P. S. Fleming,*1 S. D. Springate2 and R. A. C. Chate3
IN BRIEF
• • •
Delineates myth and reality in orthodontics. Clarifies the limitations and benefits of definitive orthodontics. Illustrates nine common misconceptions concerning orthodontic treatment.
PRACTICE
Myths and realities in orthodontics
Comprehensive orthodontic treatment typically comprises an initial phase of alignment over a period of four to six months, followed by vertical, transverse and antero-posterior corrections, space closure, finishing and detailing to enhance dental and facial aesthetics and function. Each course of treatment involves a series of decisions and alternatives relating to objectives, appliance design and treatment mechanics. In recent years there has been increasing interest in short-term approaches to treatment with more limited objectives and the avoidance of phases traditionally considered integral to successful treatment. In this review the veracity of accepted truths in orthodontics are discussed; specifically, the importance of initial molar relationship, final incisor relationship, the merits of orthodontic extractions, anticipated treatment times, the value of modern fixed appliance systems, the importance of torque expression and the relative merits of bonded retainers and inter-proximal reduction are considered. INTRODUCTION The delivery of healthcare in the UK has seen considerable change in recent years with the reconfiguration of NHS healthcare commissioners, increasing emphasis on patientreported outcome measures, and budgetary restrictions. Dentistry has not been immune to these developments with contractual changes particularly noteworthy. Historically, orthodontic treatments were predominantly undertaken by non-specialist general dental practitioner (GDP) providers within the NHS, but this situation gradually changed with the acceptance that fixed appliances in the hands of specialists were capable of superior results.1 In recent years, however, alternatives to conventional courses of fixed appliance orthodontics have emerged. Much of this treatment is offered by GDPs, predominantly in the form of ‘accelerated orthodontics’ or treatment involving aesthetic removable and fixed appliances2 but this has been accompanied by a significant increase in successful litigation claims.3 Similar patterns of care, with delivery involving both specialists and non-specialists, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Queen Mary University of London, London, E1 2AD; 2Eastman Dental Institute, London; 3Vice Dean, Faculty of Dental Surgery, The Royal College of Surgeons of Edinburgh, Nicolson Street, Edinburgh, EH8 9DW *Correspondence to: Dr Padhraig Fleming Email: [email protected] 1
Refereed Paper Accepted 26 June 2014 DOI: 10.1038/sj.bdj.2015.41 ©British Dental Journal 2015; 218: 105-110
have been observed in other dental disciplines including paediatric dentistry4 and periodontics,5 and are also established internationally in orthodontics.6 What differentiates this trend within orthodontics from that in other specialties is that a significant proportion of the treatments offered by general practitioners have more limited objectives than conventional specialist-delivered care; some of it is also suggested as an adjunct to produce a more conservative restorative solution than would be possible without recourse to orthodontics. In this paper, nine areas of debate and misunderstanding concerning orthodontic planning and treatment are discussed.
ARE MOLAR RELATIONSHIPS RELEVANT? The ideal Class I molar relationship was originally defined by Angle7 and later refined by Andrews.8 Angle’s initial belief was that the molars were the cornerstone to the occlusion. While adolescent growth may alter skeletal relationships, typically reducing the convexity of the lower face and improving skeletal II relationships slightly,9 molar relationship is generally considered to be constant once the permanent dentition is established.10 The molar relationship is integral to determining the final incisor relationship. Specifically, with Class I molar relationships and an intact dentition devoid of inter-arch toothsize discrepancy, non-extraction treatment is likely to translate into a Class I incisor relationship. Moreover, in the presence of
BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
moderate to severe crowding, consideration should be given to symmetrical extraction of four premolar units to preserve Class I molar and incisor relationships. With Class II molar relationships at the outset in an intact dentition, simple alignment is likely to translate into a residual overjet following treatment. Consequently, consideration should be given to correcting the molar relationship to Class I with one of a number of adjuncts including: a functional appliance, fixed Class II corrector, headgear or upper and lower extractions if achievement of Class I incisors is a treatment objective (Fig. 1). Alternatively, in an uncrowded lower arch, consideration could be given to accepting the Class II molar relationships by camouflaging the incisor relationship with the loss of maxillary premolars alone (Fig. 2). The alternative would be to accept a residual overjet following treatment, but this would have implications both for aesthetics and post-treatment stability, likely requiring a commitment to life-long retention.
IS A CLASS I INCISOR WORTH AIMING FOR? Traditionally, achievement of Class I incisors has been an objective of comprehensive orthodontic treatment. The rationale for this relates to the likelihood of stability and aesthetics associated with this relationship between the upper and lower incisors. Stability stems from the combination of a normal overjet and overbite with the maxillary incisors resting on the tips of the 105
© 2015 Macmillan Publishers Limited. All rights reserved
PRACTICE mandibular incisors, which in turn may be stabilised with a fixed lingual retainer. Retroclined incisors, characteristic of Class II division 2 incisor relationship, in particular are believed to be a by-product of a high resting position of the lower lip.11,12 While alignment of upper incisors in such cases tends to be particularly rapid, acceptance of a residual overjet is often unwise because of a marked tendency for the lip-totooth relationship to re-establish itself following treatment.10 It is, therefore, highly likely that the maxillary incisors will retrocline following treatment in the absence of the stabilising effect of the lower incisors. Occasionally, a decision may be made to accept a residual overjet in the presence of a skeletal II discrepancy not severe enough to warrant orthognathic correction, whereby retraction of the maxillary incisors would compromise the support of the upper lip. In such instances, permanent bonded retention is mandatory and the potential instability of the outcome should be discussed during the informed consent process.13,14
SHOULD NON-EXTRACTION TREATMENT BE UNDERTAKEN WHEREVER POSSIBLE? The reliance on extractions as part of orthodontic treatment has fluctuated over the decades. At the turn of the twentieth century, Edward Angle espoused non-extraction fixed appliance treatment with ‘arch development’ involving buccal expansion and incisor proclination.15 After initially following this philosophy, Tweed subsequently abandoned such an approach, on the basis that 80% of his recalls had poor facial aesthetics, occlusal instability and irreparable damage of the investing tissues of the teeth in the incisor and premolar regions.16 As a consequence, in the period between the early 1950s to the late 1970s, many orthodontic patients underwent premolar extraction in the expectation of enhanced post-treatment stability. Since then, there has been a widespread desire within the orthodontic community to curb the number of permanent teeth removed for orthodontic reasons; this tenet persists to the present day. Although there is short-term inconvenience and discomfort associated with dental extractions,17 the severity of associated pain has been shown to be less marked than that arising from the initial engagement of an orthodontic aligning wire.18 In addition, there is no proven risk to either the oral health and function or to the facial aesthetics of an individual who has had dental extractions as part of orthodontic treatment. Moreover, extractions are usually prescribed to relieve crowding in an
Fig. 1 In a growing patient this Class II molar relationship was corrected to Class I. Consequently, incisor and canine relationships were corrected allowing the overjet to be reduced
