the correct medication¹¹. Penolazzi et al¹¹ injected into animals a decoy oligonucleotide targeting NF-kB that could induce apotopsis of osteoclasts after the application of the orthodontic forces. Thus, they succeeded in regulating the alveolar bone resorption during the orthodontic tooth movement. If this approach could be improved, excessive osteoclastic activity in pathologic conditions such as osteoporosis, periarticular osteolysis, inflammatory arthritis, Paget’s Disease and tumor–associated osteolytic metastases could be controlled.^. Further studies need to be undertaken to get a broader view in terms of osteoporosis related effects on orthodontic tooth movements and risk factors that are involved in causing osteonecrosis of the bone. Furthermore, an orthodontist should update themselves with recent studies and research.

References

1. Burden D, Mullally B, Sandler J. Orthodontic treatment of patients with medical disorders. Eur J Orthod 2001; 23: 363-72
2. Jennifer E. Weiss, Norman T. ilowite ; Juvenile Idiopathic Arthritis; Pediatr Clin N Am; 52 2005 ;413 – 44
3. Gowri Sankar Singaraju etal ; Management Of The Medically Compromised Cases In Orthodontic Practice; Asian Journal of Medical Sciences 1 (2010) 68-74
4. Sharath Kumar; Need for determining the incidence and prevalence of JIA in developing countries: the Indian apredicament; Rheumatology (2010) 49 (8):1598-1599.
5. Pepmueller PH, Cassidy JT, Allen SH, et al. Bone mineralization and bone metabolism in children with juvenile rheumatoid arthritis. Arthritis Rheum 1996; 39(5):746– 57.
6.  Knops N, Wulffraat N, Lodder S, et al. Resting energy expenditure and nutritional status in children with rheumatoid arthritis. J Rheumatol 1999; 26:2039– 43.
7. Zahrowski JJ. Bisphosphonate treatment: an orthodontic concern calling for a proactive approach. Am J Orthod Dentofacial Orthop 2007; 131: 311-20.
8. Sidiropoulou-Chatzigiannis S, Kourtidou M, Tsalikis L. The effect of osteoporosis on periodontal status, alveolar bone and orthodontic tooth movement. A literature review. J Int Acad Periodontol. 2007 Jul;9(3):77-84.
9. Marx RE,Sawatri Y, Fortin M, Broumand V Bisphosphonate induced exposed  bone (osteonecrosis/osteopetrosis) of the jaws; risk factors , recognition , prevention and treatment .J Oral Maxillofac Surg 2005 ;63;1567-75
10. Zahrowski JJ.Bisphosphonates treatment ; A preset orthodontic concern calling for a  proactive approach.The bulletin;AAO 2006;24 (5);4,8,9
11. Fiona Y. C Leung , A.Bakrm.Rabie; Ricky W.K.Wong; Osteoporosis , osteonecrosis and orthodontics ; World J of Orthod 2009;10;261-271
12. Von Wowern N, Klausen B, Kollerup G. Osteoporosis ; A risk factor for periodontal disease. J Periodontol 1994;65;1134-1138
13. Germay A. Initial stress produced in the periodontal membrane by orthodontic loads in the presence of varying loss of alveolar bone; A three dimensional finite element analysis; Eur J Orthod 2002;24;21-33
14. Miyajima ,Nagahara K,Lizuka T; Orthodontic treatment for a patient after menopause; Angle Orthod 1996;66;173-180
15. C.F Hildebolt; Osteoporosis and oral bone loss; Dentomaxillofacial radiology;1997; Vol 26;Issue 13-15
16. Fatemeh Ezoddini Ardakani; Seyed-Jalil Mirmohamadi; Osteoporosis and oral bone resorption: a review; J Maxillofac Oral Surg ;2009; 8(2):121–126
17. Fauci As, Harrison TR;Kasper DL,Braunwald E , Hauser SL, Longo DL et al ;Harrisons principles of Internal medicine; Mc Graw Hill;2008;20^th ed.
18. Koka S, Forde MD , Khosla S ; systemic assessments utilizing saliva; part 2 osteoporosis and use of saliva to measure bone turnover; Int J Prosthodont 19 (1);53-60
19. Aarrdakani FE,Niaf N; Evaluation of the changes in the mandibular angular cortex using panoramic images . J Contemp Dent Pract ;2004; 5 (3); 1-15
20. Baum E , Peters Km ; The diagnosis and treatment of primary osteoporosis according to current guidlines ;Dtsch Arztebl Int;2008; 105 ;33;573-582
21. Vondracek SF , Linnebur SA; 2009; Diagnosis and management of osteoporosis in the older senior . Clin Interv Aging 4 (1); 121-136
22. Santini D, Vincenzi B , Avvisati G, Dicuonzo G , battistoni F , Gavasci M , etal ; Pamidronate induces modifications of circulating angiogenic factors in cancer patients. 2002;Clinc cancer Res 8;1080-1084
23. Wood J , Bonjean ,Ruetz S , Bellahcene A , Devy L , Foidart JM , etal ; Novel antiangiogenic effects of the bisphosphonate compound zolendronic acid . J Pharmacol Exp Ther ; 2002; 302;1055-1061
24. Ashcraft MB,Southa JKA, Tolley EA. The effect of corticosteroid induced osteoporosis on orthodontic tooth movement ; Am J Orthod Dentofacial Orthop 1992;102:310-19
25. Kalia S , Melsen B Ve Na C; Tissue rection to orthodontic tooth movement in acute and chronic corticosteroid treatment . Orthod Craniofac Res ;2004 ;7;26-34
26. Verna C, Hartig LE, Kalia S Melsen B. Influence of steroid drugs on orthodontically induced root resorption . Orthod Craniofac Res ;2006;9;57-62.

