Correlation Between Root Canal Isthmus And Root Vertical Fracture

Objective: The relationship between root canal isthmus and vertical root fracture(VRF)was analyzed by cone-beam computed tomography(CBCT),cases/periapical radiographs,and further verified by in vitro experiment.Methods: 1.Firstly,a total of 7,123 teeth from 297 patients were observed using CBCT in the database,and age,sex,and dental position of the patients were recorded.The isthmus was divided into 7 categories according to the Pécora classification method,and the frequency and distribution of isthmus were recorded by percentage The Chi-square test/Fisher exact probability method were used to compare the distribution differences of isthmus between sex and age groups.Secondly,a retrospective study was conducted on 115 cases/periapical radiographs diagnosed with VRF.The proportion of root fracture in different age,sex and tooth position was analyzed.Finally,descriptive language was used to analyze the distribution characteristics of isthmus and root fracture between sex,age and dental position 2.A total of 40 maxillary premolars with or without root canal isthmus were collected.After root canal preparation,a low-speed machine was used for transverse cutting,and the difference in dental microcrack formation was observed under a stereomicroscope.Results:1.(1)The frequency of mesial roots of the mandibular molars isthmus was the highest,followed by maxillary premolars,mesiobuccal roots of the maxillary molars,mandibular anterior teeth,and mandibular premolars.the maxillary anterior teeth number of RCIs was negligible.(2)Vertical root fracture was most common in the mesial root of mandibular molars,followed by the mesiobuccal root of maxillary molars,maxillary premolars,mandibular premolars,and mandibular anterior teeth.(3)Except for the higher frequency of isthmus in the mandibular central incisor and maxillary second premolars in males compared to females(P<0.05),there was no significant difference in isthmus between sexes(P>0.05).The proportion of vertical root fracture was similar in male and female.(4)The highest frequency of RCI was found in patients 20-40 years old,and the highest proportion of VRF was found in the 41-60 years age group 2.Dental microcrack formation in isthmus was higher than that without isthmus,and the direction was mostly buccal-lingual.Conclusion: The isthmus is the weak area in the root canal system of permanent teeth,sharing a similar predilection for distribution characteristics with vertical root fracture,which may be one of the internal causes of the root fissure.Attention should be paid to this weak area during mastication and root canal therapy to reduce the occurrence of vertical root fracture.