Evaluation of Arch Dimensional Changes after Orthodontic Treatment in Extraction and Non- Extraction Cases. an In-vitro Study

Orthodontic treatment for malocclusion correction may involve extraction or non-extraction of specified teeth for esthetic and functional harmony. Antero-posterior and transverse arch dimensional changes following orthodontic treatment has been evaluated using many methods. The present study evaluated the arch dimensional changes after orthodontic treatment in extraction and non-extraction cases using AUTO CAD system with medial and lateral edges of 3 rd primary rugae and mesio-incisal tip of the most prominent incisor as the reference points. A total of 100 (Group 1Upper bicuspid extraction=50; Group 2Non-extraction=50) orthodontically treated cases were selected in the age range of 19-25 years (Males=50; Females=50). Their pre and post treatment study models were collected and photographed. The photographic data was then digitized and arch dimensional changes were measured using AUTO CAD. The data obtained were subjected to statistical analyses using Paired t-test, Unpaired t-test,Levene's test and Gain score measurement test. There were significant antero-posterior tooth movements in extraction cases when compared to non extraction cases, a significant reduction in the intermolar width after premolar extractions but minimal changes in the intercanine width showing significance at 5% level. In non-extraction cases, there was no significant arch dimensional changes after orthodontic treatment in both intermolar and intercanine region. Maximum antero-posterior arch dimensional changes can be seen in orthodontically treated bicuspid extraction cases and non extraction cases show minimal changes in the antero-posterior dimensions even after orthodontic treatment. Significant amount of anchorage loss can be seen in upper bicuspid extraction cases when compared to non extraction cases. Reduction in the intermolar width and contraction of maxillary arch occurred in upper bicuspid extraction cases with minimal changes in the intercanine width. Minimal transverse arch dimensional changes occurred in non-extraction cases after orthodontic treatment.