Journal of Craniomandibular Function, 01/2015

Over the past decade, Bart Craane has been working on his PhD thesis on the subject of temporomandibular disorders (TMDs) and the efficacy of physical therapy (PT) in its management. The thesis was successfully defended in the fall of 2012. The present article aims to provide an overview of the studies included in the PhD project and the results obtained, since they are of importance in the care of TMD patients. The article is a compilation of the results obtained in studies composing the thesis; some of the text and figures are adapted and translated from the thesis, while other parts have been published elsewhere (see References).

Temporomandibular disorder (TMD) is the collective term for a number of functional disorders of the head and neck region. The main symptoms of TMD are pain and dysfunction of the muscles of mastication and/or temporomandibular joints (TMJs). The etiology of TMD is now believed to be multifactorial due to the heterogeneity of TMDs. The dental occlusion is suspected to be an etiologic factor. Originally described as playing a role ranging from a primary causative factor to a cofactor, it is now considered to play a rather insignificant part in the development of dysfunction in the temporomandibular system. Aim: To investigate the relationship between occlusal parameters and the signs and symptoms of TMDs in population- based subjects. General occlusion-related variables as well as static and dynamic contact relationships in the posterior region were analyzed for this purpose. Materials and methods: Five hundred and fifty eight subjects aged 20 to 49 years with at least 20 remaining teeth were evaluated for contact relationships between the dental arches in static and dynamic occlusion and for malocclusion (project affiliated with the Study of Health in Pomerania baseline study, SHIP0). Clinical TMJ function analysis was also performed on each subject. Bivariate relationships were examined using the chi-square test, correlation analysis, and multivariate models. Results: Of all the subjects, 5.7% had pure anterior canine guidance and 4.2% had hyperbalancing occlusal contact. Occlusal guidance patterns were not associated with TMD signs and symptoms. Likewise, no occlusal parameter was associated with signs and symptoms of TMDs (self-reported pain). Patients with no occlusal contact or only unilateral occlusal contact in the posterior region (3.6%) showed a tendency for a higher rate of tenderness of the TMJ (P = 0.055). Those with an inverted maxillary central incisor exhibited a significantly higher rate of TMJ tenderness (P = 0.02) and a tendency for a higher rate of tenderness of the masticatory muscles (P = 0.065). The following associations were found for tenderness of the TMJ (results adjusted for age, sex, and marital status; significance level P = 0.05): vertical bite/Angle Class II/2 malocclusion (cover bite): odds ratio (OR) = 2.3 (1.4-3.8); no occlusal contact or only unilateral occlusal contact in the posterior region: OR = 3.9 (1.3-11.3); bruxism: OR = 1.6 (0.9-2.7). Reciprocal clicking of the TMJ (TMJ sounds) was significantly associated with a loss of posterior support (right side: P = 0.021; left side: P = 0.041). These associations were no longer significant in the multivariate analysis of the longitudinal data. Conclusions: Subjects with a loss of posterior support due to missing teeth or the absence of occlusal contact in maximum intercuspation had a higher incidence of TMJ sounds and tenderness. Angle Class II/2 malocclusion (cover bite) in the maxillary anterior region was associated with tenderness on palpation of the TMJ and masticatory muscles. Except for cover bite, there was a low prevalence of all occlusal parameters with significant associations with TMD signs and symptoms. Although cross-sectional data analysis revealed associations between TMD and occlusal factors, causality of these relationships cannot be assumed. Keywords: etiology, occlusion, temporomandibular disorder (TMD)

The collection of patient-specific data needed for the programming of dental articulators is a classic application of axiography. This information is essential for the simulation of mandibular movements during tooth-guided border movements in the dental laboratory. The use of a valid and reliable electronic axiography system allows the dental laboratory technician to develop an interference-free occlusal design that has high-quality functional occlusal contacts with antagonist teeth. In addition, the articulator geometry can be correlated to the patient's skull in order to optimize the measurement process. In modern oral rehabilitation it is advisable to use an electronic axiography system for articulator programming of the individual patient. Keywords: articulator, axiography, prosthodontics

In previous clinical practice, findings of tooth damage and pain associated with temporomandibular disorders (TMDs) were the primary indications to search for further signs of bruxism. Today, however, it appears more prudent to perform a prospective evaluation (ie, screening) of patients for current bruxism activity before the start of treatment, for a number of reasons. First, if the screening test is positive, early preventive or curative measures (such as splint therapy or restoration of anterior canine guidance) can be planned, signs and symptoms of TMDs detected, and high-risk treatment options excluded from the outset. Second, a positive screening result gives the dentist an opportunity to educate bruxism patients about their individual risks at an early stage and include them in treatment planning. Finally, bruxism may be associated with obstructive sleep apnea, the treatment of which can contribute greatly to improving the quality of life and general health of the patient. Keywords: wake bruxism, sleep bruxism, screening bruxism, diagnosis