Biodegradation of resin-dentin interfaces is dependent on the restorative material, mode of adhesion, esterase or MMP...

To measure the effect of simulated human salivary esterases (SHSE) and metalloproteinases (MMP) inhibition on the integrity of restoration-tooth interfaces made from traditional or polyacid-modified resin composites bonded to human dentin by either total-etch or self-etch adhesives.

Resin-dentin specimens, made from traditional (Z250) or polyacid-modified (Dyract-eXtra) composites were bonded to human dentin using total-etch (TE-Scotchbond) or self-etch (SE-EasyBond) adhesives. TE was applied with or without the MMP inhibitor galardin. Specimens were incubated in phosphate-buffer or SHSE (37°C/pH=7.0) for up to 180 days, then suspended in a continuous flow biofilm fermenter cultivating biofilms of Streptococcus mutans UA159. Interfacial bacterial penetration, biofilm biomass and viability were measured by confocal laser scanning microscopy and biomarker dyes and used as interfacial biodegradation markers.

All specimens showed increased biofilm penetration and biomass with time regardless of incubation condition. SHSE increased bacterial penetration in all experimental samples after 180days (p<0.05). Galardin reduced interfacial bacterial ingress and bacterial biomass vs. non-MMP-inhibited TE-bonded specimens (p<0.05). TE interfaces showed lower interfacial bacterial biomass vs. SE after 90-day and 180-day (p<0.05). Dyract-eXtra specimens showed lower bacterial cell viability within the interface vs. Z250 (p<0.05).

The biodegradation of resin-tooth interfaces is accelerated by esterases, modulated by MMP inhibition and is dependent on the material's chemistry and mode of adhesion. The in vitro bacterial growth model used in this study facilitates the elucidation of differences in interfacial integrity and biostability between different materials and techniques and is suitable for assessment of their performance prior to clinical evaluation.