Comparative Cephalometric Analysis of Angle Class II Division 1 Malocclusion Between Nepalese and Chinese Subjects

objective: To identify the craniofacial features of Nepalese and Chinese subjects with Angle Class II division 1 malocclusion; and to compare between Nepalese and Chinese samples and Nepalese gender groups. Materials & Method: The cephalometric radiographs were obtained from 96 Nepalese (mean ages16.34 ± 5.4 years) and 39 Chinese (mean age 17.18 ± 7.1 years) subjects with Angle Cass II division 1 malocclusion. Ten skeletal, nine dental and three soft tissue variables were investigated. result: The craniofacial features between Nepalese and Chinese samples showed significant differences among fifteen of the twenty-two variables studied; whereas in comparison between gender groups, six parameters were significantly different. conclusion: Both samples showed well positioned maxilla, retrusive mandible and Class II skeletal tendency. In comparison, maxilla was more protrusive, mandible was more retrusive and overjet was more increased in Chinese. The Nepalese showed more prominent nose and chin.


IntroductIon
3][4][5] Retrognathic mandible, maxillary prognathism and reduced vertical skeletal jaw relationship are the most common characteristics of Class II division 1 malocclusion. 5[14] The ethnic aspect is an important characteristic in the morphologic variation of malocclusions. 7e purpose of the present study was to identify the craniofacial features in a sample of Nepalese and Chinese subjects with Class II division 1 malocclusion; and to compare between Nepalese and Chinese samples and Nepalese gender groups.

MaterIals and Method
The present study was performed utilizing standardized lateral cephalometric radiographs of total 135 subjects comprising of 96 Nepalese samples (42 males, 54 females) collected from Department of Orthodontics, B.P. Koirala Institute of Health Sciences, Dharan, Nepal and 39 Chinese samples (12 males, 27 females) collected from Department of Orthodontics, Dalian Medical University, Dalian, China.Written consent was obtained from all participants after explaining the nature and purpose of the radiograph.
The criteria for inclusion of the sample were natural-born ethnic Nepalese and Chinese, Angle Class II division 1 malocclusion, no craniofacial deformities, no previous orthodontic treatment, maxillofacial surgery or plastic surgery.
Tracing of the lateral cephalometric radiographs was performed with standard manual technique using sharp 3H pencil.All radiographs were traced and digitized by the principal author to minimize the error.The measurements Dr Bishnu Prasad Sharma, 1 Dr Chang Xin 2

result
The mean age of the sample was 16.34 ± 5.4 years for Nepalese and 17.18 ± 7.1 years for Chinese subjects.Comparison of craniofacial features on cephalometric, dental and soft tissue parameters between Nepalese and Chinese sample is presented in Table 1.Craniofacial features and difference between Nepalese male and female subjects is presented in Table 2.

Figure 4 :
Figure 4: dental measurements: A. U1-NA Line: The distance between U1 crown and NA line; B. L1-NB Line: The distance between L1 crown and NB line; C. U1-APg Line: The distance between incisal edges of maxillary central incisor to the line from Point A to Pogonion.

table 1 : comparison of craniofacial parameters between nepalese and chinese subjects with class II division 1 malocclusion
BP, Xin C: Comparative Cephalometric Analysis of Angle Class II Division 1 Malocclusion Between Nepalese and Chinese Subjects 1810,19B value was 74.71 o degree for Chinese and 76.52 o for Nepalese; where as another study on Chinese18found SNB value of 77 o .The SNB value for Brazilian subjects17was reported as 75.39 o .There are relevant data that accept the variations in the position of mandible as inherent characteristic.2,10,19MeanPointA-Nasion-PointB (ANB) angle in Chinese sample was 6.16 o , which was 1.4 o greater than the Nepalese.Another study18on Chinese also found similar ANB value of 6 o .It indicates that, Chinese have more of Class II skeletal tendency than the Nepalese.Sharma

table 2 : comparison of craniofacial parameters between nepalese male and female subjects with class II division 1 malocclusion
OJNGoGn-SN and non significant Z-angle were higher in Nepalese females, suggest longer and less convex facial profile.The angle of soft tissue facial convexity and total soft tissue facial convexity were higher in Nepalese males; suggesting that females have relatively straighter facial profile.conclusIonBothNepaleseandChinesesamplesshowed Class II skeletal pattern, longer anterior face with well positioned maxilla.Nepalese subjects showed protruded maxillary incisors, more prominent nose and chin.Chinese subjects showed more retrusive mandible, skeletal open bite, protruded mandibular incisors, and increased overjet.Nepalese male samples showed more prominent maxilla, retruded mandible and prominent nose than females.Nepalese samples have distinct cephalometric features, which should be used as a reference in the orthodontic treatment of Nepalese patients.However, this study cannot represent the skeletal norms as a whole; further studies with larger sample would give the overall scenario.acKnoWledGeMentWeexpress sincere gratitude to Prof Liu Qi gui, statistician at DMU, China for guidance in statistical analysis.
The total soft tissue facial convexity was 5.11 o greater and Z angle was larger in Nepalese sample; suggest more prominent nose and larger chin respectively.Angle of convexity was positive in both samples but lesser in Nepalese sample, suggesting less prominence of maxillary denture base in Nepalese.