effort to minimise either transverse or antero-posterior arch length changes during treatment; it would therefore be counterintuitive to expect significant changes in the facial profile to arise with carefully planned treatment. At various times extractions have been implicated in causing (i) temporo-mandibular joint dysfunction (TMJD), purportedly stemming from posterior displacement of the mandible and displacement of the articular disc; (ii) premature ageing, related to the loss of lip support; and (iii) compromised smile aesthetics (Table 1). Careful systematic review of the available evidence has failed to support such views;19 moreover, there is now wide acceptance that extractions have the potential to improve both smile aesthetics and facial aesthetics with careful planning.20,21 While there is some evidence of enhanced stability with extraction approaches,22 in other research little difference between posttreatment incisor irregularity with extraction or non-extraction treatment has been reported.23,24 Reliable data on the merit of orthodontic extractions cannot be derived from retrospective research due to the inevitable confounding effects of contrasting space conditions, likely to have prompted the extraction decision before treatment. The ideal study to assess this controversial area would be a randomised controlled trial with prolonged follow-up. At present, ethical concerns preclude conducting a trial in this area. However, it is accepted that the decision to extract should be made on an individual basis accounting for space conditions, including
Fig. 2 Class II division 1 incisor relationship with Class II molar and canine relationships of the left side. Non-extraction treatment without active distal molar relationship to Class I would lead to an increased overjet at the end of treatment. Maxillary premolars were therefore removed and anchorage supported with temporary anchorage devices to facilitate overjet reduction and relief of crowding. The Class II molar relationships were preserved but both incisor and canine relationships corrected to Class I
Table 1 Adverse effects of orthodontics Orthodontics is not without adverse consequences. For example, overly rapid tooth movements or heavy forces (especially in adults) can lead to pulpal death but there is no convincing evidence that orthodontic movement results in TMJD or that carefully conducted treatment leads to adverse effects on the face such as ‘dishing-in’ or collapse of the lips.
crowding, overjet, torque requirements and facial aesthetics. Ideally, such decisions should be supported with formal space analysis.25
DOES COMPREHENSIVE ORTHODONTICS TAKE TWO TO THREE YEARS TO COMPLETE? Comprehensive orthodontic treatment encompasses an initial phase of alignment BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
106 © 2015 Macmillan Publishers Limited. All rights reserved
PRACTICE Table 2 Rapid tooth movement Rapid movement of the crowns of teeth is not new. It has certainly been around since the development of the round-wire Begg technique in the 1950s. With the introduction of shape-memory effect (nickel-titanium) wires in the 1970s it has been possible to align the crowns of very irregular anterior teeth within just a few weeks, even in adults. The problem is not the speed with which the crowns are aligned; it is the stability of the result, particularly as the roots of the teeth remain close to their original positions. Therefore, while orthodontic appliances can be removed prematurely once alignment has been achieved, it is recommended that torque expression and occlusal detailing is undertaken to enhance aesthetic and functional outcomes, enhancing the prospect of prolonged stability.
A
Table 3 Be wary of claims regarding novel treatment methods
B
There should be an index of suspicion surrounding novel methods including those concerning faster tooth movement, particularly when these claims are made by those with vested financial interests.36 Tooth movement relies on the remodelling or displacement of bone. Remodelling proceeds at a finite pace, which has an upper limit as does non-surgical displacement of bone. Distraction osteogenesis provides the most rapid physiological adjustment of bone position but as yet this is not a primary orthodontic technique.
typically in nickel-titanium wires, usually taking in the region of four to six months, followed by vertical, transverse and antero-posterior corrections, space closure and finishing and detailing (Table 2). The duration of orthodontic cases in both adolescence and adulthood is typically in the region of 15 months.26 Treatment involving extractions is usually slightly lengthier than non-extraction treatment.27 Combined orthodontic-surgical care is likely to result in an extension to treatment, although treatment times can be quite variable; similarly, treatment incorporating mechanical eruption of unerupted or ectopic teeth is usually quite prolonged.28,29
IS TREATMENT FASTER WITH MODERN BRACKETS? Orthodontic appliances have undergone considerable refinement over the last 30 years. The pre-adjusted edgewise appliance was introduced by Andrews in the 1970s,30 largely based on occlusal cornerstones derived from analysis of untreated ideals. 8 Pre-adjusted edgewise brackets were the first to be programmed to impart specific degrees of tip, torque, in-out and rotational control on each tooth thereby reducing the need for wire-bending. The most vaunted and positively marketed
C Fig. 3 Class I malocclusion with severe crowding and palatal displacement of both maxillary lateral incisors (Fig. 3a). Following alignment the lateral incisors have been brought into the correct position; however, there is inadequate labial root torque on the upper left lateral incisor (Figs 3b-c). Thick wires with high elastic modulus are required to address this. Torque delivery can be time consuming but is valuable in terms of prospective stability and dental aesthetics
A
B
C
D
development since the introduction of the pre-adjusted edgewise appliance have been self-ligating brackets (Table 3), which incorporate either a slide or clip mechanism to entrap the archwire, removing the need for elastomeric or stainless steel auxiliary ligatures. However, there is no evidence to suggest reduced treatment times with modern self-ligating bracket systems.31 While these brackets have demonstrated reduced frictional resistance to archwire sliding in laboratory studies, there is now a wealth of prospective clinical evidence indicating that this theoretical advantage does not translate into shorter treatment times. In particular, there have been three randomised trials comparing treatment duration with self-ligation and conventional brackets, none of which has demonstrated a time saving with the newer systems.32–35
BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
E Fig. 4 This Class I malocclusion with palatally-displaced lateral incisors was treated with fixed appliances (Figs 4a-b). Sufficient torque was delivered to the maxillary lateral incisors producing an acceptable aesthetic result following 15 months of treatment (Fig. 4c). Routine follow-up 18 months following removal of the appliances, the result has remained stable despite the lack of bonded retention (Figs 4d-e)
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PRACTICE
Fig. 5 Class I crowded case treated with customised lingual appliances over a seven-month period. The lack of uniformity of lingual surfaces mean that stock brackets may have poor adaptation to lingual surfaces making treatment more complex
IS TORQUE DELIVERY IMPORTANT? Torque can be defined as ‘rotation without translation’ or ‘preferential movement of the root with a stationary crown’. Torque is a product of force couples generated between bracket and wire; rectangular stainless steel wires with high elastic modulus and minimal play between wire and bracket slot are necessary for effective torque delivery (Fig. 3). Torque delivery is considered to be an integral part of orthodontic treatment; effective torque delivery is one of six recognised occlusal keys necessary to produce an ideal occlusal result.8 In addition, torque delivery is often important in the buccal segments as alleviation of crowding in round wires results in bucco-lingual inclination changes, which may compromise occlusal interdigitation, overbite and stability. In the anterior regions, appropriate torque contributes to dental aesthetics; the labial face of the maxillary central incisor should lie parallel to the facial vertical for optimal dental aesthetics, with greater requirement for palatal root torque in the presence of increased lower anterior facial height.37 In addition, torque expression is important in producing stable
outcomes, particularly where teeth were significantly displaced before treatment (Fig. 4).
