| Objective:To evaluate the push-out bonding strength between adhesive resin and dentin surface of post space after treating the post space with four washing schemes,so as to provide theoretical reference for the selection of rinsing solution.Methods:60 Single-rooted extracted human teeth were used in this research,the root surface of the samples were cleaned with ultrasonic instrument.Then the teeth were stored in 0.9% physiological saline.The crowns of the teeth were removed at the cemento-enamel junction.Then the samples were divided into 4 groups randomly.All the root canals were prepared to an apical size of 25# 08 taper with Wave-one rotary NiTi instruments.The root canals were filled with hot gum with A-H plus sealer under vertical pressure,and post space were made with special drills(diameter of 1.4mm).Specimens were irrigated with 3% hydrogen peroxide in group A;5.25% sodium hypochlorite(NaOCl)and 17% ethylene diamine tetraacetic acid(EDTA)alternately in group B;0.2% chlorhexidine(CHX)in group C;17% EDTA in group D.Then followed with ultrasonic washing with distilled water for 30 seconds.Ten samples were selected from each group according to the random principle,and the glass fiber posts were adhered into the post space with dual-curing composite resin cement(3M-ESPE).Tooth slices were made with a special machine for hard tissue cutting.The bounding strength were determined by the push-out bonding strength test.SPSS statistical software was used to analyze the data,and the failure modes of the bounding surface were determined under the root canal microscope.Another 5 samples without fiber post bounding of each group were split along the buccal-lingual direction.After being dried and sprayed with gold,the microscopic state of the dentin surface of the post space was observed under a scanning electron microscope(SEM).Results:1.Fiber post bounding strengthThe bonding strength of the group A、B、C and D was 11.93±2.59(MPa)、15.87±1.79(MPa)、15.03±2.85(MPa)and 19.24±2.87(MPa)respectively(A vs B,P<0.01;A vs C,P<0.01;A vs D,P<0.01,B vs C,P>0.05,B vs D,P<0.01,C vs D,P<0.01).The result indicated that among the four groups,EDTA washing can make the fiber post obtain the maximum bonding strength.The difference between group D and the other three groups was statistically significant.The adhesion strength of group B and group C was after group D,and the difference between the two groups had no statistically significance(P>0.05).The bonding strength of hydrogen peroxide washing group was the weakest.2.Failure mode of bonding surfaceIn group A,most of the slices were fractured in resin-dentin surface or presented as mixed fracture.While,most of the fractures in group B and C happened in resin-fiber bounding surface or presented as mixed fracture.In group D all the slices fractured between resin and fiber posts or presented as mixed fracture.After statistical analysis,it was found that there was no statistically significant difference between group B and group C(P>0.05),and the differences between other groups were statistically significant(P<0.05).3.Electron microscopic observationsThe observation showed most of dentine tubules were blocked with a large amount of debris on the surface of post space in group A.The dentine tubules surrounded with white color were all open in group B.In group C,most of the dentine tubules were partially blocked,and there was no debris on the dentin surface.The dentin surface of group D appeared to be cloudy,while the tubules were all open.Conclusion:1.Irrigating with 17% EDTA solution for 1 minute can effectively clean the post space without chalky demineralization of the dentin surface.2.According to the analysis of the bonding strength and fracture modes of the tooth slices we can conclude that fiber post can get better bonding after washing the post space with 17% EDTA solution than other three groups. |
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