The Masseter Muscle and Its Role in Facial Contouring, Aging, and Quality of Life: A Literature Review.

BACKGROUND: Masseter muscle hypertrophy manifests itself as enlargement of the masseter muscle. It can be associated with a square-angled lower face, pain, dental attrition, maxillary and mandibular bone resorption, and accelerated aging process of the lower face. The objective of this study was to assess the efficacy and safety of botulinum toxin type A in contouring the masseter and its impact on quality of life and the aging process of the lower face, and its role in full face rejuvenation. METHODS: A PubMed search was conducted for articles on masseter treatment with botulinum toxin type A, masseter muscle hypertrophy, and the aging process of the lower face. Key studies are reviewed and findings are summarized. RESULTS: Botulinum toxin type A can be injected into the lower posterior aspect of the masseter muscle. Treatment decreases muscle bulk and reshapes the lower face. Furthermore, patient quality-of-life measures, including pain and symptoms of grinding and clenching, are improved. Treatment can decrease shear stress on maxillary and mandibular bones and can possibly prevent tooth loss and progressive bone resorption of the lower face. Adverse effects are minimal and short lasting. CONCLUSIONS: Botulinum toxin type A is a safe and effective treatment of masseter hypertrophy. The treatment results in improvement of functionality and cosmesis, and restoration of facial harmony.