Dr. Rupender Goel B.D.S., M.D.S.
Department of Orthodontics & Dentofacial Orthopedics,
Santosh Dental College & Hospital,
1 Santosh Nagar,Pratap Vihar
Ghaziabad – 201009
Dr. Bhavna Singh B.D.S. (M.D.S.) – (Corresponding Author)
Final year Post Graduate student
Department of Orthodontics & Dentofacial Orthopedics
Santosh Dental College & Hospital,
Santosh Nagar,Pratap Vihar
Ghaziabad – 201009
INTRODUCTION:- Every orthodontists at some point in his clinical practice has faced the dilemma of how ‘best’ to manage a mild to moderate class II malocclusion, which is by far one of the most common type of malocclusions encountered. Forsus FRD has long been used for the same.
AIMS AND OBJECTIVES:- To demonstrate the efficacy of Forsus FRD for management of class II malocclusion.
MATERIAL AND METHODS:- 2 patients having Class II malocclusion (division 2 and division 1 respectively) with functional jaw retrusion were treated using Forsus FRD appliance. MBT 0.018 prescription was used. Pre and post-treatment photographs and lateral cephalograms were taken. Cephalometric analysis was done and results were superimposed.
RESULT: 7-8 months of Forsus wear obtained stable and successful results with improvement in facial profile, skeletal jaw relationship and mild increase in IMPA. One year into retention showed a stable posterior occlusion.
DISCUSSION AND CONCLUSION: Class II malocclusions are usually seen on account of functional retrusion of the mandible, which is adequately managed with fixed functional appliances. It can thus be concluded that Forsus gives good results for class II management and it would be wise to consider treating such cases by non-extraction approach rather than contemplating extractions.
Class II malocclusion presents a major and a common challenge to orthodontists. Angle defined it as the lower molar being distally positioned relative to the upper molar, line of occlusion not specified.1 Etiology of Class II malocclusion may be due to heredity, abnormal intra-uterine fetal pressure, birth injury, and traumatic injury to mandible or TMJ. It may be a dental class II or have a skeletal component1. Skeletal class II jaw relation may be due to a prognathic maxilla, retrognathic mandible or a combination of both. Mandibular retrognathism may be due to small mandible, posterior placement of condyle in glenoid fossa or a functional retrusion.
Management of class II malocclusion depends entirely upon the severity of the problem and the age at which it presents for treatment. Numerous orthodontic techniques and appliances have been introduced to treat the same. Class II due to mandibular retrognathism in a growing patient can be managed by myofunctional therapy. If patient has not yet crossed the adolescent growth spurt, a removable functional appliance such as Activator, Bionator, Twin block, Frankel may be used. Towards the deceleration phase of growth, fixed functional appliances like fixed twin block, Jasper Jumper, Herbst, Universal bite jumper, Ritto appliance, Eureka spring, Forsus FRD can be given.2
Amongst these, the fixed twin block is a bulky, rigid appliance that causes a lot of patient discomfort, is difficult to clean and restricts jaw movements.3Though they have the advantage of not requiring patient compliance and can be used in a fully erupted permanent dentition, concurrently with brackets, they are cumbersome to install, prone to breakage, cause a lot of tissue impingement and are difficult to clean or remove.4 Intermaxillary elastics are another commonly used interarch method for Class II correction but, rely heavily on patient compliance for their effectiveness.5 Poor cooperation can lead to poor treatment results and increased treatment time.6,7
In a non growing patient orthodontic camouflage or surgical correction can be considered.
The Forsus FRD is one of the newest fixed functional appliances introduced. It offers the advantages of giving predictable results, can be used in non-compliant or handicapped patients, is easy to install, robust in clinical usage, less prone to breakages, shortens the duration of treatment and can make use of residual growth even beyond the pubertal growth spurt8. From the patient’s viewpoint, it allows freedom of jaw movements and no tissue impingement.8
To exemplify the efficacy of Forsus-FRD in class II correction two distinct cases are presented.
