Introduction. Occlusal splints are oral appliances which has been designed to relieve the temporomandibular symptoms. Anyway, the thickness of occlusal splints in order to have optimal efficacy is still controversial. Methods. An electronic search in Medline, Scopus, and Web of Science databases was conducted, using the following keywords up to January 2025:
(“occlusal splint” OR “stabilization splint” OR “bite splint”) AND (“vertical dimension” OR “thickness” OR “occlusal height”) AND (“temporomandibular disorder” OR “TMD” OR “disc displacement” OR “myofascial pain”). All titles and abstracts were screened.
Studies comparing different thicknesses of occlusal splints were included. Results. Eight studies met the inclusion criteria, from which five randomized controlled trials, one retrospective study, and two finite element analyses. Mixed quality of the studies was found. Based on current evidence, although limited, the following results could be deduced: Occlusal splints with moderate thickness, 3 mm, are recommended for those cases that involve both muscular and joint components, particularly when masticatory muscle pain is the primary complaint. Occlusal splints with minimal thickness, 2 mm, may be appropriate in internal derangements in the early stage, though evidence is low. Thicker splints, ≥4 mm for DDwoR and in cases with crepitus. Occlusal splints of ≤2 mm and >6 mm were associated with symptoms such as reduced functional outcomes or comfort. Conclusion. In most cases, occlusal splints with thicknesses of 3–5 mm seem to be optimal for most TMD cases; however, personalized treatment based on the respective diagnosis is recommended. The decision on splint thickness should be based on evidence according to the severity of the diagnosis, but also patient-centered, to achieve comfort, the compliance of the patient, and oral structure preservation. Further high-quality RCTs are needed to have evidence-based guidelines and to achieve consistent results.