Analysis Of The Anterior Loop And Mandibular Incisive Canal On Cone-Beam Computed Tomography

Objective: This study aimed to acquire three-dimensional imaging data in the anterior mandible by cone-beam computed tomography(CBCT),and to measure the anterior and cadual extension of the anterior loop(aAL and cAL)and the mandibular incisive canal(MIC)related to implant using NNT software,thus reducing complications and risks of implant and chin bone harvesting.Materials and methods: 418 Chinese patients were selected consecutively scanning by the NewTom VG device.This study included 169 males and 249 females,with average age being35.25±15.56 years.Images were reconstructed and measured by NNT software,and 60 cases were picked out repeated measurements.These measurements contained: 1.the visibility and length of aAL,cAL and MIC,and the diameter of MIC at origin;2.the diameter of MIC and the distances between MIC and tooth apex,buccal cortical border,lingual cortical border,inferior border of the mandible and the midpoint of alveolar ridge at each tooth position,as well as the start point andendpoint of MIC.SPSS 16.0 software package was applied for the reliability test,and the statistical analysis among gender,age and dental status groups was also calculated.Results: The results of 60 repeated measurements showed the intraclass correlation coefficient(ICC)was more than 0.7,thus presenting high interobserver reliability.The prevalence of aAL,cAL and MIC were 93.54%(n=782),99.94%(n=835),97.01%(n=811)respectively.The mean lengths of aAL,cAL and MIC,the mean diameter of MIC at origin were 2.53±1.26 mm,5.99±1.69 mm,10.72±4.45 mm and 1.94±0.52 mm respectively.MIC went lingually and downward on the way to the symphysis,as the diameter decreased at the same time.In the gender view,males have a longer aAL and cAL than females(P<0.05);a larger size of MIC at origin was found in males(P<0.01);MIC in females was closer to the buccal side and the inferior border in the mandible compared to males(P<0.01).As for the age group,except for over sixty years group,the mean length of aAL and cAL decreased with age(P<0.05);the mean length of MIC increased with age(P<0.01).For the analysis of dentition,patients with tooth loss in the interforaminal region displayed a longer MIC than the dentate;the diameter of MIC at origin showed a larger size in the completely edentulous cases.Conclusion: Large variations of anatomical structures such as aAL,cAL and MIC implied no absolutely safe margin in the anterior mandible for surgery.Cone-beam computed tomography could still be the essential preoperative examination in judging the spatial relationship in the anterior mandible,for the integrity of showing course and position of the anterior loop and MIC,thus reducing surgical complication and risk in implant and chin bone harvesting as much as possible.