August, 2010

An Excerpt from Dr. Raphael L. Greenfield’s new Textbook; “98.5% Nonextraction Treatment using Coordinated Arch Development.”

Coordinated Arch Development Vs. Expansion –

What are the Differences?

Order this Textbook

For more than a century, the controversy of treating tooth size/arch length discrepancies, with or without extraction of permanent teeth, has been at the forefront of diagnosis and treatment planning.^1-6 Hunter’s⁷ proposal 200 years ago to extract maxillary first bicuspids to reduce maxillary procumbencies, led to capricious extraction of teeth to resolve crowding and procumbencies for the next one hundred years.  Disregard of the functional and esthetic consequences of extraction treatment encouraged the Angle school to take the opposite position at the turn of the century.¹

Angle’s strong personality and unrelenting nonextraction stance overcame Case’s camp advocating maxillary first premolar extraction philosophy for the treatment of most malocclusions, (actually only 4% of cases). For the next 25 years, treatment was heavily weighted towards the nonextraction approach with indiscriminate expansion of the arches.  Intercanine and intermolar widths were increased well beyond the “neutral zone”, and the mandibular incisors were flared labially to resolve crowding. ^8,9 Basal bone discrepancies were corrected primarily by mandibular dental advancement and/or repositioning of the post pubertal mandible into an unstable anterior posture.  Angle also chose a heavy intra oral force (Class II elastics) as the only relevant mechanotherapy to influence favorable growth, while denying the efficacy of extra oral force.  Treatment was initiated after the eruption of second molars, which usually negated the period of significant craniofacial growth that would have reduced the complexity of the discrepancy.  The flaring of the anterior teeth to camouflage skeletal discrepancies resulted in many bimaxillary protrusions.  This compromise of facial esthetics did not sit well with many in the orthodontic community.

Over time, Case’s position would be justified as expanded arches relapsed in great frequency, resulting in disaffection with nonextraction treatment.  The pendulum then swung towards extraction treatment for the next thirty years as a routine approach to orthodontic care, (80% of cases).  The orthodontic community led by Tweed, used cephalometrics to support their position.^9,10-12 The teeth most frequently selected for extraction were the mandibular and maxillary first premolars.

Tweed’s strong and forceful personality allowed him, with minimal resistance, to establish “normal” cephalometric values for an ideal occlusion.¹² He illustrated facial types that contained these values which he considered to be esthetic to support his position.  The mandibular incisor position was the cornerstone of his analysis, and was used effectively to discredit the nonextraction approach.  He advocated “uprighting” the lower incisors to enhance stability and esthetics, and thus succeed where expansionists failed.^12,13 Tweed’s approach strongly influenced orthodontic treatment decisions well into the late 1960’s and early 1970’s – and to a lesser degree still influences our profession today. Even with Tweed’s approach, that included uprighting lower incisors over basal bone, maintaining the original transverse dimension, and  archform, root parallelism, and a relatively flat profile, the lower anterior crowding relapsed, deep bites recurred and the denture retruded relative to the facial skeleton.  Recent long term post retention studies have confirmed some of these earlier observations.^14-16 As a result of these studies, a lengthier treatment protocol was advocated – at least until the eruption of third molars.  However, several studies have indicated that the length of retention may not be a factor in long-term stability for any approach.^14,15,17,18 In fact, many studies blamed the third molars for the instability of the mandibular incisor position.^19-23 Recent studies have implied that anterior crowding is more of a normal occurrence associated with the ageing of the face.^18,24,25 It can now be suggested that retraction of the lower incisors is not necessarily more stable than reasonable proclination.  Many orthodontists attempted to legitimatize the compromised facial esthetics of extraction through various facial analyses.^8-12 While attempting to find a range of normal values, esthetics was biased by the analysts concept of esthetics.  The samples used to create these analyses were not randomly selected from a cross section of different racial and ethnic groups. ^26-29 The general public and the dental community disagreed with the almost empirical approach of extractionists and the pendulum began to swing back towards the nonextraction approach.  Initially, there was a small group that advocated second molar extraction as the new panacea.^30,31,32 However, many third molars erupted with a poor angulation and thus had to be retreated postorthodontically.^33,34 Consequently, this philosophy has seen minimal support by the orthodontic profession.

So here we are at the beginning of the 21^st century, back to a predominantly nonextraction approach – an approach that was discarded 70 years ago.  What changes have taken place to influence our profession to such a degree?  Certainly, our philosophy of treatment timing has changed radically.  Instead of waiting for the completion of second molar eruption and missing the pubertal growth spurt, we generally believe that basal discrepancies are positively impacted when we use the greatest growth increments to our advantage.  Beginning in the 60’s, and after encountering significant resistance for almost 15 years, extra oral appliances such as headgears and functional appliances to temporarily redirect growth, gained widespread popularity and considerable support in the literature.^35-44