PG Student ,Department of Orthodontics

Dr Syamala Reddy Dental College, Bangalore

Dr Prashanth Kamath,

Professor and HOD,Department of Orthodontics

Dr Syamala Reddy Dental College, Bangalore

Dr .Renu Prasad,

Professor ,Department of Orthodontics

Dr Syamala Reddy Dental College, Bangalore

Dr .Arun Kumar BR ,

Senior Lecturer ,Department of Orthodontics

Dr Syamala Reddy Dental College,Bangalore

Dr. Mamatha Thomas,

Senior Lecturer , Department of Orthodontics ,

Dr Syamala Reddy Dental College,Bangalore

Corresponding author: Dr Nagarathna KN

PG Student,phone no : 91-9986175541,   E-mail:  nagarathna_kn@yahoo.com

Abstract; Mini-implants have become a routine anchorage method in orthodontic practice given their high predictability and scientifically proven benefits. The small size of miniscrew implants allows them to be placed into bone between the teeth, thus expanding their clinical applications. With more patients treated with screw implants as anchorage, their stability is gathering attention. Despite their tremendous success in facilitating treatment outcomes, the implant failure rates are widely variable and could be as high as 10-30%.This article describes the various factors affecting success of mini-implants.

Key words: Miniscrew success, Stability, Safe zones.

Introduction:

Use of mini-implant anchorage in orthodontics has gained increasing popularity in both clinical applications and research since its introduction. Despite their tremendous success in facilitating treatment outcomes, the implant failure rates are widely variable and could be as high as 10-30%.¹

Success in mini-implant orthodontics is defined as a mini-screw with minimal mobility and inflammation and the ability to obtain full functional correction either through direct or indirect anchorage.²

Successful mini-implants require adequate primary and secondary stability.Table1,shows comparisons of primary and secondary stability.³

Table no. I :comparision of Primary stability and Secondary stability

Various factors affecting success;

I.            Implant dependent

II.            Operator dependent

III.            Patient dependent

I .Implant dependent factors

Shape

1. Conical
2. Cylindrical

Dimension

1. Length
2. Diameter
3. Head
4. Trans gingival collar

Shape: Results from insertion torque measurements suggest that a conical screw design will provide greater primary stability than cylindrical screw types. The cylindrical screw design’s superiority was evident in the pullout tests. All the miniscrews’ primary stability rose after drill-free insertion.⁴

Dimension of mini-implant; Mini-implants with increased diameter, tapering, and double threading can maximize interlocking between bone and implant, thereby increasing primary stability.

