## 2 Materials and Methods
### Surface Roughness Assessment  
The surface roughness (Ra) was measured by a contact profilometer (Marsurf PS 10, Mahr, 10, Brno, Czech Republic) before and after the simulated brushing at T\({}_{0}\), T\({}_{1}\), T\({}_{2}\), T\({}_{3}\), and T\({}_{4}\). The measurements were repeated 3 times by the operator to minimize the bias. Before each measurement, the profilometer was calibrated using the calibrating table as per the manufacturer's recommendations. The probe was placed in the middle of the sample surfaces, and measurements were performed in different directions with a transversing length of 2 mm and a constant measuring speed of 1 mm/s. The arithmetic absolute average surface roughness (Ra) values of 3 measurements were calculated for each sample.  
Moreover, each sample's macro photograph was taken with a digital camera kit (EOS 700D, Canon, Tokyo, Japan; 100 mm macro lens, Canon; YN24-EX TTL twin flash, Yongnuo, Shenzhen, China). The camera settings were set at ISO 400, f 22, shutter 1/125, and the kit was inclined at an angle of 30\({}^{\circ}\) to the sample surface. The images were collected with the same setup before and after simulated brushing for all the samples. The scorings were performed according to the Surface Roughness Index (SRI) through the collected photographs [23].  
\begin{table}
\begin{tabular}{l l l} \hline
**Toothpaste** & **Contents** & **RDA** \\ \hline \multirow{6}{*}{Instant Relief (R.O.C.S., Russia)} & Aqua, Glycerin, Dicalcium Phosphate Dihidrate, Xylitol, & \\  & Hydroxyapatite, Silica, Xanthan Gum, Aroma, Calcium & \\  & Glycerophosphate, Cocamidopropyl & Betaine, Sodium Lauroyl & \\  & Sarcosine, Hydroxyacetophenone, Sodium Benzoate, Sodium & \\  & Saccharine, Magnesium Chloride, Sodium Methylparaben, & \\  & Sodium Propylparaben, O-cymen-5-ol, & Limonene. & \\ \hline \multirow{6}{*}{Sensation Whitening (R.O.C.S., Russia)} & Sorbitol, Silica, Glycerin, Aqua, Xylitol, Cocamidopropyl & \\  & Betaine, Aroma, Xanthan Gum, Calcium Glycerophosphate, & \\  & Bromelian, Magnesium Chloride, Sodium Sacharine, Sodium & \\  & Benzoate, O-cymen-5-ol, Titanium Dioxide. & \\ \hline \multirow{6}{*}{Pro Polishing (R.O.C.S., Russia)} & Aqua, Glycerin, 2–3 μm Silica, Hydroxyapatite, Xanthan Gum, & \\  & Calcium Glycerophosphate, Polysorbate-20, Aroma, Sodium & \\ \cline{1-1}  & Lauryl Sulfate, Sodium Methylparaben, Sodium saccharin, & \\ \cline{1-1}  & Sodium Benzoate, Sodium Propylparaben, O-cymen-5-ol, & \\ \cline{1-1}  & Potassium Hydroxide, Limonene. & \\ \hline \multirow{2}{*}{Artificial saliva [22]} & 1.5 mmol/L, CaCl\({}_{2}\), 50 mmol/L KCl, 0.9 mmol/L, KH\({}_{2}\)PO\({}_{4}\), & \\  & 20 mmol/L Tris, (pH = 7.4) & - \\ \hline \end{tabular}
\end{table}
Table 2: Contents of the Toothpastes and the Artificial Saliva.  
Figure 2: Press-on Force-Guided (PFG) brushing simulator used for brushing the samples.  
Statistical analyses were conducted using SPSS version 23 (IBM Corp., Armonk, NY, USA). Analysis of Variance (ANOVA) and the Bonferroni Test were used for statistical analyses, and repeated measure ANOVA was used for the comparisons between times. The level of significance was set at \(p\) < 0.05. The Spearman rho correlation test was used to analyze the relationship between surface roughness (Ra) values and SRI scores.