Do occlusal splints achieve a statistically significant improvement of mouth opening in TMD patients?

Introduction: This article reports the results of a comprehensive systematic review and meta-analysis of the effect of occlusal splints (OSs) on active maximum mouth opening (AMMO) in patients with temporomandibular disorders (TMD).
Methods: Multiple databases (PubMed/MEDLINE, EMBASE, Cochrane Library, LIVIVO, OpenGrey, DRKS, and ClinicalTrials.gov) plus additional literature were searched for relevant randomized clinical trials (RCTs) using OSs to treat adults with painful TMD. AMMO was assessed after 6 and 12 months of treatment, and OS therapy was compared with no treatment, other active treatments (OATs), and/or placebo splints. The Cochrane Collaboration’s tool for assessing risk of bias was used to assess study quality. The threshold for statistical significance of correlations detected by meta-analysis was P ≤ 0.05.
Results: The use of OSs did not increase AMMO significantly more than no treatment (P = 0.28) or placebo splints (P = 0.76). OS therapy was significantly inferior to OATs (P = 0.02 for short-term effect, P = 0.01 for medium-term effect). In 18 of the 21 included studies, OSs increased AMMO slightly but not significantly more than no treatment (P = 0.28) or placebo splints (P = 0.76).
Conclusions: OSs made no significant contribution to improving AMMO. Therefore, OATs should be used in patients with limited jaw opening.Registration: This study was registered in the PROSPERO database under ID number CRD42019123169.