Research On The Correlation Of Tooth Widths In Permanent Occlusion From Shijiazhuang

Objective: This study is aimed to find out the tooth widths and sex difference of permanent occlusion in Shijiazhuang through measuring and analyzing the study models of teenage patients. Established a more precise equation which is used to predict the width of unerupted canine and premolars,then provided reference to clinical diagnosis,treatment and prognosis designed in orthodontics.Method: The study employed the pre-treatmentmodels of 322 patients (male 151 pairs,female 171 pairs)selected from the records of the Orthodontic Department,The Firstl Hospital of Hebei medical university. Patients in sample were selected by these conditions:Patients in sample were born in Shijiazhuang;Upper and lower denture and tooth were integrity;There were not residual crown, crown,bridge or proximal surface obtuator in their mouths;No teeth abnormity such as accessory teeth,fused teeth;No severe mesiodistal detrition;Have no history of orthodontic treatment;No severe crowding in upper and lower denture.Dental plaster casts of patients should meet the following conditions:Models should be precise,limpid,no air bubble.The models should have integrity teeth,denture,transitional plicas,palatal vaults. The widths of crown were measured by digital cernier caliper and recorded to the nearst 0.01mm.Then put the data into the computer.Calculate the mean and S.D. of male sample and female sample.Compare their left-right difference and sex difference.Then analyze the correlation between pre-erupted teeth (incisors and molars)and post-erupted teeth (canines and premolars).Select the more dependable combine of teeth,ecentually,establish a linear regression equation which could be used to predict the the widths of unerupted canines and premolars. Result:1 Anlysis of teeth widths between male and femaleThere is a distinguished difference of teeth widths between Shijiazhuang and other regions. Survey results indicate that:There are certain gender differences,and these differences are not in a level.There is a significant statistical difference between male group and female group in Shijiazhuang. Men's average teeth widths is greater than women's average teeth widths.There is not significant statistical difference between left and right homonymous tooth except upper lateral incisor.2 Dependablity anlysis of teeth widths2.1 The correlation between the first permanent upper molar and the combine of canine and premolars is better than other three teeth(upper and lower incisor,first lower permanent molar).The correlation coefficients in male group is 0.721(upper) and 0.724(lower)(p<0.001). The correlation coefficients in female group is 0.625(upper) and 0.665(lower)(p<0.001).2.2 When put two teeth in pair, the correlation between the combine of upper incisor and upper first molar and the combine of canine and permolars is more significant. The correlation coefficients in male group is 0.777(upper) and 0.794(lower)(p<0.001). The correlation coefficients in female group is 0.673(upper) and 0.681(lower)(p<0.001). The dependablity between the combine of lower incisor and upper first molar and the combine of canine and permolars is also significant. The correlation coefficients in male group is 0.734(upper) and 0.791(lower)(p<0.001). The correlation coefficients in female group is 0.649(upper) and 0.724(lower)(p<0.001).2.3 When put three teeth in a group, the correlation between the combine of upper incisor,lower incisor and upper first molar and the combine of canine and permolars is the most significant. The correlation coefficients in male group is 0.798(upper) and 0.814(lower)(p<0.001). The correlation coefficients in female group is 0.708(upper) and 0.726(lower)(p<0.001). The dependablity between the combine of upper incisor,lower incisor and lower first molar and the combine of canine and permolars is also significant. The correlation coefficients in male group is 0.788(upper) and 0.811(lower)(p<0.001). The correlation coefficients in female group is 0.676(upper) and 0.693(lower)(p<0.001).2.4 The correlation between the combine of upper incisor,lower incisor , upper first molar and lower first molar and the combine of canine and permolars is the most significant in the sixteen combines. The correlation coefficients in male group is 0.799(upper) and 0.816(lower)(p<0.001). The correlation coefficients in female group is 0.707(upper) and 0.724(lower)(p<0.001).2.5 The correlation between the traditional predicted teeth combine and the combine of canine and permolars is less significant. The correlation coefficients in male group is only 0.624(upper) and 0.647(lower)(p<0.001). The correlation coefficients in female group is only 0.613(upper) and 0.625(lower)(p<0.001).3 Established a linear regression equationAccording to the most significant correlation between the combine of upper incisor,lower incisor and upper first molar and the combine of canine and permolars ,and the correlation coefficients in male group is 0.798(upper) and 0.814(lower)(p<0.001).,The female group is 0.708(upper) and 0.726(lower)(p<0.001). establish a linear regression equation which could be used to predict the the widths of unerupted canines and premolars. Male: Y=0.75X+4.02(upper), Y=0.81X+1.63(lower); Female:Y=0.57X+8.37(upper),Y=0.68X+4.84(lower) (Y represents the summation of the mesiodistal crown widths of unerupted canine and premolars on one buccal side, while X represents half of the summation of the mesiodistal crown-widths of upper and lower central incisors and upper first molars:11,21,16,26,31 and 41)Conclusion:1 There is not a significant difference in left and right homonymous teeth in permanent occlusion sample of Shijiazhuang ,but men's average tooth widths is greater than women's.2 The correlation between the combine of upper incisor,lower incisor and upper first molar and the combine of canine and permolars is the most significant.3 Equations predicting summation ofmesiodistal crown-widths of upper and lower unerupted canine and premolars in male group and female group of Shijiazhuang permanent occlusion were established respectively. Male: Y=0.75X+4.02(upper), Y=0.81X+1.63(lower); Female:Y=0.57X+8.37(upper), Y=0.68X+4.84(lower). The equations can be used to predict the width of unerupted canine and premolars in mixed-dentition periods.