Quantitative evaluation of implemented interproximal enamel reduction during aligner therapy:

Abstract

Objectives To investigate the correspondence between programmed interproximal reduction (p-IPR) and implemented interproximal reduction (i-IPR) in an everyday-practice scenario. The secondary objective was to estimate factors that might influence i-IPR to make the process more efficient. Materials and Methods Fifty patients treated with aligner therapy by six orthodontists were included in this prospective observational study. Impressions were taken at the beginning of treatment and after the first set of aligners. Data on p-IPR, i-IPR and technical aspects of IPR were gathered for 464 teeth. Statistical analyses included the Wilcoxon signed-rank test, Kruskal-Wallis, and multilevel mixed regression. Results Mean difference between p-IPR and i-IPR was 0.15 mm (SD: 0.14 mm; P = .0001), with lower canines showing the highest discrepancy. Use of burs and measuring gauges resulted in a smaller difference (respectively: coeff.: 0.09, P = .029; coeff.: −0.06, P = .013). IPR was performed more accurately on the mesial surface of teeth than on the distal surface. Round tripping before IPR resulted in a slightly more precise i-IPR compared to the previous alignment (coeff.: −0.021, P = .041). Conclusions Implemented IPR tends to be less than p-IPR, especially for lower canines and distal surfaces of teeth. Burs tend to provide more precise i-IPR, especially compared to manual strips; however, there is variation between the techniques. Using a measuring gauge tends to increase the precision of i-iPR. As several factors influence the implementation of IPR, particular attention must be paid during the procedure to maximize its precision.

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

“…Similar findings to our study were reported by another observational study [ 16 ]. In that study, the overall difference between implemented and programmed IPR for 464 teeth was on average 0.15 ± 0.14 mm ( p = 0.0001) compared to our findings for 566 teeth (0.14 ± 0.18 mm, p < 0.0001) with the implemented IPR per tooth being less than that digitally programmed.…”

“…Accessibility of the upper posterior segments compared to the lower posterior segments is more challenging for the clinician to control the IPR procedure while using indirect visualization technique. This premise is supported by Kalemaj et al [ 16 ] who reported lesser discrepancy between planned and implemented IPR for lower premolars and higher discrepancy for the mandibular canines. Finally, this observed imprecision might be associated with the stretching of the periodontal ligament while performing IPR and using the measuring gauge in a crowded area, that it might falsely appear to the clinician that the desired amount of enamel reduction has been achieved [ 28 , 29 ].…”

“…Data assembled from the total of 566 upper and lower teeth have shown that the overall average amount of I-IPR for the upper and lower teeth was significantly smaller than that programmed in the ClinCheck®, even when teeth were analyzed individually, except for the lower left second premolar (Table 1 ). Two previous studies reported reduced amount of the I-IPR in clear aligner therapy compared to that initially programmed in the ClinCheck®[ 14 , 16 ]. De Felice et al [ 14 ] investigated differences between planned and performed IPR in 25 cases (total arch measurements) and found that the difference was on average 0.55 ± 0.64 mm ( p < 0.05) in the upper arch and 0.82 ± 0.84 mm ( p < 0.05) in the lower arch; they had an accuracy of 44.95% for the IPR in the upper and 37.02% for the lower arch.…”

“…Manual and mechanical techniques (technical factors) are usually undertaken in clinical orthodontics for precise IPR implementation: the traditional hand pulled strips, oscillating segmented disks and motor-driven abrasive strips. Accuracy of these procedures has been previously investigated; the results seem to be controversial [ 16 , 22 , 23 ]. One study reported that upon quantitative evaluation of the stripped enamel between these three commonly used stripping procedures, great variability was noticed, with all of these techniques delivering less IPR than intended [ 23 ].…”

“…Consequently, it is crucial to assess the accuracy of implementing the P-IPR clinically. Few studies have reported on quantitative evaluations of the I-IPR vs P-IPR; two of which found the amount of I-IPR less than that programmed on the ClinCheck® [ 14 , 16 ]. More recently, Lagana et al [ 17 ] found that the amount of IPR conducted in vivo corresponds to that programmed in ClinCheck®.…”