Manas Dave reflects on topics in our sister journal Evidence-Based Dentistry.

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Is bruxism associated with tempromandiubular joint disorders? A systematic review and meta-analysis was published in Evidence-Based Dentistry in 2023.1

Background

Temporomandibular disorders (TMD) is a collective term for a group of musculoskeletal conditions that cause pain and/or dysfunction in the TMJ and/or its associated structures. TMD is the most common type of non-odontogenic orofacial pain2 affecting 22-30% of the population, commonly between the ages of 20-40 years.1 The aetiology of TMD is considered multifactorial, related to biological, psychological, social and environmental factors. Bruxism is defined as repetitive jaw-muscle activity characterised by clenching or grinding of the teeth and/or bracing or thrusting of the mandible with two distinct circadian manifestations; either occurring during sleep (sleep bruxism) or during wakefulness (awake bruxism).3

Clinicians should actively check clinical signs and enquire about bruxism in their patients to ensure steps for mitigation can be introduced early to reduce the risk of developing TMD.

Some studies show a positive correlation between bruxism and TMD however others have reported conflicting results. Therefore, the aim of this systematic review was to investigate the relationship between bruxism and TMD.

Methods

An electronic database search of PubMed, Web of Science, Scopus, Cochrane, Wiley, ProQuest and Embase was conducted for studies until March 2022. Additionally, the grey literature was searched (Google Scholar and Open Grey). Only studies in English that were cross-sectional, case control and cohort (prospective and retrospective) that evaluated the association between bruxism and TMD were included. Risk of bias was assessed using the Newcastle-Ottawa Scale and odds ratio (OR) extracted to quantify the risk of TMD. For studies where an OR was not calculated, the index was calculated based on the data provided in the primary studies.

Results

  • Twenty studies were included (11 cross-sectional and nine case-control) that had been conducted in Europe, North America, South America and Asia

  • In 18 studies, TMD was determined by the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) whilst two studies used the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). A self-reported method was used in 15 studies and a clinical evaluation used in five studies

  • Any type of bruxism was found to be a risk factor for TMD (OR = 2.42, 95% CI: 2.01-2.82)

  • There was a significant association between sleep bruxism and TMD (OR = 2.12, 95% CI: 1.81-2.43). The results indicate a higher probability (OR = 2.72) of TMD patients for patients with awake bruxism compared to without sleep bruxism

  • A publication bias (using Begg's test and Egger's test) was indicated in this meta-analysis.

Conclusions

The authors concluded:

‘…bruxism is positively related to TMDs; the presence of bruxism increases the risk of developing TMDs in the future…'

Commentary

This systematic review and meta-analysis confirmed the authors' pre-study questions; that is, to determine if bruxism is positively associated with TMD. The authors have shown this association in both cohort and case-control studies with awake bruxism associated with a higher probability of TMD compared to sleep bruxism. Clinicians should actively check clinical signs and enquire about bruxism in their patients to ensure steps for mitigation can be introduced early to reduce the risk of developing TMD.