APPLIANCE DESIGN 9 (Fig. 1:- Appliance design (Courtsey : 3M Unitek – Forsus™ Fatigue Resistant Device – Installation Guide) 9)
Forsus FRD is a synthesis of many of its predecessors, incorporating elements of Herbst, Jasper Jumper and Bite Fixer design10. It consists of 3 part telescopic assembly with a compression coil spring in its exterior which is highly resistant to breakage11.
4 different lengths of the push rods are available: 25mm, 29mm, 32mm and 35mm with right and left fittings. A calibrated measuring device aids in deciding the adequate size to be used for the patient12. Attachment to maxillary arch is through the headgear tube. For the mandibular arch it can be attached directly onto the arch wire or an attachment loop may be formed distal to lower canine bracket10.
There are three clinical specifications for its usage12:-
1. 0.017 × 0.025 inch or 0.019 × 0.025 inch stainless steel wire in 0.018 or 0.022 slot respectively.
2. All brackets can be ligated using steel ligature or modules but, lower canine bracket must be ligated with steel ligature only to prevent canine rotation.
3. Lower arch wire must be securely cinched distal to molars to control anchorage and prevent mesial flaring of lower incisors.
Springs can be re-activated during regular checkups until the desired result is achieved. Reactivation can be done by crimping a stop onto mesial end of the push rod. Each ‘split crimp’ gives an activation of 2mm. If more than 2mm activation is required, it is better to replace the push rod with a longer one.12
Criteria For Case Selection For Fixed Functional Appliance
The following criteria should be considered in selecting a patient for fixed functional therapy13:-
1. Growth pattern – Horizontal
2. Residual growth – they are capable of utilizing any amount of residual growth potential remaining. So, can be considered even for young adult patients.
3. Functional Retrusion – most effective means of unlocking a functionally retruded mandible.
4. Convex profile
5. VTO – should be positive to consider functional advancement.
6. Decreased anterior facial height.
7. IMPA – fixed functional appliances tend to flare the lower anteriors. Therefore, relatively upright or even mildly retroclined incisors would be a positive factor.
8. Non compliant patients – they do not require any patient compliance.
Appraisal of functional status of patient is very essential before initiating any form of functional treatment, which includes the following13:-
1. Determination of postural rest position of mandible and freeway space.
2. Path of mandibular closure.
3. Examination of TMJ function and condylar movements.
4. Assessment of lips, cheeks, tongue and their associated functions such as mastication, deglutition, respiration and speech.
History and Examination
12 year old male patient (Fig. 2A-C) presented with the chief complaint of irregular arrangement of upper front teeth (Fig. 3A-C). There was no significant medical or dental history. On clinical examination it was found that dentally he had a full cusp class II molar relationship with retroclined maxillary central incisors, class II canine relationship, no overjet and 100% deep bite (Fig. 3A-C). His mandible was locked in a functionally retruded position on account of the retroclined incisors. Extraoral examination revealed a decreased lower anterior facial height, convex profile with obtuse naso-labial angle, deep mentolabial angle, and deficient chin (Fig. 2A-C).
Fig. 2A-C:- Pre-treatment extraoral photographs of 12 yr old male patient.
Fig. 3A-C:- Pre-treatment intraoral photographs.
Cephalometric evaluation (Fig 4, Table I) showed Class II skeletal base with an ANB of 5°, due to a small and mildly retro-positioned mandible and a normal maxilla. The growth pattern was average with an FMA of 26°. Maxillary dentoalveolar segment was severely retroclined and retruded whereas the mandibular dentoalveolar segment was mildly retroclined.
Fig. 4:- Pre-treatment Lateral Cephalogram.
Table I :- Cephalometric appraisal of skeletal and dental measurements pre and post-treatment.
|SNA||820 ± 20||78||79|
|SNB||800 ± 20||73||75|
|Cant of OP||9.30 (1.5-14)||18.5||14|
|Saddle angle||123 ± 50||130||128|
|Articulare angle||143 ± 60||133.5||138|
|Gonial angle||128 ± 70||122.5||121|
|Anterior Facial height||53 – 61 mm||66||69|
|Interincisal angle||1300 - 1350||152||135|
|U1 – NA||220 , 4mm||70 , 2.5mm||150 , 3.5|
|U1 – Apog||4 mm||4.5||5|
|L1 – NB||250 , 4mm||160 , 3mm||240 , 4.5|
|L1 – Apog||4 mm||-1.5 mm||1mm|
|U6 – Ptm (crown)||14.0 mm||12.5 mm|
|U 6 – Ptmm (root)||20 mm||19 mm|
|E line – U lip||-1.5 mm||-3 mm|
|E line – L lip||-3 mm||-3mm|
The patient was diagnosed as a skeletal class II with normal maxilla and retrognathic mandible, dental class II div 2 with an average growth pattern.