As a consequence, modern orthodontics has seen the emergence of a new controversy – is our concept of earlier intervention too early!^45-53 The so called “2 phase treatment”, with the first phase being the early resolution of basal discrepancies, and the second phase correcting the malocclusion’s dental discrepancies.  The concept is offered as an approach to create a more stable maxillo-mandibular relationship long term, and control of the leeway space during the transition of the mixed to the permanent dentition.  While a better long-term skeletal relationship and the correction of developmental crossbites and functional shifts may be true, the literature to date does not support different dentoalveolar results between a 2 phase or single phase treatment approach.  It appears that early intervention is patient specific and should not be thought of as the most productive way to treat the majority of Class II and III cases.  It is justified only if it provides “additional” benefits such as preventing tooth injury, psychosocial advantages, shorter treatment times, and enhanced function, etc.  Recent studies actually have described prolonged treatment times, resulting in premature termination of treatment in 2 phase treatment cases with compliance issues in phase 2.  Thus the most severe cases may benefit the most.  That said, it is generally agreed within the orthodontic community that the most opportune time to initiate orthodontic therapy is the late mixed dentition.^54,55 Leeway space can thus be utilized for tooth-size/arch-size discrepancy problems in addition to early resolution of basal discrepancies.

Discussion:

From the above historical perspective (review), it appears there are four distinct controversial and interrelated areas of orthodontics; extraction vs. nonextraction, lower incisor crowding, facial esthetics, and timing of treatment.

At the moment, the pendulum has clearly swung in favor of a nonextraction approach due to the following reasons;  First, lower incisor crowding appears to be a normal phenomenon and cannot be used as the deciding factor upon which to base a treatment decision.  Also, third molars generally cannot be implicated as a causative factor.⁵⁶ Second, and maybe more importantly, our management of nonextraction cases has improved.  Our knowledge of orthopedics and the positive effects it has on basal discrepancies has greatly reduced the number of extraction cases.  Non compliant appliances and space age metallurgy has clearly facilitated the attainment of nonextraction treatment goals.

That said, the management of nonextraction cases has seen the introduction of a plethora of appliances for both maxillary and mandibular (basal) discrepancies.  When treating a Class II skeletal discrepancy in a growing patient, the clinician may have to rely on cephalometrics and facial analyses to discern whether a protruded maxilla or retruded mandible is the primary cause.  Most cases do not present a clear picture as to which one is the primary cause – especially in a growing patient.  Thus one camp of orthodontists subscribe to utilizing mostly mandibular propulsive appliances to reposture the mandible forward and simultaneously redirect maxillary growth.^57-62 This philosophy is somewhat similar to Angle’s philosophy over 100 years ago, when in denying the effectiveness of extra oral force, he relied on heavy Class II elastics to favorably influence growth.¹ While providing positive orthopedic effects, side effects include a displacement of the anterior teeth labially, which is true with any Class II system.  If lower anterior teeth are upright, crowded, or procumbent to begin with, this appliance will further displace these teeth beyond the “neutral zone”, resulting in a significant relapse long term.  If lower incisors are initially recumbent, these appliances can certainly produce a positive result.  Therefore, proper case selection is imperative.  The other camp subscribes to utilizing extra oral forces such as headgears, to redirect maxillary growth and allow mandibular growth to “catch up”.^35,36,63 This method, while very effective, relies on patient compliance and therefore the results will vary.  Since the headgear is a maxillary arch appliance, the mandibular incisor position is essentially unaffected.  Thus one could argue that isolating the mandibular arch during Class II skeletal correction may have a positive effect on the long term stability of mandibular incisor position.

Regarding facial esthetics, there does not appear to be significant differences between either approach since retaining a full complement of teeth (i.e., second molar to second molar) is a common treatment goal.

Functionally, if the procumbency of the mandibular incisors is exaggerated, prematurities may develop anteriorly.  This could affect the coordination of posterior guidance with anterior guidance and also disturb condylar position.  Placing a fixed cuspid to cuspid lingual retainer to prevent incisor relapse in effect exacerbates the condition by preventing the lower incisors to return to their true position for functional equilibrium.  Thus fixed lingual retention should be relegated to the incisors in most cases.

This brings up the issue of retention following orthodontic treatment.  Most orthodontists argue that to prevent significant relapse, retainers must be a lifetime commitment by the patient.  This may have merit theoretically, but is essentially unrealistic.  That said, would it not behoove the orthodontist to allow the teeth to freely seek their position within the first six months after debanding by inserting removable retainers worn only in the evening?  If the retainers become tighter, it would indicate a “settling” of the occlusion (barring any noxious habits).  The acrylic would then be relieved until the retainers are easily inserted and removed.  If incisor crowding does reoccur due to tooth-size/arch-size discrepancies, strategies such as interproximal reduction^64,65 and/or circumferential supracrestal fiberotomies (CSF)^66-68 could be applied, and an anterior removable spring aligner inserted.  Once alignment is reestablished, a fixed lingual retainer could then be bonded to the anterior teeth excluding the cuspids.  Not incorporating the cuspids allows them to perform their important role in occlusion relatively undisturbed – thus enhancing long-term stability.