1. Length: A longer screw with a small diameter is more subjected to bending or breakage. Screws that are longer than 10 mm could result in greater risk of iatrogenic perforation (i.e. On the lingual side of the mandible or into the maxillary sinus . Table  II describes the  Ideal implant length and site of placement.⁵

Table II: Ideal implant length and site of placement

2. Diameter: An increase in screw diameter can efficiently reinforce the initial stability of miniscrews, but the proximity of the root at the implanted site should be considered. Screws with diameters of 1.2, 1.5, and 2.3 mm have acceptable levels of success.⁴

3. Miniscrew head: The head must be of sufficient dimension to accept and hold any coupling elements selected for a particular application. Different head designs also require different dimensions. A small diameter and lower profile of the miniscrew head are important for oral hygiene and patient comfort.⁴

4. The Trans-gingival Collar: The trans-gingival collar (trans-mucosal collar/neck) is the sensitive part of implant. Any perforation in the soft tissue provides a potential entry point for microorganisms and could give rise to infection. Figure 1 shows the thickness of soft tissues and length of the trans-gingival collar.⁴

Figure 1: A-standard type, B- wide collared type, C-Long collard type

  I.            Operator related factors

These include selection of implant site, bone density, soft tissue considerations, Placement technique, direction of placement, implant placement torque, loading  protocol, avoiding soft tissue over growth,  using mini-plates, sterilization and finally clinicians  experience.

1. Selection of implant site: In order to avoid root contact, implants should be placed in safe zones. The minimal space requirement between roots is 0.5 mm mesial and distal to the implant or 1 mm more than the implant diameter.  In the maxilla, the more anterior and the more apical, the safer the location becomes.

Table III shows the order of the safer sites, available in the inter-radicular spaces of the posterior maxilla.⁶ The order of the safer sites available in the inter-radicular spaces of the posterior mandible are as follows:⁶

Table III: The order of the safer sites, available in the inter-radicular spaces of the posterior maxilla:

1. Between the 1^st  and 2^nd  molar.
2. Between 1^st  and 2^nd   premolar.
3. Between the 1^st molar and 2^nd  premolar at 11 mm from alveolar crest.
4. Between the 1^st premolar and canine at 11 mm from the alveolar crest.
5.  Between the 1^st premolar and canine at 11 mm from the alveolar crest.

2. Bone density:Stationary anchorage failure is often a result of low bone density due to inadequate cortical thickness. Bone density is classified into 4 types D1, D2, D3 and D4. D1, D2, D3 are optimal for self-drilling miniscrews.⁷

Implant placement in D4 not recommended due to the reported high failure rate. Table  IV shows the various Bone types and corresponding bone density, Figure 2 and 3 shows the distribution of  bone density in the maxilla and mandible.

Figure 2: Distribution of bone density in maxilla and mandible

Figure 3 : Distribution of bone density in palate

Table IV:Bone type and corresponding bone density

3. Assessment of miniscrew site: Periapical radiographs and OPG provide two-dimensional image of three-dimensional anatomic structures. The use of CBCT with 3-D images would provide more accurate and reliable results .(Figure 4 and 5)

Figure 4: In IOPA ,the possiblility of root contact is not clear.

Figure 5: In CBCT view: The image is clear and free of distortion

4. Soft tissue considerations: Thin and keratinized mucosa is the preferred area for implant placement. Table V shows comparision of mucosal site and prognosis.

Table V: comparision of mucosal site and prognosis

5. Placement technique: A small amount of local anesthetic is sufficient, profound anesthesia of the teeth is not required. There are two methods of implant placement, the Surgical technique and the Self-drilling method.⁸

1.Surgical technique: Ideally a pilot drill should be 0.2 to 0.5 mm less than the implant diameter, and the depth should be less to obtain proper initial mechanical stability. Table VI shows Implant diameter and pilot drill size.⁹

Table VI: Implant diameter and pilot drill size

A slow drill speed (800rpm) should be used.  Excessive pressure of the drill and worn drills are contraindicated. Heat production should be minimized.  47°C is the critical temperature that can cause bone damage. Copious irrigation with saline solution is recommended.^10,11 It is safer to use a manual screw driver, if the clinician feels any resistance from roots, the implant can be withdrawn and redirected.

