Copyright @ 200 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited. 8 Three-Dimensional Cephalometric Study of Upper Airway Space in Skeletal Class II and III Healthy Patients Patrı ´cia Vale ´ ria Milanezi Alves, DDS, MS,* 1 Linping Zhao, PhD, 24 Mary O’Gara, MA, CCC-SLP, kL Pravin K. Patel, MD, 24L ** Ana M. Bolognese, DDS, MS, PhD* Rio de Janeiro, Brazil and Chicago, Illinois, USA Because the pharynx and the dentofacial structures have close relationship, a mutual interaction can be expected to occur between them. The literature presents skeletal malocclusion as etiology for air- way morphology changes and/or vice versa. The present three-dimensional cephalometric study from computed tomography scans was carried out to investigate upper airway space in normal nasal breathing patients presenting skeletal pattern of classes II and III. In addition, the statistical analysis was done according to gender criterion. The results revealed that the majority of the airway measure- ments have not been affected by type of malocclu- sion. The three-dimensional technology used in this study also allowed the volume and surface area calculations, and no statistical significance was found. The retroglossal width and posterior nasal cavity height mean were larger in males than females in the class II group, but volume and cross-section area were not statistically significant. However, in class III group, although the differ- ences in linear and angular measures means were not significant, the retropalatal volume and retro- glossal volume and cross-section area were larger in males. The authors highlight that the evaluation of upper airway space should be an integral part of diagnosis and treatment planning to achieve func- tional balance and stability of the results. Key Words: Upper airway space, malocclusion, three- dimensional study, computed tomography scans A mong the predisposing factors for obstruc- tion of the pharyngeal airways, there are hypertrophied adenoids and tonsils, chronic and allergic rhinitis, environmental irritants, infections, congenital nasal deformities, nasal traumas, polyps, and tumors that can result of narrower airway passages. 1 Malocclusion is also presented in the literature as a natural anatomic predisposing factor for airway morphology changes and respiratory problems. 2,3 The influences of airway obstruction on the development of the stomatognathic system have also been studied. 4Y9 The functional matrix theory proposed by Van der Klaauw and elaborated on by Moss 10 further supports environmental effects on craniofacial development by suggesting that the skeletal system responds to the influences of the adjoining soft tissues. 11 In accordance, Ricketts 12 pos- tulated that the oral and nasal structures are inter- dependent, and normal nasal function is conductive to normal growth of the maxilla and occlusion. Developmental pattern of the face and airway obstruction influence is presented in the literature as controversial. Martin et al 13 assess nasopharyngeal soft-tissue patterns in patients with ideal occlusion. They found differences on lower pharynx dimension in the sample and suggested new lines of investiga- tion into the relationship between skeletal and dental anomalies and airway obstruction and possible spe- cific respiratory patterns for each type of malocclu- sion. The authors highlight an important limitation of airway studies that is the use of two-dimensional (2-D) technique. This does not represent exactly the nasopharyngeal space and the difficulty in identify- ing the exact soft-tissue contours on traditional 1497 From the *Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; 1 The Craniofacial Center, University of Illinois at Chicago; 2 Plastic and Craniomaxillofacial Surgery, Shriners Hospitals for Children; 4 The Craniofacial Center at University of Illinois at Chicago; k Shriners Hospitals for Children; L Northwestern Univer- sity Feinberg School of Medicine, Chicago, Illinois; **Department of Bioengineering, Marquette University, Milwaukee, Wisconsin. Support: Brazilian government agency, CAPES Foundation (Foundation for the Coordination of Higher Education and Graduate Training), process number BEX 3638-05/7 (Dr Patricia Alves), and Shriners Hospitals for Children (grant number 8510). Address correspondence and reprint requests to Patrı ´cia Vale ´ria Milanezi Alves, DDS, MS, 2018 West Adams, Chicago, IL 60612; E-mail: patricia.alves.p@gmail.com or pvmalves@ig.com.br