| Objectives:The objects of the study were:(1)to explore the relationship between the size of condyle and the sagittal disc-condyle position by magnetic resonance imaging(MRI).(2)to evaluate the size of condyle by cone beam computed tomography(CBCT),and to explore whether there were bilateral and sex differences in the size of condyle.(3)preliminary to explore the relationship between the size of condyle and craniofacial structure.Methods:The subjects were from the Department of Orthodontics,Stomatology Hospital of Shandong University from 2019 to 2020.CBCT and lateral cephalograms were taken for orthodontics.After communication with the subjects,the subjects fully understood the process and purpose of the research and signed an informed consent.The subjects agreed to take bilateral temporomandibular joint(TMJ)MRI.A total of 44 subjects were included,including 20 male subjects and 24 female subjects,aged from 18 to 30 years old,with an average of(24.45±3.27)years old.CBCT data were used to evaluate the size of TMJ condyle.CBCT data were imported into Mimics 20.0 in DICOM format to segment and reconstruct TMJ condyle.Mimics software automatically calculated the volume and surface area of TMJ condyle.Morphometric index(MI)was manually analyzed.The volume,surface area and MI were used as the indexes to evaluate the size of condyle.MRI was used to quantitatively evaluate the sagittal position of bilateral TMJ discs.The lateral cephalograms were analyzed by Jarabak analysis,and the measurement indexes included the length of anterior skull base(S-N),posterior skull base(Ar-S),mandibular ramus(Ar-Go),mandibular body length(Go-Me),posterior height(S-Go)and anterior height(N-Me),sellar angle(∠ N-S-Ar),joint angle(∠ S-Ar-Go),mandibular angle(∠ Ar-Go-Me),upper mandibular angle(∠ Ar-Go-N),lower mandibular angle(∠N-Go-Me),total angle(∠N-S-Ar+∠ S-Ar-Go+∠ Ar-Go-Me),and S-Go/N-Me*100%.When comparing the bilateral difference in the size of condyle,the larger volume,surface area and MI of bilateral condyles were respectively divided into group A,B,C and relatively small values were divided into group a,b,c.When comparing the gender difference in the size of condyle,the larger volume,surface area and MI of bilateral condyles in the male were respectively divided into group D,E,F and the smaller ones were divided into group d,e,f.Similarly,the larger volume,surface area and MI of bilateral condyles in the female were respectively divided into group G,H,I and the smaller ones were divided into group g,h,i.When exploring the relationship between the size of condyle and the sagittal position of TMJ disc,the correlation between the size of condyle and the sagittal position of TMJ disc was firstly analyzed.And then,according to the degree of bilateral disc displacement in one subject,the condyle with more anterior sagittal disc position was divided into G1 group and the other condyle was divided into G2 group.SPSS 22.0 software was used for statistical analysis:(1)The differences of bilateral condylar volume,surface area and MI.(2)The sex differences of condylar volume,surface area and MI.(3)The relationship between condylar volume,surface area and MI and sagittal position of TMJ disc:the correlation between condylar volume,surface area and MI and sagittal position of TMJ disc;the differences of condylar volume,surface area and MI between G1 and G2.(4)The correlation between the volume,surface area and MI of condyle and craniofacial structure was analyzed.For comparison between groups,paired t-test or independent sample t-test was used if the data conformed to normal distribution,otherwise Wilcoxon signed rank sum test or Kruskal Wallis test was used;for correlation analysis,Pearson test was used if the data conform to normal distribution,otherwise Spearman test was used.Significance for all statistical tests was set at P<0.05.Results:1.There were significant differences in the volume,surface area and MI of bilateral condyles(P<0.001).2.There was no significant difference in the volume,surface area and MI of condyle between different genders(P>0.05).3.The relationship between the volume,surface area and MI of condyle and the sagittal disc-condyle position:(1)The volume and surface area of condyle were negatively correlated with the sagittal position of condylar disc(P=0.026,P=0.037),and the correlation coefficients were respectively-0.238 and-0.223.(2)The volume,surface area and MI of condyle in G2 were larger than those in G1,and the differences of condylar volume,surface area and MI between the two groups were statistically significant(P<0.001,P=0.004,P=0.014).4.The relationship between the size of condyle and craniofacial structure:(1)The Condylar volume was positively correlated with Ar-Go,S-Go and S-Go/N-Me*100%(P=0.002,P=0.002,P=0.006),with correlation coefficients of 0.464,0.455 and 0.405 respectively;and negatively correlated with ∠Ar-Go-Me,∠N-Go-Me(P=0.031,P=0.025),with correlation coefficients of-0.326 and-0.338 respectively.(2)The Condylar surface area was positively correlated with Ar-Go,S-Go and S-Go/N-Me*100%(P=0.002,P=0.008,P=0.003),with correlation coefficients of 0.455,0.395 and 0.440;and negatively correlated with ∠Ar-Go-Me,∠N-Go-Me(P=0.014;P=0.037),with correlation coefficients of-0.367 and-0.316 respectively.(3)MI was positively correlated with S-Go,S-Go/N-Me*100%(P=0.001,P=0.025),with correlation coefficients of 0.503 and 0.337 respectively;and negatively correlated with ∠ Ar-Go-Me,∠ N-Go-Me(P=0.018,P=0.008),with correlation coefficients of-0.355 and-0.392 respectively.Conclusion:1.There were significant differences in the volume,surface area and MI of condyle between different sides,but there were no differences between the male and female in adults.2.The volume and surface area of condyle were negatively correlated with sagittal displacement of TMJ disc in adults.3.The volume and surface area of condyle were related to the height of ramus and the direction of mandibular growth in adults.MI was related to the direction of mandibular growth. |
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