Evaluation of the variable anchorage straightwire technique using Ricketts' growth prediction

The purpose of this retrospective study was to evaluate the treatment effects of the variable anchorage straightwire technique (VAST) in Angle Class II patients using Ricketts' growth prediction analysis. The subjects belonged to two groups: a control, consisting of 30 untreated Class II Swedish individuals (20 girls, 10 boys) with a mean age of 11.2 years, and the other 29 Swedish patients (14 girls, 15 boys), mean age 12.6 years, post-normal and with an increased overbite (OB), treated with the VAST. Two lateral cephalograms were available for every individual. Growth prediction according to Ricketts' visual treatment objective (VTO) was used to estimate the expected growth increments for a 2-year period. It was first used in the control group to determine its validity and then applied to the treated group to evaluate the net effects of treatment. Cephalometric evaluation based on Ricketts' analysis and additional dentoalveolar variables were carried out. Statistical analysis was undertaken using a paired Student's t- and Wilcoxon signed ranks tests. The method of predicting growth according to the VTO was, in general, valid in the untreated subjects, apart from the inclination of the lower incisors, where the proclination had been underestimated. In the treated group, the net effects of treatment were significant for the dentoalveolar variables: reduction of overjet (OJ) and OB, proclination and relative intrusion of the lower incisors, extrusion of the molars, and increase in lower face height. The growth prediction method according to VTO was found to be valid in a sample of Swedish post-normal children concerning skeletal and dentoalveolar variables. The VAST treatment net effects in these growing patients were achieved mainly by dentoalveolar changes.