Mandibular condyle and fossa morphology according to vertical and sagittal skeletal patterns: a cone beam computed tomography study

Abstract

Anatomy of the temporomandibular joint (TMJ) is diagnostic and prognostic indicators of clinical conditions and TMJ-related examination before orthodontic treatment is essential. However, influence of dentofacial skeletal pattern on the joint morphology has not been completely understood. To compare the TMJ structures in the diverse skeletal patterns, it is necessary to obtain the combined classifications of skeletal type according to the vertical and sagittal patterns. The purpose of this study was to compare morphology of TMJ structures according to vertical and sagittal skeletal patterns using CBCT and to understand interactive effects of diverse skeletal patterns on the joint morphology. This retrospective study included 131 subjects who had no TMJ symptom and had taken lateral cephalogram and CBCT. The subjects were divided into 3 sagittal groups of Class I (n = 43), II (n = 42), and III (n = 46) by ANB angle. They were also divided into 3 vertical groups of hypodivergent (n = 37), normodivergent (n = 47), and hyperdivergent (n = 47) by Sella-Nasion and mandibular plane (SN-MP) angle. We measured condylar volume, condylar size (width, length, and height), fossa size (length and height), and condyle-to-fossa joint space. All measurements were analyzed by one-way ANOVA and interactive skeletal effects on the measurements were analyzed by two-way ANOVA. The results were listed below:

1. There were significant differences among three sagittal groups for condylar width, condylar height, and fossa height: the Class III group showed higher values of condylar width, condylar height, and fossa height than the Class II group (P < 0.05). 2. Condylar volume, condylar width, fossa length and height, and superior joint space were significantly different according to the vertical skeletal patterns: mean condylar volume and superior joint space in the hyperdivergent group were significantly smaller than the other two vertical groups (P < 0.05), and fossa length and height were significantly larger in the hyperdivergent group than in the other groups (P < 0.05). Condylar width in the hypodivergent group was significantly larger than in the hyperdivergent group (P < 0.05). 3. There were interactive effects of sagittal and vertical skeletal patterns on condylar width, posterior joint space, and fossa length (P < 0.05). In condylar width, the hyperdivergent group showed significantly lower value than the other vertical groups, and the Class II group was the lowest among sagittal groups. The Interaction of the hyperdivergent and the Class II skeletal patterns makes condylar width smaller, definitely. Posterior joint space showed no main effects of the sagittal and vertical skeletal patterns, but their interaction were statistically effective (p < 0.05), not clinically. Fossa length was significantly larger in the hyperdivergent group than in the other groups, and the Class III tendency amplified that vertical effect.

TMJ morphology differed according to diverse skeletal patterns. Vertical skeletal patterns were more influential on the condyle and fossa morphologies than sagittal skeletal patterns. The condylar width and fossa length were affected by both vertical and sagittal skeletal patterns.

측두하악관절(TMJ)의 해부학적 구조는 관절의 임상적인 상태에 대한 진단적 도구, 또는 치료 예후에 대한 지표라고 할 수 있으므로 교정 치료가 시작되기 전 TMJ 관련 검사를 꼭 시행해야 한다. 그러나 치열안면골격의 유형이 측두하악관절에 미치는 영향에 대해서는 완전하게 의견 일치가 되고 있지 않다. 다양한 골격 형태에 따른 TMJ 구조물의 비교를 위해서는 수직 방향과 시상 방향의 골격 유형을 조합한 분류가 필요하다. Cone-beam computed tomography (CBCT)에 의해 얻어진 3차원 영상을 통해 TMJ 구조물을 여러 각도의 평면으로 볼 수 있을 뿐만 아니라 부피의 측정도 가능해졌다. 이를 통해 더 정확하게 진단하게 되고 치료 결과도 더 믿을 만 해졌다. 이번 연구의 목적은 CBCT를 이용해 수직적, 시상적 골격 유형에 따른 TMJ 구조물의 형태학적 차이를 확인하는 것이며, 또한 골격 형태의 상호작용이 관절의 형태에 미치는 영향에 대해 알아보고자 한다. TMJ에 이상이 없으면서 lateral cephalogram과 CBCT를 모두 촬영한 교정 전 환자 131명을 선택하였다. 환자들은 ANB angle 값을 통해 skeletal Class I (n = 43), Class II (n = 42), Class III (n = 46) 군으로 분류되었고, 또한 Sella-Nasion 선과 mandibular plane 사이의 각도 (SN-MP angle)를 통해 hypodivergent (n = ...