Duygu Saraç

Effect of different surface treatments on the push-out bond strength of fiber post to root canal dentin

OBJECTIVE The purpose of this study was to evaluate the effects of different surface treatments on the bond strength of a fiber post to dentin. STUDY DESIGN Sixty extracted human maxillary incisor teeth were manually shaped with K-files using the step-back technique. ISO size 45 files were used as master apical files. Post spaces were prepared and then the root canals were subjected to one of the following 5 surface treatments: irrigation with 5% sodium hypochlorite (NaOCl); treatment with ethanol, ethyl acetate, and acetone-based cleansing agent (Sikko Tim); irrigation with 17% EDTA; etching with 37% orthophosphoric acid for 15 seconds; and etching with 10% citric acid for 15 seconds. Fiber posts were luted using self-etching/self-priming dual polymerized resin cement. From the coronal part of each root, 3 slides of 0.6-mm thickness were obtained. A push-out bond strength test was performed by a universal testing machine at a crosshead speed of 0.5 mm/min. Dentin surfaces were examined under scanning electron microscopy (SEM) after different surface treatments. Data were analyzed with a one-way analysis of variance (ANOVA) and Tukey HSD test. RESULTS ANOVA revealed that canal surface treatment affected the bond strength (P < .001). The highest bond strength was obtained in the Sikko Tim group. The results also showed that surface treatment methods increased the bond strength to dentin when compared with the control group. CONCLUSIONS Sikko Tim group was the more effective surface treatment agent compared with EDTA, orthophosphoric acid, citric acid, and control groups; however, it could not remove the smear layer and sealer remnants effectively on radicular dentin surfaces. Removal of the smear layer and opening of dentinal tubules are not recommended when a self-etching/self-priming adhesive system is used.

Effects of Three Canal Sealers on Bond Strength of a Fiber Post

INTRODUCTION This study evaluated the effects of three different endodontic sealers on the bond strength of a fiber post cemented with adhesive resin cement. METHODS Forty-eight extracted maxillary central incisors were prepared with the step-back technique and randomly divided into four groups (n=12 for each group): group 1, control group (gutta-percha points only, no sealer); group 2, resin-based sealer (AH plus; Dentsply De Trey GmbH, Konstanz, Germany); group 3, zinc oxide-eugenol-based sealer (Endofill; Produits Dentaires SA, Vevey, Switzerland); and group 4, calcium hydroxide-based sealer (Sealapex; Kerr, Romulus, MI). The roots were obturated with gutta-percha using the cold lateral compaction technique. Fiber posts were cemented into the prepared post spaces with the adhesive resin cement Panavia F 2.0 (Kuraray Medical, Okayama, Japan). A push-out test was performed in a universal machine, and failure modes were observed. Morphologic changes of the root canal dentin surfaces were examined with scanning electron microscopy (SEM). RESULTS One-way analysis of variance revealed that sealers have significant effects on bond strength (p<0.05). The control group had the highest mean push-out bond strength. No statistical difference was detected between the eugenol-based sealer group and the resin-based sealer group (p>0.05). The root surfaces were covered with the smear layer and debris in all the groups after post space preparation in SEM analysis. However, some of the dentin tubules were partially open in the control and calcium hydroxide-based sealer groups after the application of the resin monomer. CONCLUSION The results of this study showed that the type of canal sealer and chemomechanical preparation of the root canals affect the bond strength of a fiber post cemented with resin cement.

Surface Conditioning Methods and Polishing Techniques Effect on Surface Roughness of a Feldspar Ceramic

OBJECTIVE To investigate the effects of three surface conditioning methods on shear bond strength (SBS) and on surface roughness (Ra) of a feldspathic ceramic, and to compare the efficiency of three polishing techniques. MATERIALS AND METHODS A total of 106 feldspathic specimens were used. Thirty specimens were divided into three groups according to the surface conditioning methods: air-particle abrasion (APA) with 25-microm aluminum trioxide (Al(2)O(3)) (group A); hydrofluoric acid (HFA) (group H); APA and HFA (group AH). Metal brackets were bonded and subjected to SBS testing. Sixty-three specimens were divided into three groups according to the surface conditioning method. Ra was evaluated profilometrically. Then, each group was divided into three subgroups according to the polishing technique, ie, adjustment kit, diamond polishing paste, adjustment kit + diamond polishing paste. Following polishing, the second Ra values were obtained. RESULTS The lowest SBS was obtained for group H. This value was significantly different from the values of groups A and AH (P < .05). The lowest Ra value was observed for group H (P < .001). There was no significant difference between groups A and AH (P > .05). No significant differences between the subgroups in which a polishing paste was used were observed (P > .05). There was no significant difference between the adjustment kit and the adjustment kit + a diamond polishing paste (P > .05). CONCLUSION APA or APA + HFA created rougher porcelain surfaces than HFA alone. Both adjustment kit use and the adjustment kit + polishing paste application were effective to smooth the porcelain, but one was not found superior to the other.

