Stabilizing the resin : dentin interface of root canals using a novel approach : insights into interfacial integrity

Abstract

The dentin is exposed to a wide variety of chemicals during treatment procedures. During root canal treatment, the dentin is exposed to proteolytic chemicals such as sodium hypochlorite and demineralizing chemicals such as ethylene diamine tetraacetic acid, in varying sequences. While these chemicals have largely beneficial effects in terms of dissolution of pulp tissue, hard tissue remnants and microbial biofilms, their non-specific nature is likely to result in untoward effects on the dentin itself.

The exact effects of different chemical sequences on dentin remains unknown: We first reviewed the effects of different clinically relevant chemical treatment sequences on dentin, and found that there was no consensus on how different sequences affect dentin structure and ultrastructure. More importantly, we identified that the effects of some chemical sequences on dentin were not known.

Chemical application sequences have differential effects on dentin collagen, but all sequences have detrimental effects on collagen: We first performed a comprehensive investigation on the effects of different chemical application sequences on the dentin collagen ultrastructure using several qualitative and quantitative analysis, and found that all sequences resulted in exposure of collagen, which was degraded and/or denatured when exposed to the proteolytic sodium hypochlorite. Dentin biomodification is a potent approach to reinforce and protect collagen: With the understanding that collagen fibres play a pivotal role in the structural integrity of the tooth, and that these fibres are exposed and degraded by the chemicals used during treatment, we reviewed the literature to identify strategies that can “protect” this collagen from future damage by host-derived and bacteria-derived collagenolytic enzymes. Our review showed that while dentin biomodifcation using collagen cross linkers was widely studied in restorative dentistry, a significant body of research was lacking with regards to dentin exposed to chemicals in root canal treatment.

Collagen cross linking and epoxy silanization can protect the dentin collagen from enzymatic damage: In this proof-of-concept study, we demonstrated that collagen cross linking with a common laboratory cross linker and an epoxy silane, can protect the collagen from the activity of collagenolytic enzyme and also maintain/improve the elastic modulus of dentin exposed to the enzyme.

Taken together, the results of our study will help in developing an innovative method that will protect the collagen that was subject to chemically-induced damages and potentially improve the integrity of the resin-dentin interface, which will be investigated in future studies.