2. Self drilling method: The self-drilling Implant has high placement torque and high bone-implant contact values. This procedure is contraindicated in the posterior and inferior aspects of the mandible since they have been reported to have a high breakage rate.

3. Direction of placement: Angulation of the bone surface needs to be moderate, a 45 degree angulation relative to the occlusal plane is considered acceptable .¹²

4. Insertion angle of miniscrews shows that an oblique insertion is advantageous to avoid possible root damage, but it is sometimes difficult because of possible slippage on bone surface (Figure 6). Excessive angulation may weaken the cortical bone structure and part of the threaded portion may be exposed on buccal side. (Figure 7).¹²

Figure 6: Insertion angle of miniscrews

Figure 7: Exposed threaded portion

5. Implant placement torque: Motoyoshi et al recommended an implant placement torque range of 5 to 10Ncm. Very high insertion torques leads to higher failure rates due to excessicve bone compression.¹³

6. Loading  protocol: involves immediate loading or a waiting period of 2 weeks to apply orthodontic forces.¹⁴ Most mini-implants can withstand 100 to 200 g of  horizontal  immediate loading successfully. But the position of micro-implants should allow adequate distance from vital organs in expectation of some implant displacement.

7. Minimizing soft tissue over growth: This can be done by placing of a healing abutment cap, a wax pellet, or an elastic separator. Using Chlorhexidine mouthwash slows down epithelialisation.

In regions of loose alveolar mucosa partial insertion with a longer miniscrew (10 mm) is done leaving 2 or 3 threads of the shaft exposed to oral cavity. This helps to minimize the possibility of soft-tissue coverage.

8. Using mini-plates: The connection of two mini-implants with mini- plate provides a stable anchorage system and improves the versatility of the device.¹

9. Screw implants on the right side of the jaw had a higher failure rate, and the mandible

had a higher failure rate than the maxilla. ¹⁵

10.Vertical skeletal pattern is an important factor for the success of orthodontic mini-implants placed in posterior buccal areas.¹⁶

11. Sterilization and asepsis are mandatory throughout the procedure.

12. Clinician experience and skill do contribute to the success of mini implants.

III -Patient dependent factor-

Oral hygiene is the only patient dependent factor.  Poor oral hygiene leads to: Peri implantitis,  Epithelial infiltration, Bleeding on probing, Suppuration, Loss of  bony support, Mobility and finally Implant failure. ⁷

Along with regular tooth-brushing, Chlorhexidine (0.12%, 10 ml) mouthwash is recommended. Patient should be explained about the importance of oral hygiene and motivated  at every visit.

Conclusion;

Orthodontic mini-implants are a powerful aid for the orthodontic practitioner in resolving challenging malocclusions but, Implant failure might delay treatment time. A good knowledge of factors affecting miniscrew success will help us to increase their success rate, thereby achieving desired treatment results and save chair-side time.

References;

