[Effect of different molarity cathepsins specific inhibitor E-64 on dentin-resin bonding durability].

Objective To investigate,in vitro,the effect of cathepsins specific inhibitor N-(transepoxysuccinyl)-L-leucine 4-guanidinobutylamide (E-64) on dental endogenous cathepsins and to find its most effective molarity to elevate dentin-resin bonding durability.Methods Fifty recently extracted human third molars were divided into five groups according to random number table,and treated with different molarity of E-64 as follow:0,2.5,5.0,10.0 and 20.0 μmol/L.The group 0 μmol/L was control group.Then 20 specimens of dentin-resin composite were fabricated in each group.Half of the specimens were tested after 24 h water storage (37 ℃) and the other half were tested after 90 days water storage (37 ℃) followed by 3000 cycles'thermocyling(5-55 ℃) as aging treatment.Fractured specimens were analyzed using scanning electron microscopy (SEM).Results After 24 h water storage,no significant differences were found in micro-tensile bond strength(μTBS) of samples between different groups (P ＞ 0.05).However,after ageing treatment,μTBS of the samples in group 2.5,5.0,10.0 and 20.0 μmol/L [(18.7 ±2.7),(20.8 ±3.4),(18.3 ± 2.8) and (19.1 ± 2.7) MPa] were significantly higher than that in group 0 μmol/L [(15.1 ± 3.0) MPa] (P ＜ 0.05).Only in the group 5.0 μmol/L no significant difference was found between the original and the decreased value of μTBS(P ＞ 0.05),while the μTBS in other groups decreased significantly after aging treatment(P ＜ 0.05).Failure types were almost adhesive and mixed types.Collagens in hybrid layer were less degraded in the groups using E-64 after aging treatment than control group.Conclusions E-64 was effective on inhibiting cathepsins activity in dentin,and induced less collagens degradation in smear layer for better dentin-resin bond durability. Key words: Cathepsins ;  Enzyme Inhibitors ;  Dentin-bonding agents