A Cephalometric Study of Cranial Bases in Chinese Adults

Objective: The purpose of this retrospective cephalometric study is to examine the relationship between cranial base parameters and skeletal jaw pattern in Chinese adults. Methods: The subjects comprised male and female patients of Singapore Chinese descent, aged 18 years and above, prior to orthodontic treatment. The lateral cephalometric radiographs were randomly selected. A total of 309 radiographs are divided into three groups (I, II and III) based on ANB angle and Wits appraisal. The lateral cephalograms were scanned into the computer and digitized by a single examiner using CASSOS (Computer-Assisted Simulation System for Orthognathic Surgery) 2001 Software (2000 SoftEnable Technology). Thirty percent of the radiographs were redigitized again one month later to assess intra-operator reliability. Results: Analysis showed that the cranial base length was found to be significantly larger in males (p<0.01). The anterior cranial base of the skeletal II group was significantly longer than the skeletal I group (p<0.05). For cranial base flexure, the skeletal III group was statistically more acute than the skeletal I group (p<.05). This difference was not seen between the skeletal I and II groups. There was a statistical significant difference (p<0.01) in jaw size between the skeletal classes of malocclusion. The maxilla was found to be longer in the skeletal II group compared to the skeletal I and III groups, (p=0.001). The anterior cranial base length was found to be strongly correlated with the maxilla(r=0.70, p<0.01). Conclusion: The results from this study indicated that length of anterior cranial base and maxilla are important determinants in establishing the Group II category of Class III Chinese Adult patients. However for Skeletal III subjects, the cranial base flexure seems to play a more important role.