1. Wilmes B, Drescher D, Nienkemper M .A Miniplate System for Improved Stability of Skeletal Anchorage.  J Clinic Orthod 2009 ;43 (8) : 494-501.
2. Prasad N,  Sharma T ,  Dabla N  , Nandakumar T. Temporary Anchorage Devices Simplified. Idian J Dent Resear. 2010; 6(2):54-57.
3. Predrilling of the implant site: Is it necessary for orthodontic mini-implants? Am J Orthod Dentofacial Orthop;2010:137:825-9
4. Kim YK, Kim YJ, Yun PY, Kim JW. Effects of the taper shape, dual-thread, and length on the mechanical properties of mini-implants. Angle Orthod. 2009;79:908–914.
5. Ludwig B, Baumgaertel S, Bbhm B .Mini-implants in Orthodontics. Innovative Anchorage Concepts.Quimessence Publishing Co Ltd ; 21,26.
6. Poggioa PM, Incorvatib C, Stefano Velob S, Aldo Carano A  .‘‘Safe Zones’’ A Guide for Miniscrew Positioning in the Maxillary and Mandibular Arch. Angle Orthod 2006;76:191–197.
7. Kravitz ND, Kusnoto B. Risks and complications of orthodontic Miniscrews . Am J Orthod Dentofacial Orthop 2007;131:00.
8. Baumgaertel S, Mohammad R. Razavi,b and Mark G. Hansc .Mini-implant anchorage for the orthodontic practitioner. Am J Orthod Dentofacial Orthop 2008;133:621-7.
9. Critical factors for the success of orthodontic mini-implants: A systematic review . Chen Y, Kyung HM, Zhao WT, and Yud WJ. Am J Orthod Dentofacial Orthop 2009;135: 284-91.
10. Eriksson AR, Albrektsson T. Temperature threshold levels for heat-induced bone tissue injury: a vital-microscopic study in the rabbit. J Prosthet Dent 1983;50:101-7.
11. Tehemar SH. Factors affecting heat generation during implant site preparation: a review of biologic observations and future considerations. Int J Oral Maxillofac Implants 1999;14:127-36.
12. Nanda R,Uribe FA. Temporary anchorage devices in orthodontics 2009, Mosby Elsevier.91,101.
13. Motoyoshi M ,Hirabayashi M, Uemura M,Shimizu N. Recommended placement torque when tightening an orthodontic mini-implant.. Clin. Oral Impl. Res. 2006;17;109–114.
14. Ohashi E, Pechob OE,Morona M, Lagravere MO . Implant vs Screw Loading Protocols in Orthodontics, A Systematic Review Angle Orthod 2006;76:721–727.
15. Park HS, Jeong SH,b and Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofacial Orthop 2006;130:18-25.
16. Moon CH, Park HK,Nam JS,Im JS,Baek SH .Relationship between vertical skeletal pattern and success rate of orthodontic mini-implants. Am J Orthod Dentofacial Orthop 2010;138:51-7.

Authors:

Dr. JIGAR R. DOSHI  _M.D.S

Corresponding Author

Assistant Professor, Department of Orthodontics

Darshan Dental College and Hospital, Loyara, Udaipur

Phone: + 91-9537110110

E-mail: drjigar009@yahoo.co.in

Dr. KALYANI TRIVEDI  _M.D.S

Professor  & H.O.D,

Department of Orthodontics

Darshan dental college and hospital, Loyara, Udaipur

Email:  kalyanimtrivedi@rediffmail.Com

Dr. TARULATHA SHYAGALI  _M.D.S

Reader, Department of Orthodontics

Darshan Dental College and Hospital, Loyara, Udaipur

Phone:  +91- 7742129768

Email:  drdeepu20@yahoo.com

Abstract:

A deep bite is a very common malocclusion in orthodontics. Whenever a deep bite is present it is due to the extrusion of anterior teeth. There are three options to correct it. Correction of the Curve of Spee, intrusion and retraction by segmental mechanics and deep bite correction by a continuous loop archwire. Retraction and intrusion of the six anterior teeth under the edgewise system is usually carried out in two distinct steps: canine retraction followed by incisor retraction. In the begg and Tip- Edge techniques, canine and incisors are retracted and intruded by enmasse.

Key Words:  Deep bite correction, Loop mechanics, Asymmetric “T” Loop

The advantage of the separate canine retraction is that molar anchorage is conserved.  Towards the end of treatment there is frequently a need for additional maxillary anterior intrusion, space closure and lingual root torque.

The Asymmetric “T” Loop Archwire:

The asymmetric “T” loop archwire, a system made of .019 x .025” TMA (.022” brackets)  and .017 x .025 TMA (.018”brackets) has been proven effective in achieving simultaneous intrusion and retraction of incisors. This asymmetric “T” loop archwire has a loop that is placed distal to the upper lateral incisors. The loop can be activated intraorally for the multiple adjustments like, intrusion and retraction of incisors, or to increase torque during retraction.¹

Construction:

A small rounded bird beak plier is used to bend the loop into a preformed TMA archwire. Shape memory of the wire and the loop configuration make this a multipurpose system which can be incorporated into a continuous archwire. The vertical portion of the loop should be 5mm, the anterior loop 2mm, and the posterior loop 5mm. The archwire has an exaggerated reverse Curve of Spee and strong distal molar rotation. Bend the loop invards to prevent irritation to the cheek. (Fig 1)

Fig 1: Asymmetric “T” loop Archwire ( .019 x .025” TMA wire).

