![]() ![]() A sample of cone-beam computed tomography (CBCT) scans of subjects with TCS and nonsyndromic PRS was selected from the files from a single center. Informed consent for the use of records was obtained from all subjects. This retrospective study was approved by the Institutional Research Ethics Committee of Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo, Bauru, Brazil (process no. The hypothesis was that both craniofacial anomalies present similar mandibular size and shape. Therefore, this study aimed to compare the mandibular size and morphology of subjects with TCS and nonsyndromic PRS. In addition, morphologic data contribute to surgical planning and esthetical-functional outcomes. The phenotypic refinement between TCS and PRS is important for the differential diagnosis between these craniofacial anomalies. Mandibular size and shape have not been compared between TCS and PRS through 3-dimensional (3D) evaluation. TCS presents a short mandibular ramus and a relatively normal mandibular body, whereas PRS presents a reduced mandibular body and a relatively normal mandibular ramus. The most associated syndromes are Stickler syndrome, velocardiofacial syndrome, and TCS in 5% of patients.Ĭhildren with TCS and PRS present the mandibular deficiency as a similar clinical finding. , It is a heterogenic pathologic entity, and it can be found as an isolated condition or in association with other syndromes. , The incidence ranges from 1:8,500 to 1:14,000 in the general population. PRS is a congenital anomaly characterized by a triad of clinical signs: micrognathia, glossoptosis, and obstruction of the upper airways, frequently associated with cleft palate. TCS presents variable phenotypic expressiveness, and the most characteristic finding is malar and mandibular hypoplasia, frequently with limited formation of the zygomatic complex. , As a result of mutations in the TCOF1 gene, TCS originates from abnormalities in the development of craniofacial structures derived from the first and second branchial arches. Its estimated incidence is 1:50,000 births. TCS was first described in 1900 by Edward Treacher Collins. At the end of growth, surgical procedures for mandibular advancement are frequently required both in TCS and PRS. Infant interventions include mandibular distraction, endotracheal intubation, continuous positive airway pressure, or use of prone position. Inability to feed, malnutrition, airway obstruction leading to respiratory failure, and growth deficiency were also related to the small mandible in TCS and PRS. , In both situations, micrognathia may cause airway reduction or obstruction. Treacher Collins syndrome (TCS) and Pierre Robin sequence (PRS) show a small and retrognathic mandible. Severe micrognathia induces both esthetic and functional clinical implications. Mandibles were smaller and more hyperdivergent in subjects with TCS. ![]() Mandibles were more asymmetric in subjects with TCS compared with Pierre Robin sequence. Mandibular shape differed significantly in the 2 groups. Subjects with Treacher Collins syndrome (TCS) and Pierre Robin sequence had micrognathia. Young subjects with TCS presented a smaller, more vertical, and more asymmetrical mandible compared with nonsyndromic PRS. The gonial angle was greater in TCS compared with the PRS group. The condyle width and height and the ramus width were also decreased in TCS. Group TCS presented a smaller mandibular effective length and mandibular body length compared with PRS. The mandibular dimensions in PRS were more symmetrical. TCS showed a significant dimensional difference between less and more affected sides for ramus, condyles, and mandibular body. The significance level considered was 5%. Intergroup comparisons were performed using analysis of variance and Tukey tests. ![]() Intragroup comparisons were performed using paired t tests. Nine 3-dimensional measurements were performed in segmented 3D images of the mandible. Preorthodontic cone-beam computed tomography examinations of all patients were evaluated using Mimics Innovation Suite 17.0 (Materialise, Leuven, Belgium). Group PRS was composed of 17 subjects paired by age and sex with group TCS. Group TCS was composed of 17 subjects (7 male, 10 female) with a mean age of 11.5 years (standard deviation, 4.4) from a single center. This study aimed to compare the mandibular size and morphology of subjects with TCS and PRS. ![]() Treacher Collins syndrome (TCS) and nonsyndromic Pierre Robin sequence (PRS) share mandibular deficiency as a similar clinical finding. ![]()
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