## 2 Materials and Methods  
### Preparation of Samples  
Four different universal resin composites were used in this study. The contents of the resin composites and detox drinks used are given in Tables 1 and 2. The sample size (\(n=120\)) was calculated using an effect size set of 1.486, \(\alpha\) of 0.05, and power (1-\(\beta\)) of 0.95 using G*power software ver. 3.1.9.4 ([PERSON], Universitat Kiel, Kiel, Germany). \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Universal Resin Composites (Manufacturers)** & **Type** & **Shade** & **Filler (\(\
u\)/\(\
u\)/\(\%\))** & **Filler Structure** & **Monomer Structure** & **Lot Number** \\ \hline Omnichroma—OM (Tokuyama Dental, Tokyo, Japan) & Supra-nano-filled & Single shade & 68.0/79 & Spherical silica–zircona filler (260 nm) & UDMA, TEGDMA & 1152 \\ OptiShade—OS (Kerr, USA) & Nano-hybrid & A2 & 64.5/81 & PP, BaO-Al\({}_{\text{D}}\)O\({}_{\text{S}}\)SiO\({}_{\text{2}}\), silica, and F\({}_{\text{Y}}\),Organic fillers (5–400 nm, average particle size: 50 nm) & Bis-GMA, TEGDMA, Bis-EMA & 8242079 \\ Filek Ultimate Universal—FU (3M ESPE, St. Paul, MN, USA) & Nano-hybrid & A2 & 63.3/78.5 & Silica (20 nm) and zirconium fillers (4–11 nm) & Bis-GMA, TEGDMA & \\ Essentia Universal—EU (GC, Corporation, Tokyo, Japan) & Micro-hybrid & Single shade & 59/81 & Prepolymerized resin fillers (17 \(\mu\)m), strontium glass & Bis-GMA, UDMA, TEGDMA, TEGDMA, Bis-EMA, Bis-EMA & 2203161 \\  & & Micro-hybrid & Single shade & 59/81 & filler (16 nm) FAlSi glass & Bis-MEPP & \\ \hline \hline \end{tabular} Abbreviations: Bis-GMA—Bisphenol A diglycidylmethacrylate, TEGDMA—Triethylene glycol dimethacrylate; Bis-MEPP—2,2-Bis(4-methacrylopolyethoxyyphenyl) propane; Bis-EMA—Ethoxylated bisphenol A dimethacrylate, UDMA—Urethane dimethacrylate.  
\end{table} 
Table 1: Resin composites used in the study and their properties. A total of one hundred twenty samples were prepared, thirty for each resin composite. Teflon moulds with a diameter of 6 mm and a depth of 2 mm were used to prepare the samples. The Teflon moulds were placed on transparent tape placed on the microscope slide and the resin composite was placed in the moulds using a plastic spatula. A second transparent tape and a microscope glass were then placed over the resin composite. The polymerisation of the resin composites was performed by shining a 1000 W/cm\({}^{2}\) LED light device (D-Light Pro, GC, Tokyo, Japan) on the slide for 20 s. The output power of the curing light was checked every ten samples using a digital radiometer (Bluephase Meter II, Ivoclar Vivadent, Amherst, NY, USA). The upper surfaces of the polymerised samples were polished using aluminium oxide-coated polishing discs (Sof-Lex, 3M ESPE, Maplewood, MN, USA). Polishing was performed using a low-speed, water-cooled micromotor to prevent heat build-up and groove formation. After each disc was used, the samples were rinsed thoroughly with water for 10 s and dried with air for 5 s to remove any residue. To reduce variability, one operator performed all samples and procedures. Polished samples were stored separately in artificial saliva at room temperature for 24 h. The artificial saliva contained 0.7 mmol/L CaCl\({}_{2}\), 0.2 mmol/L MgCl\({}_{2}\).6H\({}_{2}\)O, 4 mmol/L KH\({}_{2}\)PO\({}_{4}\), 3 mmol/L KCl, 0.3 mmol/L NaN\({}_{3}\), and 20 mmol/L HEPES buffer, and was prepared at pH 7.11. The samples prepared from each resin composite were then randomly divided into three subgroups of ten samples, each to be exposed to different detox drinks. The study examined three different coloured detox drinks (red, green, and orange) that were commercially available (Juitox(r), Istanbul, Turkey). The initial surface roughness and colour parameters of the samples in each group were measured and recorded as baseline values (T0). The samples were then exposed to detox drinks twice a day for 15 min. The pH of each drink was measured using a pH meter (Orion 900A, Orion Research, Boston, MA, USA).