Case Report:

A 16 year old female reported with a chief complaint of irregularly and forward placed front teeth. On clinical examination and cephalometric evaluation she was diagnosed as an Angle class I dentoalveolar malocclusion with skeletal class II jaw relationship with anterior crowding in the upper and lower arch. She had an overbite of 6mm with excessive gingival display during smiling. (Fig 2) Her treatment plan was to extract the four I^st premolar teeth followed by fixed appliance therapy with the MBT pre-adjusted edgewise appliance( 0.022 slot).

Fig 2: Pre treatment photographs.

Treatment Progress:

The treatment started by banding and bonding of the upper and lower arch with a .022” preadjusted edgewise appliance. Leveling and aligning is done by .016” upper and lower Niti followed by a .019” x .025” Cu Niti and upper and lower  .019” x .025” SS wire. After leveling and aligning separate canine retraction was done by using an .011 x .030” 9mm  Niti coil spring. During retraction of the canine, anchorage control was maintained by using a .017 x .025 CIA intrusion archwire in the upper arch along with a TPA in the upper arch along with banding of  2^nd molars and a Lingual arch in the lower.  After canine retraction, simultaneous intrusion and retraction of the upper anterior teeth is done by using .019 x .025” TMA Asymmetric “T” loop archwire. (Fig 3) Reactivation was done by starching and bending of the wire behind 2^nd molar. Within 3-4 months a significant amount of intrusion and retraction was achieved. (Fig 4) After intrusion and retraction had been achieved, torque expression was achieved by using .019” x 025” TMA wire. (Fig 5) The treatment was completed within 18 months and pre and post radiographs showed absence of root resorption. (Fig 6, 7, 8)

Fig 3: With Asymmetric “T” Loop Archwire ( .019 x .025” TMA wire in .022” slot).

Fig 4: After Intrusion.

Fig 5: During Finishing Procedure ( by .019 x 25 TMA wires).

Fig 6: Post treatment photographs with corrected deep bite.

Fig 7: Pre treatment Xray.

Fig 8: Post treatment X-ray showing no root resorption.

Conclusion:

A deep bite has been considered one of the most common malocclusions and the most difficult to successfully treat. Therefore, the optimal treatment of deep bites requires a proper diagnosis, a careful treatment plan and an efficient appliance design.² Not all patients with deep overbite should be treated with the same mechanics. Some patients require intrusion of the anterior teeth, while others require primarily extrusion. This article has discussed the principles of incisor intrusion and has demonstrated the use of the Asymmetric “T” loop archwire that are capable of intruding incisors with minimal side effects on the posterior teeth. After correction, the deep bite was retained using a maxillary removable retainer with an anterior bite plane. It was needed for several years to maintain the correction.

Bibliography:

1. Hilgers JJ, Farzin N. Adjuncts to Bioprogressive Therapy The Asymmetrical “T” Archwire.  JCO 1992; 26(2):81-86.
   1. Burstone CR. Deep overbite correction by intrusion . Am J Orthod,   Volume 1977 Jul (1 – 22).
   2. Tayer BH. Modified T Loop archwire. JCO  1981;15(8)565-70.

Author:       Dr.Sridhar Kannan

Professor,Dept. of Orthodontics and Dentofacial Orthopedics

Sudha Rustagi College of Dental Sciences & Research

Kheri More,Village Bhopani

Faridabad.

Co-Author: Dr.Gaurav Gupta

Senior Lecturer, Dept. of Orthodontics and Dentofacial Orthopedics

Sudha Rustagi College of Dental Sciences & Research

Kheri More,Village Bhopani

Faridabad.

Co-Author: Dr.Abhishek Goyal

Senior Lecturer, Dept. of Orthodontics and Dentofacial Orthopedics

Sudha Rustagi College of Dental Sciences & Research

Kheri More,Village Bhopani

Faridabad

Address for

Correspondence: Dr Sridhar Kannan

B-XI/8193, Vasant Kunj, New delhi-70

Tel: 9818212912

Email: sridharkannan_in@yahoo.com

INTRODUCTION

The term “Orthodontics” and “Dentofacial Orthopedics” are essentially’ distinct in that they represent a fundamental variation in approach to the correction of dentofacial abnormalities.

