Sanjivan Kandasamy

Myths of orthodontic gnathology

D r Beverly McCollum established the Gnathologic Society in 1926. Gnathology is defined as ‘‘the science that treats the biology of the masticatory mechanism as a whole: that is, the morphology, anatomy, histology, physiology, and the therapeutics of the jaws or masticatory system and the teeth as they relate to the health of the whole body, including applicable diagnostic, therapeutic, and rehabilitation procedures.’’ Many gnathologic research endeavors have added much to our knowledge and understanding of the stomatognathic system, particularly those involving chewing (masticatory) kinematics and the early intraoral telemetry studies (to cite only a few). Although originally founded on scientific principles, the application of the valid gnathologic research to clinical practice has moved away from these founding tenets. Modern clinical gnathology (vs university-based gnathologic research) has become, for the most part, a pseudo-science based on mechanistic, perfunctory procedures, and instrumentation. There are many contemporary occlusal institutes that clearly have perverse views on gnathology that are not evidence-based. Dr Lysle Johnston sarcastically stated that ‘‘gnathology is the science of how articulators chew.’’ In the 1970s, Roth formally introduced the classic principles of clinical gnathology to orthodontics (orthodontic gnathology). The notions and considerations of modern orthodontic gnathology are not based on principles of science and do not correspond to contemporary evidence-based thinking. There might not be a unified orthodontic gnathologic view, but it seems that the one established by Roth is by far the most notable.

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.

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.

Orthodontic dental casts: The case against routine articulator mounting

A There is no doubt that dental casts, whether plaster or digital, are one of many important tools routinely used in orthodontics for assessing dentitions or malocclusions. Unfortunately, to this day, a convincing case has still not been made for the routine mounting of all casts on articulators. Drs Martin and Cocconi, however, would like you to believe otherwise. The issue of articulator mountings in orthodontics must be considered within the broad framework of orthodontic gnathology. Under the premise of pursuing “what is best for the patient,” Drs Martin and Cocconi have conveniently left out the term “gnathology” in their “Point” article; however, the principles of gnathology (right or wrong) form the basis of their argument for using articulators. We have written and expressed the evidencebased view on gnathology and articulator mounting in orthodontics several times and advise the reader to review relevant literature for a more thorough understanding on this topic. Drs Martin and Cocconi make many unsupported claims in their article. Statements such as the articulator “is just another tool . . .” an orthodontist can do good orthodontics without using an articulator, but an articulator can help him or her to provide better treatment in many clinical situations,” and “whether research is always good for clinical practice” fly in the face of evidence-based practice and the basic tenets of science. With comments like these, are they really putting forward an intellectual and scientific discussion on the use of articulators in orthodontics?

Evaluation and management of asymptomatic third molars: Watchful monitoring is a low-risk alternative to extraction

A lthough indications for the removal of symptomatic third molars are well established, a convincing case for the routine removal of unerupted asymptomatic, pathology-free third molars has not been made. Unlike the claims of Drs White and Proffit, the evidence-based literature points toward the watchful monitoring of asymptomatic third molars when there is no pathology. Despite the various guidelines, reviews, and risks associated with these extractions, many clinicians continue to routinely remove pathology-free third molars. Until recently, this practice has been predicated on reducing the risks of mandibular incisor crowding and other complications developing in the future. From an orthodontic standpoint, third molars have essentially nothing to do with mandibular incisor crowding. Late incisor crowding is multifactorial, and factors other than third molars play important roles. The removal of thirdmolars on the sole basis of preventingmandibular incisor crowding is unsubstantiated and unjustified. Furthermore, the low incidence (1%-2%) of complications developing from impacted third molars, such as odontogenic tumors, cysts, andmandibular angle fractures, also cannot be invoked to justify the removal of unerupted and asymptomatic third molars on the ground that at some point in the future these teeth will develop related pathology. According to Drs White and Proffit, there are 3 key criteria for the extraction of asymptomatic third molars: periodontal disease, age, and informed consent. Let us discuss them individually as they relate to the evidence. PERIODONTAL DISEASE

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 Associations 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.

