Evaluation of marginal fit of single implant-supported metal-ceramic crowns prepared by using presintered metal blocks.

STATEMENT OF PROBLEM: Recently, presintered metal blocks for nonprecious and precious metal implant-supported restorations have gained popularity in computer-aided design and computer-aided manufacturing (CAD-CAM) systems. However, few studies have evaluated the marginal discrepancy of implant-supported restorations made with these new alloy systems. PURPOSE: The purpose of this in vitro study was to compare the milling-sintering method with the lost-wax and milling methods in terms of the marginal fit of implant-supported metal-ceramic restorations. MATERIAL AND METHODS: Thirty implant abutments screwed to implant analogs were embedded into acrylic resin to investigate marginal fit and then divided according to fabrication methods into the following 3 groups (n=10): lost-wax (LW; control group), milling (M), and milling-sintering (MS). Porcelain material was applied to all specimens after completion of the fabrication process. Subsequently, all specimens were cemented to implant abutments for the measurement of marginal discrepancies. Twelve marginal discrepancy measurements were recorded on each implant abutment by using a stereomicroscope. The arithmetic mean of these 12 measurements was considered the mean marginal discrepancy value of each abutment. Data were statistically analyzed by using 1-way ANOVA and Tukey honest significant difference tests (α=.05). RESULTS: The lowest mean marginal discrepancy values (81 ±2 µm) were observed in the M group, which was significantly different (P<.001) from the other methods. The highest mean marginal discrepancy values (99 ±2 µm) were observed in the MS group. CONCLUSIONS: The results revealed that restorations prepared by the milling-sintering method provided clinically acceptable results (<120 µm); however, this new technique was not found to be as precise as the milling method in terms of marginal fit.

Effect of different restorative crown and customized abutment materials on stress distribution in single implants and peripheral bone: A three-dimensional finite element analysis study.

STATEMENT OF PROBLEM: In recent years, the use of resin-matrix ceramics and polyetheretherketone (PEEK) abutments has been suggested to absorb excessive stresses on dental implants. However, only a few studies have evaluated the effect of these materials on stress distribution in implants and peripheral bone structure. PURPOSE: The purpose of this finite element analysis was to evaluate the biomechanical behaviors of resin-matrix ceramics and PEEK customized abutments in terms of stress distribution in implants and peripheral bone. MATERIAL AND METHODS: Three-dimensional (3D) models of a bone-level implant system and a titanium base abutment were created by using the standard tessellation language (STL) data of original implant components. An anatomic customized abutment and a maxillary right second premolar crown were then modeled over the titanium base abutment. A bone block representing the maxillary right premolar area was created, and the implant was placed in the bone block with 100% osseointegration. Six different models were created according to combinations of restoration materials (translucent zirconia [TZI], lithium disilicate glass ceramic [IPS], polymer-infiltrated hybrid ceramic [VTE]), and customized abutment materials (PEEK and zirconia). In each model, the implants were loaded vertically (200 N) and obliquely (100 N). The stress distribution in the crown, implant, and abutments was evaluated through the von Mises stress analysis, and the stress distribution in the peripheral bone was examined through the maximum and minimum principal stress analyses. RESULTS: The oblique load resulted in high stress values in the implant components, restorative crown, and cortical bone. Low stress values were observed in the VTE crowns. Zirconia customized abutments exhibited higher stress values than PEEK customized abutments. The stress distributions in the implant and peripheral bone were similar in all models. CONCLUSIONS: Changes in restoration and customized abutment material did not affect stress distribution in the implant and peripheral bone.

Comparison of porcelain bond strength of different metal frameworks prepared by using conventional and recently introduced fabrication methods.

STATEMENT OF PROBLEM: Most studies evaluating dental laser sintering systems have focused on the marginal accuracy of the restorations. However, the bond strength at the metal-ceramic interface is another important factor that affects the survival of restorations, and currently, few studies focus on this aspect. PURPOSE: The purpose of this in vitro study was to compare the porcelain bond strength of cobalt-chromium (Co-Cr) metal frameworks prepared by using the conventional lost-wax technique, milling, direct metal laser sintering (DMLS), and laser cusing, a direct process powder-bed system. MATERIAL AND METHODS: A total of 96 metal frameworks (n=24 in each group) were prepared by using conventional lost-wax (group C), milling (group M), DMLS (group LS), and direct process powder-bed (group LC) methods according to International Organization for Standardization standard ISO 9693-1. After porcelain application, a 3-point bend test was applied to each specimen by using a universal testing machine. Data were statistically analyzed using 1-way ANOVA and Tukey honest significant difference tests (α=.05). Failure types at the metal-ceramic interfaces were examined using stereomicroscopy. Additionally, 1 specimen from each group was prepared for scanning electron microscopy analysis to evaluate the surface topography of metal frameworks. RESULTS: The mean bond strength was 38.08 ±3.82 MPa for group C, 39.29 ±3.51 MPa for group M, 40.73 ±3.58 MPa for group LS, and 41.24 ±3.75 MPa for group LC. Statistically significant differences were observed among the 4 groups (P=.016). All groups, except for LS, exhibited adhesive and mixed type bond failure. CONCLUSIONS: Both of the laser sintering methods were found to be successful in terms of metal-ceramic bond strength.

