Otespa r3 probes

A Multimode III AFM (Bruker, Santa Barbara, CA, USA) was used to image the air-dried surfaces of dentin samples and a JPK Nanowizard 4 AFM (JPK Instruments Ltd., Berlin, Germany) was used for Young’s modulus measurements. Commercially available cantilevers were used for the imaging (OTESPA-R3 probes, Bruker, spring constant 26 N/m) and for the force (RTESPA-525 probes, Bruker, spring constant 200 N/m) measurements. Force measurements (100 force curves) were performed in a 10 × 10 μm area per sample in triplicate. An optical microscope was combined with the AFM to control tip to sample positioning. Images were recorded using tapping mode and force curves were taken with force spectroscopy mode using the JPK NanoWizard^® software version 6.1.111 with a scan rate of 1 Hz to record the surface Young’s modulus values. Image processing was performed using NanoScope Analysis software (Bruker Corporation, Santa Barbara, CA, USA) and force curve analysis was performed using the JPK NanoWizard^® Analysis software version 6.1.111 (JPK Instruments, Berlin, Germany). The mean Young’s modulus values were subjected to 2-way ANOVA (toothpaste × timepoint) followed by a Tukey test (α = 0.05).