## 4 Discussion
content of calcium-releasing products, verified with Biodentine when compared to MTA, may enhance biomineralization and, consequently, magnitude of the bond strength [25, 35]. In addition, it is important to underline the considerably higher standard deviation verified in TotalFill specimens (10.32 \(\pm\) 8.41) when compared with both Biodentine (8.54 \(\pm\) 4.49) and MTA (7.44 \(\pm\) 4.07). Therefore, although TotalFill presented statistically higher mean bond strength value, a higher standard deviation might reflect a lower outcome predictability in regard to retention of the biomaterial. In the present study, all experimental procedures were performed by a single experienced operator under identical environmental conditions and testing time as well as similar adhesion area, with the ultimate goal of minimizing the impact of these variables on the results. We also hypothesize these findings to be related with dentin being an extremely heterogeneous substrate, although teeth exhibiting obvious root dentin alterations have been discarded [38]. In addition, based on the obtained results, a superior sample size should be considered in future studies. As previously described, the push-out bond strength of three hydraulic cements was assessed in two distinct conditions regarding the setting environment: presence and absence of blood. Our findings show that blood contamination did not affect the retention of the tested biomaterials (\(p\) > 0.05), with uncontaminated and contaminated specimens of each biomaterial exhibiting similar bond strength values. Therefore, the null hypothesis has been accepted. Accordingly, [PERSON] et al. found that blood contamination did not adversely affect MTA and CEM bond strength [29]. Moreover, [PERSON] et al. found no differences between uncontaminated versus contaminated Biodentine specimens regardless of push-out bond strength assessment time (24 h, 7 days, or 28 days), whereas MTA-Angelus bond strength was negatively affected over time [31]. Although blood exposure has also been identified as a factor that impairs biomaterials' dislodgement resistance [25, 26], we speculate our results to be related to the bioactive materials' hydrophilicity. Even though specimens were kept hydrated with saline solution throughout the entire experimental period, blood's presence in the initial setting of the biomaterials may have mitigated a possible negative impact [29]. Moreover, the affinity of red blood cells to type I collagen (a major component of dentin's organic phase) is expected to promote dental tubules occlusion, creation of gaps, blocking tag-like structures formation, and, consequently, impairing bond strength [4, 28, 39]. However, the penetration depth of biomaterials within the dental tubules is solely responsible for the micromechanical anchorage of the cement. By offering a moist setting environment, blood may have contributed to higher bioactivity, with greater apatite precipitation and, consequently, bonding [29]. Despite the results of this study and considering the heterogeneity of scientific evidence regarding the role played by blood on biomaterials' adhesion, ensuring complete hemostasis should be considered an essential prelude towards a favorable outcome of the endodontic treatment [9, 14, 21, 27, 28, 29]. Biomaterials' comparison according to root segment variation was also carried out. MTA yielded the lowest push-out bond strength values in the coronal region, with statistical differences observed compared with TotalFill and Biodentine. Conversely, similar bond strength results were found between TotalFill and Biodentine, meaning that in a clinical scenario in which regenerative endodontic procedures requiring the creation of a cervical barrier are performed, the use of either TotalFill or Biodentine should be recommended over MTA.