## 4 Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Material** & **Disc Type** &
\begin{tabular}{c} **Pearson’s Correlation** \\ **Coefficient Between SS and SO** \\ \end{tabular} & **P-Value** \\ \hline Biodentin & Dentin & 0.85721 & \textless{}0.0001 \\ Biodentin & Teflon & 0.86110 & \textless{}0.0001 \\ MTA & Dentin & 0.85084 & \textless{}0.0001 \\ MTA & Teflon & 0.83248 & \textless{}0.0001 \\ Well Root PT & Dentin & 0.91626 & \textless{}0.0001 \\ Well Root PT & Teflon & 0.40571 & \textless{}0.0001 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Pearson’s correlation coefficient between mean values of central and peripheral zones (SS and SO) in three groups of materials and on both disc types. in comparison with other canal sealers. The size of the cement particles ranged from 5 to 30 \(\upmu\)m and it does not shrink upon setting [43; 49]. Well-Root PT showed alkaline pH, biomineralization properties and had comparable solubility in comparison to Biodentine and MTA [17]. The contact angle indicates the capability of the material to wet the dentin surface or the ability to achieve good adhesion. Research has shown that contact angles, investigated after 10 s, for Biodentin and Well-Root PT were 15\({}^{\circ}\) and 9\({}^{\circ}\), respectively [17]. That implies that the bond of Well-Root to dentin could be more favorable than the bond created between Biodentine and dentin. On the other hand, scanning electron micrographs of the hydrated cements, Biodentine and MTA, showed that Biodentine has more pronounced hydration kinetics. Concerning Biodentine, the particles of tricalcium silicate are smaller than those in MTA, it has a larger specific surface area and a significantly denser and finer consistency is achieved by intermixing the hydration products [50]; therefore, dimensional changes should be less. The highest strain measured in this study was for Biodentine, which could be a result of adding CaCl\({}_{2}\). This is added in order to accelerate the setting reaction, but its presence increased the osmotic potential and the material expansion. An additional contributing factor to this result could be a more pronounced advancement in the hydration reaction, during which there was not enough moisture [48; 51; 52]. By placing a wet gauze underneath the sample, researchers tried to replicate real conditions during the closure of the perforations. In previous research, [PERSON] et al. illustrated that Biodentine, even though it has low porosity, showed a tendency towards creating cracks within the material, as well as at the interface with the dentin wall in dry conditions [53]. These results are in agreement with research performed by [PERSON] et al. ; MTA did not show any dimensional changes, while Biodentine demonstrated shrinkage and crack formation in dry conditions [54]. According to these authors, in wet conditions, ProRoot MTA expanded by 0.41% and 0.17% on the 3 rd and 28 th day, respectively, while Biodentine expanded by 0.85% and 1.44%. The more pronounced expansion of Biodentine is attributed to the higher concentration of liberated Ca\({}^{2+}\) ions and the accumulation of hydroxyapatite on the surface of the material. When observing the peripheral section, the greatest deformation was recorded in Biodentin samples, which could be caused by the hydrostatic tension due to shrinkage, which separated the material from the surface of dentin walls [53]. Within each group of materials, the difference in the strain between the central and peripheral zone was evaluated. A significant difference was shown between the samples of Biodentine and Well-Root PT on the dentine discs, as well as between Biodentin and MTA on the Teflon discs. Higher values of deformation were measured in the peripheral zones in all tested materials. Similar results were obtained by other authors concerning Biodentine on Teflon, with the highest deformation in the peripheral zone [55]. Worse results peripherally could be explained by the dynamic changes in the material interface zone with dentin or Teflon.