| Objective:To evaluate the influence of eugenol-containing and resin-containing endodontic sealers on the bond strength of fiber posts using different strategies of root canal irrigation and the interactive effect between two factors.Methods:Forty-eight newly extracted intact mandibular premolars for orthodontic treatment were collected. The teeth were sectioned 2mm above the cementoenamel junction. After endodontic treatment, post space was prepared one week later. The specimens were randomly assigned into two groups according to different endodontic sealers. Group A:Endofil (eugenol-containing endodontic sealer), Group B:AH-plus (resin-containing endodontic sealer). After post space preparation, each group was randomly assigned into three subgroups according to different strategies of root canal irrigation (n=8). Group A1 and B1:0.9% NaCl solution irrigation, Group A2 and B2: 17% EDTA+5.25% NaClO+0.9% NaCl solution irrigation, Group A3 and B3: ultrasonic agitation assosiated with 17% EDTA+5.25% NaClO+0.9% NaCl solution irrigation. Six specimens in each group were chosen for fiber posts cementation one week later and each specimen was sectioned perpendicular to the long axis into six slices with 1±0.05mm thickness. A thin slice push out test was performed to measure the bond strength of fiber posts. The data were analysed by three-way ANONA and Tukey test. Fracture modes of fiber posts were observed by stereomicroscope. Microstructure of the root canal surface of the left specimens was examined under SEM.Results:1. The bond strengths of six groups were as follows:Al(7.96±2.23), A2 (9.95± 2.88), A3(18.88±3.69),B1(11.41±3.70),B2(14.00±4.04),B3(19.13±3.27)MPa.2. Statistical analysis showed significant interaction between different endodontic sealers and strategies of root canal irrigation(P<0.05). Lower bond strength was found in group A1 compared to group B1(P<0.05), and the same result was revealed when comparing the group A2 to B2. There was no significant difference between the group A3 and B3(P>0.05).3. Tukey test showed that group A3 obtained higher bond strength than group Al and A2(P<0.05). No statistical difference was found between goup Al and A2(P>0.05).4. Group B3 obtained higher bond strength than group B1 and B2(P<0.05). No statistical difference was found between group B1 and B2(P>0.05).5. SEM showed that root canal achieved the cleanest surface with nearly all dentin tubules opened in group A3 and B3 when the left four goups’ dentin tubules were blocked with varying degrees.6. The majority fracture mode of specimens in each group were mixed mode which contained dentin-resin cement interface and post destruction. There was less destruction between post-resin cement interface or in dentin and resin cement.7. Higher bond strength was achieved in apical portion than middle or cervical portion(P<0.05).Conclusion:1. Eugenol-containing endodontic sealer can impair the bond strength of fiber post compared to resin-containing sealer when the root canal is irrigated by 0.9% NaCl solution or 17% EDTA+5.25% NaCIO+0.9% NaCl solution. There is no difference between two sealers when using 17% EDTA+5.25% NaCIO+0.9% NaCl solution combined with ultrasonic irrigation.2. The bond strength of fiber post can not be improved when the root canal is irrigated by 17%EDTA+5.25% NaCIO+0.9% NaCl solution.3. Ultrasonic agitation combined with 17%EDTA+5.25% NaClO+0.9% NaCl solution irrigation can significantly enhance the bond strength of fiber post.4. Dentin-resin cement is the weak interface in the bonding of fiber post.5. The bond strength of fiber post in apical root canal portion needs to be reinforced. |
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