Reliability of Two anti-MMP Dentin Treatments: 4-point Bending, Microtensile Bond Strength and Nanoleakage

Objectives: The objective of this study was to analyze the influence of two anti-matrix metalloproteinase (anti-MMPs) on 4-point bending (BS), microtensile bond strength (µTBS) and nanoleakage.
Methods: 48 molars horizontally sectioned to produce flat dentin surface were used. Ceram-X-One (DentSply) composite was built as three successive layers,2mm and light cured, 1600 mW/cm² Ortholux (3M-ESPE). In the control group, etch-and-rinse Prime&-bond-One (DentSply), was used. In the Self-etch group, Clearfil-Protect(Kurary) was used. In BAC-etch group, a Benzalkonium Chloride containing etchant (BAC-etch, Bisco) was used. Samples were sectioned (Isomet 4000) to produce beams of 1mm x1mm x10mm, 68/group, divided randomly as immediate and 6 months of water immersion (n=32) plus one slab, 1mm thick for nanoleakage (n=8) by SEM and digital image analysis. Weibull distribution, mixed model ANOVA were used to analyze mechanical and nanoleakage results. Pearson’s correlation to correlate between various tests results.
Results: All test groups showed deterioration of initial bonds (p< 0.05). Self-etch showed worst immediate µTBS (p<0.05) and BS (p>0.05); but best delayed µTBS (p>0.05), BS (p<0.05). Bac-etch didn’t improve bond stability of Prime&-Bond-One (p>0.05). µTBS and BS have moderate correlation (p = 0.13 at baseline and p = 0.004 on aging) . Nanoleakage was not eliminated in any of the groups. Self-etch group showed least nanoleakage on aging (p< 0.05). No correlation between mechanical and nanoleakage test results (p>0.05).
Conclusions: Bac-etch may not be a suitable protocol for improving etch-and-rinse adhesives bond stability. Nanoleakage is not correlated to mechanical testing of dentin bonds. BS is a valid mechanical test and might improve the clinical relevance of µTBS when both are employed with nanolakage.