Biological Performance of Modified Glass Ionomer Cement: Antibacterial Activity, Cytocompatibility, and Rabbit Pulpal Response

Background: Conventional glass ionomer cement (GIC) is widely used as a restorative base and liner owing to its chemical adhesion to dentine, fluoride release, and favourable biocompatibility. Nevertheless, its intrinsic antibacterial activity and regenerative capacity remain limited. To enhance these properties, a series of modified GIC formulations, referred to as BIOGIC, incorporating tricalcium phosphate (TCP), TCTP-derived peptides, and 10% chlorhexidine (CHX), were developed. This study evaluated their antibacterial efficacy, cytocompatibility, and pulpal responses in a rabbit-tooth model. Methods: Six formulations were examined: GIC, BIOGIC, BIOGIC+TCP, BIOGIC+TCP+3 µg TCTP, BIOGIC+TCP+10 µg TCTP, and BIOGIC+10% CHX. Antibacterial activity against Streptococcus mutans and Enterococcus faecalis was assessed using liquid culture assays and spread-plate analysis. Dental pulp cell viability was evaluated using a metabolic assay. In vivo pulpal responses were examined in rabbit incisors restored with each material and assessed histologically after 21 days, focusing on inflammation, collagen formation, and pulp–dentine integrity. Results: BIOGIC+10% CHX demonstrated the strongest antibacterial activity, significantly reducing S. mutans and E. faecalis. Dental pulp cell viability decreased significantly in the GIC, BIOGIC+TCP+10 µg TCTP, and BIOGIC+10% CHX groups, with BIOGIC+10% CHX showing the greatest cytotoxicity. In contrast, BIOGIC, BIOGIC+TCP, and BIOGIC+TCP+3 µg TCTP significantly enhanced pulp cell proliferation. Histological analysis revealed no pulpal inflammation in any group. Mild collagen deposition was noted only in the BIOGIC group, whereas the remaining formulations exhibited normal pulp morphology without adverse reactions. Conclusion: Incorporation of 10% CHX markedly enhanced the antibacterial properties of BIOGIC but increased cytotoxicity. BIOGIC formulations containing TCP and low-dose TCTP improved pulp cell viability and maintained favourable pulpal responses. These modified BIOGIC materials show promise as bioactive, pulp-compatible alternatives to conventional GIC, although CHX-containing formulations should be used with caution owing to their cytotoxic effects.