الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 117 |  |  |
| | | from | 117 | | |
Abstract
Objectives: To evaluate the effect of dentin surface pretreatment with chlorohexidine, riboflavin or papain on microtensile bond strength (μTBS) of MDPB-containing self-etch adhesive and micromorphological analysis of adhesive/ dentin interface. Materials and Methods: A total of 56 human molars were used for μTBS test. Their roots were fixed in acrylic resin blocks 2 mm below cemento-enamel junction. A flat dentin surface of each tooth was exposed. After planning, teeth were assigned into groups (n=14) so that dentin would be left untreated or treated with chlorohexidine, riboflavin or papain. For 60 sec. All specimens received MDPB-containing self-etch adhesive (Clearfil SE Protect, Kuraray Noritake Dental, Tokyo, Japan) then light cured according to manufacture instructions. A block of resin composite (Tetric N-Ceram, Ivoclar vivadent, Liechtenstein) measuring 4 mm in height and 4 mm in width was made incrementally on dentin surface. After 24 hours, half of the specimens of each group (n=7) was submitted to μTBS testing. However, the other half was tested after 6-month storage in artificial saliva using an incubator. The specimens were cut using an isomet machine to obtain beams measuring about 0.9 mm2 of thickness. A universal testing machine was used for μTBS testing then, failure mode was examined under a stereomicroscope. For micromorphological analysis of resin/dentin interface, an additional 16 molars were prepared as previously mentioned in μTBS test. Specimens were cut vertically using a diamond saw under water coolant. After polishing of cut surface with silicone carbide paper, half of specimens were prepared with acid-base challenge then, both halves were coated with gold sputtering to be observed under a scanning electron microscope. Results: Microtensile bond strength test: the two-way ANOVA test showed that the ”” surface pretreatment material ”” and ””time”” had significant differences on the μTBS results. Tukey post hoc multiple comparison test showed that the surface pretreatment of dentin in the (immediate groups) using CHX had the highest bond strength mean value followed by control, papain and riboflavin receptively. Furthermore, CHX had significant difference (p < 0.05) with riboflavin and papain groups while control group had no significant difference (p > 0.05) with any group. On the Other hand, papain group had the highest bond strength mean value in the (delayed groups) followed by riboflavin, CHX and control receptively. Papain group was also found to be significant (p < 0.05) with all groups. Failure mode analysis revealed that cohesive failure in composite was the most frequent type while adhesive failure was the least type in all groups. Scanning of immediate groups: resin tags infiltration was found the most in papain group. Scanning of delayed groups: dentin substrates showed degradation of the bonding interface over time mostly marked in riboflavin group. Resin tags infiltration was found the most in papain group also. Conclusion: Application of papain enzyme as a dentin surface pretreatment agent positively influenced the microtensile bond strength of MDPB-containing self-etching adhesive system compared to chlorohexidine or riboflavin. Clinical significance: Application of dentin surface pretreatment materials such as papain enzyme along with the use of a MDPB-containing adhesive have a promising result on bond durability.