ABSTRACT
Statement of Problem: shear bond strength [SBS] of home and office bleached enamel will be compromised by immediate application of composite restoration. Antioxidant agent may overcome this problem
Objectives: this in vitro study assessed the effect of green tea extract on shear bond strength of resin composite to in-office and home-bleached enamel
Materials and Methods: in this experimental study, 40 extracted intact human incisors were embedded in cylindrical acrylic resin blocks [2.5 ×1.5 cm], with the coronal portion above the cemento enamel junction out of the block. Then, after bleaching labial enamel surfaces of 20 teeth with 15% carbamide peroxide 6 hours a day for 5 days, they were randomly divided into two groups: A1 and A2 [n = 10], depending upon whether or not they are treated with antioxidant. Labial enamel surfaces of the remaining 20 teeth were bleached with 38% hydrogen peroxide before being randomly divided into groups B1 and B2 [n = 10], again depending on whether or not the antioxidant was used in their treatment . The experimental groups [A2,B2] were treated with 5% solution of green tea extract before resin composite restoration was done by a cylindrical Teflon mould [5×2 mm]. Shear bond strength of the specimens was tested under a universal testing machine [Zwick/Roell Z020]. The SBS data were analyzed by using One-way ANOVA and Tukey HSD tests [p < 0.05]
Results: there were no statistically significant differences between shear bond strength of the control group [A1] and treated group [A2], but there were statistically significant differences between the groups B1 and B2 [p < 0.05]
Conclusions: application of antioxidant did not increase the shear bond strength of home-bleached enamel to resin composite but its application increased the shear bond strength of in-office bleached enamel to resin composite
ABSTRACT
Statement of Problem: hemostatic agents may affect the micro-leakage of different adhesive systems. Also, chlorhexidine has shown positive effects on micro-leakage. However, their interaction effect has not been reported yet
Objectives: to evaluate the effect of contamination with a hemostatic agent on micro-leakage of total- and self-etching adhesive systems and the effect of chlorhexidine application after the removal of the hemostatic agent
Materials and Methods: standardized Class V cavity was prepared on each of the sixty caries free premolars at the cemento-enamel junction, with the occlusal margin located in enamel and the gingival margin in dentin. Then, the specimens were randomly divided into 6 groups [n = 10] according to hemostatic agent [H] contamination, chlorhexidine [CHX] application, and the type of adhesive systems [Adper Single Bond and Clearfil SE Bond] used. After filling the cavities with resin composite, the root apices were sealed with utility wax. Furthermore, all the surfaces, except for the restorations and 1mm from the margins, were covered with two layers of nail varnish. The teeth were immersed in a 0.5% basic fuschin dye for 24 hours, rinsed, blot-dried and sectioned longitudinally through the center of the restorations bucco- lingualy. The sections were examined using a stereomicroscope and the extension of dye penetration was analyzed according to a non-parametric scale from 0 to 3. Statistical analysis was performed using Kruskal-Wallis test and Mann-Whitney U-test
Results: while ASB group showed no micro-leakage in enamel, none of the groups showed complete elimination of micro-leakage from the dentin. Regarding micro-leakage at enamel, and dentin margins, there was no significant difference between groups 1 and 2, 1 and 3, and 2 and 3 [p > 0.05]. A significantly lower micro-leakage at the enamel and dentin margins was observed in group 3, compared to group 6. No significant difference was observed between groups 4 and 5 in enamel [p = 0.35] and dentin [p = 0.34]. Group 6 showed significantly higher micro-leakage, compared to group 4 and 5 [p < 0.05]
Conclusions: hemostatic agent contamination had no significant effect on micro-leakage of total- and self-etching adhesive systems. Application of chlorhexidine after the removal of hemostatic agent increased micro-leakage in self-etching adhesives but did not affect when total-etching was used
ABSTRACT
Microleakage is one of the most important problems in composite restorations. One way to reduce the microleakage is decreasing the total amount of resin by insertion of fibers in composite restorations. This study aimed to compare the microleakage of Silorane and methacrylate-based composites [a nanohybrid] in Class II restorations with gingival margins on the root surface, with or without placing glass and polyethylene fiber.60 extracted sound third mandibular molars were disinfected. Class II slot cavities were provided on both proximal sides of each tooth. Based on application of composites and fibers, the teeth were randomly divided into 6 groups [n=20]. group1: Z350; group2: Z350 + polyethylene fiber; group3: Z350 + glass fiber; group4: P90; group5: P90 + polyethylene fiber; and group6: P90 + glass fiber. The specimens were thermocycled, immersed in 2% basic fuchsine dye solution, and then sectioned to assess dye penetration under stereomicroscope [40X]. Results were statically analyzed by Kruskal-Wallis and Mann-Witney tests at a significance level of p<0.05.There was a significant decrease in microleakage in Silorane composite when compared to nanohybrid composite [p<0.001]. There was not any significant difference among groups with or without fiber inserts.The use of Silorane composite reduces the microleakage in comparison with nanohybrid composite and fiber insertion had no effect on the microleakage in class II silorane and nanohybrid composite restorations with gingival margins below the CEJ
