[The correlations between the echographic aspect of the perioral and masticatory muscles and dento-skeletal...

US of some muscular components of the stomatognathic system (orbicularis oris and masseter muscles) has proved to provide important information about their morphologic features. The purpose of this study is to explore the US features of the perioral and masticatory muscles in patients affected with any type of malocclusion and to analyze the correlations between dento-skeletal characteristics and muscle changes.

We examined 26 untreated patients (10 men and 16 women); we measured their cephalometric parameters on lateral skull teleradiographs and then we measured with US both the masseter and orbicular muscles dimensions. The US images were acquired with 5 MHz and 7.5 MHz probes, measuring the masseter muscle with transversal and longitudinal scans, and the two parts of the orbicularis oris with longitudinal scans. The cephalometric measures were calculated with: angular parameters useful to determine the sagittal relationships, both angular and linear parameters to define the vertical relationships and angular measures that define the incisor position. We applied the Spearman test to assess if there was a relationship between the US dimensions of the orbicularis oris and the masseter, and the dento-skeletal characteristics of these 26 patients.

Our results show that there is a strong correlation between mandibular morphology, the palatal plane, respectively, and the masseter length. There is a direct correlation with the masseter dimension for the palatal plane obliquity, and an inverse correlation for the mandibular morphology. The incisor position is influenced by the orbicular oris muscle dimension and by the asymmetric position of the superior and inferior incisors.

This noninvasive diagnostic examination is a useful aid to the clinical examination of the muscles, especially in orthodontic diagnosis, together with MRI and CT, respectively more expensive and unhealthier.