Evaluation of tooth demineralization and interfacial bacterial penetration around resin composites containing surface pre-reacted glass-ionomer (S-PRG) filler

Objective: To evaluate preventive effects of S-PRG-filled resin-composites on surrounding tooth demineralization and interfacial bacterial penetration. Methods: Cavities were prepared on enamel or dentin blocks and treated by BeautiBond Universal (Shofu) and filled by resin-composites containing S-PRG filler (Shofu) at 0 wt% (P0, control), 10 wt% (P10), 30 wt% (P30), 50 wt% (P50) or 70 wt% (P70). The specimens were demineralized by Streptococcus mutans biofilms for 12 days. Wall lesion depth (WL-depth) and outer lesion depth (OL-depth) were measured from fluorescence microscopy. Interfacial bacterial penetration area (BPA) was evaluated from confocal laser scanning microscopy. Wall lesion hardness (WL-hardness) and outer lesion hardness (OL-hardness) were measured with a Vickers microhardness tester. Elemental analysis of resins and surrounding lesions was conducted by scanning electron microscopy and energy dispersive X-ray spectrometry. Results: Resin-composites in P70 contained significantly more F, Na and Al than that in P0 and P10. P70, P50 and P30 showed significantly lower WL-depth than P0. P70 showed significantly lower OL-depth, fewer Ca and P loss in lesions than P0. P70 showed significantly higher WL-hardness and OL-hardness in dentin specimens than P0. Enamel margins had a higher gap frequency than dentin margins. However, BPA did not show significant differences among the groups. Significance: Resin-composites containing S-PRG fillers at ≥30 wt% can inhibit wall lesions and that at 70 wt% can further decrease outer lesions, reduce Ca and P loss in lesions and increase surrounding dentin hardness. However, S-PRG-filled resin-composites does not inhibit interfacial biofilm penetration after a short-term demineralization period.