This leads us to the treatment of tooth-size/arch-size discrepancies in the nonextraction case.  In extraction treatment, significant crowding is corrected with the removal of permanent dental units – usually bicuspids.  However, in the nonextraction case, the deficiency in arch length or arch perimeter is treated with either expansion of the arch and/or interproximal reduction.  Interproximal reduction is usually relegated to moderate discrepancies (e.g., 2-4mm.), while greater discrepancies are treated with expansion.

Expansion, according to McNamara⁶⁹, can be subdivided into arbitrary categories such as orthodontic, passive, and orthopedic.

“Orthodontic” expansion could also be described as any “mechanical” expansion that employs brackets and archwires, finger springs, removable expansion plates or quad helix type appliances.  Generally, these devices tip the crowns labially and the roots lingually.  If these movements violate the “neutral zone,” the surrounding musculature may provide an opposing force leading to long-term relapse.^9,70 Also, to retain the position of the crowns, the roots must be torqued underneath the crowns to establish the forces of occlusion through the long axes of the teeth.  Failure to do so may introduce undesirable horizontal forces.

“Passive” expansion refers to the blocking of the labial and buccal musculature from the arches.  By temporarily removing their influence on the teeth, a widening of the dental arches will frequently occur.  This expansion is not produced via biomechanical forces, but rather intrinsic forces such as the tongue. Exampls include the lip bumper ^{71, 72} and the Fränkel appliance.⁷³

“Orthopedic” expansion refers to changes that primarily occur in the underlying skeletal structures rather than the movements of teeth within the alveolus.^74-79 Orthopedic expansion not only separates the midpalatal suture, but it also affects the circumzygomatic and circummaxillary sutural systems.⁸⁰ New bone is deposited at the expansion site within 3-6 months to reestablish the integrity of the suture.⁷⁵

Orthopedic expansion, similar to orthodontic expansion, does not directly influence the opposing forces of the surrounding soft tissue envelope.  Thus the general consensus of the orthodontic community, realizing the possibility of significant relapse, is to “over-expand” the maxilla to almost a complete buccal crossbite.  Although limited orthodontic and passive expansion is possible at any age, its efficacy decreases with the age of the patient.^81,82 The greatest efficacy of maxillary expansion, at both the skeletal and alveolar levels, is usually during the mixed and adolescent dentitions – prior to the pubertal peak of growth and development.  Maxillary adaptations to expansion in patients treated after the pubertal growth peak, exhibited a shift from the skeletal level to the alveolar level.⁸³ Patients treated with rapid maxillary expansion, using a Haas type fixed expander turned ¼ turn per day, followed by fixed appliance therapy, achieved a high degree of stability eight years following the completion of expansion.⁸⁴ Rapid maxillary expansion appeared to resolve transverse deficiencies and normalize the dental and skeletal components of the craniofacial complex.⁸⁵ Also, rapid maxillary expansion does not appear to be contraindicated in patients with predominantly vertical growth patterns and/or convex facial profiles.  Any exacerbation of these discrepancies at the conclusion of RME appears to be temporary in nature, since long-term data does not support significant undesirable changes.⁸⁶

In skeletally mature patients, the possibility of successful rapid maxillary expansion progressively decreases as sutures close and the resistance to mechanical forces increases.  Transverse maxillary growth significantly  slows and the maxillary sutures close about 14 to 15 years of age in females, and 15 to 16 years for males.⁸⁷ Since the transverse dimension is the first dimension to mature, its treatment should be addressed sooner than later.  After the completion of transverse growth, orthopedic expansion is essentially composed of alveolar remodeling or dental tipping with little or no basal skeletal movement.⁸⁸ Also, RME may cause severe pain, and/or a compromised periodontium of the maxillary posterior teeth.⁸⁹

Surgically assisted RME has been suggested to produce better treatment results in adults by preventing complications due to its release of sutural resistance to expansion forces.⁸⁸ From the most recent studies, surgically assisted rapid maxillary expansion does appear to be a simpler and more effective approach for the resolution of transverse maxillary discrepancies in the mature maxilla.^88,90-92 However, when comparing the clinical results of orthopedic maxillary expansion to surgically assisted maxillary expansion, there appeared to be no significant difference.⁹³

When comparing rapid maxillary expansion to “slow” maxillary expansion long-term, there were no clinically significant differences in anteroposterior and vertical maxillary changes,⁹⁴ or mandibular behavior.⁹⁵ One adolescent dentition study initially used RME (1/4 turn twice a day), until the suture was determined to be opened from occlusal films (5-7 days).  The screw was then turned 3 times a week until a 2mm. overexpansion was achieved (about 4 months).  After evaluating the patient sample about 2 ½ years after retention, the dental and skeletal changes in the transverse dimension exhibited a high degree of stability.⁹⁶ Their hypotheses was that slower expansion produced less tissue resistance and stimulated the adaptation process in the circummaxillary structures.  These events would minimize any relapse tendency long-term.

