Journal of Craniomandibular Function, 03/2018

Aims: To explore whether awake bruxism (AB) and sleep bruxism (SB) interact in their associations with painful temporomandibular disorders (TMD) and whether the interaction is multiplicative or additive. Methods: In this case-control study, all participants (n = 705) were part of the multicenter Validation Project and were recruited as a convenience sample of community cases and controls as well as clinic cases. Logistic regression analyses were applied to test for the association between self-reported bruxism (AB and/or SB) and the presence of painful TMD. Odds ratios (ORs) with 95% confidence intervals (CIs) were computed. Regression models included an interaction term to test for multiplicative interaction. Additive interaction was calculated as the relative excess risk due to interaction (RERI). Results: Based on logistic regression analyses adjusted for age and gender, the main effects for both AB (OR = 6.7; 95% CI: 3.4 to 12.9) and SB (OR = 5.1; 95% CI: 3.1 to 8.3) were significant. While the multiplicative interaction (OR = 0.57; 95% CI: 0.24 to 1.4) was not significant, the results indicated a significant positive additive interaction (RERI = 8.6; 95% CI: 1.0 to 19.7) on the OR scale. Conclusion: This study has demonstrated that AB and SB are associated with an increased presence of painful TMD, and that both types of bruxism are not independently associated, but interact additively. As such, the presence of each factor amplifies the effect of the other. Keywords: awake bruxism (AB), interaction effect, pain, sleep bruxism (SB), temporomandibular disorders (TMD)

Background: Awake bruxism (AB) is a condition that possibly mirrors some psychological disorders and can lead to several dental and medical consequences. While the frequency of AB could be described based on the so-called ecological momentary assessment (EMA) methodology, which enables real-time reporting of the condition under study (eg, tooth contact, tooth grinding, jaw clenching), the transfer process of this approach from the research to the clinical setting has not yet been performed. Methods: An EMA for AB based on a smartphone application (app) has the potential to be an interesting strategy for introducing the advantages of EMA for bruxism evaluation. This article describes a new app that is dedicated to EMA/AB evaluation, and which may be useful as a cognitive-behavioral strategy for AB management. Results: The app has been used preliminarily to show about a 28% frequency of AB behaviors in a sample of healthy young adults over a 7-day recording period. Conclusions: The use of smartphone technology may introduce several benefits in the field of EMA-based bruxism research and clinical practice, helping to set values of normal frequency. Such data could be compared to populations with risk-associated factors, with possible clinical consequences. Keywords: awake bruxism, ecological momentary assessment, smartphone, bruxism

In dental functional analysis and therapy, the concept of centric occlusion/centric relation has been an issue - and partly a myth - for almost a century. Numerous attempts have been, and are still being, made to define the 'correct' or 'ideal' spatial classification of the jaw in static occlusion. However, the results to date are unsatisfactory. What could be the reasons for this? A logical and semantic analysis of three of the key definitions of centric reveals that all the approaches to date have been bound to fail. What is being referred to - the reference object (the 'ideal' maxillomandibular relation) - either cannot be identified or the definition is contrary to fundamental dentistry principles. There can never be an 'ideal' jaw relation, but only a set of physiologically equivalent jaw relations. For this reason, in the author's opinion, we should cease using the term centric in dental discussions. Keywords: centric, centric relation, centric condylar position, physiological centric, extension, reference object, linguistic analysis

The aim of this study was to analyze the effect of occlusal modifications on the muscular activity of the masseter and anterior temporalis muscles. The study included 41 healthy dentate subjects who were examined in relation to the muscle activity of the masseter and anterior temporalis muscles recorded by surface electromyography (EMG) bilaterally in two different sessions. Occlusal plastic strips (thickness: 0.4 or 0.8 mm) were placed on different mandibular teeth to simulate different bite constellations (unilateral, bilateral transversal, and bilateral diagonal). Controlled by visual feedback, the subjects performed submaximum occlusion at 10% and 35% of maximum voluntary contraction (MVC). The activity ratios of the muscles were analyzed by two-way repeated measurement analysis of variance (ANOVA), and the reliability of muscle activity data was determined by intraclass correlation coefficient (ICC) analysis. The activity ratios of the masseter muscles were not significantly different under various biting conditions. In contrast, the anterior temporalis muscles showed significant differences (P 0.001) between unilateral configurations and the other biting conditions (bilateral transversal or diagonal), in particular during biting at 10% MVC. In general, ICC values revealed low to moderate reliability of the measurements of muscle activity. Under controlled submaximum occlusal loading, the activity behavior of the masseter muscles remained stable, whereas the anterior temporalis muscles reacted differently to distinct occlusal biting configurations. The results support the assumption that the anterior temporalis muscles might operate as fine-tuning muscles when asymmetric bite force distributions occur, for instance during chewing, caused by food fragments between the teeth. Keywords: activity ratio, clenching, electromyography (EMG), masticatory muscles, occlusal interference, occlusal modification, visual feedback

As the evidence base for functional diagnostics expands with continuous research and development, this area of dentistry is becoming more and more integrated and interwoven with other medical fields such as psychosomatics and orthopedics. By now, many scientific studies exist in which tests have demonstrated associations between potential co-factors from these medical specialties and temporomandibular dysfunction (TMD). Even after the reform in 2012 of the German Dental Fee Schedule (GOZ), there is almost no change in the list of functional diagnostic services included in the new GOZ compared to the previous version of 1988. While the German Dentistry Act obligates dentists to practice dentistry in Germany according to the current state of scientific knowledge, it is impossible for dentists to do so if they are limited solely to the services included in the outdated contents of the official GOZ. However, German legislators deliberately drafted the new GOZ so as to include provisions for dentists to charge fees for separate services not included in its catalog of services, according to the type, cost, time requirement, and degree of difficulty of comparable services ('analogous billing procedure'). This article explains the legal framework and professional background for the implementation of this practice as well as the consequences thereof based on the example of tests to identify psychological co-factors that contribute to functional disorders of the temporomandibular system. Keywords: temporomandibular disorder (TMD), tests for the identification of psychological co-factors, clinical functional analysis, German Dental Fee Schedule (GOZ), analogous billing procedure,