Effect of different molarity cathepsins specific inhibitor E-64 on dentin-resin bonding durability / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate, in vitro, the effect of cathepsins specific inhibitor N-(trans-epoxysuccinyl)-L-leucine 4-guanidinobutylamide(E-64) on dental endogenous cathepsins and to find its most effective molarity to elevate dentin-resin bonding durability.</p><p><b>METHODS</b>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 °C) and the other half were tested after 90 days water storage(37 °C) followed by 3000 cycles'thermocyling(5-55 °C) as aging treatment. Fractured specimens were analyzed using scanning electron microscopy(SEM).</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSIONS</b>E-64 was effective on inhibiting cathepsins activity in dentin, and induced less collagens degradation in smear layer for better dentin-resin bond durability.</p>

Effects of cleaners on the color stability of prosthesis silicone rubbers / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of different cleaners on the color stability of two silicone rubbers used for maxillofacial prosthesis, and to provide recommendations for clinical use.</p><p><b>METHODS</b>Thirty skin-color columniform specimens (12 mm diameter, 10 mm height) of two silicone rubber (A:A-2000; Z:ZY-1) were prepared, randomly divided into 6 groups according to the table of random number, and cleaned with the following solutions: isopropyl alcohol (I), three kinds of denture cleaners (P: Polident, S: Steradent, C: Cleansoft) and distilled water (D), simulating the total immersion time of 1 year (1, 15, 10, 3 and 10 min each time respectively). Control group was kept in dark place without treatment. The L(*), a(*), b(*) value were tested before and after immersion. Then color difference value was calculated.</p><p><b>RESULTS</b>Color differences were different among groups. Color difference in group I (A: 2.15, Z: 2.00) were significantly greater than that in any other group. There were no significant differences between groups using denture cleaner P (A: 0.36, Z: 0.36), C (A: 0.42, Z: 0.37) and S (A: 0.33, Z: 0.38), and group D (A: 0.22, Z: 0.23).</p><p><b>CONCLUSIONS</b>Isopropyl alcohol causes the most severe fading, and denture cleaners and distilled water cause obscure fading.</p>

Effect of concentration of chlorhexidine on bonding durability of dentine and resin / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of concentration of chlorhexidine on bonding durability of dentine and resin.</p><p><b>METHODS</b>Forty extracted third molars were randomly allocated into five groups, which include one control group and four test groups. Teeth dentin surfaces in each group were treated with one of the following solution, 1.5 microl water (control), 0.02%, 0.2%, 2% and 20% chlorhexidine. Single Bond 2 adhesive was applied to the dentin surface according to manufacturer's recommendations. Then 5 mm thickness of composite (Z250) was built up on the dentin of each molar. The teeth were sectioned into microtensile samples and subdivided into two subgroups, 16 samples each. Samples in subgroup II and I were tested after being stored in distilled water for 24 h and 6 month respectively. Each fractured sample was examined with SEM.</p><p><b>RESULTS</b>No significant differences of 24 h bonding strength were found among the five groups. There were significant difference in bonding strength between 0.2%, 2% chlorhexidine groups [(24.68 ± 5.26) and (23.19 ± 5.26) MPa] and the control group [(19.10 ± 4.67) MPa] after 6 month (P = 0.007,0.045), and significant differences were also found between 0.2%, 2% and 0.02% chlorhexidine group [(19.01 ± 6.87) MPa, P = 0.006, 0.041). Most of the fractured modes were mixed or interface failures after 24 h of water storage, and the mixed failure increased after six month of water storage. In the 0.2%, 2% and 20% chlorhexidine treated group, most of the failure was found at the top of hybrid layer, while in the 0.02% group, it was found in the base part of hybrid layer.</p><p><b>CONCLUSIONS</b>Chlorhexidine could increase the bonding durability of resin and dentine. Higher than 0.2%, concentration of chlorhexidine couldn't improve bonding durability.</p>