Maxillary expansive forces appear not to be restricted to intermaxillary sutures, but are also distributed to the sphenoid and zygomatic bones and other related structures in the craniofacial complex.⁹⁷ Histologic studies on animals have also demonstrated signs of increased cellular activity at various cranial sutures.^98-102 The available data on suture mechanics appears to have a common theme that mechanical forces regulate sutural growth by inducing sutural mechanical strain.  Various orthopedic devices, including but not limited to headgear, facemask, and functional appliances may induce sutural strain, resulting in a modification of natural sutural growth.^103,104

Utilizing the effects of expansion on modifying natural, sutural growth, several investigators have applied various headgears for the treatment of skeletal Class II  and Class III malocclusions.^105-112 Although studies have emphasized the importance of starting earlier in the growth cycle to gain a maximum effect,^113-116 there does not appear to be any statistically significant differences between specific entry points in the growth cycle.¹⁰⁷ With the exception of one investigation,¹⁰⁷ most studies applied the headgears after the rapid maxillary expansion (2 quarter turns per day) was completed.^105,108-110 This approach may have positive implications in treating Class III malocclusions.  Since the maxilla tends to move downward and forward and the mandible backward and downward during rapid maxillary expansion.¹⁰⁷ However, this may tend to exacerbate a Class II malocclusion and significantly  lengthen treatment time.¹⁰⁹

Therefore, one could surmise from the above studies the following conclusions;

1. Orthodontic expansion is relegated to expanding the dentoalveolar complex.  The surrounding resistance of the soft tissue envelope may lead to long-term relapse if the neutral zone has been violated.
2. Orthopedic expansion (rapid maxillary expansion or RME) produces changes primarily in the underlying skeletal structures rather than dentoalveolar movements.  Not only does the midpalatal suture separate, but rapid expansion also positively affects the circummaxillary and circumzygomatic sutural systems as well.  The sutural strain resulting from RME appears to induce a modification of sutural growth.  While skeletal tissues offer immediate resistance to expansion force, the surrounding soft tissue complex (i.e., muscles of mastication, facial muscles, fascia, etc.,) are essentially elastic and stretch during the expansion. More research is still needed to qualify and quantify the adaptive capacity of these soft tissues to RME.                                            There appears to be greater positive changes when using headgears during expansion than when using headgears after expansion.                                                             Clinically and statistically, there is no distinguishable difference in treatment outcomes between slow expansion, (< ¼ turn per day) and rapid maxillary expansion, (> two ¼ turns/day).                                                                  Although there are no ideal entry points, orthopedic expansion should be initiated during periods of optimal growth, as the effects of RME dissipate with age.
3. Passive expansion produces a widening of the arches by shielding the buccal musculature and allowing the intrinsic forces of the tongue to expand the dentoalveolar complex.   Interestingly, the labial musculature generates a distal force to the labial shield during expansion – which tends to elicit a greater response as noted above.  From recent studies, passive expansion utilizing lip bumpers may also produce skeletal as well as dentoalveolar transverse changes.

Coordinated Arch Development^® vs. Expansion

Coordinated Arch Development^® (CAD), is a term I introduced at the 1996 American Association of Orthodontists’ scientific session, together with my partner of 30 years, Dr. Jerry Klein.  It is a combined orthopedic/orthodontic approach to long-term stability, applied during periods of optimum growth and development.  The criteria is based on the following;

1. Early treatment of maxillo-mandibular skeletal discrepancies, preferably the late mixed dentition.  The roots of the “CAD” philosophy are credited to my dear friend and mentor Dr. Norman Cetlin of Boston, Massachusetts.  He emphasized the importance of first molar position over incisor position (Tweed) as the cornerstone of long-term stability.  He also preferred the late mixed dentition as the entry point of treatment to utilize “E” space for tooth size/arch size discrepancies, and distal movement of first molars was enhanced by the absence of the unerupted second molars.
2. Uprighting upper and lower posterior segments sagittaly and transversely, slowly (i.e., slow expansion for a greater effect in the same time frame), and in equal increments, (to prevent the violation of the “neutral zone” during expansion), to their natural positions in the arch, (i.e., placing the teeth well within cancellous bone to allow the optimization of axial inclinations to accept and distribute the functional forces of occlusion through their long axes).
3. Controlling the functional occlusal plane by advocating intra-arch mechanics, (i.e., minimizing the side effects of mechanotherapy).
4. Reeducation of the intra oral musculature during dimensional changes to the arches by utilizing lip bumpers, inner bows of facebows, and myofunctional therapy when necessary.

CAD distinguishes itself from expansion by the following;

1. CAD addresses all three dimensions.  Expansion focuses on the transverse dimension.
2. CAD distalizes the arches during expansion into a wider dimension of the arch, thereby reducing the amount of necessary expansion.  Expansion solely relies on transverse changes.
3. CAD coordinates upper arch dimensional changes with lower arch dimensional changes to maximize intercuspation throughout treatment.  Maxillary expansion tends to overcorrect the maxillary arch with no corresponding changes in the lower arch.
4. CAD attempts to place and maintain the teeth in the “neutral zone” throughout treatment.  Rapid maxillary expansion (RME), or orthodontic expansion tends to violate the “neutral zone” by placing the teeth into the space of the surrounding musculature.  If the musculature cannot adapt to the new transverse dimension, relapse of the teeth towards the “neutral zone” may occur long-term.
5. CAD emphasizes the importance of placing the teeth well within cancellous bone during expansion by slowly and simultaneously expanding and distalizing in relatively equal increments.  This allows the integrity of the periodontium to be maintained.  In mesially displaced arches (eg., Class II), expanding the teeth that have already been placed in areas of narrower cancellous bone could certainly compromise the integrity of the periodontium.
6. CAD attempts to “reeducate” the surrounding musculature back to their original resting length by utilizing lip bumpers and the inner bows of facebows.  There is no attempt to reeducate the soft tissue envelope in pure expansion.                                                                           The illustrations that follow will further seek to clarify these differences, and also establish the ground rules for successfully developing the arches.