While Orthodontics implies, by definition, the correction of dental irregularities, dentofacial orthopedics conveys the much broader concept that treatment aims to significantly improve facial appearance and skeletal relationships in addition to correcting irregularities of the teeth.

Functional appliance therapy is that aspect of dentofacial orthopedics that aims to improve the functional relationship of dentofacial structures by eliminating unfavourable developmental factors and improving the muscle environment enveloping the developing dentition¹.

Functional appliances, by altering the position of the teeth and supporting tissues, establishes a new and more optimal functional behavioural pattern which leads to adaptive changes in the bone form and helps the dentofacial complex achieve, its optimal genetic growth potential^2-3.

The occlusal inclined plane is the fundamental functional mechanism of the natural dentition¹.

Twin block appliances are simple bite blocks designed for full time wear that achieve rapid functional correction of malocclusion by the transmission of favourable occlusal forces to occlusal inclined planes that cover the posterior teeth^4-5.

The goal in developing the twin block technique was to maximize the growth response to functional mandibular protrusion by using an appliance that is simple, comfortable and esthetically acceptable to the patient.

The objectives of early orthodontic intervention are to correct obvious problems and to intercept developing problems and prevent them from becoming worse. Class II malocclusion of more than 6mm of overjet can be treated early with functional appliance to^6-7:

1. To eliminate functional problems such as lip sucking habits.

2. Reduce overjet, decreasing the risk of traumatic occlusion on the upper incisors.

3. Improve the esthetic appearance of the patients with convex profiles and

retrusive lower faces

4.  Control the skeletal discrepancy between the upper and lower jaws by

stimulating the mandibular growth.

5. Help develop a normal occlusion and facial harmony and promote stability through

out the period of facial growth.

This article will analyze the clinical and cephalometric effects of twin block on patients with severe classII malocclusion in the early permanent dentition and permanent dentition. This section illustrates examples of the treatment of uncrowded ClassII division1 malocclusion in different facial types with twin block appliance to compare the response to treatment.

Case Report

A 12 year old female presented with the chief complaint of unesthetic appearance of her protuding upper incisors. On clinical examination patient had convex soft tissue profile with protruded upper lip, retrognathic mandible. the lower lip was functioning entirely behind the maxillary incisors, which were between the lips at rest.(Fig.1)

Fig.1-Pre-treatment Extraoral Photographs

The patient, who was in the early permanent dentition, had a Class II molar and canine relationship, an overjet of 13mm and an overbite of 5mm. Midline diastema was present in the upper arch with well aligned lower arch.(Fig.2)

Fig.2 Pre-treatment Intraoral photograph.

Cephalometric analysis showed a skeletal Class II malocclusion (ANB = 8°, FMA = 23°) due to mandibular deficiency (SNB = 74°) and maxillary protrusion (SNA = 82°). Both the upper and lower incisors were proclined U1-SN =120°, IMPA = 95°) with interincisal angle of 116⁰ although the maxillary proclination was more pronounced. (Fig.3) & (Table 1).

Fig.3 Lateral Cephalogram tracing

Table 1. Cephalometric Data.

A twin block was advised to stimulate mandibular growth during the development of the dentition. The bite registration was taken with a vertical opening that exceeded the freeway space by 4mm. Contact was maintained between the appliance and the maxillary posterior teeth, but the mandibular posterior teeth were encouraged to erupt by progressively trimming the acrylic on their occlusal and lingual aspect.

After 24 months of treatment with the twin block appliance, a significant improvement in the soft-tissue profile was evident, and labial competence was achieved (Fig. 4). With the overbite and the overjet reduced, the sagittal relationship between the arches improved along with the achievement of bilateral Class I molar relationship.

Fig.4 Post-functional Extraoral Photographs.

The effects of the twin block appliance therapy were evaluated cephalometrically after about two years of treatment (Table1). A reduction of 4° in ANB was achieved, mainly by a forward displacement of the mandible (SNB = 78°) and by controlling the sagittal growth of the maxilla (SNA = 83°). Mandibular  base length increased by 6mm, showing substantial growth of the lower jaw (Ar-Pog = 102mm). The vertical skeletal dimension was slightly increased (SN-MP = 29°), with decease in the inclination of the upper incisors (U1- SN = 94°).