ARE BETTER OUTCOMES ACHIEVED WITH MODERN BRACKETS? While novel techniques such as the use of temporary anchorage devices (TADs) have broadened the scope and enhanced the predictability of treatment (Table 4), there is no evidence to suggest that refinement of brackets has been accompanied by better outcomes. Prospective research comparing treatment times with self-ligating brackets have also alluded to comparable levels of occlusal improvement with these systems.32–35 Clearly, the quality of a course of orthodontics is contingent more on the standards and skills of the operator than on the bracket system used. Both labial and lingual customised appliances have been produced, with either brackets, wires or both tailored to the individual patient. Customised lingual appliances have become particularly popular due to the wide variation in the morphology of lingual surfaces, which complicates adaptation of stock brackets to these teeth and has a bearing on torque delivery (Fig. 5).
IS BONDED RETENTION A GUARANTEE OF STABILITY? The increasing emphasis on non-extraction treatment has brought the use of fixed retainers into sharper focus (Table 5). Bonded retention is not without problems: fixed lingual retainers may encourage plaque accumulation with potential periodontal implications.38 Consequently, their use may not be appropriate in the presence of poor oral hygiene. Failure rates with fixed retainers have been shown to be high.39 As such, ‘permanent’ retention does not remove the requirement that the teeth are placed in positions of soft tissue balance. Additionally, prediction of relapse on an individual basis has proven impossible, invoking the need for a long-term retention strategy for many patients. Furthermore, while bonded retainers may maintain rotational correction of teeth, they may be inadequate to resist soft tissue pressures, for example, those arising following correction of bimaxillary proclination. Consequently, inclination changes and tooth migration may arise despite intact retainers; augmentation of fixed retainers with BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Table 4 Some newer techniques are well proven and highly effective TADs have dramatically advanced the range and type of orthodontic tooth movements that are achievable. Where growth has slowed to adult levels, certain types of tooth movement that were once impossible can now be carried out routinely including intrusion of blocks of teeth to reduce a deep overbite or to intrude over-erupted molars, thereby correcting anterior open bites previously only correctable through a combined orthodontic-surgical approach, involving superior repositioning of the posterior maxilla with an osteotomy.
Table 5 Fixed retainers will not always hold poorly planned tooth positions If the dentition is moved beyond the zone of soft tissue balance, the standard methods of retention will not hold the new tooth positions for long. Even fixed retainers will allow relapse, the magnitude, nature and direction of which is unpredictable.
removable retainers may moderate this tendency. It has also been demonstrated that residual activity in bonded retainers may lead to dramatic inclination changes;40 prolonged supervision of retention is therefore advisable (Fig. 6).
IS INTER-PROXIMAL REDUCTION SAFE? There is long-term evidence indicating the safety of inter-proximal reduction.41 In this research no increased risk of either caries or periodontal problems ten years subsequent to the procedure was demonstrated. All inter-proximal reduction in the study was carried out by an internationally-renowned orthodontist; therefore, while the procedure may well be performed safely, it is important that it is undertaken with care and attention aiming to produce a smooth surface without inter-proximal ledges risking plaque accumulation and associated risk of periodontal compromise, sensitivity and caries progression (Fig. 7).
Fig. 6 Presentation of an orthodontic case ten years following removal of fixed appliances with rotation and axial inclination changes of terminal teeth on the retainer (22, 43). The changes may stem from residual activity in the bonded retainer wire
may improve alignment in the short term, it is important that treatment of this nature is carefully planned, restricted to amenable cases and suitably retained. 1.
2. 3. 4.
5.
6.
7.
CONCLUSION Traditional orthodontics involves a complex decision-making process not merely a binary decision of whether one form of treatment is appropriate or otherwise. The treating clinician is charged with choosing between an array of treatment options, appliances and auxiliaries based on a range of considerations including facial aesthetics, dental aesthetics, and intra- and inter-arch relationships. There is a wide diversity of presentations of malocclusion warranting tailored treatment planning and mechanics. Therefore, while short courses of orthodontics performed on a non-extraction basis
8. 9. 10. 11.
12. 13.
Richmond S, Andrews M, Roberts C T. The provision of orthodontic care in the general dental services of England and Wales: extraction patterns, treatment duration, appliance types and standards. Br J Orthod 1993; 20: 345–350. Maini A. Short-term cosmetic orthodontics for general dental practitioners. Br Dent J 2013; 214: 83–84. Dental Protection website. Available at: http://www. dentalprotection.org/uk/ (accessed 12 September 2013). McQuistan M R, Kuthy R A, Daminano P C, Ward M M. General dentists’ referrals of 3- to 5-year-old children to paediatric dentists. J Am Dent Assoc 2006; 137: 653–660. Lee J H, Bennett D E, Richards P S, Inglehart M R. Periodontal referral patterns of general dentists: lessons for dental education. J Dent Educ 2009; 73: 199–210. Aldawood S, Ampuan S N, Medara N, Thomson W M. Orthodontic treatment provision and referral preferences among New Zealand general dental practitioners. Aust Orthod J 2011; 27: 145–154. Angle E H. Treatment of malocclusion of the teeth, 7th ed. Philadelphia: White Dental Manufact Co, 1907. Andrews L F. The six keys to normal occlusion. Am J Orthod 1972; 62: 296–309. Pollard L E, Mamandras A H. Male postpubertal facial growth in Class II malocclusions. Am J Orthod Dentofacial Orthop 1995; 108: 62–68. Nanda R S, Meng H, Kapila S, Goorhuis J. Growth changes in the soft tissue facial profile. Angle Orthod 1990; 60: 177–190. Lapatki B G, Mager A S, Schulte-Moenting J, Jonas I E. The importance of the level of the lip line and resting lip pressure in Class I I, Division 2 malocclusion. J Dent Res 2002; 81: 323–328. Lambrechts H, De Baets E, Fieuws S, Willems G. Lip and tongue pressure in orthodontic patients. Eur J Orthod 2010; 32: 466–471. Chate R A C. Truth or consequences: the potential implications of short-term cosmetic orthodontics general dental practitioners. Br Dent J 2013; 215: 551–553.
