Studies On The Facial Morphology Of The Skeletal Class â…¢ Malocclusion With Different Growth Stages

Objective:To evaluate gender differences and growth of craniofacial morphology in the cephalometric records of a cross-sectional sample of skeletal classâ…¢malocclusion at different age stages.Methods:The sample examined consisted of 237 pre-treatment lateral Cephalo- metric records of skeletal classâ…¢patients(122 female,115 male)collected from the Orthodontic Department of Tianjin Stomatological Hospital from Jan.1 2005 to Dec. 31 2007.The age range was between 7 years and 27 years.Both male and female subjects were divided into three age groups:the 7-11yr age group,the 12-16yr age group and the 17-27yr age group.A detailed gender differences and growth changes of skeletal classâ…¢malocclusion ware performed using Independent sample t-test on 56 cephalometric variables which are associated with classâ…¢malocclusion.Results:The facial lengths and heights were larger in males than in females.The differences were very significant in the 12-16yr age group and the 17-27yr age group. There were no significant differences of the rates in facial lengths and heights. Females' Y-axis angle was smaller than males' in the 7-11yr age group and the 17-27yr age group,but was similar as males' in the 12-16yr age group.There were no significant differences between males and females in the position of the maxilla and mandible,intermaxillary relationships,dental measurements and the position of the upper and lower lips in the 12-16yr age group and the 17-27yr age group.With growth,the length of the mandible and vertical facial heights were significantly increased for both males and females.As for the rates of facial heights changed in the 17-27yr age group,the lower anterior facial height of males and the posterior facial heights of both males and females were increased more significantly. With growth,the maxillary position which related to the cranial base was remained relatively constant while the mandible continually protruded forward.The ANB angle and Wits appraisal showed a statistically significant decrease between the 12-16yr age group and the 17-27yr age group in females.The mandibular plane angle decreased persistently in males while it decreased more significantly between the 12-16yr age group and the 17-27yr age group in females.The total decrease of the mandibular plane angle was slightly larger in males than females.Conclusions:1.Skeletal classâ…¢malocclusion is associated with a significant degree of sexual dimorphism in craniofacial,especially after the age of 12.Females with Skeletal classâ…¢malocclusion present with significantly smaller linear dimensions in the cranial base,maxilla,mandible,and facial heights when compared with males.2.With growth,in males the direction of facial growth remained relatively constant while in females it changed from a more horizontal growth pattern than males to the same as males then return to a more horizontal growth pattern than males.3.There was no sexual dimorphism found in the maxillary and mandibular saglttal positions after 12 years old.4.With growth,the length of maxilla increased mildly and the relationship of maxilla to the cranial base remained relatively constant.In contrast,the length of mandible increased significantly and became more protrusive.5.After 17 years old,the mandibular length and facial height increased more significantly in males than females,especially the lower anterior facial height and posterior facial height.6.With growth,the mandibular plane angle decreased in both sexes,while the total decrease was slightly larger in males than females.