Correlations Of Root Diameter And Root Canal Diameter Of Maxillary Central Incisors With Age In Chinese Han Population

Objective:To investigate the correlations between root diameter and root canal diameter of maxillary central incisors and age by using cone–beam computed tomography.Methods:1、The points used to mark root canal diameter and root diameter in maxillary central incisors were determined. The picture was adjusted to a specified position in the longitudinal section of the radiographs. Root diameter and root canal diameter were measured by a dedicated software together with cone-beam computed tomography, the ratios of root canal diameter and root diameter were calculated. All measurements were carried out three times by one examiner. A random sample of root canal diameter and root diameter were re-examined after an interval of one month to test intra-examiner reproducibility by paired t-test. Researchers were trained on CBCT supporting software operation and the measuring method of root canal system of right maxillary central incisor. Adjust CBCT images of right maxillary central incisor according to the method,calibrated and measured the measurement parameters. 1 researcher calibrated and measured again after one month. The consistency between researchers using intraclass correlation coefficient. Paired t test was put for statistical analysis of two measurement differences before and after one month. To validate the accuracy and reliability of the measurement method, one researcher examined the consistency between measured values of CBCT and in vitro teeth. The measured values by CBCT and the measured values by vernier caliper were recorded. Intraclass correlation coefficient was used to test the consistency of these two groups of data.2、A total of 420 cone–beam computed tomography images of Chinese Han population were chosen and divided into 7 age groups; Root diameter and root canal diameter of maxillary central incisors at the 3/4 level from the cemenal-enamel junction(CEJ) to root apical were measured. Linear-regression analysis was used to analyze the correlations between root diameter and root canal diameter of maxillary central incisors and age, and T-test was used to examine the gender differences.3、Put the lateral cemento-enamel junction of right maxillary central incisor as a standard point to draw a standard line. Divided the distance between this line and root apical into 4 equal parts, Measured the height from the top of pulp chamber to the standard line, root canal diameter and root diameter of the 4 equal parts using measurement software of Galileo cone beam CT. The differences between age groups was evaluated through analysis of covariance(ANCOVA). Linear regression analysis was performed to show the correlation between the height from the top of pulp chamber to the standard line as well as ratio of root canal diameter and root diameter at the 4equal parts and age.Result:1、This experiment established measurement method is feasible and good consistency(Intraclass Correlation Coefficient of 4 researchers, ICC >0.80. Paired t test showed there has no significant difference of two measurements, P=0.491). The measurement method is reliable and high accuracy( There had no obvious difference between measured values of CBCT and in vitro teeth and the consistency is well, ICC>0.80).2、Mean of root diameter(mm) of the teeth in males and females were 5.81±0.445,5.53±0.489; Mean of root canal diameter(mm) in males and females were 1.20±0.396,0.96±0.236; Mean of the ratio of root canal diameter and root diameter of the teeth in males and females were 0.21±0.072, 0.17±0.043, respectively. Gender differences was significant(P<0.05). There were negative correlations between the ratio of root canal diameter and root diameter of the teeth and age(R2=0.576,P<0.05). The differences between age groups was statistical(P< 0.05).3、The correlation coefficient of the height from the top of pulp chamber to the standard line as well as ratio of root canal diameter and root diameter at the 4 equal parts and age are 0.64, 0.56, 0.51, 0.56, 0.51.Regression equation of age estimation, male: Y=101.628-5.109H-172.558X2,R2=0.521,SE=4.003. Female: Y=115.049-6.131H-237.224X2,R2=0.541,SE=4.727.Conclusion:1、The measurement method established in our experiment is feasible and high r epeatability. The accuracy of CBCT measured value using this method is high, a nd has a good consistency with the real value.2、There are correlations between the ratio of root canal diameter and root diam eter of maxillary central incisors and age in Chinese Han population. The decrea se of root canal diameter in males is more significant than females. The change of maxillary central incisors’ pulp cavity along with the age in each age group i s different.3、There has a high correlation between the height of pulp chamber top to stan dard line and age. The closer to the root apical the smaller the correlation betwe en age and the ratio of root canal diameter and root diameter. Method to establi sh a regression equation for age estimation using CBCT is feasible, age estimati on regression equation is established in this research.