BIBLIOGRAPHY

1. Angle E:  Treatment of Malocclusion of the Teeth.  Ed 7. Philadelphia, SS White Dental Mfg Co, 1907
2. Case CS:  The question of extraction in orthodontia.  Am J Orthod 50:658, 1964
3. The Extraction Debate of 1911 by Case, Dewey, and Cryer.  Discussion of Case:  The question of extraction in orthodontia.  Am J Orthod 50:751, 1964
4. The Extraction Debate of 1911 by Case, Dewey, and Cryer.  Discussion of Case:  The question of extraction in orthodontia.  Am J Orthod 50:843, 1964
5. The Extraction Debate of 1911 by Case, Dewey, and Cryer.  Discussion of Case:  The question of extraction in orthodontia.  Am J Orthod 50:862, 1964
6. Dewey BF:  The Case-Dewey-Cryer extraction debate.  A Commentary.  Am J Orthod 50:862-865, 1964
7. Weinberger BW:  Orthodontics:  A Historical Review of its Origin and Evolution.  Vol I and II.  St. Louis, CV Mosby Co. 1926
8. Strang RWH:  Factors of influence in producing a stable result in treatment of malocclusion.  Am J Orthod 32:313, 1946
9. Strang RWH:  Fallacy of denture expansion as a treatment procedure.  Angle Orthod 19:12, 1949
10. Downs WB:  Role of cephalometrics in orthodontic case analysis and diagnosis.  Am J Orthod 38:162-182, 1952
11. Tulley WJ:  The role of extractions in orthodontic treatment.  Br Dent J 107:200-205, 1959
12. Tweed CH:  Frankfort-mandibular incisor angle (FMIA) in orthodontic treatment, planning and prognosis. Angle Orthod 24:121, 1954
13. Tweed CH:  Indications for the extraction of teeth in orthodontic procedure.  Am J Orthod 30:405-428, 1944
14. Little, RM, Riedel R, Artun J:  An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention.  Am J Orthod Dentofac Orthop 93:423-428, 1988
15. Little RM, Wallen T. Riedel R:  Stability and relapse of mandibular alignment:  First premolar extraction cases treated by traditional edgewise orthodontics.  Am J Orthod 80:349-365, 1981
16. Shields, T, Little R, Chapko M:  Stability and relapse of mandibular anterior alignment:  A cephalometric appraisal of first premolar extraction cases treated by traditional edgewise orthodontics.  Am J Orthod 87:27-38, 1985
17. Riedel R:  A review of the retention problem.  Angle Orthod 30:179, 1960
18. Sinclair P, Little R:  Maturation of untreated normal occlusions.  Am J Orthod 68:554-563, 1975
19. Keene HK:  Third molar agenesis spacing and crowding of teeth and tooth size in caries resistant naval recruits.  Am J Orthod 50:445, 1964
20. Laskin DM:  Evaluation of the third molar problem.  J Am Dent Assoc 82:824, 1971
21. Linqvist B, Thilanber B:  Extraction of third molars and cases of anticipated crowding of the lower jaw.  Am. J Orthod 81:130-139. 1982
22. Richardson, ME:  Late lower arch crowding>Facial growth or forward drift.  Eur J Orthod 1:219-225, 1979
23. Richardson, ME:  The role of the third molar in the cause of the late lower arch crowding:  A review. Am J Orthod Dentofac Orthop 95:79-83, 1989
24. Bishara S; Jakobbsen J, trader J, et al:  Changes in the maxillary and mandibular tooth size-arch length relationship from early adolescence to early adulthood.  A longitudinal study, Am J Orthod Dentofac Orthop 95:46-59, 1989
25. Moorrees CFA:  The dentition of the growing child.  Cambridge, Massachusetts, Harvard University Press, 1959
26. Holdaway R:  A soft tissue cephalometric analysis and its use in orthodontic treatment planning.  Part I. Am J Orthod 84:8-13, 1983
27. Legen H, Burstone C:  Soft tissue cephalometric analysis for orthognathic surgery.  J Oral Surg 38:745, 1980
28. Peck H, Peck S:  A concept of facial esthetics.  Angle Orthod 40:302-305, 1970
29. Ricketts R:  Divine proportion in facial esthetics.  Clinics in Plastic Surgery 9:408-412, 1982
30. Lehman, R:  A consideration of the advantages of second molar extractions in orthodontics.  Eur J Orthod 1:119-24, 1979
31. Light A:  Second molar extractions in orthodontic therapy.  Penn Dent J 86:14-26, 1986
32. Williamson EH:  Second molar extractions and open coiled springs for distalization of buccal segments.  Facial Orthop Temporomandibular Anthol 4:3-6, 1987
33. Bishara S, Burkey P:  Second molar extractions:  A Review. Am J Orthod 89:415-424, 1986
