## 4 Discussion
In fact, regarding [PERSON] et al. [38], the prevailing shape of a natural lateral canal (all types of teeth) is cylindrical, with a diameter of less than 100 \(\upmu\)m. Most of the lateral apical canals reveal diameters of less than 50 \(\upmu\)m, and some between 50 and 100 \(\upmu\)m. Similar diameters were also seen in the middle and coronal third, even if larger sizes were sometimes found. In the present study, BioRoot(r) RCS (bioceramic sealer) and GuttaFlow(r) bioseal (cement based on silicone, gutta-percha particles and bioceramics) have been compared. Statistically significant differences between root canal sealers have been reported. The control group was filled without root canal sealer to verify that the SLC sealing technique was valid. We know that is not the correct way to seal, since cement is always used, but we understood that this way we could know if the clearing technique, the creation of SLC, and subsequent sealing occurred. The control group did not take part in the statistical comparisons. BioRoot(r) RCS has allowed more grade 2 fillings (33.3%) in 3 mm SLC than GuttaFlow(r) bioseal (4.5%). At 10 mm, BioRoot(r) RCS has allowed more grade 2 fillings (23.8%) in SLC than GuttaFlow(r) bioseal (0%). On the other hand, GuttaFlow(r) bioseal has allowed more grade 3 fillings (27.3%) in SLC at 6 mm than BioRoot(tm) RCS (4.8%). Among the properties of a root canal sealer, fluidity is an essential property as it allows the filling of hard-to-reach areas such as narrow dentin irregularities, isthmus, accessory canals, and gaps [14]. Flow values for BioRoot(r) RCS have not been found. However, [PERSON] et al. compared the physicochemical and volumetric properties of AH Plus(r) (epoxy resin-based cement that has been used as Gold Standard in evaluations root canal sealer), Total Fill(r) BC Sealer (FKG, bioceramic cement), and GuttaFlow(r) bioseal; they performed a flow test according to ISO 6876, and for GuttaFlow(r) bioseal it had significantly lower flow values compared to the other sealants [9]. That could explain that in the coronal third at 10 mm from the apex, BioRoot(r) RCS obtained a higher proportion than GuttaFlow(r) bioseal and was statistically significant (\(p\)-value < 0.05) (Figure 4). In addition, the heat instantly set GuttaFlow(r) bioseal placed in the canal. However, more research is needed on the properties of these cements to be able to explain the results. [PERSON] et al. reported there was no difference between the filled thirds [37]. [PERSON] et al. reported 49.1% of canals with acceptable filling [28]. In this study, global acceptable filling was of 25%. An acceptable filling (grades 2 to 4) was greater in the middle third than in the apical and coronal thirds and was statistically significant, then apical third (3 mm), and, finally, coronal third (10 mm). The difference between apical and coronal thirds could be significant. These results correspond to the results obtained in other studies regarding the apical third [28; 38; 39; 40]. [PERSON] et al. [38; 39] agree that the SLC of the apical third are the most difficult to fill, like [PERSON] et al. [40], who obtained a higher percentage of unobstructed or partially filled SLC in the apical third. This is clinically important because the frequency of lateral canals was greatest in the apical third. [PERSON] et al. [38] founded in maxillary molars natural lateral canals in 65.5% of the specimens, most of them in the apical third (66.8%). [PERSON] et al. [28] reported that the percentage of SLC with acceptable filling was significantly higher in the apical third, followed by the middle third and the coronal third, but the differences were not significant between the middle third and the coronal third. According to [PERSON] et al. [41] the apical third had less filling, followed by the middle third, followed by the coronal third with greater filling, but this was not significant.