Imaging Study Of The Effect Of Unilateral Posterior Scissors Bite On The Osseous Structure Of Temporomandibular Joint

Objective: To measure and analyze the morphological differences of scissors-bite side,no scissors-bite side,age and gender related the bony structure of temporomandibular joint(TMJ)in patients with unilateral posterior scissors bite by cone beam computed tomography(CBCT)and three-dimensional reconstruction.Methods: From July 2016 to December 2021,95 patients with unilateral posterior scissors bite in the Temporomandibular Joint Specialist Clinic of The First Affiliated Hospital of Xinjiang Medical University were analyzed retrospectively,including 71 females and 24 males with an average age of 24.83±9.45 years(12-54 years).The subjects were divided into two groups: the scissors-bite side(n= 95)and the no scissors-bite side(n= 95),and divided into three groups according to age: group 1(12-20 years old),group 2(21-30 years old)and group 3(> 30 years old),divided into male(n=24)and female(n=71)groups according to gender.Mimics19.0 software was used to reconstruction the condylar volume(CV),condylar superficial area(CSA),condylar morphological index(CMI),fossa volume(FV),fossa superficial area(FSA),fossa morphological index(FMI),the proportion of the condylar volume in the articular fossa(CV%),the proportion of the condylar superficial area in the articular fossa(CSA%),anterior joint space(AJS),posterior joint space(PJS),superior joint space(SJS),and medial joint space(MJS)were measured and analyzed.The bilateral condyle was fitted and compared,and the position of the difference between the scissors-bite side and the no scissors-bite side was described.Results: CV,CSA,SIS,AJS were significantly different between scissors-bite side and no scissors-bite side.Age-related changes in the CV %,CSA %(no scissors-bite side),SJS,AJS(no scissors-bite side),MJS(no scissors-bite side)was statistically significant(P < 0.05).CV,CSA and CMI of different genders were statistically significant(P < 0.01),and FV,FSA(no scissors-bite side),FMI(scissors-bite side)and AJS(no scissors-bite side)were statistically significant(P < 0.05).After 3D condyle model fitting,the difference ratio was 23% on the back slope,21% on the top slope,20% on the front slope,19% on the outer side and 17% on the inner side.Conclusion: Due to the abnormal occlusal state for a long time,the pathological occlusal force stimulation in TMJ could cause condylar morphological changes,and related to age and gender.It was found that there was a great difference in the posterior oblique plane after bilateral condylar fitting.