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Fig. 7 This patient presented having commenced treatment with a general practitioner with a removable aligner system. The practitioner had undertaken liberal inter-proximal reduction of the lower anteriors to facilitate alignment, introducing unaesthethic morphological changes and ledges inter-proximally. The teeth were subsequently aligned with fixed appliances in less than six months 14. Chate R A C. Short-term orthodontics debate. Br Dent J 2014; 216: 388–389. 15. Angle E H. Treatment of malocclusion of the teeth and fractures of the maxillae, 6th ed. Philadelphia: SS White, 1900. 16. Tweed C H. Indications for the extraction of teeth in orthodontic procedure. Am J Orthod Oral Surg 1944; 30: 405–428. 17. Chaushu G, Becker A, Zeltser R, Vasker N, Branski S, Chaushu S. Patients’ perceptions of recovery after routine extraction of healthy premolars. Am J Orthod Dentofacial Orthop 2007; 131: 170–175. 18. Jones M, Chan C. The pain and discomfort experienced during orthodontic treatment: a randomized controlled clinical trial of two initial aligning arch wires. Am J Orthod Dentofacial Orthop 1992; 102: 373–381. 19. Luther F, Layton S, McDonald F. Orthodontics for treating temporomandibular joint (TMJ) disorders. Cochrane Database Syst Rev 2010; CD006541. 20. Parekh S, Fields H W, Beck F M, Rosenstiel S F. The acceptability of variations in smile arc and buccal corridor space. Orthod Craniofac Res 2007; 10: 15–21. 21. Hagler B L, Lupini J, Johnston L E Jr. Long-term comparison of extraction and nonextraction alternatives in matched samples of African American patients. Am J Orthod Dentofacial Orthop 1998; 114: 393–403. 22. Little R M, Riedel R A, Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention. Am J Orthod 109
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PRACTICE Dentofacial Orthop 1988; 93: 423–428. 23. Luppanapornlarp S, Johnston L E Jr. The effects of premolar-extraction: a long-term comparison of outcomes in “clear-cut” extraction and nonextraction Class II patients. Angle Orthod 1993; 63: 257–272. 24. Paquette D E, Beattie J R, Johnston L E Jr. A longterm comparison of nonextraction and premolar extraction edgewise therapy in ‘borderline’ Class II patients. Am J Orthod Dentofacial Orthop 1992; 102: 1–14. 25. Kirschen RH, O’Higgins E A, Lee R T. The Royal London Space Planning: an integration of space analysis and treatment planning: Part I: Assessing the space required to meet treatment objectives. Am J Orthod Dentofacial Orthop 2000; 118: 448–455. 26. Hamilton R, Goonewardene M S, Murray K. Comparison of active self-ligating brackets and conventional pre-adjusted brackets. Aust Orthod J 2008; 24: 102–109. 27. Mavreas D, Athanasiou A E. Factors affecting the duration of orthodontic treatment: a systematic review. Eur J Orthod 2008; 30: 386–395. 28. O’Brien K, Wright J, Conboy F et al. Prospective, multi-centre study of the effectiveness of orthodontic/orthognathic surgery care in the United Kingdom. Am J Orthod Dentofacial Orthop 2009; 135: 709–714.
29. Fleming P S, Scott P, Heidari N, Dibiase A T. Influence of radiographic position of ectopic canines on the duration of orthodontic treatment. Angle Orthod 2009; 79: 442–446. 30. Andrews L F. The straight-wire appliance. Explained and compared. J Clin Orthod 1976; 10: 174–195. 31. Fleming P S, Johal A. Self-ligating brackets in orthodontics: a systematic review. Angle Orthod 2010; 80: 575–584. 32. Fleming P S, DiBiase A T, Lee R T. Randomized clinical trial of orthodontic treatment efficiency with self-ligating and conventional fixed orthodontic appliances. Am J Orthod Dentofacial Orthop 2010; 137: 738–742. 33. Di Biase A T, Nasr I H, Scott P, Cobourne M T. Duration of treatment and occlusal outcome using Damon3 self-ligated and conventional orthodontic bracket systems in extraction patients: a prospective randomized clinical trial. Am J Orthod Dentofacial Orthop 2011; 139: e111–e116. 34. Johannson K, Lundstrom F. Orthodontic treatment efficiency with self-ligating and conventional edgewise twin brackets. A prospective randomized clinical trial. Angle Orthod 2012; 82: 929–934. 35. Songra G, Clover M, Atack N E et al. Comparative assessment of alignment efficiency and space closure of active and passive self-ligating vs
36. 37.
38.
39.
40.
41.
conventional appliances in adolescents: a singlecentre randomized controlled trial. Am J Orthod Dentofacial Orthop 2014; 145: 569–578. O’Brien K, Sandler J. In the land of no evidence, is the salesman king? Am J Orthod Dentofacial Orthop 2010; 138: 247–249. Ross V A, Isaacson R J, Germane N, Rubenstein L K. Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics. Am J Orthod Dentofacial Orthop 1990; 98: 422–429. Pandis N, Vlahopoulos K, Madianos P, Eliades T. Long-term periodontal status of patients with mandibular lingual fixed retention. Eur J Orthod 2007; 29: 471–476. Booth F A, Edelman J M, Proffit W R. Twenty-year follow-up of patients with permanently bonded mandibular canine-to-canine retainers. Am J Orthod Dentofacial Orthop 2008; 133: 70–76. Renkema A M, Renkema A, Bronkhorst E, Katsaros C. Long-term effectiveness of canine-to-canine bonded flexible spiral wire lingual retainers. Am J Orthod Dentofacial Orthop 2011; 139: 614–634. Zachrisson B U, Nyøygaard L, Mobarak K. Dental health assessed more than 10 years after interproximal enamel reduction of mandibular anterior teeth. Am J Orthod Dentofacial Orthop 2007; 131: 162–169.
BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
110 © 2015 Macmillan Publishers Limited. All rights reserved
IN BRIEF
• • •
Delineates myth and reality in orthodontics. Clarifies the limitations and benefits of definitive orthodontics. Illustrates nine common misconceptions concerning orthodontic treatment.
PRACTICE
Myths and realities in orthodontics
Comprehensive orthodontic treatment typically comprises an initial phase of alignment over a period of four to six months, followed by vertical, transverse and antero-posterior corrections, space closure, finishing and detailing to enhance dental and facial aesthetics and function. Each course of treatment involves a series of decisions and alternatives relating to objectives, appliance design and treatment mechanics. In recent years there has been increasing interest in short-term approaches to treatment with more limited objectives and the avoidance of phases traditionally considered integral to successful treatment. In this review the veracity of accepted truths in orthodontics are discussed; specifically, the importance of initial molar relationship, final incisor relationship, the merits of orthodontic extractions, anticipated treatment times, the value of modern fixed appliance systems, the importance of torque expression and the relative merits of bonded retainers and inter-proximal reduction are considered. INTRODUCTION The delivery of healthcare in the UK has seen considerable change in recent years with the reconfiguration of NHS healthcare commissioners, increasing emphasis on patientreported outcome measures, and budgetary restrictions. Dentistry has not been immune to these developments with contractual changes particularly noteworthy. Historically, orthodontic treatments were predominantly undertaken by non-specialist general dental practitioner (GDP) providers within the NHS, but this situation gradually changed with the acceptance that fixed appliances in the hands of specialists were capable of superior results.1 In recent years, however, alternatives to conventional courses of fixed appliance orthodontics have emerged. Much of this treatment is offered by GDPs, predominantly in the form of ‘accelerated orthodontics’ or treatment involving aesthetic removable and fixed appliances2 but this has been accompanied by a significant increase in successful litigation claims.3 Similar patterns of care, with delivery involving both specialists and non-specialists, Barts and The London School of Medicine and Dentistry, Institute of Dentistry, Queen Mary University of London, London, E1 2AD; 2Eastman Dental Institute, London; 3Vice Dean, Faculty of Dental Surgery, The Royal College of Surgeons of Edinburgh, Nicolson Street, Edinburgh, EH8 9DW *Correspondence to: Dr Padhraig Fleming Email: [email protected] 1
Refereed Paper Accepted 26 June 2014 DOI: 10.1038/sj.bdj.2015.41 ©British Dental Journal 2015; 218: 105-110
have been observed in other dental disciplines including paediatric dentistry4 and periodontics,5 and are also established internationally in orthodontics.6 What differentiates this trend within orthodontics from that in other specialties is that a significant proportion of the treatments offered by general practitioners have more limited objectives than conventional specialist-delivered care; some of it is also suggested as an adjunct to produce a more conservative restorative solution than would be possible without recourse to orthodontics. In this paper, nine areas of debate and misunderstanding concerning orthodontic planning and treatment are discussed.
ARE MOLAR RELATIONSHIPS RELEVANT? The ideal Class I molar relationship was originally defined by Angle7 and later refined by Andrews.8 Angle’s initial belief was that the molars were the cornerstone to the occlusion. While adolescent growth may alter skeletal relationships, typically reducing the convexity of the lower face and improving skeletal II relationships slightly,9 molar relationship is generally considered to be constant once the permanent dentition is established.10 The molar relationship is integral to determining the final incisor relationship. Specifically, with Class I molar relationships and an intact dentition devoid of inter-arch toothsize discrepancy, non-extraction treatment is likely to translate into a Class I incisor relationship. Moreover, in the presence of
BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
moderate to severe crowding, consideration should be given to symmetrical extraction of four premolar units to preserve Class I molar and incisor relationships. With Class II molar relationships at the outset in an intact dentition, simple alignment is likely to translate into a residual overjet following treatment. Consequently, consideration should be given to correcting the molar relationship to Class I with one of a number of adjuncts including: a functional appliance, fixed Class II corrector, headgear or upper and lower extractions if achievement of Class I incisors is a treatment objective (Fig. 1). Alternatively, in an uncrowded lower arch, consideration could be given to accepting the Class II molar relationships by camouflaging the incisor relationship with the loss of maxillary premolars alone (Fig. 2). The alternative would be to accept a residual overjet following treatment, but this would have implications both for aesthetics and post-treatment stability, likely requiring a commitment to life-long retention.
IS A CLASS I INCISOR WORTH AIMING FOR? Traditionally, achievement of Class I incisors has been an objective of comprehensive orthodontic treatment. The rationale for this relates to the likelihood of stability and aesthetics associated with this relationship between the upper and lower incisors. Stability stems from the combination of a normal overjet and overbite with the maxillary incisors resting on the tips of the 105
© 2015 Macmillan Publishers Limited. All rights reserved
PRACTICE mandibular incisors, which in turn may be stabilised with a fixed lingual retainer. Retroclined incisors, characteristic of Class II division 2 incisor relationship, in particular are believed to be a by-product of a high resting position of the lower lip.11,12 While alignment of upper incisors in such cases tends to be particularly rapid, acceptance of a residual overjet is often unwise because of a marked tendency for the lip-totooth relationship to re-establish itself following treatment.10 It is, therefore, highly likely that the maxillary incisors will retrocline following treatment in the absence of the stabilising effect of the lower incisors. Occasionally, a decision may be made to accept a residual overjet in the presence of a skeletal II discrepancy not severe enough to warrant orthognathic correction, whereby retraction of the maxillary incisors would compromise the support of the upper lip. In such instances, permanent bonded retention is mandatory and the potential instability of the outcome should be discussed during the informed consent process.13,14
SHOULD NON-EXTRACTION TREATMENT BE UNDERTAKEN WHEREVER POSSIBLE? The reliance on extractions as part of orthodontic treatment has fluctuated over the decades. At the turn of the twentieth century, Edward Angle espoused non-extraction fixed appliance treatment with ‘arch development’ involving buccal expansion and incisor proclination.15 After initially following this philosophy, Tweed subsequently abandoned such an approach, on the basis that 80% of his recalls had poor facial aesthetics, occlusal instability and irreparable damage of the investing tissues of the teeth in the incisor and premolar regions.16 As a consequence, in the period between the early 1950s to the late 1970s, many orthodontic patients underwent premolar extraction in the expectation of enhanced post-treatment stability. Since then, there has been a widespread desire within the orthodontic community to curb the number of permanent teeth removed for orthodontic reasons; this tenet persists to the present day. Although there is short-term inconvenience and discomfort associated with dental extractions,17 the severity of associated pain has been shown to be less marked than that arising from the initial engagement of an orthodontic aligning wire.18 In addition, there is no proven risk to either the oral health and function or to the facial aesthetics of an individual who has had dental extractions as part of orthodontic treatment. Moreover, extractions are usually prescribed to relieve crowding in an
Fig. 1 In a growing patient this Class II molar relationship was corrected to Class I. Consequently, incisor and canine relationships were corrected allowing the overjet to be reduced
