## 4 Discussion
internal porosity, and total porosity volume percentage [25; 27; 28; 29; 30; 31; 32]. Only [PERSON] et al. [27] reported a higher rate of porosity with Biodentine than MTA-Angelus. According to micro-CT investigations, Biodentine demonstrated a TPV% within a range of 2.48-6.66% and external porosity volume percentage (EPV) between 0.616-3.78%, and CPV% varied between 0.024-4.46% [23; 24; 25; 26; 27; 28]. Only [PERSON] et al. [32] reported an unusually high porosity percentage of 50.45%, making this result difficult to interpret. While previous research indicated that Biodentine demonstrated appropriate adaptability, the OPV% of Harvard MTA (0.91%) in this investigation was significantly lower than that of almost all of those studies. [PERSON] et al. are the lone exception, reporting a lower OPV of 0.616%. Interestingly, they found a much greater value of CPV% with Biodentine (3.642%) than OPV% [27]. Concerning the CPV% found by us, its value is lower than the findings of some other authors [27; 29]. In contrast with our results and all other research, [PERSON] et al. [28] reported a minor CPV% of 0.024%. Conventional MTA products, **ProRoot MTA** and **MTA-Angelus**, have been investigated to a relatively lesser extent. ProRoot MTA exhibited an external gap volume of 0.224 mm\({}^{3}\)[33], an EVV% of 1.882%, a CPV% of 0.021% [32], and a TPV% of 5.32% [28]. [PERSON] et al. [32] found a porosity percentage of 51.94%. MTA-Angelus showed an EVV% of 0.888-2.07% [27; 31], a CPV% of 3642 [27], and a TPV% of 4.079-8.93% [27; 31]. According to our findings, Harvard MTA showed better marginal adaptation and a lower rate of micropores than most studies on conventional CSCs (first and second generations). Only [PERSON] et al. [27] reported a similar OPV% with MTA-Angelus, and [PERSON] et al. [32] found an even lower CPV% with ProRoot MTA. The porosity volume of **bioeramics**, i.e., third generation CSCs available on the market, used as retrofilling materials has been scarcely investigated. Among them, Neo MTA Plus showed the lowest EPV% of 0.888% [2; 27], which is very similar to our results. Endosequence BC exhibited the lowest CPV% of 0.039% [32], with these results being significantly lower than ours. Bioaggregate exhibited the highest values of both porosity parameters: an EVV% of 9.42% and a CPV% of 17.62% [29], followed by MTA HP with a TPV% of 10.2% [34], and Retro MTA with an EVV% of 3.86% and a CPV% of 8.25% [29]. Harvard MTA Universal showed a very low percentage of total porosity volume (1.85%) in the present study, despite the fact that it was not comparative in nature. These findings suggest that this biomaterial does, in fact, possess a very high filling capacity of 99.15%. Furthermore, we found a small fraction of interfacial voids (0.91%), which shows excellent marginal adaptation of the cement to dentin. An almost equal volume of external and internal pores was found, both in volumetric units and percentages, which suggest that the material's handling characteristics allow dense condensation during its application. As can be seen, the results reported by previous research are very divergent, both in terms of absolute and relative values of external gaps and void volume exhibited by the various CSCs. Moreover, differences in the retrograde cavity dimensions also seem to have an impact on the results reported by previous investigations. As a rule, the most common depth of retrograde cavities was 3 mm, but their diameter was a variable parameter, and even it was not specified by most authors. Therefore, the absolute values of the results found by other authors were not mentioned, and only relative values (in percentage) were compared and discussed. Overall, compared to other examined biomaterials, the porosity rate of Harvard MTA--both internal and interfacial--found in this work was lower than that of most of the previously cited authors. The higher porosity of conventional MTA products, observed by other investigators, may be due to the inclusion of bismuth oxide in their composition as a radiopacifier [35].