## 4 Discussion  
The purpose of this study was to investigate the effect of silane treatment of a resin-coated RBC base material on its microtensile bond strength to a CAD/CAM ceramic  
Figure 5: SEM images of representative fractured surfaces in each group. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Group**} & **Resin** & \multirow{2}{*}{**Silane**} & \multirow{2}{*}{**\#TBS \({}^{*}\) Mean (S.D.)**} & \multirow{2}{*}{**A**} & \multirow{2}{*}{**B**} & \multirow{2}{*}{**C**} & \multirow{2}{*}{**D**} & \multirow{2}{*}{**E**} & \multirow{2}{*}{**F**} & \multirow{2}{*}{**G**} & \multirow{2}{*}{**H**} & \multirow{2}{*}{**I**} & \multirow{2}{*}{**Total**} \\ \cline{5-16}  & \(-\) & & & 17.6 (5.9) B & & 0 & 0 & 20 & 6 & 2 & 0 & 0 & 0 & 0 & 28 \\ II & \(-\) & + & 20.2 (4.0) b & NS & 0 & 0 & 14 & 5 & 0 & 0 & 1 & 0 & 0 & 20 \\ III & + & \(-\) & 21.3 (7.2) A & & 0 & 0 & 6 & 13 & 7 & 2 & 0 & 0 & 0 & 28 \\ IV & + & + & 24.9 (3.8) a & & 0 & 0 & 4 & 15 & 4 & 0 & 1 & 0 & 0 & 24 \\ \hline \hline \end{tabular}  
* The uppercase letters (A’ and ’B’) indicate the absence of a significant difference with and without silane groups (\(p>0.05\)); the lowercase letters (“a’ and ’b’) indicate the absence of a significant difference between silane-treated groups (\(p>0.05\)).  
\end{table} 
Table 3: Microtensile bond strength (MPa) and failure mode analysis. restorative material. To achieve this objective, we evaluated the effect of silane treatment on RBCs with and without a resin coating. We used a combination of Clearfil SE Bond and Clearfil Majesty ES Flow for the resin coating material [18]. Clearfil SE Bond is the \"gold standard\" two-step, self-etch, filled adhesive [19], which has very high bonding performance on both enamel and dentin [20; 21]. The mechanical properties of the adhesive itself are also good because of its filler loading (\(\sim\)10%) [22]. [PERSON] et al. [23] reported that an additional coating with flowable RBCs can significantly improve the microdensile bond strength compared to immediate dentin sealing with a resin adhesive system alone. When the cavity is reinforced with a base material, the cavity surface is composed of a mixture of exposed dentin and RBC. In clinical situations, it is difficult to apply a resin coating only to the surface of the exposed dentin, and thus the resin coating is applied to the entire cavity wall, including the surface of the base material. The results of this study indicated that resin coating to the RBC base material enhanced the \(\upmu\)TBS. Therefore, the application of the resin-coating technique to an RBC base material is effective, as it is the dentin surface [24]. Regarding the failure mode after \(\upmu\)TBS testing, almost all specimens in Group I (without resin coating) showed Pattern C (mixed failure at the adhesive interface between the ceramic and luting cement, and within the luting cement). The results indicated that the adhesion between the surface of the base material and the luting cement is good, even if resin coating is not applied to the RBC base material. In addition, almost all specimens in the resin-coated group (Group III) showed Pattern D (cohesive failure in the luting cement), suggesting that the resin coating did not adversely affect the adhesion between the surface of the base material and the luting cement. The Porcelain Bond Activator used in this study is a silane coupling agent, whose main component is 3-methacrylopropyltrimethoxysilane (3-MPS). Silane coupling agents have an organofunctional terminal group for bonding to organic resins, and a hydrolysate alkoxyl group for bonding to inorganic elements, as well as a hydrocarbon chain spacer. The hydrolysis alkoxyl group is activated by an acid to form silanol. Silanol is attached to the hydroxy group on the surface of an inorganic substrate, producing a strong bond called a polysiloxane bond (Si-O-Si)\({}_{n}\)[15; 25; 26].