Effects of surface-conditioning methods on shear bond strength of brackets bonded to different all-ceramic materials

The aims of this study were to investigate the effects of two surface-conditioning methods on the shear bond strength (SBS) of metal brackets bonded to three different all-ceramic materials, and to evaluate the mode of failure after debonding. Twenty feldspathic, 20 fluoro-apatite, and 20 leucite-reinforced ceramic specimens were examined following two surface-conditioning methods: air-particle abrasion (APA) with 25 μm Al(2)O(3) and silica coating with 30 μm Al(2)O(3) particles modified by silica. After silane application, metal brackets were bonded with light cure composite and then stored in distilled water for 1 week and thermocycled (×1000 at 5-55°C for 30 seconds). The SBS of the brackets was measured on a universal testing machine. The ceramic surfaces were examined with a stereomicroscope to determine the amount of composite resin remaining using the adhesive remnant index. Two-way analysis of variance, Tukeys multiple comparison test, and Weibull analysis were used for evaluation of SBS. The lowest SBS was with APA for the fluoro-apatite ceramic (11.82 MPa), which was not significantly different from APA for the feldspathic ceramic (13.58 MPa). The SBS for the fluoro-apatite ceramic was significantly lower than that of leucite-reinforced ceramic with APA (14.82 MPa). The highest SBS value was obtained with silica coating of the leucite-reinforced ceramic (24.17 MPa), but this was not significantly different from the SBS for feldspathic and fluoro-apatite ceramic (23.51 and 22.18 MPa, respectively). The SBS values with silica coating showed significant differences from those of APA. For all samples, the adhesive failures were between the ceramic and composite resin. No ceramic fractures or cracks were observed. Chairside tribochemical silica coating significantly increased the mean bond strength values.

The effects of different desensitizing agents on the shear bond strength of adhesive resin cement to dentin.

STATEMENT OF THE PROBLEM   The choice of desensitizing agent can affect the bond strength of adhesive resin cement to dentin. PURPOSE   The purpose of this study was to evaluate the effects of different dentin desensitizing agents on the bond strength of adhesive resin cement to dentin. MATERIALS AND METHODS   Sixty specimen teeth were randomly divided into six groups (n=10). Five groups of teeth were treated with a desensitizing agent containing sodium and calcium fluoride in cellulose alone, hydroxyethyl methacrylate (HEMA), benzalkonium chloride and sodium fluoride, HEMA and glutaraldehyde, an ormocer-based or a resin-based dentin desensitizer. The remaining 10 specimens served as controls. Adhesive resin cement was applied to the dentin surface. The shear bond strength was measured using a universal testing machine at a 0.5 mm/minute crosshead speed. The data were analyzed statistically with one-way analysis of variance and a Tukeys Honestly Significant Difference (HSD) test (α=0.05). In addition, dentin surfaces were examined by a scanning electron microscope. RESULTS   THE lowest bond strength was in the group treated with desensitizing agent containing sodium and calcium fluoride and the highest bond strength was from the group treated with desensitizing agent containing HEMA and sodium fluoride. CONCLUSIONS   Desensitizing agents containing sodium and calcium fluoride reduced the bond strength of adhesive resin cement. CLINICAL SIGNIFICANCE The type of desensitizer used is an important factor regarding the bond strength of adhesive resin cements to dentin.

Effect of fluoride-containing desensitizing agents on the bond strength of resin-based cements to dentin

Objective: The objective of this study was to evaluate the effect of desensitizing agents containing different amounts of fluoride on the shear bond strength of a dual polymerized resin cement and a resin-modified glass ionomer cement (RMGIC) to dentin. Material and Methods: One hundred human molars were mounted in acrylic resin blocks and prepared until the dentin surface was exposed. The specimens were treated with one of four desensitizing agents: Bifluorid 12, Fluoridin, Thermoline and PrepEze. The remaining 20 specimens served as untreated controls. All groups were further divided into 2 subgroups in which a dual polymerized resin cement (Bifix QM) or a resin-modified glass ionomer cement (AVANTO) was used. The shear bond strength (MPa) was measured using a universal testing machine at a 0.5 mm/min crosshead speed. The data were analyzed statistically with a 2-way ANOVA, Tukey HSD test and regression analysis (α=0.05). The effect of the desensitizing agents on the dentin surface was examined by scanning electron microscopy. Results: The fluoride-containing desensitizing agents affected the bond strength of the resin-based cements to dentin (p<0.001). PrepEze showed the highest bond strength values in all groups (p<0.001). Conclusion: Regression analysis showed a reverse relation between bond strength values of resin cements to dentin and the amount of fluoride in the desensitizing agent (p<0.05).

