Influence of bioceramic intracanal medication on the bond strength of bioceramic root canal sealer

Patrícia Maria ESCOBAR(a), Alice Corrêa SILVA-SOUZA(a), Rafael Verardino de CAMARGO(a), Marco SIMÕES-CARVALHO(b), Yara Teresinha SILVA-SOUZA(c), Jardel Francisco MAZZI-CHAVES(a), Gustavo DE-DEUS(b), Manoel Damião SOUZA-NETO(a)

(a)Universidade de São Paulo - USP, School of Dentistry of Ribeirão Preto, Departament of Restorative Dentistry, Ribeirão Preto, SP, Brazil. (b)Universidade Federal Fluminense - UFF, School of Dentistry, Department of Endodontics, Niterói, RJ, Brazil. (c)Universidade de Ribeirão Preto - Unaerp, Faculty of Dentistry, Ribeirão Preto, SP, Brazil.
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Objective:
To investigate the influence of the remaining volume of a new intracanal medication based on bioceramic compounds on the bond strength and formation of an adhesive interface between calcium silicate-based and epoxy resin endodontic sealers.

Clinical implications:
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• Remaining volume of intracanal medication: it is important to remove as much intracanal medication as possible from the canal, as this is a temporary medication and not a permanent one. In the case of BIO-C® Temp, any remaining product will interact with the BIO-C® Sealer, providing an airtight, three-dimensional filling in addition to being easily and effectively removed.
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• Bond strength test: bond strength refersto the adhesive capacity of the filling sealer and the root canal walls. In the case of this study, it was concluded that when using BIO-C® Temp as the intracanal medication and BIO-C® Sealer as the root canal filling sealer, it waspossible to notice a greater bond strength.
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• Quality of theadhesive interface: It is critical tohave a high-quality adhesive interface, with no gaps that could lead to bacterial re-infection and treatment failure.
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• Penetration of thefilling sealer into the dentinal tubules: when filling root canals, it is important that the sealer penetrates as deeply as possible in to the lateral canals, accessory canals and dentinal tubules in order to achieve the most complete seal possible and avoid bacterial recontamination.
FIGURE 1Three-dimensional models in microcomputed tomography (microCT) images before and after removal of intracanal medication based on (A) bioceramic compounds - BIO-C® Temp (Angelus, Londrina, Paraná, Brazil) and (B) calcium hydroxide - Ultracal XS (Ultradent Products Inc., SouthJordan, UT, USA). In red (I): root canal filled with intracanal medication. Inblue (II): intracanal medication remaining after removal with a final instrument and conventional irrigation with sodium hypochlorite. (III) Overlapping of images before and after the removal of intracanal medication.
TABLE 1Mean ± standard deviation and minimum andmaximum percentage value (%) of the remaining volume of intracanal medication (BIO-C® Temp and Ultracal XS) after using the last instrument and conventionalirrigation with 2.5% sodium hypochlorite and 17% EDTA for three minutes.
TABLE 2Mean and standard deviation of bond strength values (Mpa) found for the push-out test in groups according to intracanal medication (BIO-C® Temp or Ultracal XS) and root canal sealer (AH Plus and BIO-C® Sealer).
TABLE 3. Mean and standard deviation of the bond strength values (Mpa) found for the push-out test of the root thirds (cervical, middle, and apical) according to the intracanal medication (BIO-C® Temp or Ultracal XS) and root canal filling (AH Plus and BIO-C® Sealer). 
Resultados:

Experiment #1: Determining the remaining volume of intracanal medications
The t-test showed a statistically significant difference in the percentage of remaining intracanal medication volume (p < 0.0001) (Table 1), with a lower amount of intracanal remnant of the bioceramic composite-based medication (BIO-C® Temp) (1.77 ± 0.86) when compared to the calcium hydroxide-based medication (Ultracal XS) (10.47 ± 5.78), regardless of a third of the tooth evaluated.