ABSTRACT
Despite the increasing demand for tooth-colored restorations in dentistry, polymerization shrinkage and marginal microleakage still remains a problem.The purpose of the present study was to evaluate microleakage in three different resin composites, P90, Z250 and Z250 XT, in class V cavity of permanent human premolars.Standardized class V cavities were prepared on the buccal surface of 45 extracted human premolars. The occlusal margins of cavities were prepared at the enamel and gingival margins extending 1mm below the cementoenamel junction. The teeth were randomly assigned into three groups [N=15] and preparations restored with three different composites following the manufacturer instructions: Group A, Filtek Z250 [microhybrid composite] with Adper Single Bond total etch adhesive system; Group B, Filtek Z250 XT [nanohybrid] with Adper Single Bond total etch adhesive system;Group C, Filtek P90 [silorane] with its self-etch adhesive system [P90 system adhesive]. its adhesive system [P90 system adhesive]. The teeth were then subjected to thermal cycles [1000 cycle, 5 degrees and 55 degrees Celsius +/- 2 degrees Celsius] with a dwell time of 30 seconds, and immersed in 2% basic fuchsine for 24 hours. Longitudinally sectioned teeth were examined under the stereomicroscope. Kruskal-Wallis and Mann-Whitney U test at 95% significance level were used.Filtek Z250XT showed significantly higher microleakage than the other two composites [p<0.001]. However, there was no statistically significant difference between P90 and Filtek Z250 [p=0.217].Although all of the restorative systems had microleakage, silorane-based composite showed less microleakage compared to two other methacrylate-based composites
ABSTRACT
Statement of Problem: Microleakage is one of the most frequent problems associated with resin composites, especially at the gingival margin of posterior restorations. Insertion of fibers in composite restorations can reduce the total amount of composite and help to decrease the shrinkage
Purpose: The aim of this study was to evaluate the effect of polyethylene fiber inserts on gingival microleakage of class II composite restorations using two different adhesive systems
Materials and Method: In this experimental study, class II cavities were prepared on 60 premolars. The gingival floor was located 1.0 mm below the CEJ. Dimension of each cavity were 3 mm buccolingually and 1.5 mm in axial depth. The specimens were divided into 4 groups according to the adhesive type and fiber insert [n=4]
Single bond and Clearfill SE bond and Filtek p60 were used to restore the cavities. In groups without fiber inserts composite was adapted onto cavities using layering technique. For cavities with fiber inserts, 3 mm piece of fiber insert was placed onto the composite increment and cured. The specimens were stored in distilled water at 37oC for 6 months. All specimens were subjected to 3000 thermo-cycling. The tooth surfaces except for 1 mm around the restoration margins covered with two layers of nail varnish
The teeth were immersed in 2% Basic Fuchsin for 24 hours, then rinsed and sectioned mesiodistally
The microleakage was determined under a stereomicroscope [40X]. Data were statistically analyzed by Kruskal-wallis and Mann-Whitney U tests [p< 0.05]
Results: The Kruskal-Wallis test revealed no significant differences in mean microleakage scores among all groups [p= 0.281]
Conclusion: Use of polyethylene fiber inserts and etch-and-rinse and self-etch adhesives had no effect on microleakage in class II resin composite restorations with gingival margins below the CEJ after 6- month water storage
ABSTRACT
Statement of Problem: The flexure of the fiber- reinforced composites [FRC] which can be generally used instead of fixed metal- framework prostheses have been more advocated due to the enormous demands for the conservative and esthetic restoration. The flexure of the fiber should be well-fitted to its covering composite. No study has been reported the comparison of the combination of glass and polyethylene fiber with particulate filled composite and fiber reinforced composite yet
Purpose: This study compared the flexural strength of two types of fibers combined with three types of composites
Materials and Method: Sixty-six specimens were prepared in a split mold [25x2x2 mm]. The specimens were divided into six groups according to the type of resin and the fiber [N = 11]: group 1: Z250 composite + Polyethylene fiber; group 2: Build It composite + Polyethylene fiber; group 3: Nulite F composite+ Polyethylene fiber; group 4: glass fiber + Z250 composite; group 5: glass fiber + Build-It composite and group 6: glass fiber + Nulite F. The mean flexural strengths [MPa] values were determined in a 3-point bending test at a crosshead speed of 1 mm/min by a universal testing machine [Zwick/Roell Z020, Germany]. The results were statistically analyzed, using one and two- way ANOVA and LSD post-hoc tests [p< 0.05]
Results: The highest flexural strength was registered for glass fiber in combination with Z250 composite [500 MPa] and the lowest for polyethylene fiber in combination with Build-It composite [188 MPa]. One-way ANOVA test revealed that there was no statistically significant difference between polyethylene fiber combinations [p= 0.62] but there was a significant difference between glass fiber combinations [p= 0.0001]. Two way ANOVA revealed that the fiber type had a significant effect on flexural strength [p= 0.0001]
Conclusion: The choice of fiber and composite type was shown to have a significant positive influence on the flexural properties of the fiber-reinforced composite. Glass fiber has a significant influence on the flexural properties of directly- made specimens