[A study of the relationship between the capacity of oral cavity proper and skeletal malocclusions].

A new method was developed for evaluating the quantitative capacity of the oral cavity proper with a three dimensional measurement system, and this was used to measure the capacity in 50 cases of adult female malocclusions. Morphologies of the dental arches, palates and maxillo-facial structures were measured on dental casts and both P-A and lateral cephalograms. Correlation coefficients were calculated between those measurements and the capacity of the oral cavity. Results are shown below: 1. Class III cases were statistically larger than classes I and II in the capacity of the oral cavity proper but there were no significant differences between those of class I and class II. 2. There were no significant differences among classes I, II or III in the maxillary capacity of the oral cavity proper. Class III, however, was significantly larger than classes I and II in the mandibular capacity of the oral cavity proper. 3. There was no significant difference among the three types of palatal morphology: Horizontal, Convex, and Concave. 4. Porions where high correlations were shown were different for classes I, II and III as to the relationship between both the dental arch length and width, and the capacity of the oral cavity proper. The general indication was that width was more related to the size of the capacity of the oral cavity proper than length was. 5. There were significant correlationships between the capacity of the oral cavity proper and maxillo-facial skeletal size in class I, the vertical dimension in class II, and the mesio-distal dimension in class III for the mandibular and maxillary measurements of both P-A and lateral cephalograms.