Silver diamine fluoride pretreatment enhances the protective effect of resin-modified glass ionomer restorations on adjacent dentin caries: an in vitro study.

OBJECTIVE: To investigate whether 38% silver diamine fluoride (SDF) pretreatment enhances the caries-preventive effect of resin-modified glass ionomer cement (RMGIC) restorations on adjacent root dentin in an in vitro model. MATERIAL AND METHODS: Human tooth blocks with box-shaped cavities were allocated into two groups: 38% SDF pretreatment followed by RMGIC restorations (Group SDF+RMGIC), and RMGIC restorations alone (Group RMGIC). Dentin specimens simulating adjacent tooth root surface were placed 1mm from the restored tooth blocks and underwent a 7-day cariogenic challenge with a cross-kingdom biofilm of Streptococcus mutans, Lacticaseibacillus casei and Candida albicans. The biofilm on the surfaces of dentin specimens were assessed by PMA-qPCR, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM), respectively. Dentin demineralization was assessed by micro-computed tomography (Micro-CT), SEM, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR), respectively. RESULTS: PMA-qPCR demonstrated lower microbial growth on dentin surfaces in Group SDF+RMGIC compared to Group RMGIC. CLSM showed that dead-to-live ratio in Groups SDF+RMGIC and RMGIC were 0.89 ± 0.04 and 0.49 ± 0.05, respectively (p<0.001). SEM revealed sparse biofilms with damaged microbial cells in Group SDF+RMGIC, whereas Group RMGIC exhibited dense and structurally intact biofilms. Micro-CT showed that lesion depths (µm) in Groups SDF+RMGIC and RMGIC were 120±9 and 249±11, respectively (p<0.001). SEM demonstrated less mineral loss and collagen exposure in SDF+RMGIC. XRD showed stronger and sharper hydroxyapatite reflections, while FTIR showed a lower amide I: HPO42- value ratio in SDF+RMGIC than in RMGIC (0.12 ± 0.03 vs 0.20 ± 0.06; p=0.01). CONCLUSION: Within the limitations of this study, SDF pretreatment was associated with an enhanced caries-preventive effect of RMGIC restorations on adjacent root dentin. CLINICAL SIGNIFICANCE: SDF pretreatment before RMGIC restoration may enhance protection against dentin caries on adjacent tooth. This combined approach may be beneficial for patients at high risk caries.