New design of interdental rubber picks - does the archimedean screw design bring an improvement for experimental cleaning efficacy and force?

Background: Up to date, interdental brushes (IDB) are the first choice for interdental cleaning because of their cleaning efficacy. Cylindrical ones must be selected individually according to the size/morphology of the interdental area (IDR), whereas conical ones cover a larger variability of IDR. However, there is a trend on the part of patients towards interdental rubber picks (IRP) which are in general conically shaped, and which seem to be linked with lower cleaning efficacy. A new IRP with an Archimedes screw design was developed to overcome this limitation. Therefore, the in vitro study aimed to measure the experimental cleaning efficacy (ECE) and force (ECF) during interdental use of IDBs versus the new IRP type. Methods: Three IRPs with different tapers (PHB angled: 0.039, PHB straight S: 0.027, Vitis straight M: 0.045; all Flexipicks, Dentaid, Cerdanyola del Vall & egrave;s, Spain) were compared to one IDB (Interprox micro PHD 0.9, Dentaid, Cerdanyola del Vall & egrave;s, Spain). IDR were reproduced by a 3D-printer (Form2, Formlabs Sommerville, MA, USA) according to human teeth and matched to equivalent pairs (isosceles triangle, concave, convex) in three different diameters (1.0 mm,1.1 mm,1.3 mm). Covered with simulated biofilm, pre-/ post-brushing situations of IDR (standardized, computer-aided ten cycles) were photographed and quantified by digital image subtraction to calculate ECE [%]. ECF were registered with a load cell [N]. Statistically significant differences were detected using the Mann-Whitney-U-test and the Kruskal-Wallis-test with Bonferroni correction for multiple testing. Results: Overall, the ECE (mean +/- SD) was higher for IDB micro 0.9 (45.95 +/- 11.34%, p < 0.001) compared to all IRPs (PHB angled: 25.37 +/- 15.29%; PHB straight: 22.28 +/- 16.75%; Vitis straight: 25.24 +/- 12.21%; p <= 0.001), whereat best ECE was achieved in isosceles triangle IDR of 1.0-1.1 mm (IDB micro 0.9: 70.7 +/- 7.7%; PHB angled S: 57.30 +/- 4.43%; p < 0.001). The highest ECF occurred for Vitis straight M with 2.11 +/- 0.46 N, while IDB micro 0.9 showed lowest ECF values (0.64 +/- 0.14 N; p < 0.001). Conclusions: IRP with an Archimedes screw design and a higher taper were associated with advanced ECE but also higher ECF, nevertheless, ECE didn't reach the cleaning efficacy of conventional IDBs.