Following alternative treatment could have been considered for the above patient. However, the reason for each of them being ruled out is mentioned alongside:-
a. Twin Block/Removable Functional appliance –they are large in size, have unstable fixation, cause discomfort, exert pressure on mucosa (encourage gingivitis), pose difficulty in deglutition and speech. All these factors contribute towards their cumbersome adaptation and poor patient acceptance3.
b. Fixed Twin Block – adaptation and intraoral adjustment better than removable functional appliances. But, the appliance design and bulk make it difficult to maintain oral hygiene; jaw movements are restricted and cause great patient discomfort4.
c. Class II Elastics – they rely heavily on patient compliance, achieve only 10% skeletal improvement compared to 66% with fixed functional14.
d. Other Fixed Functional Appliances – cumbersome to install, prone to breakage, cause a lot of tissue impingement4.
On account of these reasons, the Forsus FRD was the best option for the given patient, considering age, patient comfort, ease of installation, predictable results and patient compliance.
1. To relieve crowding in upper anteriors.
2. To correct deep bite.
3. To correct the mandibular functional retrusion.
4. To achieve a stable class I molar and canine relationship.
5. To establish a canine guided occlusion.
6. To establish an adequate overjet and overbite.
It was planned to start fixed mechanotherapy using MBT .018 slot preadjusted appliance to level and align both arches. After correcting the inclination of maxillary anteriors and establishing proper overjet, mandible would be advanced using a fixed functional appliance. The appliance selected was Forsus FRD with direct push rod method.
Class II div 2 had lead to the mandible being locked in a functionally retruded position. This if left untreated, would lead to a skeletal Class II.
Treatment was started using 0.014 Niti in upper arch initially. After 3 months, as the alignment of upper arch progressed and some overjet was established, the lower arch was bonded. This was followed by 0.016 Niti, 0.016 × 0.022 Niti, 0.016 × 0.022 stainless steel and finally 0.017 × 0.025 inch stainless steel. Leveling and alignment was completed in 8 months. At the end of stage I, overjet was 7mm and overbite was 5.5mm. This was followed by mandibular advancement using a Forsus FRD from class II to a class I relationship (Fig. 5A-C).
Fig. 5A-B:- Intraoral photographs with Forsus FRD appliance.
Length of push rod chosen for the patient was 29mm. After 4 months of appliance wear, it was activated by crimping stops onto the push rod. The appliance was deactivated after 6 months, by loosening the pin in the region of upper molars. It was worn for a total of 8 months. After appliance removal, light class II elastics were given for 2 months to retain the skeletal correction (Fig 6A-B). Finally a 4 month phase of detailing and finishing followed. The elastics were gradually waned off. The case was debonded after 22 months of active treatment
Fig. 6A-B:- Class II elastics to retain molars in Class I relationship after correction with Forsus FRD.
22 months of active treatment produced excellent correction of skeletal and dental relationships (Fig. 7). Comparison of pre and post treatment lateral cephalograms (Table I) showed an increase in SNA from 780 to 790 indicating that the appliance did not limit the growth of maxilla. SNB increased from 730 to 750 indicating an increased forward growth of mandible. ANB decreased from 5° to 4°.
Fig. 7:- Post-treatment Lateral Cephalogram.
