Quantification of collagen cross-linking and permeability at dentin-resin interface

Objective: To evaluate the effects of dentin surface treatment with collagen cross-linkers on (1) emission intensity (EI) of collagen and (2) permeability at the dentin-resin interface. Method: Ground flat occlusal dentin surfaces of 48 extracted human molars were restored with resin composite using either One step plus (OS - Bisco) or Adper single bond plus (SB - 3M ESPE) adhesive systems. Prior to application of bonding system, except for the control (no treatment), dentin surfaces were treated with one of the following agents (n = 6): 6.5% grape seed extract (GSE), 5.75%carbodiimide/1.38%N-Hydroxysuccinimide (EDC), and 5% glutaraldehyde (GD) for 10 min. After 24 hours, samples were sectioned into 0.8x0.8 beams, which were embedded in epoxy resin, polished, infiltrated with 0.1% Rhodamine-B for 1 hour, rinsed and evaluated by CLSM (confocal laser scanning microscope, LSM 510 Meta, Carl Zeiss). EI at the dentin-resin interface was quantified for collagen (auto-fluorescence) and Rhodamine-B infiltration (porosities). Data were analyzed by ANOVA, Scheffe, t-test and Pearson correlations (α = 0.05). Result: Greater fluorescence intensity was observed with greater collagen cross-linking. Glutaraldehyde provided highest intensity (p < 0.05), followed by GSE. Overall, presence of porosities (Rhodamine-B fluorescence) was statistically higher for OS when compared to SB, regardless of the cross-linker (p < 0.05). Surface treatment with GSE prior to SB application provided the lowest permeability at the dentin-resin interface (p < 0.001). Positive correlations were observed between EI of collagen and Rhodamine-B for control and EDC, regardless of the bonding system. Negative correlations observed for GSE and GD indicates that higher EI collagen resulted in lower Rhodamine-B fluorescence for SB. Conclusion: CLSM is a useful tool to quantify collagen cross-linking and effect on permeability at resin-dentin interface. Immediate sealing of the resin-dentin interface is not affected by most cross-linkers and is improved following GSE application.