Effects Of Two Canal Sealers On The Shear Bond Strength Of Fiber Posts Cemented Using Different Adhesive Approaches: Push-out Test And SEM Study

PartΙEffects of two canal sealers on the shear bond strength of fiber posts cemented using different adhesive approaches:push-out testObjectives The aim of this study was to verify the influence of two different endodontic sealers on the bond strength of fiber posts cemented with etch-and-rinse or self-etched luting agents. Methods 36 crownless human maxillary central incisors were prepared with the step-back technique and randomly divided into 6 groups (n = 6) according to the tested sealers (Cortisomol and Guttaflow), adhesive materials (etch-and-rinse luting agents: ONE—Step/DuoLink and self-etched luting agents: Futurabond DC/Rebilda DC) and fiber posts(MacrolockTM Post and Rebilda Post).group1: Cortisomol+ ONE—Step/DuoLink + MacrolockTM Post,group2: Guttaflow + ONE—Step/DuoLink + MacrolockTM Post,group3: Cortisomol+Futurabond DC/Rebilda DC+ MacrolockTM Post ,group4: Guttaflow +Futurabond DC/Rebilda DC+ MacrolockTM Post,group5: Cortisomol+Futurabond DC/Rebilda DC+Rebilda Post,group6: Guttaflow +Futurabond DC/Rebilda DC+Rebilda Post,6 slices with a thickness of 1.50±0.05 mm were prepared from each root. The Thin-slice push-out test was performed on different sections of each root(S2,S4,S6)at a crosshead speed of 1 mm/min, and failure modes of fractured specimens were analyzed using stereomimscop. The data were recorded and analyzed statistically (a= 0.05).Results Mean bonding strengths(Mpa): 9.31±3.61, 9.71±3.42,7.46±2.71,9.24±3.03,5.89±2.89,7.66±3.00.There was significant difference among the groups. Three-factor analysis of variance revealed that the bond strength of group5 was the lowest. Bond strengths decreased significantly from coronal to apical root canal regions (p<0.01). Mixed failure occurs with more frequency (40%) followed by failure in cement-dentin interface (29%) and cement -post interface (18%). Conclusion The shear bonding strength has close relationship with the endodontic sealer, adhesive materials, fiber and region of root canal.PartⅡEffects of two canal sealers on bond of fiber posts cemented using different adhesive approaches:SEM studyObjectives The aim of this study was to investigate the effects of two different endodontic sealers on the regional root canal bonding interface of quartz fiber posts using 2 luting materials by SEM analysis. Methods 36 intact extracted maxillary central incisors were sectioned perpendicular to the long axis at a point of 2.00mm-occlusal to the buccal cement-enamel junction (CEJ) and then endodontically prepared with the step-back technique and randomly divided into 6 groups (n = 6) according to the tested sealers, adhesive materials and fiber posts:6 slices with a thickness of 1.50±0.05 mm were prepared from each root. The cervical,middle,apical sections (S1,S5,S7) of each root were used for SEM study. And another 4 crownless human maxillary central incisors were selected and randomly divided into 4 groups according to the tested sealers and adhesive materials:groupⅠ: Cortisomol root canal sealer without etchinggroupⅡ:Guttaflow root canal sealer without etchinggroupⅢ:Cortisomol root canal sealer to be acid etchedgroupⅣ:Guttaflow root canal sealer to be acid etchedAfter being obturated by the two root canal sealers respectively, specimens of groupⅢandⅣwere acid etched. All specimens of the four groups were sectioned longitudinally. Morphologic structure of the root canal dentin surfaces and their changes after etching were observed under SEM.Results The root surfaces were covered with the smear layer and debris in all the groups after post space preparation in SEM analysis. Most of the dentin tubules were open after etching, however, the dentin tubules in the apical third were partly covered with the smear layer.Typical hybrid layer was found while the effects of two different endodontic sealers on penetration of resin tags into the dentinal tubules were clearly observed at the resin-dentin interfaces. Increased thickness of hybrid layer and penetration of resin tags into the dentinal tubules were observed in group Guttaflow regardless of adhesive materials.Conclusion The non-eugenol sealer(Guttaflow)provided good self-etched luting agents infiltration, producing a three-dimensional interlocking micro-network of resin tags in the dentin tubules with multiple lateral branches, which positively influenced the adhesion between dentin and the luting materials.When etched by phosphonic acid,morphologic structure of the root canal dentin surfaces and bonding interface were not influenced by endodontic sealer.