# Evaluation of Biodentine Tricalcium Silicate-Based Cement after Chlorhexidine Irrigation
## 4 Discussion  
Perforation closure requires specialistic endodontic skills, choice of the adequate material, and its proper management. The knowledge of how this material will behave in chosen clinical situations can impact therapeutic decisions and further treatment success. This research considered specific biocenter being used under certain circumstances, i.e., Biodentine used for perforation closure before the finalization of endodontic treatment, thus being exposed to various mechanical and chemical factors, such as irrigation with 2% chlorhexidine digluconate. The study was part of a wider project researching the influence of different irrigating solutions used in endodontics on Biodentine tricalcium silicate-based cement consisting of 5.25% and 2% sodium hypochlorite [19], 40% citric acid [22], and 17% ethylenediaminetetraacetic acid [30]. The study plan included material specimen division into three setting time-based groups. While 45 min and 24 h proved to be sufficiently long for Biodentine to achieve the stability needed to withstand the researched irrigation protocol, the 12 min setting time, as recommended by the manufacturer was not enough. The results of the study showed that the irrigation with 2% chlorhexidine solution degraded the three-dimensional form of the cement specimen and thus reduced the stability of the material. The effect was aggravated when ultrasonic activation was applied. This means that the biocenter used for perforation closure can be completely removed in a corresponding clinical situation. In the light of the results of this study, the 12 min setting time of Biodentine used in perforation closure is not enough to proceed with further cleaning and shaping of the canal space. Nevertheless, it should be noted that biocenter specimens from group A retained their shape and dimensions after being removed from the polyvinyl molds. This suggests that 12 min Biodentine setting time may be sufficient for use, under special circumstances, in conservative dentistry for procedures such as dentin structure reconstruction and indirect or direct pulp capping [31; 32], as well as in endodontic microsurgery as retrograde root canal filling [17]. This aspect has been confirmed in previous studies that show Biodentine as a weak material for hard tissues restoration in its early setting phase [33]. It was concluded that composite restoration covering biocenter should be delayed for two weeks in order to allow sufficient Biodentine maturation to withstand contraction forces from the overlaying material [33]. Biodentine surface microappearance visualized under SEM revealed various forms of deposits and no clear signs of the main structure degradation of the material. Previous studies have shown that 2% chlorhexidine digluconate solution alone is not able to properly clean the root canal surface and remove the smear layer deriving from root canal chemomechanical preparation [34; 35]. This study shows that chlorhexidine can also induce the formation of unwanted deposits on the surface of the tested material. The EDS results should be interpreted with the awareness that the software equalizes the obtained data up to 100%. Clear peaks of carbon, calcium, silica, and zirconium in the EDS analysis may be treated as a confirmation of the chemical composition of the tested material: tricalcium silicate, calcium carbonate, zirconium oxide, and calcium hydroxide [36]. Rinsing with 2% CHX slightly modified the atom percentage of each element. This may be the result of creating a CHX-derived coating on the specimen's surface. C and Cl, whose atom percentage rose in most of the specimens, are the constituents of CHX with the chemical formula [-(CH\({}_{2}\))\({}_{3}\)NHC(=NH) NHC(=NH)NHC\({}_{6}\)H\({}_{4}\)Cl]\({}_{2}\)[37]. The observed trends in the atom weight percentage of individual elements in the surface composition of Biodentine specimens, visualized in the form of tables and graphs, are only a preliminary indicator of the changes taking place.