New experimental setup for the measurement of cleaning efficacy and force of interdental aids in 3D-reproduced interdental areas

Abstract

Background: Interdental rubber picks (IRP) have become a frequent and convenient alternative for interdental cleaning. However, only little evidence exists supporting the effectiveness of newer designs available on the market. Therefore, a new in vitro model was evaluated to measure the experimental cleaning efficacy (ECE), as well as the force needed for insertion and during the use of IRP, with high reproducibility. Methods: Five different sizes of commercially marketed IRP with elastomeric fingers (IRP-F) (GUM SOFT-PICKS® Advanced, Sunstar Deutschland GmbH, Schönau, Germany) or slats (IRP-S) (TePe EasyPick™, TePe D-A-CH GmbH, Hamburg, Germany) were tested. Interdental tooth surfaces were reproduced by a 3D-printer (Form 2, Formlabs Sommerville, MA, USA) according to human teeth and matched to morphologically equivalent pairs (isosceles triangle, concave, convex) fitting to different gap sizes (1.0 mm, 1.1 mm, 1.3 mm). The pre−/post brushing situations at interdental areas (standardized cleaning, computer aided ten cycles) were photographically recorded and quantified by digital image subtraction to calculate ECE [%]. Forces were registered with a load cell [N]. Results: IRP-F have to be inserted with significant higher forces of 3.2 ± 1.8 N compared to IRP-S (2.0 ± 1.6 N; p < 0.001) independent of the size and type of artificial interdental area. During cleaning process IRP-S showed significantly lower values for pushing/pulling (1.0 ± 0.8 N/0.5 ± 0.4 N) compared to IRP-F (1.6 ± 0.8 N/0.7 ± 0.3 N; p < 0.001) concomitant to significantly lower ECE (19.1 ± 9.8 vs. 21.7 ± 10.0%, p = 0.002). Highest ECE was measured with largest size of IRP-F/IRP-S independent the morphology of interdental area. Conclusions: New interdental cleaning aids can be tested by the new experimental setup supported by 3D printing technology. Within the limitations of an in vitro study, IRP-F cleaned more effectively at higher forces compared to IRP-S.

In vitro comparison of cleaning efficacy and force of cylindric interdental brush versus an interdental rubber pick

“…1 . As explained in detail in our previous publication [ 10 ], we used a computer software (Autodesk Fusion 360, Autodesk Direct Limited, Hampshire, United Kingdom) and in vivo data of interdental morphologies [ 12 – 14 ] to design and print 3D composite replicas in stereolithography manner (Form 2, Formlabs Sommerville, MA, USA) by using liquid photopolymer resin (White Resin V04 (RS-F2-GPWH-04), Formlabs, Sommerville, MA, USA). This experimental setup was originally developed, in order to achieve the highest possible reproducibility and accuracy [ 15 ].…”

“…Subsequently, the interdental area replicas were stained by one investigator (K.S.) with Occlu Spray Plus (Hager & Werke, Duisburg, Germany) as described in previous studies [ 10 , 16 , 17 ]. A standardized powder thickness (mean ± SD: 20 ± 5 µm) was ensured by a standardized procedure and appropriate time protocol.…”

“…After the test, all artificial interdental area replicas were again photographed in order to subsequently perform an evaluation of ECE by digital image subtraction (Image J, NIH, Bethesda, USA). Testing in a reproducible manner was proofed [ 10 ].

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“…The images were extracted via XN View to enhance the most important area of the interdental space. Afterwards the picture section was edited by Photoshop in the same procedure as described in detail in our first study [ 10 ] to get a digital image subtraction (ImageJ, NIH, Bethesda, MD, USA). The cleaned areas have a different color in contrast to non-cleaned areas.…”

“…In a previously published investigation, our primary aim was to develop a new experimental setup to test in vitro , under standardized, controlled, and reproducible conditions, the interdental experimental cleaning efficacy (ECE) and the cleaning force of different types of rubber picks [ 10 ]. This was necessary, as the currently available clinical measurements lack the absolute validity and reliability to assess the interdental cleaning efficacy in vivo [ 11 ] and on the other hand, the majority of in vitro studies are neglecting more clinically relevant morphologies of the interdental areas, such as convex or concave shapes of the proximal root surfaces [ 12 ].…”