As the permanent dentition was completed, a Class I molar and canine relationship was obtained, and the overjet and overbite were corrected (Fig. 5).

Fig.5 Post-funtional Intraoral Photographs.

The twin block was then worn at night only for retention.

Post-treatment cephalometric analysis indicated an improvement in the sagittal jaw relationship (ANB = 4°), due almost entirely to a forward movement of B point (SNB = 78°) and a further increase in mandibular base length (Ar-Pog = 102mm). The vertical dimension, as expressed by FMA, increased by 2°.

Case Report-2.

An 11 year old female reported with forwardly placed upper incisors. After clinical examination and cephalometric evaluation she was diagnosed as Class II Division1 malocclusion with convex facial profile, retrognathic mandible, increased overjet and overbite(Fig.6-7).

Fig.6 Pre-treatment Extraoral Photographs

Fig.7 Pre-treatment Intraoral Photograph

After complete diagnosis and treatment planning, functional appliance therapy was chosen as the first line of treatment. Twin block appliance was delivered to the patient after following the standard procedure of bite registration. Functional appliance therapy continued for two years to achieve desired improvement in the facial profile. Marked post functional changes were seen with improvement in the convex facial profile, reduced overjet and overbite (Fig.8-9). Cephalometrically, there is reduction in ANB angle by 4⁰ indicating the improvement in sagittal jaw relationship predominantly because of forward movement of point B and increase in mandibular base length.

Fig.8 Post-functional Extraoral Photographs

Fig.9 Post functional Intraoral Photograph

Case Report-3

An 11 year old male was diagnosed with Class II Division1 malocclusion on account of retrognathic mandible, convex facial profile, angle’s Class II molar relation, proclined maxillary incisors, increased overjet and overbite (Fig.10-11).

Fig.10Pre-treatment Extraoral Photographs

Fig.11 Pre-treatment Intraoral Photographs

Considering the clinical examination, cephalometric analysis and age of the patient, it was decided to treat the patient by functional growth modification. Twin block functional appliance was given to the patient to be worn for next two years. After 24 months of treatment with the twin block appliance, a significant improvement in the soft-tissue profile was evident with improved lip competence (Fig.12).

Fig.12 Post Functional Extraoral Photographs

With evident reduction in overjet and overbite, the sagittal relationship between the arches improved along with the achievement of bilateral Class I molar relationship (Fig.13). Post-treatment cephalometric analysis indicated an improvement in the sagittal jaw relationship (ANB = 4°), due almost entirely to a forward movement of B point (SNB = 77°) and a further increase in mandibular base length (Ar-Pog = 102mm).

Conclusion

The principal advantage of functional appliances in Class II therapy is that they not only correct the malocclusion, but are also effective in improving the soft-tissue profile and the intermaxillary relationship. Early treatment can eliminate etiologic factors such as sucking habits, restoring normal growth and reducing the severity of skeletal abnormalities. Once the growth period is over, treatment options become more limited. Mixed-dentition therapy can therefore help create a more stable and esthetic occlusion than if treatment is delayed until the permanent dentition.

References

1. Clark WJ. Twin Block functional therapy. Applications in Dentofacial Orthopaedics.Mosby, 2nd edition

2002; 1-10.

2. White, L.: Early Orthodontic intervention, Am. J. Orthod.113:24-28, 1998

3. Bench, R.W.; Gugino, C.F.; and Hilgers, J.J.: Bioprogressive therapy, Part 8, J. Clin. Orthod. 12:279-

298, 1978.

4. Bishara, S.E. and Ziaja, R.R.: Functional appliances: A review, Am. J. Orthod. 95: 250-258, 1989.

5. Arvystas, M.G.: The rationale for early orthodontic treatment, Am. J. Orthod. 113:15-18, 1998

6. Murillo, J.C.: Mixed-dentition treatment with the selective functional appliance, Am. J. Orthod. 63:596-

605, 1973.

7. Cozza P, De Toffol L. Funtional appliance treatment for Severe classII malocclusion in the early mixed

dentition. J. Clin. Orthod.2003; 37(2): 69-74.