## 2 Materials and Methods
The nanohybrid composite resin was placed in 2 mm increments and light cured for 20 s (1100 mW/cm\({}^{2}\)) using BluephaseR Style (Ivoclar Vivadent, 5 VDC, Liechtenstein, Austria) [27]. The restorations were polished using the same rubber system as the previous group. Negative Control Group  
Group 3: SpectraTM ST HV nanohybrid composite (Dentsply-Sirona, Konstanz, Germany, LOT 1136) was used to restore the class V cavities of 5 specimens. The enamel was etched in the same way as described for group 2. This was followed by the application of a universal adhesive system, Prime & Bond ActiveTM (Dentsply-Sirona, Konstanz, Germany, LOT1908001303) used according to the protocol described for group 2. The nanohybrid composite resin was placed in 2 mm increments and light cured for 20 s (1100 mW/cm\({}^{2}\)) using BluephaseR Style (Ivoclar Vivadent, 5 VDC, Liechtenstein, Austria). The light device was calibrated with a radiometer (BluephaseR Meter II, Ivoclar Vivadent, Liechtenstein, Austria). The restorations were polished using the same rubber system mentioned above. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Characterization** & **Chemical** & \multicolumn{2}{c}{**Physical and Mechanical**} \\ \hline \multirow{3}{*}{Surefill OneTM} & Composition: & & \\  & \(\bullet\) & Aluminum phosphorus crystals, magnesium, & \(\checkmark\) & Self-Adhesive composite hybrid \\  & electrolyte, sodium fluoride and sodium silicate & \(\checkmark\) & Dual curing \\  & \(\bullet\) & Water & \(\checkmark\) & Releases fluor \\  & \(\bullet\) & Highly dispersed silicon dioxide & \(\checkmark\) & Recharge fluor \\  & \(\bullet\) & Acrylic acid & \(\checkmark\) & Indicated for Class I, II and V, and for the \\  & \(\bullet\) & Polycarboxylic acid & \(\checkmark\) & construction of cores. \\  & \(\bullet\) & Ytrebium fluoride & \(\checkmark\) & Application in large increments, and dual \\  & \(\bullet\) & Bifurcational acrylate & \(\checkmark\) & configuration to fill any depth \\  & \(\bullet\) & Self-adjusting launcher & & \\  & \(\bullet\) & 4-tert-butyl-N,N-dimethylaniline & & \\  & \(\bullet\) & Iron oxide pigments & & \\  & \(\bullet\) &arium sulfate pigment & & \\  & \(\bullet\) & manganese pigment & & \\  & \(\bullet\) & Camborquinone (photoinitiator) & & \\  & \(\bullet\) & Stabilizer & & \\ \hline \hline \multicolumn{2}{l}{SpectraTM ST HV} & Composition: & & \\  & \(\bullet\) & Methacrylate modified polysiloxane (organically & \(\checkmark\) & Nano-ceramic \\  & modified ceramic) & \(\checkmark\) & Light-cured \\  & \(\bullet\) & Dimethacrylate resins & \(\checkmark\) & Radiopaque \\  & \(\bullet\) & Fluorescent pigment UV stabilizer & \(\checkmark\) & Universal composite with novel SphereTEC® filler \\  & \(\bullet\) & Stabilizer & & technology (granulated spherical fillers in \\  & \(\bullet\) & Camborquinone & & combination with an optimized resin matrix) \\  & \(\bullet\) & Ethyl-4(dimethylamino) benzoate & \(\checkmark\) & Indicated: Direct anterior and posterior \\  & \(\bullet\) & Bis-(4-methyl-phenyl)-iodonium & & restorations (including occlusal surfaces); Core \\  & hexafluorophosphate & & build-ups; Splitting; Indirect restorations \\  & \(\bullet\) &arium-aluminum-borosilicate glass & & including inlays, onlays and veneers \\  & \(\bullet\) & Ytrebium fluoride & & \\  & \(\bullet\) & Iron oxide pigments and titanium oxide pigments & & \\  & according to shade & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the main chemical, physical and mechanical characterizations of the materials tested. Positive Control Group  
Group 4: Class V cavities of five specimens have not undergone any intervention, so they have not been restored. As previously mentioned, only one operator performed all cavity preparation and restorative procedures. The specimens in groups 1, 2 and 4 were all coated with two layers of varnish (Cliche, 1100-063, Lisbon, Portugal, LOT J257) up to a 2 mm margin around the restorations. Group 3 specimens were coated with the same varnish over their entire surface.