Association of Marginal Ridge Discrepancies (MRDs) and Root Angulation Errors

Methods: One hundred consecutive cases which met the following inclusion criteria were examined: treatment fully completed, and the pre-treatment and post-treatment casts and panoramic radiographs were available. Cases with unerupted teeth, interproximal restorations, or extracted premolars were excluded. The pre-treatment and post-treatment root angulations and marginal ridge relationships were scored on both sides of the arch between the mandibular-second-premolar and mandibular-first-molar, and mandibular-first-molar and mandibular-second-molar, according the American Board of Orthodontics Objective Grading System criteria. Logistic models were used to test for association between the direction of root angulation observed in either tooth with the respective marginal ridge score. A comparison was then made to determine how often root angulation errors were present in one or both of the teeth when there was a MRD.

Results: Although they can occur independently, when a MRD was present, the odds of having a root angulation error in an adjacent tooth was 4.7 times greater pretreatment and 4.1 times greater posttreatment. When there was a MRD in the positive direction, the associated root angulation error was 5.8 times more likely to be in the positive direction pretreatment (Odds Ratio = 5.8, 95% Confidence Interval = (2.5, 13.9), p= < .001), and 7.5 times more likely posttreatment (Odds Ratio = 7.5, 95% Confidence Interval = (4.4, 12.8), p= < .001).

Conclusions: There was a significant association between MRDs and root angulation errors. This data is important to clinicians because it indicates that if cases are finished with properly aligned marginal ridges, the odds of having root angulation errors are significantly reduced. Supported by the Indiana University School of Dentistry Student Research Subcommittee.