Influence of porcelain firing and cementation on the marginal adaptation of metal-ceramic restorations prepared by different methods

Statement of problem. Marginal adaptation plays an important role in the survival of metal‐ceramic restorations. Porcelain firings and cementation may affect the adaptation of restorations. Moreover, conventional casting procedures and casting imperfections may cause deteriorations in the marginal adaptation of metal‐ceramic restorations. Purpose. The purpose of this in vitro study was to compare the marginal adaptation after fabrication of the framework, porcelain application, and cementation of metal‐ceramic restorations prepared by using the conventional lost‐wax technique, milling, direct metal laser sintering (DMLS), and LaserCUSING, a direct process powder‐bed system. Alterations in the marginal adaptation of the metal frameworks during the fabrication stages and the precision of fabrication methods were evaluated. Material and methods. Forty‐eight metal dies simulating prepared premolar and molar abutment teeth were fabricated to investigate marginal adaptation. They were divided into 4 groups (n=12) according to the fabrication method used (group C serving as the control group: lost‐wax method; group M: milling method; group LS: DMLS method; group DP: direct process powder‐bed method). Sixty marginal discrepancy measurements were recorded separately on each abutment tooth after fabrication of the framework, porcelain application, and cementation by using a stereomicroscope. Thereafter, each group was divided into 3 subgroups according to the measurements recorded in each fabrication stage: subgroup F (framework), subgroup P (porcelain application), and subgroup C (cementation). Data were statistically analyzed with univariate analysis of variance (followed by 1‐way ANOVA and Tamhane T2 test (&agr;=.05). Results. The lowest marginal discrepancy values were observed in restorations prepared by using the direct process powder‐bed method, and this was significantly different (P<.001) from the other methods. The highest marginal discrepancy values were recorded after the cementation procedure in all groups. Conclusions. The results showed that the direct process powder‐bed method is quite successful in terms of marginal adaptation. The marginal discrepancy increased after porcelain application and cementation.

Effect of various surface treatments on the bond strength of porcelain repair.

This study evaluated the effect of surface treatments on the repair strength of composite resin on a feldspathic ceramic. Ninety ceramic specimens were divided into six groups. In the experimental groups, 4% hydrofluoric acid etching, Er:YAG laser irradiation, CO2 laser irradiation, airborne-particle abrasion, and silica coating were used as surface treatments. After the application of a porcelain repair kit, composite resin was placed on the treated surfaces. After a shear bond strength test, data were statistically analyzed (α = .05). Surface treatments increased the repair bond strength values (P < .05). Airborne particle abrasion and silica coating were found to be the most effective. CO2 laser showed higher repair strength values than Er:YAG laser.

The Effect of Finishing and Polishing Techniques on the Surface Roughness and the Color of Nanocomposite Resin Restorative Materials.

BACKGROUND Rough, poorly polished surfaces contribute to staining, plaque accumulation, gingival irritation and recurrent caries. Finishing and polishing techniques are critical factors contributing to the longevity of the direct composite resin restorations. OBJECTIVES The aim of this in vitro study was to evaluate the effects of finishing and polishing systems on surface roughness of six nanocomposite restorative resins. MATERIAL AND METHODS Thirty specimens of each restorative material (n=180) were placed in a teflon mould (6 mm in diameter and 3 mm in depth) and cured with a LED curing unit. Six specimens from each of restorative material were randomly assigned to four groups for finishing and polishing (carbide burs, diamond burs, aluminium oxide discs, silicon rubber polisher) techniques. Mylar strip formed specimens were served as control group. After finishing and polishing procedures surface roughness was evaluated by a profilometer. The data was analyzed by 2-way analysis of variance and the Tukey HSD test (α=0.05). RESULTS Significant differences were found between the groups in terms roughness (p<0.001). The control group and aluminium oxide discs group had the lowest Ra values and were significantly different from other groups (p<0.001). The roughest surface was obtained with diamond burs followed by silicon rubbers and carbide burs. Overall, the smoothest surfaces were obtained with the use the complete sequence of aluminum oxide discs. CONCLUSIONS In areas that could not be reached by the aluminum oxide discs, the carbide burs produced satisfactory surface smoothness for the nanocomposite restorative materials. Although mylar matrix strip formed surfaces presents lower surface roughness values, recountouring and polishing of resin restorations are often required in clinical situations. Aluminium oxide discs and carbide finishing burs are suitable for finishing and polishing procedures for nanocomposite restorative resins.

Effect of pre‐processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

OBJECTIVES This study evaluated the effects of various pre-processing methods on the bond strength between resin and denture teeth. BACKGROUNDS Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures. MATERIALS AND METHODS Four experimental groups (n = 30) were investigated by subjecting tooth-resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre-processing surface treatments of teeth were applied: (i) ST(1), no treatment applied (control); (ii) ST(2) , wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST(3), boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST(4), boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine. RESULTS All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST(1) group and the highest values were in the ST(4) group. CONCLUSIONS Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.