Original article
Condyle and fossa shape in Class II and Class III skeletal patterns: A morphometric tomographic study

https://doi.org/10.1016/j.ajodo.2004.05.024Get rights and content

Introduction: The purpose of this investigation was to study the shapes of the condyle and the glenoid fossa in patients with Class II Division 1, Class II Division 2, and Class III malocclusions. Methods: Axially corrected tomograms of 189 patients were used (109 Class II Division 1, 47 Class II Division 2, and 33 Class III). Five points on the condyle and 7 on the outline of the fossa were digitized. Size was assessed by the centroid size of each structure, and measurements of shape were made by principal component analysis of the Procrustes residuals. Results and Conclusions: Inspection of the principal components of shape showed that shape variability of the condyle was mainly related to inclination of the condylar head; shape variability of the fossa was related to inclination of the eminence and fossa height. Centroid size was correlated to age in the Class III group only. Condylar and fossa shapes were found to be different between the groups; the Class III group had a more elongated and anteriorly inclined condylar head and a wider and shallower fossa. In the Class III group, the condyle was closer to the roof of the fossa. The 2 Class II divisions differed only in the position of the condyle in the fossa, which was situated more anteriorly in the Class II Division 1 group.

Section snippets

Material and methods

The sample consisted of right and left, corrected TMJ tomograms of 189 patients. The records were selected retrospectively and included all patients for whom corrected tomograms were available, excluding those with TMJ dysfunction signs and symptoms. These tomograms had been taken before orthodontic treatment, when functional appliances, chincups, or orthognathic surgery was planned. For standardization purposes, a submentovertex radiograph was used to measure the inclination of the long axis

Results

Computation of average shapes and PCs was performed with Viewbox 3 cephalometric software. Statistical calculations were made by using StatsDirect (StatsDirect, Cheshire, United Kingdom)14 and PAST (Palaeontologia Electronica, Oslo, Norway)15 software.

Age distribution was skewed toward the right (larger ages) for all 3 malocclusion groups. Comparison of the 3 groups by Kruskal-Wallis ANOVA, followed by multiple comparisons, showed that the Class II Division 1 group was younger than the Class II

Discussion

Condylar and fossa shapes have traditionally been assessed by subjective evaluation, ie, by assigning to “shape groups,” such as convex, flattened, irregular, or triangular. We present, to the best of our knowledge, the first effort to subjectively measure and compare condylar and fossa shapes between different malocclusion groups using morphometric methods. In addition, we present results related to condyle and fossa size, and condyle position within the fossa.

Centroid size was used to measure

Conclusions

  • 1

    Shape variability of the condyle was mainly related to inclination of the condylar head.

  • 2

    Shape variability of the fossa was related to inclination of the eminence and depth of the fossa.

  • 3

    Sizes of the fossa and condyle were found to be correlated to age in the Class III sample only.

  • 4

    Condylar shape was different in the Class III group compared with the 2 Class II groups: the condyle was more elongated and inclined anteriorly.

  • 5

    Fossa shape was different in the Class III group—wider and shallower than

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    Copyright © 2005 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.