effort to minimise either transverse or antero-posterior arch length changes during treatment; it would therefore be counterintuitive to expect significant changes in the facial profile to arise with carefully planned treatment. At various times extractions have been implicated in causing (i) temporo-mandibular joint dysfunction (TMJD), purportedly stemming from posterior displacement of the mandible and displacement of the articular disc; (ii) premature ageing, related to the loss of lip support; and (iii) compromised smile aesthetics (Table 1). Careful systematic review of the available evidence has failed to support such views;19 moreover, there is now wide acceptance that extractions have the potential to improve both smile aesthetics and facial aesthetics with careful planning.20,21 While there is some evidence of enhanced stability with extraction approaches,22 in other research little difference between posttreatment incisor irregularity with extraction or non-extraction treatment has been reported.23,24 Reliable data on the merit of orthodontic extractions cannot be derived from retrospective research due to the inevitable confounding effects of contrasting space conditions, likely to have prompted the extraction decision before treatment. The ideal study to assess this controversial area would be a randomised controlled trial with prolonged follow-up. At present, ethical concerns preclude conducting a trial in this area. However, it is accepted that the decision to extract should be made on an individual basis accounting for space conditions, including
Fig. 2 Class II division 1 incisor relationship with Class II molar and canine relationships of the left side. Non-extraction treatment without active distal molar relationship to Class I would lead to an increased overjet at the end of treatment. Maxillary premolars were therefore removed and anchorage supported with temporary anchorage devices to facilitate overjet reduction and relief of crowding. The Class II molar relationships were preserved but both incisor and canine relationships corrected to Class I
Table 1 Adverse effects of orthodontics Orthodontics is not without adverse consequences. For example, overly rapid tooth movements or heavy forces (especially in adults) can lead to pulpal death but there is no convincing evidence that orthodontic movement results in TMJD or that carefully conducted treatment leads to adverse effects on the face such as ‘dishing-in’ or collapse of the lips.
crowding, overjet, torque requirements and facial aesthetics. Ideally, such decisions should be supported with formal space analysis.25
DOES COMPREHENSIVE ORTHODONTICS TAKE TWO TO THREE YEARS TO COMPLETE? Comprehensive orthodontic treatment encompasses an initial phase of alignment BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Table 2 Rapid tooth movement Rapid movement of the crowns of teeth is not new. It has certainly been around since the development of the round-wire Begg technique in the 1950s. With the introduction of shape-memory effect (nickel-titanium) wires in the 1970s it has been possible to align the crowns of very irregular anterior teeth within just a few weeks, even in adults. The problem is not the speed with which the crowns are aligned; it is the stability of the result, particularly as the roots of the teeth remain close to their original positions. Therefore, while orthodontic appliances can be removed prematurely once alignment has been achieved, it is recommended that torque expression and occlusal detailing is undertaken to enhance aesthetic and functional outcomes, enhancing the prospect of prolonged stability.
A
Table 3 Be wary of claims regarding novel treatment methods
B
There should be an index of suspicion surrounding novel methods including those concerning faster tooth movement, particularly when these claims are made by those with vested financial interests.36 Tooth movement relies on the remodelling or displacement of bone. Remodelling proceeds at a finite pace, which has an upper limit as does non-surgical displacement of bone. Distraction osteogenesis provides the most rapid physiological adjustment of bone position but as yet this is not a primary orthodontic technique.
typically in nickel-titanium wires, usually taking in the region of four to six months, followed by vertical, transverse and antero-posterior corrections, space closure and finishing and detailing (Table 2). The duration of orthodontic cases in both adolescence and adulthood is typically in the region of 15 months.26 Treatment involving extractions is usually slightly lengthier than non-extraction treatment.27 Combined orthodontic-surgical care is likely to result in an extension to treatment, although treatment times can be quite variable; similarly, treatment incorporating mechanical eruption of unerupted or ectopic teeth is usually quite prolonged.28,29
IS TREATMENT FASTER WITH MODERN BRACKETS? Orthodontic appliances have undergone considerable refinement over the last 30 years. The pre-adjusted edgewise appliance was introduced by Andrews in the 1970s,30 largely based on occlusal cornerstones derived from analysis of untreated ideals. 8 Pre-adjusted edgewise brackets were the first to be programmed to impart specific degrees of tip, torque, in-out and rotational control on each tooth thereby reducing the need for wire-bending. The most vaunted and positively marketed
C Fig. 3 Class I malocclusion with severe crowding and palatal displacement of both maxillary lateral incisors (Fig. 3a). Following alignment the lateral incisors have been brought into the correct position; however, there is inadequate labial root torque on the upper left lateral incisor (Figs 3b-c). Thick wires with high elastic modulus are required to address this. Torque delivery can be time consuming but is valuable in terms of prospective stability and dental aesthetics
A
B
C
D
development since the introduction of the pre-adjusted edgewise appliance have been self-ligating brackets (Table 3), which incorporate either a slide or clip mechanism to entrap the archwire, removing the need for elastomeric or stainless steel auxiliary ligatures. However, there is no evidence to suggest reduced treatment times with modern self-ligating bracket systems.31 While these brackets have demonstrated reduced frictional resistance to archwire sliding in laboratory studies, there is now a wealth of prospective clinical evidence indicating that this theoretical advantage does not translate into shorter treatment times. In particular, there have been three randomised trials comparing treatment duration with self-ligation and conventional brackets, none of which has demonstrated a time saving with the newer systems.32–35
BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
E Fig. 4 This Class I malocclusion with palatally-displaced lateral incisors was treated with fixed appliances (Figs 4a-b). Sufficient torque was delivered to the maxillary lateral incisors producing an acceptable aesthetic result following 15 months of treatment (Fig. 4c). Routine follow-up 18 months following removal of the appliances, the result has remained stable despite the lack of bonded retention (Figs 4d-e)
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PRACTICE
Fig. 5 Class I crowded case treated with customised lingual appliances over a seven-month period. The lack of uniformity of lingual surfaces mean that stock brackets may have poor adaptation to lingual surfaces making treatment more complex
IS TORQUE DELIVERY IMPORTANT? Torque can be defined as ‘rotation without translation’ or ‘preferential movement of the root with a stationary crown’. Torque is a product of force couples generated between bracket and wire; rectangular stainless steel wires with high elastic modulus and minimal play between wire and bracket slot are necessary for effective torque delivery (Fig. 3). Torque delivery is considered to be an integral part of orthodontic treatment; effective torque delivery is one of six recognised occlusal keys necessary to produce an ideal occlusal result.8 In addition, torque delivery is often important in the buccal segments as alleviation of crowding in round wires results in bucco-lingual inclination changes, which may compromise occlusal interdigitation, overbite and stability. In the anterior regions, appropriate torque contributes to dental aesthetics; the labial face of the maxillary central incisor should lie parallel to the facial vertical for optimal dental aesthetics, with greater requirement for palatal root torque in the presence of increased lower anterior facial height.37 In addition, torque expression is important in producing stable
outcomes, particularly where teeth were significantly displaced before treatment (Fig. 4).
