Evaluation of interproximal reduction in individual teeth, and full arch assessment in clear aligner therapy: digital planning versus 3D model analysis after reduction

Aim: To evaluate the correspondence between the interproximal reduction (IPR) performed clinically and that programmed in ClinCheck (R) and further assess which teeth showed an amount of implemented IPR (I-IPR) that corresponds with that programmed in ClinCheck (R). Materials and methods: Pre- (T0) and post-treatment (T1) ClinCheck (R) digital models for 75 subjects (30 males and 45 females), mean age (38 +/- 15) years, were included. To calculate the amount of I-IPR, Ortho Analyzer software (3Shape, Copenhagen, Denmark) was used to measure the mesiodistal widths for the maxillary and mandibular teeth from second premolar to the contralateral second premolar on the initial (T0) and final (T1) STL models. I-IPR performed by tooth was obtained by comparing the mesiodistal width of each tooth at T0 and T1.The amount of programmed IPR (P-IPR) in ClinCheck (R) was compared to that implemented clinically using the following formula: IPR difference= (P-IPR) - (I-IPR). Results: Statistically significant differences were observed between the average value of digitally programmed and implemented IPR per tooth for both the maxillary (p < .0001) and mandibular (p < .0001) teeth. The mean P-IPR for the maxillary teeth was 0.28 +/- 0.16 mm versus the mean I-IPR of 0.15 +/- 0.15 mm. In the mandibular arch, the mean P-IPR was 0.31 +/- 0.17 mm, while the I-IPR was 0.17 +/- 0.16 mm. The mean I-IPR was consistently lower than the mean P-IPR regardless of teeth and sites (p < 0.0001). The difference between the P-IPR compared to the I-IPR was larger for mandibular anterior teeth than for maxillary anterior teeth (p = 0.0302) and larger for maxillary posterior teeth than mandibular posterior teeth (p = 0.0059). Conclusion: The amount of implemented-IPR in clear aligner therapy is less than that digitally programmed for most teeth. Regardless of the regions, I-IPR was consistently lower than that programmed. Mandibular anterior teeth and maxillary posterior teeth showed greater discrepancy between P-IPR and I-IPR than the maxillary anterior and mandibular posteriors. Further prospective studies are needed to determine the factors affecting the precision of IPR and the clinical implications of a significantly reduced I-IPR on treatment outcomes.