From molecular interactions to clinical potential: Strontium-calcium polyelectrolyte synergy for biomimetic dentin repair and remineralization.

AIMS AND OBJECTIVES: This study aimed to evaluate effects of calcium carbonate (CaCO3) and anhydrous strontium carbonate polyelectrolyte-cation complexes on dentin adhesive bonding, mechanical properties and intrafibrillar mineralization of dentinal collagen fibers.

MATERIALS AND METHODS: Dentin discs were prepared from collected human premolars and treated with 1%SrF₂CaCO3, 0.5%SrF₂CaCO3, 2% SrF₂CaCO3 and distilled water for 15 days under controlled pH. Raman spectroscopy, transmission and scanning electron microscopy were performed to evaluate intrafibrillar mineralization and topographical changes. Diffusional coefficient and density functional theory were calculated. Resin-dentin bond specimens were prepared and microtensile bond strength was measured. Statistical analysis was performed using a one-way ANOVA with subsequent post-hoc comparisons, with significance of p < 0.05.

RESULTS: Raman spectroscopy demonstrated a concentration-dependent increase in dentin mineralization, with enhanced phosphate and organic matrix signatures following SrF₂CaCO3 treatment. TEM and HRTEM confirmed organised intra- and extrafibrillar hydroxyapatite deposition, particularly in the 2% SrF₂CaCO3 group, showing aligned crystallites along the collagen axis and well-defined D-periodicity. SEM revealed progressive crystal elongation and surface densification with increasing concentration. Diffusion analysis indicated higher ionic mobility in modified groups, supported by DFT calculations showing increased Ca and P occupancy and crystallographic stability. µ-tensile testing demonstrated significantly improved bond strength in the 1% SrF₂CaCO3 and 2% SrF₂CaCO3 groups without compromising adhesive performance.

CONCLUSION: The present study demonstrated the modification of dentinal surface using a range of concentrations of SrF₂CaCO3 as a multifunctional modifier indicating favourable bond strength and extensive crystallisation capability. The 2% SrF₂CaCO3 polyelectrolyte formulation has a significant potential for clinical application and offers a novel potential solution to address significant challenges in adhesive dentistry.

CLINICAL SIGNIFICANCE: Strontium/fluoride/calcium carbonate polyelectrolyte complexes promote biomimetic dentin remineralization, enhance crystal organisation, and improve resin-dentin bond strength. This strategy offers a biologically guided approach to reinforce compromised dentin, potentially increasing the longevity and reliability of adhesive restorative procedures.