Remineralization of partially demineralized dentin using calcium-silicate cements

Objectives: To characterize the remineralization potential of calcium-silicate cements (CSC’s) including biomimetic analogs in clinical-like conditions.
Methods: A class-I dentin cavity was prepared in 24 non-carious third molars. The cavity was coated with a self-etch adhesive (Clearfil SE Bond, Kuraray Noritake), after which a smaller cavity inside was prepared to limit the demineralization area. This area was demineralized using a pH-cycling protocol (50 cyclic immersions in a pH-4.8 and pH-7 bath for 0.5h and 2.5h successively). The cavities were filled with an experimental CSC (‘TCS50’ containing 50% Ca₃SiO₅ and 50% ZrO₂) or the commercial cement Biodentine (Septodont). To half of the specimens, biomimetic analogs (3% polyacrylic acid, 8% sodium tripolyphosphate) were added prior to cement mixing. After 1-week and 6-week storage in phosphate-buffered SBF, the specimens were cross-sectioned and polished using a cross-section polisher (IB-09010CP, JEOL). Interfacial interaction was characterized using a Feg-SEM/EPMA analyzer (JXA-8530F, JEOL).
Results: pH-cycling partially demineralized dentin (100±20 μm thick). After 1-week storage, both cements were found to have filled interfacial voids and to have deposited CaP precipitates within dentin tubules. Also Zr0₂ was detected 30 μm deep in demineralized dentin in TCS50-filled specimens. No additional interfacial effect by the biomimetic analogs was observed, which may be due to their slow dissolution kinetics. After 6-week storage, tubular occlusion had increased and some indication of initiated intertubular remineralisation was detected at the cement-dentin interface. Adding biomimetic analogs resulted in denser remineralization for both cements. Over time, the cements became more porous, indicating that Ca was transferred to the partially demineralized dentin.
Conclusions: CSC’s with biomimetic analogs were shown to have initiated remineralization of artificial carious-like partially demineralized dentin; 6-week however appeared insufficient to achieve significant remineralization of a 100-μm deep partially demineralized dentin layer. Further in-depth structural investigation of the formed CaP precipitates is also needed.