34. Gooris CG, Artun J, Joondeph DR:  Eruption of mandibular third molars after second-molar extractions:  a radiographic study.  Am J Orthod Dentofac Orthop 98:161-7, 1990
35. Poulton DR:  Changes in class II malocclusion with and without occipital headgear-therapy.  Angle Orthod 29:234-250, 1959
36. Poulton DR:  The influence of extra-oral traction.  Am J Orthod 53:8-18, 1967
37. Bernstein L, Ulbrich R, Gianelly A:  Orthopedics versus orthodontics in class II treatment:  An implant study.  Am J Orthod 72:549-559, 1977
38. Nielsen IL:  Facial growth during treatment with the functional regulator appliance.  Am J Orthod 88:401-410, 1984
39. Pancherz H:  A cephalometric analysis of skeletal and dental changes in contributing to class II correction in activator treatment.  Am J Orthod 85:125-134, 1984
40. Pancherz H, Hagg V:  Dentofacial orthopedics in relation to somatic maturation.  Am J Orthod 88:273-287, 1985
41. Ghafari J, Shofer JS, Jacobsson-Hunt U, Markowitz DL, Laster LL.  Headgear versus function regulator in the early treatment of Class II Division 1 malocclusion:  a randomized clinical trial.  Am J Orthod Dentofac Orthop 1998;113:51-61
42. O’Brien KD, Wright J, Conboy F, Sanjie Y, Mandall N, Chadwick S, et al.  Effectiveness of early orthodontic treatment with the Twin-block appliance:  a multicenter, randomized, controlled trial.  Part 1:  dental and skeletal effects.  Am J Orthod Dentofacial Orthop 2003;124:234-43
43. Elms TN, Buschang PH, Alexander RG.  Long-term stability of Class II, Division 1, nonextraction cervical facebow therapy:  Part I.  Model analysis.  Part II.  Cephalometric analysis.  Am J Orthod Dentofac Orthop 1996;109:271-6, 386-92
44. Keeling SD, Wheeler TT, King GJ, Garvan CW, Cohen DA, Cabassa S, et al.  Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear.  Am J Orthod Dentofac Orthop 1998;113:40-50
45. Livieratos FA.  Class II treatment:  a comparison of one and two stage non-extraction alternatives.  In:  McNamara JA Jr, ed. Orthodontic Treatment Outcome and Effectiveness.  2^nd ed.  Ann Arbor, Mich:  Center for Growth and Development, University of Michigan; 1995:163-193.
46. Tulloch JF, Phillips C, Proffit WR.  Early versus late treatment of Class II malocclusion:  Preliminary results from the University of North Carolina clinical trial.  In:  McNamara JA Jr, ed. Orthodontic Treatment Outcome and Effectiveness.  Ann Arbor, Mich:  Center for Growth and Development, University of Michigan; 1995:113-138
47. Tulloch JFC, Phillips C, Koch G, Proffit WR.  The effect of early intervention on skeletal pattern in Class II malocclusion:  a randomized clinical trial.  Am J Orthod Dentofac Orthop 1997;111:391-400
48. Tulloch JF, Phillips C, Proffit WR.  Benefit of early Class II treatment:  progress report of a two-phase randomized clinical trial.  Am J Orthod Dentofac Orthop 1998;113:62-72
49. King GJ, Wheeler TT, McGorray SP, Aiosa LS, Bloom RM, Taylor MG.  Orthodonitsts’ perceptions of the impact of phase 1 treatment for Class II malocclusion on phase 2 needs.  J Dent Res 1999;78:1745-53
50. Sadowsky PL.  Craniofacial growth and the timing of treatment.  Am J Orthod Dentofac Orthop 1999;113:307-15
51. Kluemper GT, Beeman CS, Hicks EP.  Early orthodontic treatment:  what are the imperatives?  J Am Dent Assoc 2000;131:613-20
52. Wheeler TT, McGorray SP, Dolce C, Taylor MG, King GJ.  Effectiveness of early treatment of Class II malocclusion.  Am J Orthod Dentofac Orthop 2002;121:9-17
53. Hsieh T, Pinskaya Y, Roberts WE.  Assessment of orthodontic treatment outcomes:  Early treatment versus late treatment.  Angle Orthod 75:162-70, 2005
54. Gianelly, A.A:  Crowding:  Timing of treatment, Angle Orthod  64:415-418, 1994
55. Gianelly, A.A:  Treatment of crowding in the mixed dentition.  Am J Orthod Dentofac Orthop 121:569-71, 2002
56. Kaplan R:  Mandibular third molars and post retention crowding.  Am J Orthod 66:411-430, 1974
57. Frankel, R.  Guidance of eruption without extraction.  Trans. Europ. Orthod. Soc. 47:303-315, 1971
58. Jacobson A:  Jasper Jumper Color Atlas Franz-Peter Schwindling. Am J Orthod Dentofac Orthop 108:341-50, 1995
59. McNamara JA:  The correction of interarch malocclusion using a fixed force module Am J Orthod Dentofac Orthop 108:641-50, 1995
