Occlusal interventions for managing temporomandibular disorders

Background: Temporomandibular disorders (TMD) are conditions related to the musculoskeletal structure of the temporomandibular joint, which may lead to muscle or joint pain and other health issues. TMD may present in muscles only (myogenous), joints only (arthrogenous), or both (mixed), and may affect one side or both sides of the face. Myogenous TMD may present with or without limited mouth opening. Arthrogenous TMD may present as disc displacement with or without reduction ('reduction' meaning the articular disc resumes its normal position when the jaw is moving). Occlusal interventions change the occlusal relationship of maxillary and mandibular teeth to improve the alignment of the tooth contact, with the aim of relieving pain, and improving psychosocial functioning and quality of life. Occlusal interventions include splints and adjustments. Occlusal splints are specially designed mouth guards; they are generally classified as stabilisation, reflex or repositioning splints. Occlusal adjustment is the grinding down of teeth to improve occlusion.

Objectives: To assess the effects of occlusal interventions in people diagnosed with temporomandibular disorders (TMD), compared to other interventions or no treatment, on joint pain, muscle pain at rest and when chewing, quality of life, discomfort, and recurrence.

Search methods: Cochrane Oral Health's Information Specialist searched following sources up to 9 August 2022: Cochrane Oral Health's Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via Ovid, Embase via Ovid, and two trials registers.

Selection criteria: We included randomised controlled trials (RCTs) of occlusal interventions (splints or adjustment) for managing TMD compared with no treatment, placebo, occlusal splint with a different mechanism of action, or other active treatments.

Data collection and analysis: We adopted standard Cochrane methods to select studies, extract and analyse data, assess the risk of bias in the studies, and judge the certainty of the evidence. We reported outcomes as short term (three months or less) or long term (more than three months).

Main results: We included 57 studies (2846 participants) that compared occlusal splints with no treatment, placebo, or another treatment. Most of the studies evaluated full hard stabilisation splint (FHSS) as the occlusal splint. We judged only one study to be at low risk of bias. Our key outcomes of interest were self-reported joint pain when chewing, muscle pain at rest and when chewing, discomfort, severity and frequency of joint noise, and recurrence rate. The duration of the studies ranged from 5 weeks to 84 months. The key results presented below were measured between 4.4 weeks and 4 months. It is important to note that we have very low certainty in the evidence for all comparisons and outcomes assessed. There may be little to no difference in self-reported joint pain when chewing between occlusal splint (FHSS) and placebo (non-occlusal splint) (RR 1.88, 95% CI 0.94 to 3.75; 1 study, 60 participants with mixed TMD), or pharmacological therapy (diclofenac) (RR 2.10, 95% CI 0.83 to 5.30; 1 study, 29 participants with osteoarthritis), but the evidence is very uncertain. Occlusal splint (FHSS) may reduce muscle pain when chewing compared to no treatment (MD -1.97, 95% CI -2.37 to -1.57; 1 study, 84 participants with disc displacement without reduction), but may have little to no effect when compared to physical therapy (low-level laser) (RR 0.17, 95% CI 0.02 to 1.26; 1 study, 40 participants) or acupuncture (with needles) (MD 0.10, 95% CI -0.80 to 1.00, 1 study, 40 participants) in people with myofascial pain TMD, but the evidence is very uncertain. There may be little to no difference in muscle pain at rest when occlusal splint (FHSS) is compared to no treatment (MD -11.63, 95% CI -29.37 to 6.11; 1 study, 37 participants) or physical therapy (physiotherapy) (MD -0.19, 95% CI -1.25 to 0.87; 1 study, 72 participants) in myofascial pain TMD, but the evidence is very uncertain. There may be little to no difference in severity of joint noise when occlusal splint (FHSS) is compared to no treatment, but the evidence is very uncertain (MD -0.58, 95% CI -7.09 to 5.93; 1 study, 20 participants). When FHSS is compared to physical therapy (specifically, orofacial myofunctional therapy), physical therapy may reduce severity of joint noise, but the evidence is very uncertain (MD 5.92, 95% CI 0.18 to 11.66; 1 study, 20 participants with mixed TMD). There may be little to no difference in frequency of joint noise when occlusal splint (FHSS) is compared to placebo (non-occlusal splint) (RR 1.18, 95% CI 0.63 to 2.20; 1 study, 60 myofascial pain TMD participants), occlusal splint with a different mechanism of action (RR 0.80, 95% CI 0.07 to 9.18; 1 study, 9 participants with disc displacement with reduction), or physical therapy (jaw exercise) (RR 1.50, 95% CI 0.32 to 6.94; 1 study, 18 participants with myofascial pain TMD), but the evidence is very uncertain. Discomfort and recurrence rate were not reported in any study. We judged the certainty of the evidence to be very low for all outcomes in all comparisons due to limitations in study design and imprecision.

Authors' conclusions: This review included 57 RCTs with 2846 participants, but the final results are inconclusive, so the research questions remain unanswered. Occlusal splints of the FHSS type may reduce muscle pain when chewing compared to no treatment, but the evidence is very uncertain. Orofacial myofunctional therapy may reduce severity of joint noise compared to occlusal splint (FHSS), but the evidence is very uncertain. For all other comparisons and outcomes, there may be little or no difference between groups, although the evidence is also very uncertain for these findings. Overall, we found insufficient evidence to reach conclusions regarding the effectiveness of occlusal interventions for managing symptoms of TMD, despite the available studies including almost 3000 participants. To make a useful contribution to the debate about the best way to treat TMD, any further research must be well-designed, with enough participants to reach the optimal information size for meaningful results; it requires recruitment from primary care, consensus around key outcomes and measures, and, ideally, long-term follow-up of three to five years, plus inclusion of a cost-effectiveness component.