The effect of proanthocyanidins on the bond strength and durability of resin sealer to root dentine.

AIM: To investigate the effect of proanthocyanidins (PAs)-rich grape seed extract on the biodegradation resistance of demineralized root dentine and on the bond strength and durability between resin-based sealer and root dentine. METHODOLOGY: Single-rooted premolars (n = 28) were divided into PAs-treated and nontreated specimens. Root canals were instrumented to apical size 40, filled with RealSeal SE sealer/Core, sectioned into slices of 1 mm thickness from middle and coronal thirds and stored for 1 week or 3 months in distilled water. Specimens were subjected to push-out strength testing with the load applied perpendicularly in an apical to coronal direction using a universal testing machine. Remaining apical thirds were viewed by scanning electron microscopy after 3-months storage. Additional root canals were filled with rhodamine-B-labelled sealer and viewed by confocal laser scanning microscopy. Unfilled roots (n = 6) were sliced, demineralized, PAs-treated or left untreated and exposed to 24 h collagenase to determine hydroxyproline release in the supernatant. Two-way anova was used to test the effect of both dentine treatment with PAs and anatomical locations on bond strength and hydroxyproline release. Tukey-Kramer multiple comparison post hoc test was used to compare between groups. RESULTS: No difference in bond strength was found after 1-week storage between both PAs-treated (crosslinked) and untreated (noncrosslinked) groups in the coronal thirds. However, treatment with PAs revealed higher 1-week bond strength values (P ≤ 0.05) in the middle thirds. Generally, 3-month storage decreased the bond strength compared to 1-week within each of the crosslinked and noncrosslinked groups. However, the decrease in the bond strength after 3 months was less for the crosslinked specimens compared to the noncrosslinked specimens. Confocal images revealed a relatively uniform fluorescent interfacial layer and tubular penetration after 1 week in both groups. SEM images revealed more intact resin sealer/dentine interfaces with PAs crosslinking after 3 months. In addition, hydroxyproline release was significantly less (P ≤ 0.05) with crosslinked specimens. CONCLUSION: Treating root dentine with PAs-rich grape seed extracts improved the biodegradation resistance of demineralized root dentine and enhanced the bond strength and durability between resin-based sealer and root dentine after short-term water storage.

Characterization of riboflavin-modified dentin collagen matrix.

Crosslinking is considered a possible approach to increasing the mechanical and structural stability and biodegradation resistance of the dentin collagen matrix. The aim of this study was to investigate the mechanical and chemical variations and collagen degradation resistance associated with crosslinking of the dentin collagen matrix with UVA-activated riboflavin. Dentin collagen matrix specimens were treated with 0.1 and 1% riboflavin for 2 min and photo-activated with 7 mW/cm(2) UVA (368 nm) for 2 min. The structural change of the dentin collagen network with collagenase exposure was investigated by AFM and SEM at different time-points. The variations in surface/bulk mechanical properties and biodegradation resistance were characterized by nano-indentation, conventional mechanical testing, and hydroxyproline liberation at different time-points. Chemical changes associated with riboflavin/collagen-matrix interaction were analyzed by micro-Raman spectroscopy. UVA-activated riboflavin increased the mechanical properties, mechanical stability, and biodegradation resistance of the dentin collagen matrix. Higher collagen-network structural resistance against collagenolytic challenges was found with crosslinking. micro-Raman spectroscopy showed a strong dependency, in both intensity and wave-number, of certain Raman bands (1242-1667 cm(-1)) with crosslinking indicating the collagen/riboflavin interactions. UVA-activated riboflavin (1%) more efficiently crosslinked the dentin collagen matrix within a relatively clinically acceptable time-frame compared with 0.1% riboflavin.