| Objective : To observe the root morphology of mandibular second molars in some people in Hohhot using CBCT(cone-beam computed tomography),and to perform statistical analysis on root typing,mesial root canal typing,and C-shaped root canal section typing.The research aims to provide clinical reference for mandibular second molar root canal treatment in Hohhot.And by analyzing the root canal morphology of Mongolian mandibular second molars,we can understand the differences of root canal system among different ethnic groups.Method:1.Choose the CBCT imaging data of 449 mandibular second molars from 244 patients registered in Hohhot,and obtain the following information,including the patient’s name,age,Data registration and grouping of gender,ethnicity,household registration,and jurisdiction where the current address is located.2.This experiment consists of a graduate student in dental science and a doctor in imaging science,both of whom have undergone software reading training and repeated accuracy tests.The 3D reconstruction of CBCT data was performed by the interpretation software system.The C-shaped root canal was observed and recorded in three levels using Fan[1]classification:root canal crown 1/3(medullary floor),root canal 1/3(1/2 of root length),and root canal tip 1/ 3(at a distance of 2 mm from the apex);non-C-shaped root canal configurations were recorded according to the Vertucci[2]classification.3.The data is divided into left and right groups according to the position of the teeth.Basic information is recorded and experimental data such as root type and root canal structure are recorded.4.The left and right teeth will be divided into two groups,according to age(18 ~ 35 years old(young age group),36 ~ 55 years old(middle age group),56 years old(older age group)),gender(Male,female),ethnic(Mongolian,Han)group count.To study the relationship between root typing and root canal morphology of double root teeth,age,gender,and ethnicity.5.The characteristics of the C-shaped root canal in the root canal cross-section at the 1/3,middle 1/3,and apical 1/3 of the root canal and the detection rate of the C-shaped root canal were analyzed.6.SPSS22.0 software was used for data analysis.Count data was expressed by composition ratio.Differences between groups were analyzed by Chi-square test or Fisher exact probability method.P <0.05 was considered statistically significant.Results:1.Root morphology distribution of mandibular second molar Gender: Divided into two groups according to the left and right tooth positions,the root morphology distribution of different genders,the results showed that there was no significant difference in root morphology distribution of different age groups under different genders and gender groups(P> 0.05).Age: The left and right teeth are divided into 2 groups.The root morphology distribution of different ages shows that the distribution of root morphology is the same in the three age groups.The incidence of the root subtypes from high to low is: double Root type,C-shaped root type,single root type,three root type.There were no significant differences in tooth root morphology distribution at different ages(P> 0.05).Ethnic groups: Mongolian and Han ethnic groups have statistically significant differences in tooth root morphology distribution(P <0.05).Among them,the proportion of double roots in the Han ethnic group(68.97%)is significantly higher than that in the Mongolian ethnic group(55.45%).The proportion of roots is higher than that of Han people(24.14%).(P < 0.05)2.Root canal morphology of mandibular second molars Gender / Age: According to the left and right teeth,the statistics were divided into two groups and the overall incidence was calculated.The same conclusion was reached.The results showed that the bilateral mandibular molars in the mesial root canal showed that the incidence of type IV was much higher than For other root canal forms,the incidence of type IV in men: 50.00% on the left and 45.68% on the right;the incidence of type Ⅳ in women:47.62% on the left and 56.75% on the right.Second,type I and type Ⅱ also have a higher incidence.Gender and age did not affect the distribution of mesial root canal morphology.(P> 0.05)Ethnic groups: According to the left and right teeth,the statistics were divided into two groups and the overall incidence was calculated.The same conclusion was reached.The results showed that the Mongolian and Han ethnic groups in Hohhot had the highest incidence of type IV root canals.The incidence of Mongolian type IV: left: 66.66%;right: 64.52%;Han:left: 45.03%;right: 47.58%.Types Ⅱ and Ⅰ also have a higher incidence in Mongolian and Han nationalities.Chi-square test analysis showed that ethnic groups did not affect the morphological distribution of the mesial root canal of the double root mandibular second molar.(P > 0.05)3.Morphological distribution and detection rate of C-shaped root canal in mandibular second molar The C-shaped root canal cross-section morphology of the population in Hohhot area is significantly different.The incidence of C1-type(left: 66.23%;right: 66.67%)of the crown1/3 section is significantly higher than other cross-section morphologies,followed by C2 type;The incidence of C2 and C3 b in the 1/3 cross section was higher;the incidence of C3 b in the apical 1/3 was significantly higher than other types.(P < 0.001)The detection rate of C-shaped root canals was 27% for Hans and 42.6% for Mongolians.There was a significant difference among ethnic groups and it was statistically significant(P<0.05).C-shaped root canals related to gender and age showed that there was no significant correlation between the detection rate and age and gender.(P > 0.05)4.Symmetry related statistics Full bilateral symmetry analysis showed that the left and right mandibular second molars coexisted and the roots and root canals were completely symmetrical.A total of 209 cases met the requirements.The statistical results showed no significant correlation between the symmetry rate and gender,age,and ethnicity.(P > 0.05)Conclusion1.The root typing in Hohhot is dominated by double roots,followed by C-shaped roots.Root morphology distribution was not significantly related to age and gender.C-shaped roots are ethnically different.The incidence of C-shaped roots in Mongolians is higher than that in Hans(P <0.05).2.In the Hohhot region,the incidence of type IV root canals was highest in the double-rooted mandibular second molars in the mesial root canal system,and its morphological distribution was not significantly related to age,gender,and ethnicity.3.The shape distribution of C-shaped root canal sections had obvious differences(P <0.001).And found that the detection rate of Mongolian C-shaped root canals was significantly higher than that of Hans,which was statistically significant(P <0.05).The detection rate of C-shaped root canals was not significantly related to age and gender.4.The research shows that the complete symmetry rate of tooth roots and root canals of the population in Hohhot has no significant correlation with age,gender and ethnicity.In clinical work,attention should be paid to bilateral diagnosis and examination,and symmetry should not be used as a diagnostic indicator. |
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