## 3 Results
### Characterization of Protonated Glass Surface  
_Results of Contact Angle (CA)_  
Wetting ability is an important factor in adhesion. The contact angle describes the wetting ability of a liquid on a solid surface. The contact angle measurements are summarized in Table 4. The water  
Figure 4: Core level spectra of untreated (red) and acid-etched (blue) glass samples: O 1s, Na 1s, Ca 2p, and Si 2p. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Si\%** & **O\%** & **Ca\%** & **Na\%** \\ \hline Untreated glass & 40.27 & 57.01 & 2.48 & 0.25 \\ Etched glass & 42.28 & 56.51 & 1.21 & 0.09 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Surface elemental composition in glass samples determined by X-ray photoelectron spectroscopy (XPS). contact angle was 25.20\({}^{\circ}\) on the unprotonated glass that means the microscope slide has a hydrophilic nature (Figure 5A). The water CA was 5.12\({}^{\circ}\) on a protonated microscope slide that significantly (\(p<0.05\)) decreased compared to the untreated surface (Figure 5C). The significantly decreasing effect can also be observed at MDP containing bond material CA on the bare and protonated glass surface (Figure 5B,D) (\(p<0.05\)). The water CA on epoxy, bone, and titanium was 81.60\({}^{\circ}\), 95.51\({}^{\circ}\), and 91.04\({}^{\circ}\), respectively. The components significantly differ from each other in the aspect of water wetting ability (\(p<0.05\)). (Figure 6A-C). The glass hydrophilic nature and hydrophobic nature of epoxy, bone, and titanium have to fit each other in a good adhesion situation. To reach this state a well-chosen adhesive is required that moisturizes all ingredients well. The MDP containing bond material CA data on epoxy, bone, and titanium were 14.73\({}^{\circ}\), 16.40\({}^{\circ}\), and 14.88\({}^{\circ}\), respectively (Figure 6D-F). Consequently, the MDP containing bond moisturizes the components of the thin bone section very well. Statistical analysis showed significant differences between the epoxy and bone (\(p<0.05\)), but epoxy and titanium did not differ significantly at the wetting study of MDP adhesive. Based on the contact angle measurements it was found that the MDP containing bond material behaves like a good wetting liquid on the glass and components (epoxy, bone, titanium) and it can be a well-chosen adhesive to contribute to a stronger adhesion between the glass slide and thin section. \begin{table}
\begin{tabular}{c c c c c c} \hline  & **Bare Glass** & **Protonated Glass** & **Epoxy** & **Bone** & **Titanium** \\ \hline Water & 25.20\({}^{\circ}\)\(\pm\) 0.74 & 5.12\({}^{\circ}\)\(\pm\) 0.36 & 81.60\({}^{\circ}\)\(\pm\) 0.68 & 95.51\({}^{\circ}\)\(\pm\) 0.87 & 91.04\({}^{\circ}\)\(\pm\) 0.56 \\
10-MDP containing bond & 13.38\({}^{\circ}\)\(\pm\) 0.43 & 7.21\({}^{\circ}\)\(\pm\) 0.41 & 14.73\({}^{\circ}\)\(\pm\) 0.94 & 16.40\({}^{\circ}\)\(\pm\) 0.99 & 14.88\({}^{\circ}\)\(\pm\) 0.85 \\ \hline \end{tabular}
\end{table} 
Table 4: The contact angle of water and MDP containing bond material on a bare, protonated glass slide, epoxy, bone, and titanium (n = 10). Figure 5: The representative contact angle pictures of the water (**A,C**), and MDP containing bond material (**B,D**) on bare glass (**A,B**) and the protonated glass surface (**C,D**), respectively. Figure 6: Representative pictures of the contact angle of the water (**A–C**) and MDP containing bond material (**D–F**) on epoxy (**A,D**), bone (**B,E**), and titanium surface (**C,F**), respectively. The principles of adhesion as surface free energy, contact angle, surface roughness, and wettability are studied by several works. The rougher surface presents a larger surface area available for bonding at the same time may challenge adhesive wettability since they can entrap air inside the irregularities reducing the total area available for bonding [17]. Therefore, some researchers have not found any correlation between roughness and wettability.