Investigation Of The Craniofacial Structure Of Young Adults With Angle's Classâ… Malocclusion

ObjectiveAngle's class I malocclusion is most frequently seen among all types of malocclusions. It is necessary to study its characteristics since adult orthodontic treatment is getting widely spread and the adult craniofacial structure varies with races, geographical zones, gender and ages. For clinical reference ,we have investigated the adults' craniofacial structure of Angle's Class I malocclusion in Xi'an.Materal and MethodThe subjects were carefully selected and composed of 101 adults of Han Nationality in Xi'an, male 53,with an average age of 19.2; female 48,with an average of 19.1. Twelve kinds of cephalometric analysis methods were used in this study, including Downs, Steiner, Tweed, Wylie, Wits, Bjork, Ricketts, Quadrilaterial, Coben, Holdaway, Burstone and Bishara .Alabama analyses and the Fourth Military Medical University optimum seeking method were also used. Every measurement wascompared with that of the adults with normal occlusion in Xi'an, the good-looking people of China and the Whites in America.Results1. Only a few items(21) were significantly different between males and females in the angular and ratio measurements. But obvious sexual differences (42) were found in the linear measurements. All of the differential items(63) were more than those of normal occlusion(13) in Xi'an.2. Compared with normal occlusion in Xi'an , there was a Class II malocclusion tendency with backward mandible position, larger mandible cirsoidity and more concave chin in Angle's Class I malocclusion. The items which were larger than those of the normal occlusion's are the convexity of the upper central incisors ,the inclination of the lower incisors, occlusion plane, palate plane, and mandible plane as well as the lower jaw angle and the nasolabial angle. But the items which were smaller than those of the normal occlusion's are the length of the mandible, the ratio of the mandible to the maxilla ,the convexity of the maxilla and mandible, the facial convex angle, Z angle, lip gap and lip protrusion. Its growth style was backward and downward with bigger vertical development and smaller saggital development. To male, the maxilla length and the ratio of the upper facial height to the total front facial height were larger, whereas the ratio of the lower facial height to the total front facial height was smaller. It showed that the adult was characteristic of Angle's class II tendency with ill-developed jaws on vertical and saggital directions.3. Compared with the good-looking people in China, the local adults with Angle's Class I malocclusion had more inclined lower central incisors, occlusion plane and palate plane. The mandible position was a little more backward than that of good-looking people. The vertical line measurements of the front face indicated that they were smaller than those of the beauty along with large standard difference between individuals. And so it appeared that the adults with Angle's Class I malocclusion in Xi'an had an ill-developed mandible on sagittal and vertical directions.4. Compared with the Whites in America, the facial profile of Xi'an adults was protruding with more convex maxilla and mandible, steeper occlusion and more inclined upper and lower central incisors. In addition, both the distance of the lower incisor to NB line and the angle of the Y axis to SN plane were larger, which showed a backward and downward growth tendency of mandible. So the adults with Angle's Class I malocclusion in Xi'an were characteristic of bigger jaw bone convexity, more labial inclined incisors and more backward and downward mandible.ConclusionsCompared with the people with normal occlusion in Xi'an , more obvious sexual differences were found .And the adults were characteristic of Angle's class II tendency with ill-developed jaws on vertical and saggital directions. Compared with the good-looking people in China, they got worse. Compared with the Whites in America, the adults with Angle's Class I malocclusion in Xi'an were characteristic of bigger jaw bone convexity, more labial inclined incisors and more backward and downward mandible.