Qualitative analysis of three-dimensional models and axial sections of the distal root before and after intracanal medication removal revealed a medication remnant in both products tested (Figure 1). When the remaining intracanal medication was compared in terms of chemical composition, it was clear that the medication based on bioceramic compounds (BIO-C® Temp) remained homogeneous and regular, particularly in the apical third (Figure 1A). In contrast to the calcium hydroxide-based intracanal medication.

Experiment #2: Bond strength test
The two-factor analysis of variance showed a statistically significant difference for the factors intracanal medication and root third and for the interaction of the factors intracanal medication x root third (p<0.0001). With regard to intracanal medication, it was observed that teeth that received intracanal treatment with a medication based on bioceramic compounds (BIO-C® Temp) and were filled with bioceramic sealer (BIO-C® Sealer) had higher bond strength values (3.70 ± 1. 22) when compared to teeth that received bioceramic-based medicaments and were filled with epoxy resin-based sealer (AH Plus) (2.15 ± 1.07), or calcium hydroxide-based medicament (Ultracal XS) and filled with bioceramic (3.18 ± 1.09) or epoxy resin-based sealer (AH Plus) (2.11 ± 1.02) (p < 0.001) (Table 2).
In reference to the root thirds, the cervical third exhibited higher bond strength values than the middle third (p < 0.001), with the middle third showing higher bond strength values (p < 0.001), and irrespective of the intracanal medication and cement (Table 3).
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Experiment #3: Adhesive interface quality
FIGURE 5Light micrographs showing portions of capsule from sections subjected to immunohistochemistry for IL-10 detection (brown/yellow color) and counterstained with hematoxylin. It can be seen that few immunolabeled cells are present in the capsules of all groups, especially at 7 days (A-C). In all groups, obvious immunolabeling is present in mast cells (MC). Arrows: inflammatory cells; BV: blood vessels; material particles: arrowheads. Bars: 18 μm. (M) The graph shows the values (expressed as mean ± standard deviation) of the numerical density of cells immunolabeled with IL-10 in the capsules. In each period, the comparison between the groups is indicated by superscript letters; different letters = significant difference. The superscript numbers indicate the analysis of each group over time; different numbers = significant difference. Tukey's test (p ≤0.05).
In specimens in which intracanal medication (BIO-C® Temp) and bioceramic-based sealer (BIO-C® Sealer) were used, there was better adaptation of the filling material to the root dentin, also in polar areas (Figure 3), areas with juxtaposition of the adhesive interface and fewer interfacial gaps between sealer/dentin; and when they did occur, the gaps were smaller than in the other groups.
FIGURE 6A. Confocal laser scanning microscopy images with fluorescence after using bioceramic-based intracanal medication (BIO-C® Temp) and filling with bioceramic-based sealer (BIO-C® Sealer). The presence of intracanal medication remnants inside the dentinal tubules was visible in fluorescent green. The penetration of root canal sealer into the dentinal tubules was observed in fluorescent blue, with the formation of longer and uniform tags. The formation of tags with product resulting from the interaction of intracanal medication and sealer was observed in light fluorescent blue.
B. Confocal laser scanning microscopy images displaying fluorescence obtained subsequent to intracanal administration of bioceramic compound-based medication (BIO-C® Temp) and filling with epoxy resin-based sealer (AH Plus). The presence of intracanal medication remnants inside the dentinal tubules could be seen in fluorescent green. In fluorescent red, the penetration of root canal sealer into the dentinal tubules with the formation of short tags without continuity was observed. The interaction between intracanal medication and sealer resulted in the formation of tags with the product, which were visible in fluorescent orange.
The CLSM images revealed that the group that received medication based on bioceramic compounds (BIO-C® Temp) and filling with bioceramic sealer (BIO-C® Sealer) had greater penetration of intracanal medication (in fluorescent green) and filling sealer (in fluorescent blue) into the dentinal tubules in a regular and homogeneous manner, with the formation of long tags (Figure 6A).
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Conclusions:
‍The study concluded that the intracanal medication based on bioceramic compounds (BIO-C®Temp) chemically interacted with the bioceramic filling sealer (BIO-C®Sealer) to form a biomineralizing layer, allowing for an increase in bond strength and the formation of an adhesive interface between the two materials with no or little gap formation.