TMD and Its Medicolegal Considerations in Contemporary Orthodontic Practice

The diagnosis and management of patients exhibiting temporomandibular disorders (TMD) in the orthodontic setting is fraught with great debate, confusion, diverse opinions, and philosophies. Because TMD has a multifactorial etiology and is layered in nature, it currently is viewed as reflecting more of a medical and psychosocial model regarding its diagnosis and subsequent management. As such, it is critical that orthodontists understand their limitations, the need for adequate training in this continually evolving area, and the need for thorough and well-documented records [1, 2].

Temporomandibular disorder and gnathologic splints

We would like to comment on the case report by Dr Ichiro Takahashi in the June 2008 issue (Takahashi I. Surgical-orthodontic treatment of a patient with temporomandibular disorder stabilized with a gnathologic splint. Am J Orthod Dentofacial Orthop 2008;133:909-19). From the comparison of the before and after treatment records, this case appears to be successfully treated and well documented. However, apparent (or perceived) success of treatment does not necessarily equate to correctness of treatment, and it appears that many of Dr Takahashi’s clinical procedures (and justifications for their use) do not to agree with the modern evidencebased model of care for patients with temporomandibular disorders (TMD). The written tone of the article also seemed to indicate that the author presented this case as an example of the standard by which similar patients should be treated. The patient, a 21-year-old woman diagnosed with chronic TMD (disc displacement), was treated with a combination of gnathologic splints, orthodontic treatment with 4 premolar extractions, and orthognathic surgery. A gnathologic splint was used for 35 months before treatment to stabilize the condyles. The patient then had 27.5 months of comprehensive orthodontic treatment involving a mandibular orthognathic procedure (she wore a gnathologic splint over the brackets for 17 months). She also wore a positioner for 5 months after the orthodontic treatment. Total active treatment time was 63 months (5 years). Dr Takahashi stated, “The first step of TMD treatment should be to stabilize the condylar position.” However, we argue that the first step in TMD management (after preliminary diagnosis) is to control pain (this patient’s chief complaint) in the most conservative and least invasive way. In addition, the author concluded that the main goal in the TMD management of this patient was again to stabilize the condyles. This was supposedly determined after the condylar position indicator (CPI, Panadent articulator) showed “a small amount of condylar distraction.” McNeil et al summarized the goals of TMD management: reduce pain, restore normal jaw function, reduce the need for future care, and restore normal lifestyle functioning. Interestingly, there seems to be no good evidence that centric slides cause TMD (there is evidence of an association between these variables). Next, Dr Takahashi indicated that CPI is a reliable and valid method to track condylar stability. Lavine et al found large enough standard deviations in all planes relative to the actual measurements to seriously question the reliability of CPI articulator recordings. Furthermore, Leever wrote, “The CPI instrumentation has no quantifiable correlation with any

Management of TMD Signs and Symptoms in the Orthodontic Practice

Like all other dentists, orthodontists are likely to encounter some patients with TMD signs and symptoms in their practices that require some form of professional treatment. These patients may come into their office as referrals from other dentists, or they may develop TMD problems while under the orthodontist’s care. While some benign TMD signs and symptoms may be present in new patients, or may arise in patients under treatment, not all of these need to be treated (see Chap. 3). However, as discussed in Chap. 2, there are a number of significant TMD conditions that need to be properly diagnosed and appropriately treated.

Orthodontics and TMD

In 1987, a landmark court case entitled Brimm versus Malloy [1] in the USA prompted an in-depth examination on the issue of whether or not orthodontic treatment causes temporomandibular disorders (TMDs). The Brimm case resulted in a million-dollar judgment against a Michigan orthodontist for allegedly causing TMD in a 16-year-old girl. The orthodontic treatment involved the extraction of two maxillary first premolar teeth and the use of a headgear to address the patient’s Class II Division I malocclusion. The TMD symptoms experienced by the plaintiff were temporomandibular joint pain and headaches following the removal of the appliances. The argument regarding the cause of these TMD symptoms was that the orthodontic treatment carried out resulted in the overretraction of the upper incisors, leading to the distal displacement of the mandible, and thereby causing temporomandibular joint (TMJ) internal derangements. Regardless of the lack of scientific evidence behind such an argument, the jury awarded the plaintiff US