Study And Comparison Of Tooth Size And Arch Length In Angle Class â…¢ Malocclusion Between Nepalese And Chinese Population

Objective: The purpose of this study was to determine the tooth size (Mesio-Distal), arch length, Bolton's anterior ratio and overall ratio in Angle class III malocclusion groups of Nepalese and Chinese subjects and to compare them.This study was done to find out the tooth size discrepancy in overall ratio and anterior ratio for class III patient by comparing with the normal values for both Nepalese and Chinese subjects.Methods: The mesio-distal tooth size and arch length were measured on the dental casts of total 39 pairs of Angle class III malocclusion aged 15-24 years. A vernier caliper was used for the measurement for tooth size and for arch length was measured by a brass wire. Among the casts17 pairs belong to Chinese subjects and 22 pairs belong to Nepalese subjects.The tooth size (mesio-distal) and arch length were measured. Bolton's overall and anterior ratios were figured out. The mean, standard deviation, maximum, minimum, coefficient of correlation were calculated. Independent t-test was applied for comparing the subjects.Results:Variability in tooth size was greater in Nepalese than in Chinese.1.Tooth size:Upper lateral incisor (7mm nepalese, 6.91mm chinese), upper canine (7.54mm nepalese,7.97mm chinese) and upper second premolar (U15 7.13 nepalese,7mm Chinese) shows significant difference between Nepalese and Chinese (P=0.02, P=.01, P=.003). Lower teeth show no significant difference between Nepalese and Chinese. Among Nepalese male and female lower lateral incisors (L42 male 6.30mm, female 5.83mm),lower second premolar (L35 7.3 mm male, female 7.25mm) and lower molar (L46 male11.4mm and female 10.83mm) show significant difference (P=0.035, P=0.032, P=0.049), upper second premolar (U15male 6.9mm, female7.33) shows significant difference between Nepalese male and female (P=0.020). Among Chinese male and female shows no significant difference between upper teeth while lower first molar (L46 male 11.36, female 11mm) shows significant difference (P=0.041, P=0.00).2.Bolton ratio:For Nepalese OR 90.42 and AR 78.76 while for Chinese OR 89.58 and AR 78.16. No significant difference between Chinese and Nepalese OR and AR. Nepalese class III malocclusion subject's OR out of 2 SD from the Bolton standard was 14% (outside -2 SD 0% and outside +2 SD 14%). AR outside Bolton 2 SD was 45.4% (outside -2 SD 13.6% and outside +2 SD 31.8%). Chinese class III malocclusion OR outside Bolton 70.6% 2 SD (outside -2 SD 29.4% and outside +2 SD 41.2). AR outside 2 SD are 40.8% (outside -2 SD 29% and outside +2 SD 11.8%). No significant difference between OR (91.22) and AR (78.04) for normal occlusion and class III malocclusion (OR=90.41,AR=78.76) of Nepalese (P=0.251, P=0.438). Significant difference between OR (91.5) and AR (78.8) for normal occlusion and class III malocclusion (OR=89.58, AR=78.16) for Chinese (P=0.09, P =0.58). No significant difference in OR between Nepalese male (OR=91.95, AR=79.63) and female (OR=89.13, AR=78.03) but AR is significant different (P=0.02). No significant difference between Chinese male (OR=89.23, AR= 78.28) and female (OR=90.22, AR = 78.50) .3. Arch length :Upper arch length for Nepalese male and female having angle class III malocclusion are 79.5 and 77 respectively. Lower arch length for Nepalese male and female with Angle class III malocclusion are 73.8 and 69.25. No statistically significant difference in upper and lower arch length between Nepalese and Chinese (P>0.05). Among Nepalese significant difference in upper arch length between male and female (P<0.05) but no significant difference between male and female in lower arch length (P>0.05).Conclusions: Variability in tooth size was greater in Nepalese than in Chinese.Tooth size difference between Nepalese male and female is not significant but for Chinese there was significant for upper second premolars and first molars. There is no significant difference between Nepalese and Chinese in OR and AR. Male and female show significant difference in upper arch length for Nepalese. Lower arch length for Nepalese and both upper and lower arch length for Chinese showed no significant difference between male and female.