The evolution of temporomandibular disorders: A shift from experience to evidence.

After over 80 years of much obsession as well as avoidance of the subject of temporomandibular disorders (TMDs), the dental profession is still divided over what they are and how to deal with them. Over this period, nearly every discipline in dentistry has played some role in the development of this field. Unfortunately, a significant amount of this information has been based on personal opinion, experience-based philosophies, or poorly conducted research. Furthermore, each dental specialty has been responsible for contributing to the concepts of the etiology and management of TMDs with their own professional bias; for example, orthodontists describe these problems in orthodontic terms and offer orthodontic treatments or solutions for their patients. As various treatment approaches were found to be effective at least some of the time, this has further led to misinformation and confusion within the profession. Advances in research from diverse fields, including neurophysiology, pain pathophysiology, genetics, endocrinology, behavioral sciences, and psychology, have significantly altered our understanding of TMDs and how they should be managed. The rigid mechanical and dental-based model of the past has been gradually replaced by a biopsychosocial medical model for the diagnosis and treatment of TMDs as well as other acute and chronic pain disorders. This paper discusses the evolution of our understanding of TMDs since they were first described 85 years ago. Contemporary scientific findings and their implications are presented in some detail for clinicians who wish to provide the appropriate management for their orofacial pain patients.

Condylar position assessed by magnetic resonance imaging after various bite position registrations.

INTRODUCTION: In this study, we evaluated the reliability and validity of 3 bite registrations in relation to condylar position in the glenoid fossae using magnetic resonance imaging in a symptom-free population. METHODS: Nineteen subjects, 14 men and 5 women (ages, 20-39 years) without temporomandibular disorders were examined. Three bite registrations were taken and evaluated on each subject: centric occlusion, centric relation, and Roth power centric relation. The differences in condyle position among the 3 bite registrations were determined for the left and right condyles: centric occlusion-centric relation, centric occlusion-Roth power centric relation, and centric relation-Roth power centric relation for each plane of space. RESULTS: The results indicated that (1) all measurements collected had large standard deviations and ranges with no statistical significance, and (2) of the 19 subjects and 38 condyles assessed, 33 condyles (87%) were concentric in an anteroposterior plane. In the transverse anatomic plane, all condyles were concentric. CONCLUSIONS: The clinical concept of positioning the condyles in specific positions in the fossae with various bite registrations as a preventive measure for temporomandibular disorders and as a diagnosis and treatment planning tool is not supported by this study.

Orthodontics and temporomandibular disorders: a curriculum proposal for postgraduate programs.

In a previous article, we reported the results of a survey of American and Canadian orthodontic postgraduate programs to determine how the topics of occlusion, temporomandibular joint, and temporomandibular disorders were currently being taught. Based on the finding of considerable diversity among those programs, we decided to write a curriculum proposal for temporomandibular disorders that would be compatible with and satisfy the current curriculum guidelines for postgraduate orthodontic programs. These guidelines arose from a combination of the requirements published by the American Dental Association's Commission on Dental Accreditation and the written guide (July 2010) of the American Board of Orthodontics for the its clinical examination. The proposed curriculum, based on the latest scientific evidence in the temporomandibular disorder field, gives program directors a template for covering these subjects thoroughly. At the same time, they can focus on related orthodontic issues, so that their future graduates will be prepared to deal with patients who either have or later develop temporomandibular disorder problems.

Survey of orthodontic residency programs: teaching about occlusion, temporomandibular joints, and temporomandibular disorders in postgraduate curricula.

INTRODUCTION: Teaching orthodontic postgraduate students about occlusion and the temporomandibular joint is a fundamental component of their education, but faculty members are confronted with disputes and controversies about these topics. The purpose of this study was to ascertain where the orthodontic teaching community currently stands on the topics of occlusion, temporomandibular joint, and temporomandibular disorder. METHODS: A 46-question survey was sent to every orthodontic program director in the United States and Canada (n = 69). Responses were submitted by 46, and the results were tabulated. RESULTS: Three interrelated topics (normal or ideal temporomandibular joint, normal or ideal occlusion, and management of temporomandibular disorder) are being taught in diverse ways in these postgraduate orthodontic programs. CONCLUSIONS: The results of this survey will help us to understand and improve how these topics are being taught at accredited orthodontic programs in the United States and Canada. Perhaps a standardized curriculum can be developed.

Implications of the inclination of the mandibular first molars in the extractionist versus expansionist debate.

Some orthodontic expansionists (versus extractionists) hold a notion that in the decision to treat nonextraction, expansion treatment can be predicated and dictated based on the degree of facial-lingual inclination of the mandibular molars (particularly the mandibular first molars). For instance, some modern-day expansionists argue that mandibular first molars with a facial crown lingual inclination of approximately -30 degrees (based on Andrews' measurement) indicate that the mandibular arch, and subsequently the maxillary arch, needs to be developed or expanded to allow for more arch and tongue space. However, this thinking is based on a false premise; the mandibular first molars are normally lingually inclined approximately -30 degrees and not naturally found in an upright facial-lingual position of approximately -12 degrees.

Deconstructing evidence in orthodontics: making sense of systematic reviews, randomized clinical trials, and meta-analyses.

