Improved Orthodontic Retention Following Corticotomy Using ABO Objective Grading System

Objectives: To compare immediate post treatment and retention outcomes in Class I, non-extraction orthodontic patients treated with (n=28) and without alveolar corticotomy (n=28) to resolve crowding. Methods: All patients were treated with fixed, edgewise orthodontic therapy and were requested to wear removable Hawley retainers for 6 months full time then night time thereafter. Study casts and panoramic radiographs were evaluated using the ABO Objective Grading System and scoring instrument for 8 criteria plus total score at immediate post orthodontic treatment and at least one year retention. Results: Wilcoxon Signed Rank testing demonstrated significant (p<.05) improvements during the retention phase in 5 of 9 grading criteria for the group with corticotomy and 3 of 9 criteria without corticotomy. Mann-Whitney U testing showed that the two groups were statistically homogeneous (p>.05) at post treatment, but at retention, the corticotomy-facilitated group was significantly better for alignment (1.7 vs 3.8, p=.001), marginal ridges (3.3 vs 4.9, p=.018) and total score (22.1 vs 27.2, p=.01). Mann-Whitney U testing for effect sizes demonstrated the total score dropped precipitously (improved) during retention in the group that had undergone alveolar corticotomy compared to group without corticotomy (7.6 vs 3.7, p=.0.18). Conclusions: Alveolar corticotomy-facilitated orthodontic treatment resulted in significantly greater improvements during the orthodontic retention period and a better retention outcome as judged using the ABO Objective Grading System.