There was a mild decrease in Saddle angle and Gonial angle and an increase in Articulare angle indicating a favorable forward growth of mandible. Anterior facial height was increased from 66 to 69mm. Upper incisor inclination and linear measurement (U1 – NA) changed from 7°, 2.5mm to 16°, 3.5mm. Lower incisor inclination and linear measurement (L1-NB) improved from 160, 3mm to 240, 4.5mm. The IMPA showed a mild increase from 910 to 1000, which is well within the stable range for a horizontal grower15. Normal inter-incisal angle was established. Upper molar to Ptm measurement showed an overall mild distal movement, with very slight tipping (crown moved distally by 1.5mm and root by 1mm). All results were confirmed by superimposition of pre-treatment and post-treatment cephalogram tracings (Fig 8 A-E).
Fig. 8A-E:- Super-imposition of pre-treatment (black) and post-treatment (red) lateral cephalogram tracings.
Dentally there was a full cusp correction of molar relationship from class II to class I. At the end of treatment, 2 mm overjet and 2.5 mm overbite, Class I canine relation and proper canine guidance were established (Fig. 9A-C), which was maintained one year post retention.
Fig. 9A-C:- Post-treatment intraoral photographs.
There was a remarkable improvement in the soft tissue profile of the patient in relation to E line and a pleasing smile was achieved (Fig. 10A-C)
Fig. 10A-B:- Post-treatment extraoral photographs.
A maxillary removable hawley’s appliance with anterior inclined plane to hold the corrected jaw relation was used for 6 months (Fig. 11A-B). This was followed by permanent bonded lingual retainers.
Fig. 11A-B:- Hawley’s appliance with anterior inclined plane for retention.
History and Examination
12 year old female patient (Fig. 12A-C) presented with the chief complaint of forwardly placed upper front teeth. There was no significant medical or dental history. On clinical examination, she revealed a convex profile with deficient chin, incompetent lips (Fig. 12A-C) and a positive VTO.
Fig. 12A-C:- Pre-treatment extraoral photographs of 12 yr old female patient.
Dentally she had a class II molar relationship, proclined upper anteriors, 9 mm overjet, 8mm overbite (more than 100% deep bite) and deep curve of spee (Fig. 13A-C).
Fig. 13A-C:- Pre-treatment intraoral photographs.
The lower jaw was functionally retruded into a class II position. Cephalometric evaluation (Fig. 14, Table II) showed a class II skeletal base with an ANB of 7°, on account of a small mandible and normal maxilla. The growth pattern was average with 24.5° FMA. Dentoalveolar readings suggest a normal maxillary anterior segment with mildly retroclined and retruded mandibular anteriors.
Fig. 14:- Pre-treatment Lateral Cephalogram.
Table II :- Cephalometric appraisal of skeletal and dental measurements pre and post-treatment.
|SNA||820 ± 20||80||80.5|
|SNB||800 ± 20||73||75|
|Cant of OP||9.30 (1.5-14)||11.5|
|Saddle angle||123 ± 50||124.5||119|
|Articulare angle||143 ± 60||141||131|
|Gonial angle||128 ± 70||125||121.5|
|Anterior Facial height||53 – 61 mm||61||66|
|Interincisal angle||1300 - 1350||131||133|
|U1 – NA||220 , 4mm||24.50 , 5mm||180 , 3.5mm|
|U1 – Apog||4 mm||8.5||7|
|L1 – NB||250 , 4mm||18.50 , 3mm||24.50 , 5.5mm|
|L1 – Apog||4 mm||-2mm||+1.5mm|
|U6 – Ptm (crown)||12mm||12mm|
|U6 – Ptm(root)||19mm||19mm|
|E line – U lip||-2.5mm||-2.5mm|
|E line – L lip||-3.5mm||-2mm|
Etiology and Diagnosis
Patient was diagnosed as a skeletal class II due to a retrognathic mandible and a normal maxilla, dental class II div 1 with an average growth pattern.
1. To correct the upper anterior proclination.
2. To correct deep bite.
3. To correct the mandibular functional retrusion.
4. To improve profile of the patient
5. To achieve a stable class I molar and canine relationship
6. To establish a canine guided occlusion
7. To establish an adequate overjet and overbite
Following alternative treatment could have been considered for the above patient.
a. Twin Block/Removable Functional appliance
b. Fixed Twin Block
c. Class II Elastics
d. Other Fixed Functional Appliances
However, Forsus FRD was the best option, considering age, patient comfort, ease of installation, lack of breakages in clinical use, predictable results and no need for patient compliance8.
