The European Journal of Orthodontics Advance Access originally published online on July 15, 2005
The European Journal of Orthodontics 2005 27(5):501-506; doi:10.1093/ejo/cji029
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The relationship between temporomandibular joint disc morphology and stress angulation in skeletal Class III patients
Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kanazawa University, Japan
Address for correspondence Koichiro Ueki, Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kanazawa University, 13-1 Takaramachi, Kanazawa 920-8641, Japan. E-mail: kueki{at}med.kanazawa-u.ac.jp
The aim of this study was to examine the relationship between disc position and stress direction on the condyle by means of stress analysis using the rigid body spring model (RBSM) theory. The material consisted of 88 joints of 44 Class III dentofacial deformity patients, divided into symmetry and asymmetry groups on the basis of the Mx–Md midline position. The asymmetry group was identified by comparison with a reference midline vertical plane passing through a plane from ANS to Me. Asymmetry was diagnosed when the angle between these two planes was greater than 3 degrees. The geometry of the stress analysis model was based on sagittal tomography of the subject. The first molar, gonial angle, and the most anterior, superior, and posterior points on the condyle were plotted on a computer display, and stress angulation on the condyles was calculated with the RBSM program.
In addition to anterior displacement with or without reduction, three types of disc position could be identified using magnetic resonance imaging (MRI): anterior, fully covered and posterior. In the asymmetric group, stress angulation was significantly higher (P < 0.05) at the deviation side compared with the non-deviation side. There was also a significant correlation between disc position and stress angulation (P < 0.05). In the asymmetry group, regression analysis indicated a significant correlation (P < 0.001) between the difference in stress angulation (between the deviation side and the non-deviation side) and the degree of asymmetry (measured by the angle of asymmetry). This study demonstrated that temporomandibular joint (TMJ) stress was associated with TMJ morphology in Class III patients whether or not they were asymmetric.
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  K. Ueki, K. Nakagawa, S. Takatsuka, and E. Yamamoto The change of stress distribution on the condyle after mandibular setback surgery Eur J Orthod, October 1, 2006; 28(5): 433 - 439. [Abstract] [Full Text] [PDF]
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