60. Trenouth MJ:  Evidence-based orthodontics and the Twin-block appliance  Am J Orthod Dentofac Orthop 121:13a-14a, 2002
61. Altuna, G. and S. Niegel.  Bionators in Class II treatment.  J. Clin. Orthod.  19:185-191, 1985
62. Pancherz, H.  The mechanism of Class II correction and Herbst appliance treatment:  a cephalometric investigation.  Am J Orthod 83:104-113, 1982
63. Watson, W.  A computerized appraisal of high-pull headgear.  Am J Orthod  62:561-579, 1972
64. Sheridan JJ.  Air-rotor stripping. J Clin Orthod 19:443-59, 1985
65. Sheridan JJ.  Air-rotor stripping. J Clin Orthod 21:781-8, 1987
66. Edwards JG.  A surgical procedure to eliminate rotation relapse.  Am J Orthod 57:35-46, 1970
67. Edwards JG.  A long-term prospective evaluation of the circumferential supracrestal fiberotomy in alleviating orthodontic relapse.  Am J Orthod Dentofac Orthop 93:423-8, 1988
68. Boese, L.R.  Fiberotomy and reproximation without lower retention, 9 years in retrospect.  Angle Orthod. 50:88-97 and 169-178, 1980.
69. McNamara, JA, Brudon WL.  Orthodontic and Orthopedic Treatment in the Mixed Dentition.  Needham Press, 1993.
70. Little RM. Riedel RA, Stein A.  Mandibular arch length increase during the mixed dentition:  postretention evaluation of stability and relapse.  Am J Orthod Dentofacial Orthop 1990;97:393-404.
71. Bjerregaard, J., Bundgaard, A.M. and Melsen, B.  The effect of the mandibular lip bumper and maxillary bite plate on tooth movement, occlusion, and space conditions in the lower dental arch.  Europ J Orthod 84:147-155, 1983.
72. Nevant, C.T. The effects of lip-bumper therapy on deficient mandibular arch length.  Unpublished Master’s Thesis, Department of Orthodontics, Baylor University, Dallas, Texas, 1989.
73. Fränkel R. and C. Fränkel.  Orofacial Orthopedics with the Function Regulator.  S. Karger, Munich, 1989.
74. Haas, A.J.  Rapid expansion of the maxillary dental arch and nasal cavity by opening the mid-palatal suture.  Angle Orthod. 31:73-90,1961.
75. Hass, A.J. Treatment of maxillary deficiency by opening the mid-palatal suture. Angle Orthod. 65:200-217,1965.
76. Haas, A.J. Palatal expansion:  just the beginning of dento-facial orthopedics.  Am. J. Orthod. 57:219-255,1970.
77. Haas, A.J.  Long-term post-treatment evaluation of rapid palatal expansion.  Angle Orthod. 50:189-217, 1980.
78. Timms, D.J.  Long-term follow-up cases treated by rapid maxillary expansion.  Trans. Eur. Orthod. Soc., pp.211-215,1976.
79. Wertz, R.A.  Skeletal and dental changes accompanying rapid mid-palatal suture opening.  Am. J. Orthod.  58:411-466,1970.
80. Starnbach, H., Bayne, D.,  Cleall, J., and Subtelny, J.D. Facioskeletal and dental changes resulting from rapid maxillary expansion.  Angle Orthod.  36:152-164, 1966.
81. Melsen, B. A histological study of the influence of sutural morphology and skeletal maturation of rapid palatal expansion in children.  Trans. Europ. Orthod. Soc., 99. 499-507, 1972.
82. Melsen, B.  Palatal growth studied on human autopsy material.  Am. J. Orthod. 68:42-54, 1975.
83. Baccetti T, Franchi L, Cameron CG, McNamara JA.  Treatment timing for rapid maxillary expansion.  Angle Orthod. 71:343-50, 2001
84. Cameron CG, Franchi L, Baccetti T, McNamara JA.  Long-term effects of rapid maxillary expansion:  A posteroanterior cephalometric evaluation.  Am. J. Orthod. Dentofac Orthop.  121:129-35, 2002
85. McNamara JA, Baccetti T, Franchi L, Herberger TA.  Rapid maxillary expansion followed by fixed appliances.  A long-term evaluation of changes in arch dimensions.  Angle Orthod.  73:  344-53, 2003
86. Garib DG, Henriques JFC, Carralho PEG, Gomes SC.  Longitudinal effects of rapid maxillary expansion – a retrospective cephalometric study.  Angle Orthod. 77:442-48, 2007
87. Baumrind S, Korn EL.  Transverse development of human jaws between the ages of 8.5 and 15.5 years studied longitudinally with the use of implant.  J Dent Res. 1990, 69:1298-1306.
88. Betts, NJ, Vanarsdall RL, Barber HD, Higgins-Barber K, Fonseca RJ.  Diagnosis and treatment of transverse maxillary deficiency.  Int J Orthod Orthognath Surg. 1995;10:75-96
