How effectively do hydraulic calcium-silicate cements re-mineralize demineralized dentin
Introduction
Hydraulic calcium-silicate cements (hCSCs), being widely used for various pulp-related and endodontic indications [1], [2], [3], are currently also materials of interest to serve as dentin re-mineralization agents. Re-mineralization of artificial caries-like demineralized dentin has been achieved in a study using a so-called ‘biomimetically modified mineral trioxide aggregate’ (MTA mixed with biomimetic analogs such as polyacrylic acid and sodium tripolyphosphate) in the presence of simulated body fluid (SBF) [4]. In addition to the primary pulp-related/endodontic indications, the commercially available hCSC Biodentine (Septodont, Saint Maur des Fosses, France) has also been claimed for direct restorative applications, such as permanent dentin-replacement [5], [6]. Its capability to re-mineralize demineralized dentin has been explored [7]. Another study evaluated the effectiveness of Biodentine as an indirect pulp-capping material; it revealed a success rate of 83.3% in patients with reversible pulpitis after 12-month follow-up [8]. Besides resin-free hCSCs, light-curing resin-based calcium-silicate cements, such as TheraCal LC (Bisco, Schaumburg, IL, USA), have been developed for indirect (and direct) pulp capping as well.
To date, the dentin re-mineralization potential of hCSCs reported in literature can only be considered as ‘proof-of-concept’, so far without direct clinical implementation potential. Laboratory studies conducted by various research groups reporting on the dentin re-mineralization potential of hCSCs utilized thinly sectioned dentin slabs [4], [7], [9], [10] rather than that they subjected dentin exposed in actually prepared tooth cavities to re-mineralization protocols. In some studies, the dentin slabs were immersed in biomimetic analogs containing SBF to generate fluid nano-precursors [11], [12]. Hence, there remains a need to characterize the re-mineralization potential of hCSCs under more clinically simulated conditions. Using a tooth-cavity model, demineralized dentin should be exposed to the cements, like we characterized in a previous study the interfacial interaction of hCSCs with unaffected sound dentin [13].
The purpose of this study was therefore to characterize the chemical interplay and to quantify the re-mineralization effectiveness of two resin-free hCSCs (Biodentine, Septodont; ProRoot MTA, Dentsply Sirona) and one resin-based hCSC (TheraCal LC, Bisco), when applied onto demineralized dentin in tooth cavities; the specimens were stored in SBF for different time periods. The null hypotheses tested were (1) that there is no difference in the chemical interplay of the resin-free and resin-based hCSCs with demineralized dentin, (2) that all hCSCs effectively (completely) re-mineralize demineralized dentin, and (3) that the re-mineralization potential does not depend on the SBF-storage period.
Section snippets
Specimen preparation
Thirty-six healthy human third molars (gathered as approved by the Commission for Medical Ethics of KU Leuven under the file number S57622) were stored in 0.5% chloramine solution at 4 °C and were used within 3 m after extraction. Each tooth was mounted in a gypsum block to facilitate manipulation. The occlusal third of the crown was removed using a diamond saw (Isomet 1000, Buehler, Lake Bluff, IL, USA). The dentin surfaces were verified for absence of enamel and/or pulp tissue under a
The elemental composition of unaffected sound and demineralized dentin
Representative EPMA line-scan analysis along the demineralized dentin together with the corresponding BSE image, is shown in Fig. 1. Along this demineralized dentin, both Ca and P contents were lowest at the most superficial demineralized dentin, which had been in the closest contact with 10% formic acid; the Ca and P contents increased gradually towards the inner deeper demineralized dentin zone (Fig. 1b).
Representative Feg-EPMA mappings of Ca, P and C at unaffected sound and demineralized
Discussion
Hypothesis (1) that there is no difference in the chemical interfacial effect induced by the resin-free and resin-based hCSCs at demineralized dentin, was rejected. Hypothesis (2) that all investigated cements effectively (completely) re-mineralize demineralized dentin, was rejected as well. Re-mineralization, identified as increases in Ca and P at the demineralized dentin zone, could be detected for both the resin-free and resin-based hCSCs investigated. Although the degree of
Conclusion
In view of the fully quantitative chemical Feg-EPMA analysis, hCSCs were shown to induce re-mineralization of artificially demineralized dentin. Compared with the resin-based cement TheraCal LC (Bisco), the resin-free hCSCs Biodentine (Septodont) and ProRoot MTA (Dentsply Sirona) induced re-mineralization at a higher speed and intensity. Yet, the overall dentin re-mineralization efficacy of the three hCSCs appeared insufficient, as the deepest demineralized dentin zone was never re-mineralized,
Acknowledgments
Dr. Li’s research stay at KU Leuven is supported by the China Scholarship Council (File No. 201206270126). This research project was in part conducted within the framework of the FWO (Research Foundation of Flanders) research project G.0893.15.
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