It was planned that fixed mechanotherapy would be started using MBT 0.018 slot pre-adjusted appliance to level and align both arches. After leveling and alignment, a fixed functional appliance would be given to advance the mandible into a class I relationship. Forsus FRD with direct push rod method was the appliance selected.
Treatment was started using 0.014 NiTi in both arches. This was followed by 0.016 × 0.022 NiTi, 0.016 × 0.022 stainless steel and finally a 0.017 × 0.025 stainless steel wire. Leveling and alignment was completed in 8 months. At the end of stage I, there was an 8mm overjet and 6mm overbite. This was followed by mandibular advancement using Forsus FRD (Fig. 15A-B). 29mm length of push rod was selected. Molar correction was achieved after 6-7 months of wearing the appliance. This was followed by 3 months of detailing and finishing of occlusion combined with light class II elastics which were gradually tapered off. The patient was observed for 2-3 months with the appliance in place, without any active forces to check the stability of correction and any occurrence of dual bite. Appliance was removed after 21 months of treatment.
Fig. 15A-B:- Intraoral photographs with Forsus at rest and during jaw movement.
Active treatment produced excellent correction of skeletal and dental relationships (Fig. 16).
Fig. 16:- Post-treatment Lateral Cephalogram.
Comparison of pre and post treatment lateral cephalograms (Table II) showed an increase in SNA from 800 to 80.50, while the SNB increased from 730 to 750 indicating an increased mandibular growth compared to maxilla. ANB thus decreased from 70 to 5.50. There was a decrease in saddle angle from 124.50 to 1190 indicating a forward growth of mandible. Upper incisor position (U1 – NA) improved from 24.50, 5mm to 180, 3.5mm. Lower incisor position (L1 – NB) changed from 18.50, 3mm to 24.50, 5.5mm. Mild increase in IMPA from 94.50 to 98.50 was seen. No tipping of the maxillary first molar was observed. Results were confirmed by superimposition of pre-treatment and post-treatment lateral cephalogram tracings (Fig 17 A-E).
Fig. 17A-E:- Super-imposition of pre-treatment (black) and post-treatment (red) lateral cephalogram tracings.
Dentally the molar relationship was corrected from class II to class I (Fig. 18A-C).
Fig. 18A-C:- Post-treatment intraoral photographs.
At the end of treatment, 2 mm overjet and 3 mm overbite, Class I canine relation and proper canine guidance were established. There was tremendous improvement in the soft tissue profile of the patient. Lip competence and a pleasing smile were achieved (Fig. 19A-C).
Fig. 19A-C:- Post-treatment extraoral photographs.
A maxillary removable Hawley’s appliance with anterior inclined plane to hold the corrected jaw relation was used for 6 months. This was followed by permanent bonded lingual retainers in both the arches.
Class II malocclusions resulting from mandibular retrusion are generally treated with functional orthodontic appliances that create orthopedic forces directed at the mandibular structures. These appliances influence the jaws via the following mechanisms: remodeling of the mandibular condyle, remodeling of the glenoid fossa, repositioning the mandibular condyle in the glenoid fossa, and autorotation of the mandibular bone16.
Amongst the fixed functional appliances available, Forsus-FRD has long been proved to be one of the best treatment modality for mild to moderate class II malocclusion. It is capable of achieving class II correction in 3 to 6 months depending upon the baseline situation and the biological response17. The correction achieved is by a combination of skeletal and dental effects, 66% being dental and remaining 34% skeletal8,18.
The two case reports illustrated above display the diversity of successful treatment attainable with the use of Forsus. Case 1 has a class II div 2 malocclusion while Case 2 is class II div 1, both with a retrusive lower jaw and normal maxilla. Excellent correction of skeletal and dental problems was observed, following treatment with Forsus FRD. The mandible experienced a shift anteriorly as the most significant effect of the Forsus appliance8,18 (Fig. 8A, Fig 17A). Both the cases showed a good change in SNB (20 increase for each case) and saddle angle (5.50 and 3.50 decrease for case1 and case2 respectively). This clearly indicated an increased growth and improved forward mandibular position. SNA also showed a mild increase (10 increase for case 1 and 0.50 for case 2) indicating that the maxillary growth was restrained but not completely hampered by the appliance8. Thus, the class II jaw relationship was improved more due to forward growth of the mandible than the maxilla.