Much has been written in support of systematic reviews and the randomized clinical trials and meta-analyses upon which they are based. Clearly, the medical profession (as opposed to the dental profession) has been the leader in publishing the benefits of systematic reviews over the traditional, qualitative narrative reviews. At the same time, the medical profession also appears to be ahead of the dental profession in recognizing the limitations of such reviews. That said, there are a number of inherent problems with systematic reviews, as well as the randomized clinical trials and meta-analyses that back them up. To better facilitate evidence-based decision making, this article discusses the shortcomings of systematic reviews so that practitioners are fully aware of their drawbacks, as well as their benefits.

An evidence-based evaluation of the concept of centric relation in the 21st century.

The concept and application of a temporomandibular joint (TMJ) relationship identified as centric relation (CR) has changed significantly over the past century. Originally proposed as a biologically reasonable position where maxillary and mandibular dentures should occlude, it later was applied to the dentate population as well. The term "ideal" was used by the gnathologic dental community as they sought to define the exact details of CR in terms of condyle-fossa relationships. Assessments of patients' occlusion were then made in relation to CR, and discrepancies between the two positions were described as being problematic. Since not all dentists have accepted this concept, the clinical application of CR has become a topic of major dental confusion and controversy. To further complicate things, the formal definitions of CR have continuously changed over the past 40 years. In this paper, the biologic development of occlusal and TMJ relationships is reviewed, followed by a discussion about the validity of applying CR concepts and procedures in contemporary clinical and research settings. Special attention is devoted to the alleged relationships between occlusion, jaw positions, and temporomandibular disorders (TMDs). Current evidence suggests that it is time to stop applying CR concepts to the evaluation and dental treatment of healthy dentate individuals. For patients with TMDs, it is time to apply current concepts of biopsychosocial assessment and management rather than following the 20th century mechanistic models of fixing dental and skeletal malalignments.

Changes in interdental papillae heights following alignment of anterior teeth.

BACKGROUND: Orthodontic alignment of overlapped incisors can reduce the apparent heights of the interdental papillae leading to unsightly dark triangles or open gingival embrasures. AIM: To determine if certain pretreatment contact point relationships between the maxillary anterior teeth were accompanied by changes in the heights of the interdental papillae after orthodontic alignment. METHODS: Pre- and post-treatment intra-oral 35 mm slides, lateral cephalometric radiographs and study casts of 143 patients (60 males, 83 females) between 13 and 16 years of age were used. The patients had diastamata closed, imbricated teeth aligned and palatally or labially placed teeth repositioned. A sample of 25 patients (12 males, 13 females) between 13 and 16 years of age who had well-aligned anterior teeth at the start of treatment acted as a control group. All patients were treated for approximately 18 months. The clinical crowns of the maxillary incisors and the heights of the interdental papilla between the incisors were measured on projected images of the slides. The percentage increases or reductions in the heights of the interdental papillae were compared. RESULTS: The heights of the interdental papillae increased following palatal movement of labially placed (p < 0.05) or imbricated (p < 0.05) incisors and the intrusion of one incisor relative to an adjacent incisor (p < 0.01). The heights of the interdental papillae reduced following labial movement of an imbricated (p < 0.05) or palatally placed (p < 0.05) incisor or closure of a diastema (p < 0.01). Before treatment the midline papillae in the diastema subgroup were of similar length to the midline papillae in the control group, but after treatment they were markedly shorter. The interdental papillae associated with crowded or imbricated incisors were shorter than the interdental papillae in the control group before and after treatment. CONCLUSIONS: Dark triangles are less likely to develop following palatal movement of labially placed or imbricated teeth and the intrusion of one tooth relative to another. On the other hand, dark triangles are more likely to develop following labial movement of imbricated or palatally placed incisors and closure of a diastema. Clinicians should be alert to the possibility of dark triangles developing in the latter group, particularly in older patients.

Centric relation: A historical and contemporary orthodontic perspective.

BACKGROUND: Centric relation (CR) has been a controversial subject in dentistry for more than a century. For at least the past four decades, issues involving CR have been of interest to orthodontists. The definition of CR has changed over the past half-century from a retruded, posterior and, for the most part, superior condyle position to an anterior-superior condyle position. TYPE OF STUDIES REVIEWED: The authors addressed the historical and contemporary orthodontic perspective of CR. The source material for this review came mainly from literature and searches the lead author accumulated over the last 30 years. As there is no evidence-based (EB) model level 3 (systemic) review on the topic of CR, the best evidence on this subject was gleaned only from a thorough examination and evaluation at EB model level 2 (experience plus best available sample studies). There was, however, enough high-quality EB model level 2 information on the topic of CR for the authors to draw conclusions on the basis of a scientific appraisal of relevant research. RESULTS: Although the reliability of CR records has been substantiated, the records' validity has little to no evidentiary support. In addition, population-based sample studies and consensus statements from national conferences support the view that the positions of the temporomandibular joint (TMJ) condyles in relation to the glenoid fossa or CR position are not diagnostic of temporomandiblar disorders. There appears to be little to no benefit of using gnathologic records and articulator-mounted dental casts to discern discrepancies in maximum intercuspation of the teeth coincident with TMJ condyles in an anterior-superior CR position in orthodontic patients. CLINICAL IMPLICATIONS: The benefit of using gnathologic CR records and articulators in orthodontics has not been substantiated by scientific evidence.