Effects of Jaw Clenching While Wearing a Bite-Aligning Mouthguard on Performance in Athletes: A Systematic Review.

Background: Emerging evidence suggests functional connectivity between the masticatory and musculoskeletal systems, yet the extent to which jaw clenching modulates athletic performance remains uncertain. Bite-aligning mouthguards (MGs) are designed to optimize occlusion and stability, but systematic quantification of their impact on performance across athletes is limited. It is important to distinguish between conventional protective MGs and performance-oriented devices designed to modify mandibular position, as their mechanisms and potential effects may differ. This review synthesizes available data to clarify whether jaw clenching with bite-aligning devices enhances strength, power, endurance, precision, or neuromuscular efficiency. Objectives: The objective of this study was to systematically review the literature on the effect of bite-aligning MGs on athletic performance. Materials and Methods: A comprehensive search of PubMed, Scopus, and Web of Science was conducted until 1 February 2024. Inclusion criteria were (1) randomized controlled trials (RCTs), (2) crossover trials, and (3) controlled clinical trials evaluating MGs' effects on muscle strength, power, agility, quickness, and sports performance. A narrative synthesis approach was adopted due to heterogeneity in study design, interventions, and outcome measures, which precluded meta-analysis. Results: Thirteen trials with 335 athletes (mean age: 24.13 ± 5.64 years) were included. At least four studies reported positive effects on some variables, while none reported negative effects. Main findings indicate neuromuscular benefits, particularly in rugby, football, and weightlifting. Custom-made MGs (CMGs) showed a particularly positive impact. Neutral results were also observed, showing no difference between using a MG or not. Conclusions: Athletes may benefit from wearing MGs not only to prevent orofacial trauma but also to potentially enhance performance in specific actions. Benefits are associated with increased peak acceleration, force, muscle activity, and power in upper- and lower-body exercises. However, given the high heterogeneity across studies, these findings should be interpreted with caution, and the effects cannot be considered universal. Further high-quality studies are required to clarify the potential performance-enhancing role of specific MG designs.