Impact of Clear Aligners on the Temporomandibular Joint: A Systematic Review.

The temporomandibular joint (TMJ) may experience alterations during orthodontic treatments. Furthermore, gaps in the literature highlight a lack of robust evidence on the impact of clear aligner therapy (CAT) on the TMJ. This review aims to find the current evidence regarding the effects of CAT on the TMJ. Electronic searches were conducted in PubMed, Web of Science, Scopus, Embase, LILACS, The Cochrane Library and ProQuest Theses and Dissertations. The eligibility followed PECOS: Permanent-dentition patients (P); CAT (E); CAT group baseline parameters (C); TMJ structural parameters (O). Data extraction included sample size, age, control group characteristics, assessed outcomes, evaluation tools and it periods and main results. Risk of bias was assessed with the Joanna Briggs Institute checklist and the ROBINS-E tool. Certainty of evidence was determined using the GRADE approach. Of the 1490 references identified, only five met the eligibility criteria and were included. CAT was associated with dimensional alterations in the condyle volume and surface area, increased superior joint space and fossa depth and decreased condylar bone density. For condylar inclination or position, there are no significant changes. The certainty of evidence was low and very low, reasoned by studies design limitations and heterogeneity. Despite the lower number of studies and low evidence level, CAT seems to induce modest, predominantly increased changes in TMJ spaces and fossa depth, with insufficient clinical significance regarding if CAT effects on TMJ are positive or not. Future studies with standardised TMJ imaging are essential to establish more robust evidence. Trial Registration: PROSPERO CRD42024547484.