The CBCT Study Of Maxillary First Premolars And Application Of Two Root Canal Classification Systems

Objective This cone beam computed tomography（CBCT）study aimed to evaluate the root and canal morphology of maxillary first premolars in Hohhot’s part of population using two classification systems.The Vertucci root canal classification system and the new Ahmed root canal classification system were used to classify the common root canal morphology and variation types of maxillary first premolars,so as to provide reference for not only the dental anatomy but also clinical diagnosis and treatment in this area.Methods A total of 785 cases of CBCT images of patients in Hohhot Stomatological Hospital from January 2019 to January 2021 were selected.400 patients（all with informed consent）were selected according to the inclusion criteria,and a total of 800 maxillary first premolars were used as the research objects,Record the included patients’information（name,gender,age,ethnicity）and group them.The French Kodak9500 oral cone-beam CT was used to observe the root type,root bifurcation position and root canal type of the maxillary first premolars.After data sorting,SPSS 20.0statistical software was used for analysis.The count data were expressed by frequency and composition ratio,and the comparison between groups was performed by chi-square test or Fisher’s exact probability test.The difference was statistically significant with P<0.05.Results 1.Root morphology distribution:Among 800maxillary first premolars,there are 586 single-rooted premolars,with a detection rate of73.25%,double-rooted 204,with a detection rate of 25.5%,and three-rooted with 10teeth,with a detection rate of 1.25%.（1）Distribution of male and female genders:The detection rate of single root maxillary first premolar in women was higher than that in men,and the detection rate of double root maxillary first premolar in men was higher than that in women.There was a significant difference in the distribution of the two root types between men and women（χ²=7.202,P<0.05）;（2）Distribution in the three age groups:the detection rates of the three root types in the low-age group,middle-age group,and senior-age group are all:Single-rooted type>double-rooted type>three-rooted type,the distribution is not significantly related to age（P>0.05）;（3）Distribution in different ethnic groups:the detection rate of three-rooted type in Mongolian nationality is higher than that of Han nationality（χ²=21.644,P<0.05）.2.Root bifurcation position:The total bifurcation rate of the maxillary first premolars is40%,and the bifurcation rate of the root cervix 1/3,root middle 1/3,and apical 1/3 are10%,62.5 and 27.5%.The number of teeth branched in the middle 1/3 of the root is the most.3.Distribution of root canal types:（1）According to the Vertucci classification,the most common root canal type of maxillary first premolars is type Ⅳ（40.13%）.Among the single root canals,type Ⅰ to Ⅶ root canals were detected,and the common root canal type was type Ⅱ（31.06%）.All double-rooted root canal types are type Ⅳ,and three-rooted type is type Ⅷ.The detection rate of type Ⅰ root canal in the low-age group,middle-age group and senior-age group:21.07%,16.42%,12.41%,the detection rate decreases with age,while the total detection rate of the other types of root canals increase.The detection rate of type Ⅷ root canals in Mongolian group was higher than that in Han group,and the distribution difference was statistically significant（χ²=25.092,P<0.05）.There was no statistically significant difference in the distribution of root canal types between male and female genders and different ages（P>0.05）;（2）The results of Ahmed root canal classification showed that the²MfpB¹P¹code was the most common in maxillary first premolars,accounting for 25.5%,and the most common root canal configuration of single maxillary first premolars was¹Mfp^2-1（31.06%）.The coding type of the double-root maxillary first premolar is²MfpB¹P¹,and the three-root code is³MfpMB¹DB¹P¹.4.Bilateral symmetrical distribution of roots and root canals:The total bilateral symmetry rate was 81.25%,and there was no statistically significant difference in symmetry rates among different age groups,genders,and nationalities.Conclusion 1.The maxillary first premolars in Hohhot have extensive root and root canal anatomical variation.The root morphology of the single-rooted is the most common type,mostly in women,the double-rooted type is more common in men,and the incidence of the three-rooted type in Mongolians Higher.Most of the teeth bifurcate in the middle 1/3 of the root.2.Root canals have many shapes,with Vertucci Ⅳ and Ahmed²MfpB¹P¹being the most common.Vertucci type Ⅷ also called Ahmed³MfpMB¹DB¹P¹has a high incidence in Mongolian.In clinical treatment,we should pay attention to this type of root canal variation in order to prevent the failure of treatment due to the omission of buccal root canal.The detection rate of Vertucci type Ⅰ root canal showed a decreasing trend with age,while the total detection rate of the other types increased,suggesting that with age,the root canal morphology tends to become more complicated.Therefore,the understanding of root canal morphology should be based on mastering its basic morphology and deeply understanding its characteristics of"aging dynamic change",which is of great significance in clinical treatment.3.The bilateral symmetry rate of the root and root canal morphology of the maxillary first premolars is relatively high.It can be used as a reference in the diagnosis and treatment of bilateral root canals,but it cannot be used as a basis for diagnosis and treatment.4.In this study,compared with Vertucci root canal classification system,Ahmed root canal morphology classification system can describe the detailed morphological information of root and root canal at the same time,and can describe the root and root canal morphology in a more accurate and practical way,which can be widely used in clinical practice.Cone beam CT three-dimensional imaging has high performance,which can accurately evaluate the root and root canal anatomy of maxillary first premolar,and can be widely used in the study of internal and external root anatomy.