Comparison of Class I and Class II Treatment Duration Among Three Different Orthodontic Practices

The purpose of this investigation was to assess the relative treatment time difference (months/appointments) between Class II Division 1 patients and Class I patients from 3 different orthodontic offices. In addition, we also compared the estimated treatment length with the actual treatment length to determine how accurate the orthodontists were in predicting treatment duration. A total sample of 237 patients representing 3 observational groups (Angle Class I nonextraction, and Class II Division I extraction and nonextraction) were selected from the active retention files of each office. Pretreatment ANB angle, pretreatment overjet, and the pre- and posttreatment PAR scores (weighted) were measured. The results of this investigation indicated that among the 3 orthodontic offices, Class II Division 1 cases took an average of 5 more months than Class I cases. There was no significant treatment time difference (months) between the Class II extraction and nonextraction groups. Class II treatments including Herbst therapy were significantly longer (around 8 months) than treatments including headgears. The treatment length in 4 of the 9 observational groups was significantly underestimated and our data demonstrated no association of pretreatment PAR scores and percentage PAR reduction with treatment duration.