Evaluation of a long-term antimicrobial dental adhesive via in vitro biodegradation and in vivo rodent secondary caries models

Bacterial-derived secondary caries is a primary cause of dental treatment failure at the artificial material-tissue interface. We previously developed ultra-long-term antimicrobial/antidegradative drug-silica particles (DSPs) to counter this interfacial failure. The aim of the current study was to evaluate a novel DSP-filled-adhesive system via in vitro and in vivo (rat) anti-secondary-caries studies. DSPs were incorporated into commercial total-etch dental adhesive at 10 % wt. to make DSP-SBMP. Interfacial specimens of DSP-SBMP-dentin and control SBMP-dentin were incubated 0- or 6-months in simulated salivary esterase, and subsequently with S. mutans/L. rhamnosus co-culture. Interfacial biomarkers were assessed via confocal microscopy and micro-computed-tomography. DSP-SBMP and SBMP were used to restore teeth in 16 SD rats in a 7-week split-mouth secondary caries study followed by clinical and µCT caries analysis and organ histology to assess biocompatibility. In vitro, interfacial biofilm viability (-23.1 ± 4.3 %) and biomass (-19.2 ± 4.9) were reduced by DSP-SBMP, as was cavitated (-78.6 ± 13.8 %) and demineralized (-33.4 ± 8 %) volume (ANOVA, Tukey HSD, p < 0.05). In vivo clinically observed primary and secondary caries counts were reduced on DSP-SBMP-restored teeth (χ2 p < 0.05). No significant toxic effects were observed. This comprehensive in vitro and in vivo antimicrobial/antidegradative analysis of a new dental biomaterial, accurately modeling the chemical and biological environment these materials must perform in, provided comprehensive understanding of potential material performance that strongly supports continued development and clinical evaluation. The clinical relevance of the in vitro model used in this study was validated by the in vivo animal model and could be used to assess new dental biomaterials.