Effect of ultraviolet A-induced crosslinking on dentin collagen matrix

• For the first time, we evaluated the inhibitory effect of UVA-induced crosslinking on both MMPs and cathepsin-K.
• UVA-induced crosslinking was tested in the presence/absence of photosensitizer in terms of the loss of dentin mass, degradation by MMPs and cathepsin-K.
• The results of the study showed that UVA-induced crosslinking significantly inactivated endogenous proteases of dentin.

ObjectivesThe aim of this study was to evaluate the effect of using UVA-induced crosslinking with or without riboflavin as photosensitizers on degradation of dentin matrix by dentin proteases.MethodsDemineralized dentin specimens (0.4 × 3 × 6 mm3, n = 10/group) were subjected to: (RP1), 0.1% riboflavin-5 phosphate/UVA for 1 min; (RP5), 0.1% riboflavin-5 phosphate/UVA for 5 min; (R1), 0.1% riboflavin/UVA for 1 min; (R5), 0.1% riboflavin–UVA for 5 min; (UV1), UVA for 1 min; (UV5), UVA for 5 min. Specimens were incubated in 1 mL zinc and calcium containing media for 1 day and 1 week. An untreated group served as control (CM). After incubation, the loss of dry mass of samples was measured and aliquots of media were analyzed for the release of C-terminal fragment telopeptide (ICTP vs. CTX) of collagen to evaluate for cathepsin K (CA-K) and total matrix metalloproteinase (MMP)-mediated degradation. Data were analyzed using repeated measures ANOVA at α = 0.05.ResultsAlthough UVA radiation alone reduced dentin degradation, UVA-activated riboflavin or riboflavin-5 phosphate inhibited MMP and CA-K activities more than UVA alone. The effects of crosslinking were more pronounced in 7-day samples; only with CA-K were the effects of crosslinking with or without photosensitizer significantly different from controls in 1-day samples.SignificanceThe use of bioactive forms (RP) or longer treatment time did not result with better effect. The use of UVA crosslinking reduces dentin matrix degradation, especially with photosensitizers.