The aim of this study was to highlight the current dilemma of gonial angle measurement on orthopantomograms and lateral cephalograms of adults with different skeletal malocclusion types. The sample consisted of 50 Class I, 50 Class II and 50 Class III (25 males and 25 females for each group) orthopantomograms and cephalograms obtained from previously treated orthodontic patients. For each malocclusion group, the angle between Tweeds mandibular plane and the tangent from the line running along the gonion to the distal point of the condyle was measured on the right and left sides on orthopantomograms and the superimposed images of the mandible on cephalograms. Paired t-test demonstrated no significant difference between the values of gonial angles determined by cephalograms and orthopantomograms in Cl I patients. Pearson correlation also showed a high correlation between gonial angle values measured on the two diagnostic tools in Cl I patients. In Cl II and Cl III patients, statistical analysis showed a significant difference between the gonial angles defined by cephalograms and orthopantomograms. Orthopantomograms can be used for determining gonial angle as accurately as cephalograms in Cl I patients. Hovewer, orthopantomograms are not appropriate tools for measuring the gonial angle in Cl II and Cl III patients.
Key words: Gonial angle, orthopantomogram, cephalogram
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