A Retrospective study of patients orthodontically treated without extraction for angle class I malocclusion: correction and relapse of mandibular anterior crowdin

Abstract

Correction and relapse of mandibular anterior crowding were evaluated in a cohort of 58 Angle Class I malocclusion patients treated by Dr. Andrew J. Haas using tandem mechanics without extraction of per.manent teeth. The subjects were evaluated, retrospectively, from records taken before treatment (BT), post-treatment (PT), to postretention (PR) . The PR period averaged 8 years with a minimum of 4 years and a maximum of 20 years. Each subject received maxillary expansion as part of the therapy: Group A (N=32) had rapid palatal expansion using a Haas appliance, Group B (N=26) subjects had a headgear with an expanded inner bow and an expanded archwire. The response variables measured at each of the three time intervals were: overbite, overjet, intercanine distance, inter.molar distance and irregularity index. Groups A and B were not significantly different for either subject age (A 14.8, B 14.5 years), retention time (A 7.1, B 6.8 years), or post.-retention time (A 8.2, B 7.8 years). Moreover, groups A and B did not show significant difference for any of the response variables at BT. However, there was a statistically significant difference in the treatment times of Group A (2.2 years), and Group B (2.7 years) (p=0.0133). A statistically significant treatment effect was observed for most response variables in Groups A and B. Overbite, overjet, and irregularity index were significantly reduced, intermolar distance was significantly increased,· and intercanine distance showed no significant change in Groups A and B. In the post-retention p~riod, there was a tendency for variables to change slightly toward the.tr BT values but no compromise of orthodontic correction was noted. Irregularity index in Group A was corrected from 4.8 to 1.1 mm and remained at 1.1 mm in the PR period. Irregularity index in Group B was corrected from 5.1 to 1.2 mm (p=.0001) and changed slightly from 1.2 to 1.7 mm (p=.0540) in the PR period. Contrary to many published ~eports, the irregularity index in this cohort of subjects was quite constant at an average of eight years of post-retention follow-up.