Classification of occlusion reconsidered

Katz's quantitative modification of Angle's occlusion classification has been found to have a high intra- and inter-examiner agreement among orthodontists. In the present study an attempt was made to introduce a 'combined' system comprising Katz's modification and overjet/overbite millimetric measurements in order to attain a more meaningful and complete classification of malocclusion than is presently available. A group of 32 raters (16 orthodontists and 16 senior-year students) examined 14 study models twice, with an interval of at least 1 month between examinations. In total, 448 x 2 determinations were performed. The percentage agreement of the Angle, the modified and the 'combined' systems, as well as the performance of the orthodontists versus the students were compared using the paired t-test. The percentage agreement obtained by both orthodontists and students was highest for Katz's modification and lowest for Angle's method. The overjet/overbite measurements affected the agreement in Katz's modified technique. The orthodontists surpassed the students with respect to Angle's method (P = 0.025), whereas no statistically significant difference existed between orthodontists and students regarding Katz's modification or the 'combined' system. It is concluded that in view of the relatively low agreement in the 'combined' method, it cannot be recommended for clinical application. The Katz's modified method, on the other hand, may be a helpful supplement to Angle's classification.