One undesirable effect with all fixed functional appliances is protrusion of the lower anteriors as the force is concentrated on the lower, anterior segment. This can however be prevented with the use of Forsus FRD by use of sectional arch, using a pretorqued wire prior to insertion of the forsus or using brackets with built in labial root torque8. MBT appliance was used for both patients, with -60 torque in the lower incisor brackets. The lower arch wire was securely cinched distal to lower first molars. This helped to counteract the protrusive effect of Forsus on mandibular incisors. IMPA of case 1 showed a mild increase from 910 to 1000 and case 2 increased from 940 to 98.50. Since both the patients had an average growth pattern, IMPA up to 1050 is acceptable and stable15. The lower incisor position in relation to NB line also showed improvement from 160, 3mm to 240, 4.5mm for case 1 and from 18.50, 3mm to 24.50, 5.5mm for case 2.
Another significant effect of Forsus is the distal tipping effect on the maxillary incisors and molars. Even though the attachment to maxilla is at the molar tubes, the effect is seen on the incisors as well, since the entire maxillary arch is consolidated with a multibracket appliance8,19. The position of retroclined incisors (U1 – SN) of case 1 was improved from 70, 2.5mm to 150, 3.5mm and for case 2 from 24.50, 5mm to 180, 3.5mm. Normal Interincisal angle was established for both cases. The maxillary first molars of case 1 showed a mild distal tipping as confirmed by superimposition of the cephalograms (Fig. 8D). In relation to the Ptm perpendicular, the crown moved distally by 2.5mm whereas the root moved by 1mm indicating a net distal tipping of the crown. No molar tipping was observed for case 2 (Fig. 17D).
Significant improvement was noted in the soft tissue profile and pleasant smile was achieved for both the patients (Fig. 10, Fig. 19). An improvement of facial convexity and increase of anterior facial height was seen. The position of lower lip in relation to E line showed improvement for case 2, from -3.5mm to -2mm (Fig. 17E). The results achieved were stable and highly satisfying for both the clinician as well as the patients.
Thus, it can be summarized that Forsus FRD offers the following advantages to the clinician:-
1. Predictable results8.
2. Long term reliability10.
3. Can be used in non-compliant or handicapped patients4.
4. Ease of installation (can be installed and removed in 5 minutes, and is activated in 30 seconds) 20.
5. Less breakages and robust in clinical usage11.
6. Shortens the duration of treatment10.
7. Can make use of residual growth even beyond the pubertal growth spurt11.
8. Susceptibility to mechanical fatigue is negligible due to the spring design (the maximum force delivered is in the order of 2000N with the mouth closed and this decreases very little over time) 21.
9. Force applied on the arches is proportional and progressive as the mouth closes21.
From the patient’s viewpoint,
1. It allows freedom of jaw movements8.
2. No tissue impingement8.
We conclude that most class II situations are on account of a functional retrusion of the mandible. It would be very unwise to consider extractions in such situations. They are best managed by a non-extraction approach of mandibular advancement wherein Forsus FRD is the treatment of choice, especially for non-compliant patients. Although they can serve as last-resort appliances in cases of non-compliance, it is preferable to incorporate them into the treatment plan from the beginning21. Advance planning also makes treatment time estimates much more accurate, because the factor of patient cooperation has been largely eliminated21.
Thus, Forsus FRD is one of the best treatment options for class II correction, with stable long term results achieved by saggital forward displacement of mandible and remodeling at glenoid fossa. The various options of push rod lengths and their combination with activation stops, allows the orthodontist an individualized treatment plan for each case.
It is superior to all other modes of class II management in terms of the amount of dental vs skeletal effects8, better and more effective appliance design, ease of installation, superior clinical performance and less breakages10, no need for patient compliance and improved patient comfort3,10.
The Author would sincerely like to thank Dr. Priyanka Sethi Kumar for her invaluable inputs in the compilation of this article.
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