A Correlation Study of Two Methods of Assessing Skeletal Pattern

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Abstract
A study was carried out to compare the two current methods, Downs' method and the conversion (Ballard's) method, of assessing skeletal pattern. Correlations were moderate to high for the Class I and Class III groups (+0·6 and +0·76 respectively), but low for the Class II group(+0·35). The latter correlation, however, improved to +0·54 when the angle ANB was corrected for the value of the angle SNA. The point of rotation of the incisors, whether at the apex or apical third of the root, and the adjustment in the lower incisor angulation for the maxillary-mandibular plane angle value did not make any appreciable difference to the correlations obtained. The correlation for the total sample was about +0·7. When the cases were classified into the three skeletal categories the correspondence between the two methods was about 69 per cent. It is concluded that there are insufficient grounds for the recent criticism of the conversion method.

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