Effects of 35% Carbamide Peroxide Gel on Surface Roughness and Hardness of Composite Resins

Objective: Bleaching agents may not be safe for dental materials. The purpose of this invitro study was to evaluate the effects of Opalescent Quick "in-office bleaching gel" containing 35% carbamide peroxide on the surface roughness and hardness of microfilled(Heliomolar) and hybride (Spectrum TPH) composite resins.Materials and Methods: Twenty specimens of Spectrum TPH composite resins and twenty Heliomolar composite resins were fabricated using a metallic ring (6.5 mm diameter and 2.5 mm thickness) and light cured, then their surfaces were polished. Specimens of each composite resin were divided into two equal groups. Ten specimens of each type of composite were stored in water at 37°C as the control groups and 35% carbamide peroxide gel (Opalescence Quick) as the other group for 30 minutes a week for 3 weeks. Then the specimens were subject to roughness and hardness tests.Results: This study revealed that using 35% carbamide peroxide bleaching gels had no significant effect on the surface roughness of Spectrum TPH "hybrid" and Heliomolar "microfilled" composite resins. The surface hardness of Spectrum TPH composite treated with the subject gel significantly increased compared to heliomolar, which had no significant change after treatment with this bleaching gel.Conclusion: If tooth color matching of the composite had been satisfactory after office bleaching with 35% carbamide peroxide gel, this material would have been acceptable because it has no adverse effect on Heliomolar and Spectrum TPH composite resins

Short-Burst Bipolar Coagulation for Repairing Partially Damaged Brain Arteries Preserving Their Flow : Technical Note

Peer reviewe

Microleakage of Class II Combined Amalgam-Composite Restorations Using Different Composites and Bonding Agents

Objective: The purpose of the present study was to assess the microleakage of composite restorations with and without a cervical amalgam base and to compare the results of dif-ferent composites and bonding agents.Materials and Methods: One hundred and twenty mesio-occlusal (MO) and disto-occlusal (DO) Class II cavities were prepared on sixty extracted permanent premolar teeth. The teeth were randomly divided into four groups of 30 and restored as follows:In group A, the mesio-occlusal cavity (MO), Scotchbond multi purpose plus + Z250 and in the disto-occlusal (DO) cavity, Prompt-L-Pop + Z250 were applied. As for group B, in the MO and DO cavities, Clearfil SE Bond + Clearfil APX, and varnish + amalgam (In box) + Clearfil SE Bond + Clearfil APX were used respectivelywhile in group C; the teeth were restored with amalgam and varnish mesio-occlusally and with amalgam only disto-occlusally. As for group D, varnish + amalgam (in box) + Scotchbond multi purpose plus + Z250 were applied mesio-occlusally and Varnish + Amalgam (in box) + Prompt–L–Pop + Z250 disto-occlusally.Marginal leakage was assessed by the degree of dye penetration into various sections of the restored teeth. Chi-square and Fisher's exact tests were used for data analysis.Results: Microleakage in gingival margin was more than that in occlusal margin (P<0.05) and microleakage of combined amalgam-composite restorations was significantly lower than that of conventional composite and amalgam restorations.Conclusion: Marginal microleakage decreased by using amalgam at the base of the box in Class II composite restorations

Evaluation of Microleakage in Class V Cavities Filled with Methacrylate-based versus Silorane-based Composites

Statement of Problem: Despite the increasing demand for tooth-colored restorations in dentistry, polymerization shrinkage and marginal microleakage still remains a problem. Objectives: 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. Materials and Methods: 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° and 55°C ± 2°C) 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. Results: 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). Conclusions: Although all of the restorative systems had microleakage, siloranebased composite showed less microleakage compared to two other methacrylatebased composite

The Effect of Incorporation of Polyethylene and Glass Fiber on the Microleakage of Silorane-based and Methacrylate-based Composites in Class II Restorations: An in Vitro Study

Statement of Problem: 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. Objectives: 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. Materials and Methods: 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. Results: 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. Conclusions: 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

The Effect of Fracture Pattern of Anterior Teeth on Fracture Strength of Silorane- Based and Nanohybrid Composite Restorations

Statement of problem: One of the most important concerns in choosing a treatment plan for a fractured anterior teeth is their fracture pattern. Selecting the best restorative material is crucial in restoration of them. Objective(s): The present study was aimed to evaluate the effects of fracture pattern and the composite type on the fracture strength of frac-tured anterior maxillary teeth. Materials and Methods: 40 sound maxillary anterior teeth were randomly divided into four groups of ten teeth (H1, H2, O1, and O2). In H1 and H2, the incisal edges were cut horizontally by 3mm below the incisal edge and in O1 and O2 the incisal edges were cut obliquely from the middle of incisal edge to 6mm below the incisal edge on the proximal side. A nanohybrid composite (Z350) was used for restoring the samples of H1 and O1 whilst a silorane-based composite (P90) was used in H2 and O2. Fracture strength was measured and the failure mode was recorded. Data were analyzed using one way analysis of variance (ANOVA) and Tamhane’s post hoc tests. The level of significance was p ˂0.05. Results: Restoration with composite resin Z350 showed a higher strength in both cutting patterns (p <0.001). Fracture strength was greater in horizontal pattern, regardless of the composite type used for restoration; however, the difference was not statistically significant for P90 (p= 0.930). Conclusions: Fracture resistance of the fractured anterior teeth restored with Z350 is higher than that achieved with P90 for both fracture pat-terns

Effect of Green Tea Extract as Antioxidant on Shear Bond Strength of Resin Composite to in-Office and Home-Bleached Enamel

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

Combination Effect of Hemostatic and Disinfecting Agents on Micro-leakage of Restorations Bonded with Different Bonding Systems

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

Evaluation of Surface Microhardness of Silver and Zirconia Reinforced Glass-ionomers with and without Microhydroxyapatite

Statement of problem: Hardness of restorative materials like glass-ionomer is an important factor in the longevity of restoration. Objectives: The aim of this study was to evaluate the microhardness of glass-ionomer modified with different materials. Materials and Methods: Sixty disk-shaped specimens were examined in six groups in this study, including conventional glass-ionomer (Shofu, Japan), zirconia-reinforced glass-ionomer (Zirconomer, Shofu, Kyoto, Japan), silver-reinforced glass-ionomer (HI-DENSE XP, Shofu, Kyoto, Japan) and mixture of these three types of glass-ionomer with 20 wt% of microhydroxyapatite (Sigma-Aldrich, St. Louis, USA). All the specimens were stored in deionized water for 24 hours. Then Vickers microhardness test was carried out and the results were analyzed by using two-way ANOVA test and paired t-test (P<0.05). Results: Zirconia-reinforced glass-ionomer with microhydroxyapatite exhibited significantly higher microhardness in comparison with other groups (P<0.001). Conventional glass-ionomer with microhydroxyapatite showed the lowest microhardness (P<0.001). After incorporation of microhydroxyapatite in both conventional and silver-reinforced glass-ionomer groups, microhardness decreased significantly (P<0.001).The microhardness of top and bottom of all groups was significantly different. (P<0.001). Conclusions: Incorporation of 20% microhydroxyapatite to zirconia-reinforced glass-ionomer can improve microhardness