Three-dimensional Study On The Mandibular Morphology And Position Of Patients With Unilateral Brodie Bite

Objective: This study aims to explore the morphological symmetry of the mandible and position of the temporomandibular joint in patients with unilateral multiple scissors-bites(Brodie syndrome or Brodie bite)in three dimensions,thus providing thesis for the early diagnosis and treatment in patients with unilateral Brodie bite.Methods: 14 cases with unilateral brodie bites who visited stomatology center,xiangya hospital attached to Central South university between October 2016 and October 2021 were collected as study group(male 10 cases,female 4 cases,mean age 18.43 ± 4.24y),and other 14 age-,gender-matched patients with Angle I malocclusion(male 6 cases,female8 cases,mean age 18.07 ± 5.48y)were selected as control group.We utilized cone beam computed tomography to scan the jaws of all subjects in both groups and gained their DICOM files.Mimics Research 19.0 and Geomagic Control X software were used to perform surface-to-surface analysis in mandibular structure of these subjects.By setting tolerance at±0.50 mm,±0.75 mm and ±1.00 mm respectively,the influences of unilateral brodie bites on the morphological symmetry of mandibles were evaluated.Next,we used Invivo 5.0 software to perform the threedimensional reconstruction for CBCT of all the subjects in both groups.We measured the sizes,angle inclinations and positions of both condylar processes and temporomandibular joint spaces,thus investigating the role of brodie bites in morphology and positions of temporomandibular joints.SPSS 21.0 package software was used to analyze the statistics.Results: 1.The volume of hemi-mandible on the scissors-bite side showed no significant difference with the volume of hemi-mandibular on the non-scissors-bite side.2.When the tolerance was set at ±1.00 mm,the average matching percentage of the control group was 89.56%,while the average matching percentage was 73.43% in the study group,with significant difference(P < 0.001).3.Compared with the non-scissors-bite side in patients with Brodie syndrome,the condyle on the scissors-bite side significantly showed more anterior movement with 1.49 mm(P = 0.03),AP condyle joint positions(P = 0.01),and larger posterior joint spaces with0.39 mm(P = 0.03).4.In contrast with the control group,the condylar heights of patients with unilateral Brodie syndrome decreased remarkably on both the scissors-bite side(P = 0.03)and non-scissors-bite side(P =0.01),which decreases 1.63 mm and 2.05 mm respectively,the AP condyle joint position was more anterior(P = 0.02)on the scissors-bite side,while the condyles showed significant more posterior inclination with 7.89°(P= 0.01)and more lateral movement with 3.29 mm(P = 0.03)on the nonscissors-bite side.Conclusions: 1.The mandible of patients with unilateral Brodie bites showed significant asymmetry between the scissors-bite side and nonscissors-bite side,though without remarkable volumetric difference.2.The condylar heights of patients with Brodie bite on both sides decreased significantly.Patients with unilateral scissors-bite had more anterior AP condylar joint positions and larger posterior joint spaces.