ARE BETTER OUTCOMES ACHIEVED WITH MODERN BRACKETS? While novel techniques such as the use of temporary anchorage devices (TADs) have broadened the scope and enhanced the predictability of treatment (Table 4), there is no evidence to suggest that refinement of brackets has been accompanied by better outcomes. Prospective research comparing treatment times with self-ligating brackets have also alluded to comparable levels of occlusal improvement with these systems.32–35 Clearly, the quality of a course of orthodontics is contingent more on the standards and skills of the operator than on the bracket system used. Both labial and lingual customised appliances have been produced, with either brackets, wires or both tailored to the individual patient. Customised lingual appliances have become particularly popular due to the wide variation in the morphology of lingual surfaces, which complicates adaptation of stock brackets to these teeth and has a bearing on torque delivery (Fig. 5).
IS BONDED RETENTION A GUARANTEE OF STABILITY? The increasing emphasis on non-extraction treatment has brought the use of fixed retainers into sharper focus (Table 5). Bonded retention is not without problems: fixed lingual retainers may encourage plaque accumulation with potential periodontal implications.38 Consequently, their use may not be appropriate in the presence of poor oral hygiene. Failure rates with fixed retainers have been shown to be high.39 As such, ‘permanent’ retention does not remove the requirement that the teeth are placed in positions of soft tissue balance. Additionally, prediction of relapse on an individual basis has proven impossible, invoking the need for a long-term retention strategy for many patients. Furthermore, while bonded retainers may maintain rotational correction of teeth, they may be inadequate to resist soft tissue pressures, for example, those arising following correction of bimaxillary proclination. Consequently, inclination changes and tooth migration may arise despite intact retainers; augmentation of fixed retainers with BRITISH DENTAL JOURNAL VOLUME 218 NO. 3 FEB 16 2015
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PRACTICE Table 4 Some newer techniques are well proven and highly effective TADs have dramatically advanced the range and type of orthodontic tooth movements that are achievable. Where growth has slowed to adult levels, certain types of tooth movement that were once impossible can now be carried out routinely including intrusion of blocks of teeth to reduce a deep overbite or to intrude over-erupted molars, thereby correcting anterior open bites previously only correctable through a combined orthodontic-surgical approach, involving superior repositioning of the posterior maxilla with an osteotomy.
Table 5 Fixed retainers will not always hold poorly planned tooth positions If the dentition is moved beyond the zone of soft tissue balance, the standard methods of retention will not hold the new tooth positions for long. Even fixed retainers will allow relapse, the magnitude, nature and direction of which is unpredictable.
removable retainers may moderate this tendency. It has also been demonstrated that residual activity in bonded retainers may lead to dramatic inclination changes;40 prolonged supervision of retention is therefore advisable (Fig. 6).
IS INTER-PROXIMAL REDUCTION SAFE? There is long-term evidence indicating the safety of inter-proximal reduction.41 In this research no increased risk of either caries or periodontal problems ten years subsequent to the procedure was demonstrated. All inter-proximal reduction in the study was carried out by an internationally-renowned orthodontist; therefore, while the procedure may well be performed safely, it is important that it is undertaken with care and attention aiming to produce a smooth surface without inter-proximal ledges risking plaque accumulation and associated risk of periodontal compromise, sensitivity and caries progression (Fig. 7).
Fig. 6 Presentation of an orthodontic case ten years following removal of fixed appliances with rotation and axial inclination changes of terminal teeth on the retainer (22, 43). The changes may stem from residual activity in the bonded retainer wire
may improve alignment in the short term, it is important that treatment of this nature is carefully planned, restricted to amenable cases and suitably retained. 1.
2. 3. 4.
5.
6.
7.
CONCLUSION Traditional orthodontics involves a complex decision-making process not merely a binary decision of whether one form of treatment is appropriate or otherwise. The treating clinician is charged with choosing between an array of treatment options, appliances and auxiliaries based on a range of considerations including facial aesthetics, dental aesthetics, and intra- and inter-arch relationships. There is a wide diversity of presentations of malocclusion warranting tailored treatment planning and mechanics. Therefore, while short courses of orthodontics performed on a non-extraction basis
8. 9. 10. 11.
12. 13.
Richmond S, Andrews M, Roberts C T. The provision of orthodontic care in the general dental services of England and Wales: extraction patterns, treatment duration, appliance types and standards. Br J Orthod 1993; 20: 345–350. Maini A. Short-term cosmetic orthodontics for general dental practitioners. Br Dent J 2013; 214: 83–84. Dental Protection website. Available at: http://www. dentalprotection.org/uk/ (accessed 12 September 2013). McQuistan M R, Kuthy R A, Daminano P C, Ward M M. General dentists’ referrals of 3- to 5-year-old children to paediatric dentists. J Am Dent Assoc 2006; 137: 653–660. Lee J H, Bennett D E, Richards P S, Inglehart M R. Periodontal referral patterns of general dentists: lessons for dental education. J Dent Educ 2009; 73: 199–210. Aldawood S, Ampuan S N, Medara N, Thomson W M. Orthodontic treatment provision and referral preferences among New Zealand general dental practitioners. Aust Orthod J 2011; 27: 145–154. Angle E H. Treatment of malocclusion of the teeth, 7th ed. Philadelphia: White Dental Manufact Co, 1907. Andrews L F. The six keys to normal occlusion. Am J Orthod 1972; 62: 296–309. Pollard L E, Mamandras A H. Male postpubertal facial growth in Class II malocclusions. Am J Orthod Dentofacial Orthop 1995; 108: 62–68. Nanda R S, Meng H, Kapila S, Goorhuis J. Growth changes in the soft tissue facial profile. Angle Orthod 1990; 60: 177–190. Lapatki B G, Mager A S, Schulte-Moenting J, Jonas I E. The importance of the level of the lip line and resting lip pressure in Class I I, Division 2 malocclusion. J Dent Res 2002; 81: 323–328. Lambrechts H, De Baets E, Fieuws S, Willems G. Lip and tongue pressure in orthodontic patients. Eur J Orthod 2010; 32: 466–471. Chate R A C. Truth or consequences: the potential implications of short-term cosmetic orthodontics general dental practitioners. Br Dent J 2013; 215: 551–553.
