Study of a classification of occlusion

A functional classification of occlusion based on the sounds produced by tooth contact was first proposed in 1970. The classification was found useful for identifying patients prone to gnathic dysfunctions as a significantly higher proportion of these patients were in Class C than in Class A. In the studies described in this paper other parameters of occlusion were measured to find if there were differences between the classes in addition to the differences in occlusal sound duration which identified the classes. The first study found highly significant differences in co-ordination between Class A and Class C as measured by the coincidence of sound patterns. Many significant differences at the 1% level were found in the F test of samples of 5 successive occlusal sounds in series of 25 sounds in Classes A and C, but these differences diminished as the series of sounds was prolonged, suggesting that the subject's ability to find stable occlusal positions improved with successive occlusal contacts. No significant differences were found in time intervals between the sounds in different classes, but significant differences were found in masseter muscle activity in relation to the presence or absence of silent periods between occlusal classes. It was concluded that the functional classification of occlusion based on the duration of tooth contact sounds was valid.