Mandibular characterization of individuals with isolated Robin sequence and Treacher Collins syndrome: three-dimensional evaluation

Abstract

INTRODUCTION: The Robin sequence (RS) is a congenital anomaly, characterized by micrognathia and glossoptosis, and can or cannot be associated with cleft palate. The incidence in the general population varies between 1: 2000 and 1: 30.000, and can manifest itself in isolation or associated with other syndromes. The phenotypic refinement of this sequence compared to Treacher Collins syndrome is important to aid in the differential diagnosis between the two craniofacial anomalies. Objectives: The purpose of this work will be to characterize the mandibular structures of individuals with isolated Robin Sequence and to compare them with individuals with Treacher Collins mandibulofacial dysostosis (TCMD). Methods: The study sample will consist of two study groups: RS group, composed of 30 individuals with isolated Robin Sequence from 7 to 20 years of age and TC group, composed of 30 patients with Treacher Collins from 7 to 20 years. Cone-beam computed tomography (CBCT) from the HRAC-USP file will be used for both groups. CBCT from the RS group will be complemented throughout the study period in patients who will undergo orthodontic-surgical treatment or otorhinolaryngological interventions that benefit from the three-dimensional examination. The exams will be analyzed in three different ways: 1. Three-dimensional cephalometric analysis after segmentation of the images; 2. Morphological analysis of three-dimensional segmented images; 3. Analysis of the mandibular symmetry. The software used will be Dolphin (Dolphin Imaging 11.0 & Management Solutions, California, USA) and Mimics Innovation Suite (Materialize, Leuven, Belgium). Data analysis: The data collected will be transferred to the SPSS software (version 16.0, SPSS, Chicago, I11). The Shapiro-Wilk test will be used to verify the normal distribution of the data. The intergroup and the mandibular symmetry comparison will be performed by independent t test and paired t test, respectively. The level of significance considered will be 5%.Key words: Pierre Robin Syndrome. Mandibulofacial dysostosis. Cone-beam computed tomography.