Analysis of Masseter Muscle Activity Following Treatment of Fully Edentulous Patients With Mono-arch and Bi-arch All-on-4 Prostheses: A Systematic Literature Review

In the current modern era, edentulism of multifactorial origin remains a widespread condition with a rapidly increasing annual prevalence. This condition impairs various components of the stomatognathic system, particularly the masticatory muscles, with the masseter muscle being the most notably affected. However, ongoing innovations in surgical prosthodontics have made the All-on-4 (AO4) prosthetic concept a sustainable and minimally invasive option for the rehabilitation of fully edentulous patients, showing promising improvements in oral function. The objective of this systematic review was to analyze existing research on changes in masseter muscle activity in fully edentulous patients treated with mono- and bi-arch AO4 prostheses, assessed through electromyography (EMG), bite force, and occlusal contact analysis. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, and the research question was formulated using the population, intervention, control, and outcomes (PICO) framework: "How is the activity of the masseter muscle affected in fully edentulous patients rehabilitated with mono- and bi-arch AO4 prostheses?" According to the inclusion and exclusion criteria, articles were sourced from PubMed, Google Scholar, and ScienceDirect. All included studies were published within the past five years. Risk of bias was assessed using the Cochrane Risk-of-Bias 2 (RoB-2) tool. Out of 447 screened articles, only three met the inclusion criteria, comprising a total of 37 patients. Two studies focused on mono-arch and one on bi-arch AO4 prostheses. All three studies consistently demonstrated increased masseter muscle activity in both mono- and bi-arch AO4 groups compared to other prosthetic rehabilitation options, such as two-implant-supported overdentures and conventional dentures (CDs). However, bi-arch AO4 prostheses demonstrated superior masseter muscle neuromuscular activity compared to mono-arch AO4. Nevertheless, the type of prosthesis fixation (fixed or overdenture) and the material used (porcelain fused to metal or acrylic resin) may influence masseter muscle EMG analysis. Understanding these prosthetic influencing factors in mono- and bi-arch AO4 prostheses will help clinical practitioners rehabilitate fully edentulous patients more effectively.