pH-Responsive mesoporous silica nanoparticle-reinforced composite resin with remineralization capability

Enhancing the mechanical properties of composite resins and promoting dentin remineralization are effective strategies for extending the longevity of restorations. In this study, we developed a pH-responsive composite resin reinforced with phosphorylated chitosan (Pchi)/amorphous calcium phosphate (ACP) and amino-functionalized mesoporous silica nanoparticles (MSNs) (Pchi/ACP@A-MSN complexes).

MSNs and Pchi/ACP were synthesized, and the resulting composite resins were classified into five groups based on the filler compositions: Group A (45wt.% A-MSNs + 15wt.% Pchi/ACP + 40wt.% resin matrix), Group B (22.5wt.% A-MSNs + 37.5wt.% Pchi/ACP@A-MSNs + 40wt.% resin matrix), Group C (45wt.% nonporous silica + 15wt.% Pchi/ACP + 40wt.% resin matrix), Group D (15wt.% Pchi/ACP + 85wt.% resin matrix), and Group E (100wt.% resin matrix). The degree of double-bond conversion and mechanical properties (Flexural modulus, flexural strength, and Vickers hardness) of each group were measured. The remineralization performance and calcium ion (Ca²⁺) release performance were observed. Cell viability was evaluated by CCK-8 assay.

Group A exhibited the highest mechanical performance, with flexural strength of 115 ± 9.68 MPa, flexural modulus of 5.99 ± 0.44 GPa, and Vickers hardness of 31.73 ± 2.39 HV. All groups achieved double-bond conversion rates > 50% after 60 s of light curing (P > 0.05). At pH 4.0, Group B exhibited the highest Ca²⁺ release (276 µg/mL), while Group D had the highest release at pH 7.4 (128 µg/mL). SEM and EDS analyses indicated that Group D achieved the most substantial dentin remineralization, followed by Groups C and A. All groups maintained cell viability above 75% throughout the 7-day assay, with no significant cytotoxicity observed.

A composite formulation containing 45 wt% A-MSNs and 15 wt% Pchi/ACP (Group A) significantly enhanced mechanical strength. The 15 wt% Pchi/ACP formulation (Group D) demonstrated the greatest remineralization effect. Group B, combining A-MSNs and Pchi/ACP@A-MSNs, provided pH-responsive Ca²⁺ release with a favorable balance of mechanical performance and remineralization potential. All formulations met the biocompatibility requirements for dental applications.