Quantitative assessment of interproximal tooth reduction performed as part of invisalign® treatment in 10 orthodontic practices

Abstract

Background: Interproximal reduction (IPR) is a treatment option for orthodontic space gain. The attainment of prescribed objectives in aligner treatment may require IPR that is accurately performed both qualitatively and quantitatively. Objective: This study assesses the in vivo accuracy of IPR carried out in 10 orthodontic practices as a method of orthodontic space creation. Methods: A comparison of proposed and achieved amounts of IPR completed (accuracy), the accuracy of IPR within and between upper and lower dental arches, and the accuracy of IPR within and between posterior and anterior arch segments were performed using 3-dimensional digital study models gained via Align’s® ClinCheck. Results: The findings indicated that IPR was routinely underperformed by all practices studied. On average, the amount of IPR achieved represented only 44.0% of the total prescribed per tooth in the sample assessed, with a mean discrepancy of 0.16 mm per tooth. There were statistically significant differences only between the overall anterior and posterior groups (p < 0.01) and between maxillary anterior and maxillary posterior groups (p < 0.01); however, these were not clinically significant. Significant differences in IPR performance were noted between different orthodontic practices. Conclusions: This study demonstrates that the clinical performance of IPR in 10 orthodontic practices consistently fails to achieve the prescribed amount often by large variations. The effect of this under-performance on clinical outcomes remains to be quantified.