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 (α=.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.

Effects of Dentin Surface Treatments on Hypersensitivity to Bond Strength of Restorations: An In Vitro Study.

This study evaluated the effects of desensitizing treatments on the shear bond strength (SBS) of adhesive resin cement (Rely X U100) applied to dentin. Human molars (n = 120) with exposed dentin were divided into 12 groups. In the experimental groups, dentin surfaces were treated with (1) an erbium:yttrium- aluminium-garnet (Er:YAG) laser, (2) a neodymium:yttrium-aluminium-garnet (Nd:YAG) laser, (3) glutaraldehyde (Gluma)-, (4) fluoride (Aqua Prep-F)-, and (5) oxalate (BisBlock)-containing desensitizing agents, (6) Gluma preceding the Er:YAG laser, (7) Aqua Prep-F preceding the Er:YAG laser, (8) BisBlock preceding the Er:YAG laser, (9) Gluma preceding the Nd:YAG laser, (10) Aqua Prep-F preceding the Nd:YAG laser, (11) and BisBlock preceding the Nd:YAG laser, in groups EL, NL, G, F, O, EL-G, EL-F, EL-O, NL-G , NL-F, and NL-O, respectively. Then, lithium disilicate ceramics were cemented to the treated surfaces. Subsequently, an SBS test was performed and the data were statistically analyzed (α = .001). The results suggested that the combined treatment of Gluma preceding Er:YAG laser increased the bond strength of ceramic to the dentin surface using a self-adhesive resin cement.

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.

Evaluation of shear bond strength of repair acrylic resin to Co-Cr alloy.

PURPOSE: The purpose of this study was to investigate the impact of different surface treatment methods and thermal ageing on the bond strength of autopolymerizing acrylic resin to Co-Cr. MATERIALS AND METHODS: Co-Cr alloy specimens were divided into five groups according to the surface conditioning methods. C: No treatment; SP: flamed with the Silano-Pen device; K: airborne particle abrasion with Al2O3; Co: airborne particle abrasion with silica-coated Al2O3; KSP: flamed with the Silano-Pen device after the group K experimental protocol. Then, autopolymerized acrylic resin was applied to the treated specimen surfaces. All the groups were divided into two subgroups with the thermal cycle and water storage to determine the durability of the bond. The bond strength test was applied in an universal test machine and treated Co-Cr alloys were analyzed by scanning electron microscope (SEM). Two-way analysis of variance (ANOVA) was used to determine the significant differences among surface treatments and thermocycling. Their interactons were followed by a multiple comparison' test performed uing a post hoc Tukey HSD test (α=.05). RESULTS: Surface treatments significantly increased repair strengths of repair resin to Co-Cr alloy. The repair strengths of Group K, and Co significantly decreased after 6,000 cycles (P<.001). CONCLUSION: Thermocycling lead to a significant decrease in shear bond strength for air abrasion with silica-coated aluminum oxide particles. On the contrary, flaming with Silano-Pen did not cause a significant reduction in adhesion after thermocycling.

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.

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.

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 Tukey's 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.

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, Tukey's 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.

In vitro evaluation of marginal adaptation in five ceramic restoration fabricating techniques.

OBJECTIVE: To compare in vitro the marginal adaptation of crowns manufactured using ceramic restoration fabricating techniques. METHOD AND MATERIALS: Fifty standardized master steel dies simulating molars were produced and divided into five groups, each containing 10 specimens. Test specimens were fabricated with CAD/CAM, heat-press, glass-infiltration, and conventional lost-wax techniques according to manufacturer instructions. Marginal adaptation of the test specimens was measured vertically before and after cementation using SEM. Data were statistically analyzed by one-way ANOVA with Tukey HSD tests (a = .05). RESULTS: Marginal adaptation of ceramic crowns was affected by fabrication technique and cementation process (P < .001). The lowest marginal opening values were obtained with Cerec-3 crowns before and after cementation (P < .001). The highest marginal discrepancy values were obtained with PFM crowns before and after cementation. CONCLUSION: Marginal adaptation values obtained in the compared systems were within clinically acceptable limits. Cementation causes a significant increase in the vertical marginal discrepancies of the test specimens.

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.

A survey of cross-infection control procedures: knowledge and attitudes of Turkish dentists.

