Remineralisation of Mineral-Deficient Dentine Induced by Bioactive/Biomimetic ion-Releasing Materials

Objectives: Evaluate the remineralisation ability of an experimental resin-based system containing fluoride-doped calcium phosphate fillers (FDCP), applied in mineral-deficient dentine (artificial caries dentine) in combination with a biomimetic dual-analogue primer.
Methods: Artificial mineral-deficient dentine caries lesions were created in standardised occlusal cavities of human molars [pH cycling: (pH 4.8; 8h); (pH 7.0; 16h)]. An experimental resin-based adhesive and flowable composite, containing FDCP (10wt% and 20wt%, respectively), were applied (+/-) in combination with a water-based primer containing two analogues of remineralisation (60s). A glass-ionomer cement and a conventional adhesive/composite system were also employed as comparative materials. The specimens were firstly submitted to a dual-movement chewing simulator (49N, 1.6 Hz; 100,000 cycles) in artificial saliva (AS). Each specimen was cut into three 1.5 mm material-dentine slabs and submitted to Knoop microhardness testing (10 gf; 5s) and Raman spectroscopy analysis at baseline and after storage in AS (15, 30 and 60 days). Further specimens were prepared and then immersed in fluorescein-isothiocyanate; these were finally analysed through confocal scanning microscopy (CLSM) analysis at baseline and after 60-days AS storage. Total demineralised dentine and disc-shape materials specimens were analysed via FTIR, SEM and EDX (Ca/P ratio). Data were statistically analysed using the two-way ANOVA and multiple comparison Bonferroni test (α=0.05).
Results: The specimens in the experimental FDCP groups, showed a significant increase (p>0.05) in microhardness; a total recovery of the microhardness was obtained after 60-day AS storage in the specimens pre-treated with the biomimetic primer, except at 50 µm underneath the bonding interface. Such results were corroborated by those obtained during the Raman and CLSM analysis. The SEM-EDX and FTIR analysis demonstrated the ability of the experimental FDCP resin-based materials to induce deposition apatite-like minerals.
Conclusions: Resin-based materials containing fluoride-doped calcium phosphates may mineralise mineral-deficient dentine through apatite-like deposition, especially when used in combination with primers containing biomimetic analogues.