89. Vanarsdall RL.  Periodontal/orthodontic interrelationships.  In:  Graber TM, Vanarsdall RL, eds. Orthodontics:  Current Principles and Techniques, 2^nd ed.  St. Louis, Mo:  CV Mosby; 1994;712-749.
90. Glassman, AS, Nahigian SJ, Medway JM, Aronowitz HI.  Conservative surgical orthodontic adult rapid palatal expansion:  sixteen cases.  Am J Orthod. 1984;86:207-213.
91. Mossaz CF, Byloff FK, Richter M.  Unilateral and bilateral corticotomies for correction of maxillary transverse discrepancies.  Eur J Orthod. 1992, 14:110-116.
92. Kennedy JW, Bell WH, Kimbrough OL, et al.  Osteotomy as an adjunct to rapid maxillary expansion.  Am J  Orthod. 1976;70:123-137.
93. Atac ATA, Karasu HA, Aytac D.  Surgically assisted rapid maxillary expansion compared with orthopedic rapid maxillary expansion.  Angle Orthod.  76:353-59,2006.
94. Filho RMAL, Ruellas ACO.  Long-term anteroposterior and vertical maxillary changes in skeletal Class II patients treated with slow and rapid maxillary expansion.  Angle Orthod.  77:870-74,2007.
95. Filho RMAL, Ruellas ACO.  Mandibular behavior with slow and rapid maxillary expansion in skeletal Class II patients.  Angle Orthod.  77:625-31,2007.
96. Iseri H, Özsoy S.  Semi-rapid maxillary expansion – a study of long-term transverse effects in older adolescents and adults.  Angle Orthod.  74:71-7,2004.
97. Jafari A, Shetty KS, Kumar M.  Study of stress distribution and displacement of various craniofacial structures following application of transverse orthopedic forces – a three-dimensional FEM study.  Angle Orthod.  73:12-20,2003.
98. Gardner GE, Kronman JH.  Cranioskeletal displacement caused by rapid palatal expansion in the Rhesus monkey.  Am J Orthod. 1971;59:146-155.
99. Starnbach H, Bayne D, Cleall J, Subtelny JD.  Facioskeletal and dental changes resulting from rapid maxillary expansion.  Angle Orthod. 1966;36:152-164.
100. Starnbach HK, Cleall JF.  The effects of splitting the midpalatal suture on the surrounding structures.  Am J Orthod. 1964;50:923-924.
101. Storey E.  Tissue response to the movement of bones.  Am J Orthod. 1973;64:229-247.
102. Ten Cate AR, Freeman E, Dickinson JB.  Sutural Development:  structure and its response to rapid expansion.  Am J Orthod. 1977;71:622-636.
103. Mao JJ, Wang X, Kopher RA.  Biomechanics of craniofacial sutures:  Orthopedic implications.  Angle Orthod.  73:128-35,2003.
104. Mao JJ, Oberheim M, Cooper RA, Tassick M.  In:  McNamara JA Jr, ed.  Stress Patterns of Craniofacial Bones Upon Orthopedic Headgear Loading in Dry Human Skulls.  I:  Growth Modification. Craniofacial Growth Series 35.  Ann Arbor, MI:  Center for Human Growth and Development, The University of Michigan; 1999:87-104.
105. Turley RK.  Orthopedic correction of Class III malocclusion with palatal expansion and custom protraction headgear.  J Clin Orthod. 1988;22:314-25.
106. Campbell RM.  The dilemma of Class III treatment.  Angle Orthod.  1983;53:175-91.
107. Baik HS.  Clinical results of the maxillary protraction in Korean children.  Am J Orthod Dentofac Orthop;  108:583-92,1995.
108. Fenderson FA, McNamara JA, Baccetti T, Veith CJ.  A long-term study on the expansion effects of the cervical-pull facebow with and without rapid maxillary expansion.  Angle Orthod; 74:439-49,2003.
109. Lima RMA, Lima AL.  Case report:  long-term outcome of Class II Division 1 malocclusion treated with rapid palatal expansion and cervical traction.  Angle Orthod 2000;70:89-94.
110. Turley PEN, Turley PK.  Cephalometric effects combined palatal expansion and facemask therapy on Class III malocclusion.  Angle Orthod;  68:217-24,1998.
111. Irie M, Nakamura S.  Orthopedic approach to severe skeletal Class III malocclusion.  Am J Orthod 1977;67:377-92.
112. Proffit WR.  Contemporary orthodontics.  St. Louis:  CV Mosby, 1992:237-43, 453-62.
113. Dellinger EL.  A preliminary study of anterior maxillary displacement.  Am J Orthod 1973;63:509-16.
114. Kambara T.  Dentofacial changes produced by extraoral  forward force in the Macaca irus.  Am J Orthod 1977;71:249-76.
115. Nanda R.  Biomechanical and clinical considerations of a modified protraction headgear.  Am J Orthod 1980;78:125-39.
116. Cozzani G.  Extraoral traction and Class III treatment.  Am J Orthod 1981;80:638-50.