ACTN3 genotype influences masseter muscle characteristics and self‐reported bruxism.

Objectives: Main aim of the study was to explore the association between genetic polymorphisms in ACTN3 and bruxism. Secondary objectives included masseter muscle phenotypes assessment between bruxers and non‐bruxers and according to genetic polymorphisms in ACTN3. Materials and Methods: Fifty‐four patients undergoing orthognathic surgery for correction of their malocclusion were enrolled. Self‐reported bruxism and temporomandibular disorders status were preoperatively recorded. Saliva samples were used for ACTN3 genotyping. Masseter muscle samples were collected bilaterally at the time of orthognathic surgery to explore the muscle fiber characteristics. Results: There were significant differences in genotypes for rs1815739 (R577X nonsense) (p = 0.001), rs1671064 (Q523R missense) (p = 0.005), and rs678397 (intronic variant) (p = 0.001) between bruxers and non‐bruxers. Patients with self‐reported bruxism presented a larger mean fiber area for types IIA (p = 0.035). The mean fiber areas in individuals with the wild‐type CC genotype for rs1815739 (R577X) were significantly larger for type IIA fibers (1394.33 μm2 [572.77 μm2]) than in those with the TC and TT genotypes (832.61 μm2 [602.43 μm2] and 526.58 μm2 [432.21 μm2] [p = 0.014]). Similar results for Q523R missense and intronic variants. Conclusions: ACTN3 genotypes influence self‐reported bruxism in patients with dentofacial deformity through specific masseter muscle fiber characteristics. [ABSTRACT FROM AUTHOR]