OBJECTIVES: The objective of this study was to investigate the knowledge, attitudes and behavior of Turkish dentists in Samsun City regarding cross-infection control. MATERIAL AND METHODS: A questionnaire was designed to obtain information about procedures used for the prevention of cross-infection in dental practices and determine the attitudes and perceptions of respondent dental practitioners to their procedures. The study population included all dentists in the city of Samsun, Turkey, in April 2005 (n=184). The questionnaire collected data on sociodemographic characteristics, knowledge and practice of infection control procedures, sterilization, wearing of gloves, mask, use of rubber dam, method of storing instruments and disposal methods of contaminated material, etc. Questionnaire data was entered into a computer and analyzed by SPSS statistical software. RESULTS: From the 184 dentists to whom the questionnaires were submitted, 135 participated in the study (overall response rate of 73.36%). As much as 74.10% dentists expressed concern about the risk of cross-infection from patients to themselves and their dental assistants. Forty-three percent of the participants were able to define 'cross-infection' correctly. The greatest majority of the respondents (95.60%) stated that all patients have to be considered as infectious and universal precautions must apply to all of them. The overall responses to the questionnaire showed that the dentists had moderate knowledge of infection control procedures. CONCLUSIONS: Improved compliance with recommended infection control procedures is required for all dentists evaluated in the present survey. Continuing education programs and short-time courses about cross-infection and infection control procedures are suitable to improve the knowledge of dentists.

A survey of cross-infection control procedures: knowledge and attitudes of Turkish dentists

OBJECTIVES: The objective of this study was to investigate the knowledge, attitudes and behavior of Turkish dentists in Samsun City regarding cross-infection control. MATERIAL AND METHODS: A questionnaire was designed to obtain information about procedures used for the prevention of cross-infection in dental practices and determine the attitudes and perceptions of respondent dental practitioners to their procedures. The study population included all dentists in the city of Samsun, Turkey, in April 2005 (n=184). The questionnaire collected data on sociodemographic characteristics, knowledge and practice of infection control procedures, sterilization, wearing of gloves, mask, use of rubber dam, method of storing instruments and disposal methods of contaminated material, etc. Questionnaire data was entered into a computer and analyzed by SPSS statistical software. RESULTS: From the 184 dentists to whom the questionnaires were submitted, 135 participated in the study (overall response rate of 73.36 percent). As much as 74.10 percent dentists expressed concern about the risk of cross-infection from patients to themselves and their dental assistants. Forty-three percent of the participants were able to define "cross-infection" correctly. The greatest majority of the respondents (95.60 percent) stated that all patients have to be considered as infectious and universal precautions must apply to all of them. The overall responses to the questionnaire showed that the dentists had moderate knowledge of infection control procedures. CONCLUSIONS: Improved compliance with recommended infection control procedures is required for all dentists evaluated in the present survey. Continuing education programs and short-time courses about cross-infection and infection control procedures are suitable to improve the knowledge of dentists.

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 (alpha=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).

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).

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.

The effect of dentin-cleaning agents on resin cement bond strength to dentin.

BACKGROUND: Provisional cement remnants on dentin affect the bond strength of resin cements to dentin. The authors investigated the effects of dentin-cleaning agents and etching systems on the bond strength of adhesive resin cement. METHODS: The authors removed the provisional cement from the dentin surfaces of the specimens and then cleaned the surfaces with the dentin-cleaning agents Sikko Tim (VOCO GmbH, Cuxhaven, Germany), Cavity Cleanser (Bisco, Schaumburg, Ill.) or Consepsis Scrub (Ultradent, South Jordan, Utah). They used adhesive resin cement after applying the different etching adhesive systems. Then they examined the dentin surfaces by using scanning electron microscopy. RESULTS: The authors analyzed data by means of a two-way analysis of variance with Tukey honestly significant difference tests (alpha= .05). They found that specimens cleaned with Sikko Tim and Consepsis Scrub had higher shear bond strength values than did those in the no-treatment control group or the group cleaned with Cavity Cleanser. The specimens treated with the total-etching adhesive system had higher shear bond strength than did those treated with the self-etching adhesive systems. CONCLUSIONS: Sikko Tim and Consepsis Scrub were effective in removing provisional cement. Adhesive resin cement showed higher bond strength when used in conjunction with the total-etching adhesive system. CLINICAL IMPLICATIONS: The use of an effective dentin cleaner before cementation with resin cement can increase bond strength.

Comparison of 3 polishing techniques for 2 all-ceramic materials.

The aim of this study was to compare the surface roughness produced by polishing 2 all-ceramic materials after surface conditioning. Air particle abrasion (APA) with 25-microm aluminum oxide, 9.6% hydrofluoric acid (HFA,) and APA + HFA were applied for ceramic surface conditioning. Subsequently, the ceramics were subjected to 3 polishing techniques: polishing kit, polishing paste, and polishing kit + polishing paste. Surface roughness (Ra) was evaluated profilometrically. The highest deltaRa values were obtained with the polishing kit and polishing kit + paste for the APA + HFA groups. No significant differences were observed among the polishing paste groups. Combining a polishing kit and polishing paste produced the smoothest ceramic surfaces.