The Interfacial Integrity Of Dental Restorations: Exploring The Effect Of Oral Biofilms, Mechanical Challenges, And Antimicrobial Treatments

Abstract

Better tools to study the interfacial integrity of dental composites and the factors associated with its eventual breakdown are needed. The initial work focused on the optimization of techniques to study leakage and bond strength. We developed a method for 3D quantification of leakage around dental restorations by using silver nitrate infiltration, micro-CT and image subtraction, overcoming previous limitations of this technique. Also, a new variant of the Brazilian Disk Test specimen was developed for testing dentin-composite bond strength. This novel test provided several advantages including: zero premature failure, simpler testing procedures, a consistent failure mode involving the adhesive interface, and reduced variation in the measurements. We also developed a model to investigate the role of oral biofilms on the degradation of the adhesive interface. Our results suggested that oral biofilms in the presence of sucrose led to active degradation of the adhesive interface. Furthermore, we studied the combined effect of mechanical and biofilm challenge on the interfacial integrity of dental restorations. The results showed that when specimens are subjected to both challenges, a greater reduction in fracture strength is seen compared to the effects of fatigue and biofilm alone, demonstrating the additive effect of both. Again, the presence of biofilm showed a substantial effect in the degradation of the adhesive interface, which was significant in the presence of sucrose. The effect of fatigue was much less pronounced. Antimicrobial containing adhesives are used to prevent the breakdown of the adhesive interface. In the final part of this project, a multispecies oral biofilm/culture model was developed to test the effectiveness of commercially available MDPB-containing adhesive system. We found that the polymerized antimicrobial adhesive reduced biofilm formation and metabolic activity when tested in a closed multispecies biofilm model; however complete inhibition of oral biofilm formation was not observed. The presence of sucrose in the media abolished the antimicrobial effect seen under basal growing conditions. In addition, the polymerized MDPB-containing adhesive failed to inhibit multispecies oral biofilm formation in the absence and presence of sucrose when tested in a Drip Flow Reactor.