Evaluation of Orthodontic Treatment Success in Terms of Symmetry in Patients with Class III Malocclusion after Maxillary Expansion and Protraction

Abstract

Background: Facial asymmetries are common in patients with skeletal class III malocclusion and posterior crossbite. Maxillary expansion and protraction (ME&P) and then fixed orthodontic treatment may affect positively on these asymmetries. Objectives: We aimed to investigate the effects of applying ME&P by the rapid maxillary expansion (RME) and face mask and then fixed orthodontic treatment on soft tissue asymmetries in adolescent patients with skeletal class III malocclusion and posterior crossbite. For this purpose, the 3D facial imaging system of stereophotogrammetric (3dMD) recordings was analyzed quantitatively in the pre-treatment (T0), ME&P (T1), and post-fixed orthodontic treatment periods (T2). Materials and methods: The study included 28 (11 females, 17 males) individuals with skeletal class III malocclusion and posterior cross-bite (5 patients with bilateral and 23 patients with unilateral cross-bite) and soft tissue facial convexity angle of 175.11º±1.06º with a mean age of 9.37 ± 0.54 years. Three-dimensional photographs were taken from the individuals before the ME&P (T0), 6 months after the ME&P procedure and before starting fixed orthodontic treatment (T1), and after removing all orthodontic appliances from the mouth at the end of the fixed orthodontic treatment (T2). 3dMD Vultus® software was used to evaluate the data of 34 linear and 16 volumetric as a total of 50 measurements in soft tissue analysis. Results: The right-left volume differences, the Root Mean Square (RMS) values, and linear width measurements in the upper, mid, and lower face regions when evaluated at the T1-T0, T2-T1, and T2-T0 period intervals, were found to a decrease in these values and improvement of asymmetry. Conclusion: The asymmetry in the soft tissue in all face regions was corrected with ME&P and fixed orthodontic treatment. The most obvious asymmetry improvement occurs in the lower face area. It should be taken into consideration that asymmetry will improve with RME and face mask application and fixed orthodontic treatment in adolescents with Class III malocclusion and posterior cross-bite and treatment planning should be done according to that.