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Fig. 7 This patient presented having commenced treatment with a general practitioner with a removable aligner system. The practitioner had undertaken liberal inter-proximal reduction of the lower anteriors to facilitate alignment, introducing unaesthethic morphological changes and ledges inter-proximally. The teeth were subsequently aligned with fixed appliances in less than six months 14. Chate R A C. Short-term orthodontics debate. Br Dent J 2014; 216: 388–389. 15. Angle E H. Treatment of malocclusion of the teeth and fractures of the maxillae, 6th ed. Philadelphia: SS White, 1900. 16. Tweed C H. Indications for the extraction of teeth in orthodontic procedure. Am J Orthod Oral Surg 1944; 30: 405–428. 17. Chaushu G, Becker A, Zeltser R, Vasker N, Branski S, Chaushu S. Patients’ perceptions of recovery after routine extraction of healthy premolars. Am J Orthod Dentofacial Orthop 2007; 131: 170–175. 18. Jones M, Chan C. The pain and discomfort experienced during orthodontic treatment: a randomized controlled clinical trial of two initial aligning arch wires. Am J Orthod Dentofacial Orthop 1992; 102: 373–381. 19. Luther F, Layton S, McDonald F. Orthodontics for treating temporomandibular joint (TMJ) disorders. Cochrane Database Syst Rev 2010; CD006541. 20. Parekh S, Fields H W, Beck F M, Rosenstiel S F. The acceptability of variations in smile arc and buccal corridor space. Orthod Craniofac Res 2007; 10: 15–21. 21. Hagler B L, Lupini J, Johnston L E Jr. Long-term comparison of extraction and nonextraction alternatives in matched samples of African American patients. Am J Orthod Dentofacial Orthop 1998; 114: 393–403. 22. Little R M, Riedel R A, Artun J. An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention. Am J Orthod 109
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PRACTICE Dentofacial Orthop 1988; 93: 423–428. 23. Luppanapornlarp S, Johnston L E Jr. The effects of premolar-extraction: a long-term comparison of outcomes in “clear-cut” extraction and nonextraction Class II patients. Angle Orthod 1993; 63: 257–272. 24. Paquette D E, Beattie J R, Johnston L E Jr. A longterm comparison of nonextraction and premolar extraction edgewise therapy in ‘borderline’ Class II patients. Am J Orthod Dentofacial Orthop 1992; 102: 1–14. 25. Kirschen RH, O’Higgins E A, Lee R T. The Royal London Space Planning: an integration of space analysis and treatment planning: Part I: Assessing the space required to meet treatment objectives. Am J Orthod Dentofacial Orthop 2000; 118: 448–455. 26. Hamilton R, Goonewardene M S, Murray K. Comparison of active self-ligating brackets and conventional pre-adjusted brackets. Aust Orthod J 2008; 24: 102–109. 27. Mavreas D, Athanasiou A E. Factors affecting the duration of orthodontic treatment: a systematic review. Eur J Orthod 2008; 30: 386–395. 28. O’Brien K, Wright J, Conboy F et al. Prospective, multi-centre study of the effectiveness of orthodontic/orthognathic surgery care in the United Kingdom. Am J Orthod Dentofacial Orthop 2009; 135: 709–714.
29. Fleming P S, Scott P, Heidari N, Dibiase A T. Influence of radiographic position of ectopic canines on the duration of orthodontic treatment. Angle Orthod 2009; 79: 442–446. 30. Andrews L F. The straight-wire appliance. Explained and compared. J Clin Orthod 1976; 10: 174–195. 31. Fleming P S, Johal A. Self-ligating brackets in orthodontics: a systematic review. Angle Orthod 2010; 80: 575–584. 32. Fleming P S, DiBiase A T, Lee R T. Randomized clinical trial of orthodontic treatment efficiency with self-ligating and conventional fixed orthodontic appliances. Am J Orthod Dentofacial Orthop 2010; 137: 738–742. 33. Di Biase A T, Nasr I H, Scott P, Cobourne M T. Duration of treatment and occlusal outcome using Damon3 self-ligated and conventional orthodontic bracket systems in extraction patients: a prospective randomized clinical trial. Am J Orthod Dentofacial Orthop 2011; 139: e111–e116. 34. Johannson K, Lundstrom F. Orthodontic treatment efficiency with self-ligating and conventional edgewise twin brackets. A prospective randomized clinical trial. Angle Orthod 2012; 82: 929–934. 35. Songra G, Clover M, Atack N E et al. Comparative assessment of alignment efficiency and space closure of active and passive self-ligating vs
36. 37.
38.
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conventional appliances in adolescents: a singlecentre randomized controlled trial. Am J Orthod Dentofacial Orthop 2014; 145: 569–578. O’Brien K, Sandler J. In the land of no evidence, is the salesman king? Am J Orthod Dentofacial Orthop 2010; 138: 247–249. Ross V A, Isaacson R J, Germane N, Rubenstein L K. Influence of vertical growth pattern on faciolingual inclinations and treatment mechanics. Am J Orthod Dentofacial Orthop 1990; 98: 422–429. Pandis N, Vlahopoulos K, Madianos P, Eliades T. Long-term periodontal status of patients with mandibular lingual fixed retention. Eur J Orthod 2007; 29: 471–476. Booth F A, Edelman J M, Proffit W R. Twenty-year follow-up of patients with permanently bonded mandibular canine-to-canine retainers. Am J Orthod Dentofacial Orthop 2008; 133: 70–76. Renkema A M, Renkema A, Bronkhorst E, Katsaros C. Long-term effectiveness of canine-to-canine bonded flexible spiral wire lingual retainers. Am J Orthod Dentofacial Orthop 2011; 139: 614–634. Zachrisson B U, Nyøygaard L, Mobarak K. Dental health assessed more than 10 years after interproximal enamel reduction of mandibular anterior teeth. Am J Orthod Dentofacial Orthop 2007; 131: 162–169.
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