Effects on Facial Growth Following Masseter Muscle Resection in Growing Rats—A Systematic Review

SIMPLE SUMMARY: Facial symmetry is a crucial determinant of facial appearance; treatment of asymmetry can be challenging. When it comes to the mandible’s development the muscles play a significant role in the development and growth direction of the mandible. However, it is unclear how the masticatory muscles contribute to early facial development, nor do we know to what extent they are involved in asymmetry. Our objective was to investigate the impact of masseter resection on mandibulofacial growth by reviewing the data of previously published studies on rats up to October 2022. The results of this study provide evidence that experimental masseter muscle excision in developing rats causes atrophic changes in the angular process, asymmetry in the maxilla, and overall shortening of the mandible. These changes occur as a direct outcome of the removal of the masseter muscle. Due to the mandible’s posterior rotation, muscular excision did cause specific articular alterations in the temporomandibular joint. Lateral X-rays of the mandible of the rats who were part of the experimental group revealed that their mandibular plane angles were higher than those of the control group. ABSTRACT: An individual’s facial appearance is heavily influenced by facial symmetry. In the asymmetric mandible, periosteal apposition and endochondral ossification in one of the condyles may stimulate asymmetric growth of the body. Our aim was to review the impact on the growth following masseter resection. Relevant studies up to October 2022 were retrieved from PubMed, Scopus, and Web of Science. The PICOS method was utilized to determine eligibility, and the SYRCLE risk of bias tool was utilized to provide an estimate of potential bias. A predetermined algorithm was used to search the databases. The results of our systematic review of seven studies indicate that the masseter muscle strongly impacts craniofacial growth and development. Resection of the masseter muscle significantly reduces the sagittal and vertical development of the jaw in rats. In addition, the masseter muscle excision influences the mandibular morphology, including the condylar area, angle, and development direction of the jaw.