Evaluation of the effects of traditional and modified rapid maxillary expander appliances on masticatory muscles by ultrasonography

The aim of this study is to evaluate the effects of conventional and modified rapid maxillary expansion appliances on masticatory muscles in patients with transversal construction of the maxilla, using ultrasonographic and shear wave elastography. Individuals who applied to Gaziantep University Faculty of Dentistry Department of Orthodontics for treatment, had skeletal maxillary stenosis, aged 8-15 years, and were routine patients of the clinic were included in the study. 31 randomly selected individuals were divided into two groups: Group 1; Conventional Hyrax RME (HRME) appliance (n=15), Group 2; Acrylic Cap Modified RME (AcRME) appliance application (n=16). Ultrasonography and elastography recordings were taken from the individuals at T0 (before appliance application), T1 (end of activation) and T2 (3rd month following completion of activation). The thickness and stiffness values of the masseter, anterior temporal and lateral pterigoid muscles were analyzed through the recordings. In both AcRME and HRME groups, no significant difference was observed in the inter-time comparisons of the mean thickness and hardness values; when analyzed by making a right-left distinction, it was seen that both appliances affected the muscles significantly. The thickness and stiffness values of the lateral pterigoid muscle, which is one of the most affected muscles in the study, measured at different times were higher in the AcRME group. It was thought that this situation was caused by the difference in occlusion height in the design of the AcRME appliance.