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    The effect of C-factor and flowable resin or fiber use at the interface on microtensile bond strength to dentin
    (QUINTESSENCE PUBLISHING CO INC, 2006) Belli, Sema; Doenmez, Nazmiye; Eskitascioglu, Guercan
    Purpose: As polymerization shrinkage is compensated by flow of the composite, several attempts have been performed for relief of the contraction stresses. The aim of this in vitro study was to evaluate the effect of flowable composite or fiber use under composite restorations on microtensile bond strength of composite to dentin in Class I cavities or flat dentin surfaces. Materials and Methods: Twenty-four sound extracted human first or second mandibular molars were randomly assigned to two groups (Class I cavities with a high c-factor or flattened dentin surfaces with a low c-factor). The dentin surfaces were treated with adhesive resin and restored with resin composite using four different techniques (bulk; with flowable composite; with a glass fiber (everStick NET); with a polyethylene fiber [Ribbond]). After 24 h storage at 37 degrees C in water, the specimens were thermocycled 600 times between 5 and 55 degrees C. Microtensile test specimens with a 0.9x0.9 (+/- 0.1) mm(2) cross-sectional area were produced, and bond strength tests were carried out at a crosshead speed of 1 mm/min. Mean bond strengths were analyzed using two-way ANOVA and Bonferroni's test at a 95% significance level. Results: Flowable composite decreased dentin bond strength in cavities with a high c-factor (p<0.05). The group restored with everStick NET showed stable bond strengths regardless of the effect of c-factor. Ribbond THM used under composite restorations increased dentin bond strength in cavities with a high c-factor (p<0.05). Conclusion: Flowable composite decreased dentin bond strength in cavities with a high c-factor; however, using a glass fiber in combination with flowable resin, stable bond strengths can be achieved in cavities with a high c-factor. Polyethylene fiber in combination with flowable resin increases the microtensile bond strength to the dentin floor in cavities with a high c-factor.
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    Effect of post-restoration on stresses in premolars with endodontic-periodontal lesion: an FEA study
    (TAYLOR & FRANCIS LTD, 2017) Belli, Sema; Eraslan, Oguz; Hakki, Sema Sezgin; Eskitascioglu, Murat; Eskitascioglu, Guercan
    Aim: This finite elemental stress analysis (FEA) study was aimed to test the effect of fiber and metal posts on stress distribution in premolar teeth with endodontic-periodontal (EP) lesion. Methodology: Three FEA models representing different EP lesions (primary endodontic disease (PED), PED with periodontal involvement and true-combined) were created. Tooth-model without EP lesion was used as control. The root-canals were assumed as root-filled, restored using glass-fiber or metal posts, resin composite build-up, and ceramic crown. A 300 N load was applied from the palatal surface of the crown with a 135 degrees angle. The SolidWorks/Cosmosworks structural analysis program was used for FEA analysis. Results were presented by considering von Mises criteria. Results: Maximum stress values for PED, PED with periodontal-involvement and true-combined lesions were 2.26, 1.25, 0.74 MPa for glass-fiber post; 2.08, 1.51, 1.18 MPa for metal post, respectively. If there is PED, fiber-post gave an advantage to the tooth at core structure and coronal third of the root. Metal post kept the stress inside its body however caused small, high stress concentrated areas at cervical. When there is PED with periodontal-involvement, metal post forwarded less stress toward the apical while fiber-post saved the coronal structure. In true-combined lesion model, metal post kept the stresses within its body and forwarded less stress toward the remaining root structure and periodontium. Conclusion: EP lesions have an effect on stress distribution therefore the post material selection should be done based on the severity of the lesion. Metal posts might be preferrable since it forwards less stress toward the surrounding periodontal tissues during wound healing.
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    Which is effective on bond strength of resin-based sealers: incorporation of powdered dentin to primer or adhesive?
    (TAYLOR & FRANCIS LTD, 2015) Akman, Melek; Belli, Sema; Ozcopur, Betul; Eskitascioglu, Guercan
    The aim of this study was to investigate the effect of adding powdered dentin to primer or adhesive in a self-etch system on the shear bond strength of three resin-based sealers. Seventy-two premolars were sectioned buccolingually, and 144 root halves were divided into three groups according to the sealer used: epoxy resin-based sealer (AH Plus), methacrylate resin-based (RealSeal, Hybrid Root SEAL) n=48. The surfaces were irrigated with 5% NaOCl, 17% EDTA, distilled water for 5min. Four subgroups were created (n=12): control group; Clearfil Liner Bond 2V treated group; powdered dentin added to the primer of Clearfil Liner Bond 2V (40 wt.%); and powdered dentin added to the adhesive of Clearfil Liner Bond 2V (20 wt.%). Dentin powder was prepared. Three mm high buildups with a constant surface area of 3.45mm(2) were created using the sealers and allowed to set (37oC, 100% humid, 72h). The samples were tested to failure for shear bond strength (1mm/min). The data were calculated (MPa) and analyzed using two-way ANOVA, one-way ANOVA, and Tukey HSD tests. Adhesive use decreased the bonding performance of AH Plus (p=0.00). Mean bond strength of the other sealers was found similar to control. Primer or adhesive resin with powdered dentin did not increase the adhesive performance of the self-etch system used. The shear bond strength of RealSeal was significantly increased when powdered dentin was added to primer or adhesive (p=0.00). The effect of adding powdered-dentine to primer or adhesive in a self-etch system on the shear bond strength was sealer-dependent .