The relationship between hard and soft tissue changes following treatment of Class II division 1 malocclusions using Edgewise and Fränkel appliance techniques.

Lateral-skull radiographs were used to examine the hard and soft tissue changes following overjet reduction in 62 children with moderately severe Class II division 1 malocclusions. Thirty-two patients were treated by non-extraction methods using Fränkel appliances, and the remainder by a standard Edgewise technique involving extractions and extra-oral traction. The relationships between changes in upper and lower lip positions, naso-labial angle, and labiomental fold with those in the underlying dento-skeletal elements were examined. The ratio between movement of the upper lip prominence and upper incisor crown was also calculated. Finally, the patterns of correlation between the two groups were compared. Both Spearman and partial correlations were calculated. The latter were used in an attempt to separate the true treatment effects from those of growth. This reduced the number of significant correlations considerably, 'sharpening' the results so that expected levels of agreement were enhanced, whereas spurious results were reduced. Few correlations reached a level of r = 0.7 or above. Incisor retraction was correlated with upper lip movement at this level only in the Edgewise group. No correlations were found between changes in naso-labial angle, labio-mental fold, and their underlying hard tissues. The Spearman correlations largely agreed with those of other authors, indicating that most of their apparently concordant hard and soft tissue movement was due to growth rather than appliance therapy. The use of ratios to compare upper lip and maxillary incisor retraction was not relevant in the functional appliance group because the average lip change was very small. It is concluded that the relationship between hard and soft tissue movement is too complex to be examined in a relatively simplistic way.