Evaluation of Muscle Activity in Unilateral Posterior Crossbite

Posterior crossbite (PCB) is defined as the presence of one or more teeth of the posterior group (canine to third molar) in an inverted buccolingual relationship, where the vestibular cusp of the upper tooth is in contact with the central fossa of its lower antagonist tooth. It is one of the most common malocclusions in children, with a prevalence of 8 to 22% among orthodontic patients in primary and mixed dentition and 5 to 15% among the general population. It can be bilateral (MCPB) or unilateral (MCPU). In 71-84% of cases, CCM in growing patients appears as a functional CCBM and is therefore associated with a functional mandibular deviation. The hypothesis of this study is, that unilateral posterior crossbite correction by Rapid Maxillary expansion achieves improved symmetry and muscle activation potential in treated patients. The objective of this study is to evaluate the muscle activity of masticatory muscles in patients with unilateral posterior crossbite with superficial electromyography before and after treatment with rapid maxillary expansion. Superficial electromyography will be measured in masseter and temporalis muscle before treatment, when the patients bite is corrected and after the treatment. Three static and two dynamic tasks will be measured.