Dentin remineralisation by light-curable calcium-silicate cements: cross-sectional microhardness and EDX-depth-profiling

Method: Dentin slices (5±2 mm side, 1.0±0.1 mm thickness) obtained from caries-free human molars were demineralized in EDTA 17% (2h, 37°C). Coronal dentin surface was restored with experimental light-curable calcium silicate cement (containing di-tri-calcium silicates and calcium sulphate into a HEMA-based resin, with L/P ratio 0.81) and soaked in simulated body fluid (HBSS). Experimental groups: 1) untreated dentin, 2) EDTA-treated dentin (EDTA), 3) EDTA-treated dentin tested after 14days in HBSS (EDTA-14d HBSS), 4) EDTA-treated dentin restored with the experimental material and tested after 14days in HBSS (EDTAM-14d HBSS). Nanoindentation and EDX-depth-profiling test were performed at cross- sectional interfaces.

Nanohardness testing was performed using an AFM with Triboscope indentor under water immersion using a Berkovich cube corner indenter (approx. 20 nm radius, depth resolution 5.1 microns). Ten indentations were performed (4000nN load, 10s time) in a straight line through the cross surface from coronal to apical side (first indentation at 0.5 microns from dentin interface, distance between subsequent indentations 10 microns). One-way ANOVA with Student-Newman-Keuls test (significance level p=0.05) were performed (letters and numbers mean significant differences between groups and among indentations within a group, respectively).

EDX-depth-profiling was carried out to detect calcium and phosphorous by ESEM-EDX throughout cross surfaces.

Result: Nanohardness results (expressed in GPa) in the table.                                           

EDX-depth-profiling in demineralized dentin showed two areas with different mineral content: demineralized area (D) till approx. 50 microns depth and mineralized (M) starting from 50 microns depth. EDX-depth-profiling in dentin treated with the calcium silicate composite showed the disappearance/reduction of the D area and appearance of a remineralized area (R). 

Conclusion: Calcium silicates-containing composites can remineralize apatite-depleted dentin surface to a depth of more than 100 microns.