Pre-Heating of Low-Shrinkage Composite Resins: Effects on Color Stability and Surface Roughness

Objectives: The present study aimed to investigate the effect of preheating on the color stability and surface roughness of a silorane-based composite resin. Materials and Methods: A total of 44 Filtek P90 composite resin disks, (10mm×1mm), were fabricated using plastic molds and were divided into two groups. In group 2, the composite resin syringes were placed in a thermostatically controlled water bath at 55‒60°C before preparing the disks. After polishing the samples with silicon carbide papers, they were stored in distilled water for 48 hours. Roughness and color parameters were then measured in two stages: immediately after retrieval from distilled water and after 40 days of storage in tea solution. Finally, the differences in roughness and color parameters were recorded. Independent sample t-test and regression analysis were used at a significance level of P<0.05. Results: Based on the findings of the present study, there was no significant difference among the mean ∆E values (P=0.4); however, a significant difference in mean surface roughness (P=0.01) was found between the two groups. Regression analysis showed a significant relationship between the study groups in terms of surface roughness and ΔE values​ (preheated: r2 = 0.73; non-preheated: r2= 0.76). Conclusion: Filtek P90 silorane-base composite showed ΔE>3.3 and surface roughness above 0.2µ under preheated and non-preheated conditions and discoloration increased following preheating.

The effects of different surface contaminators on the shear bond strength of a universal adhesive system to dentin: an experimental study

Background. Contamination of dentin surface is one of the common problems in restorative dentistry. The aim was to investigate the effects of different surface contaminators on the dentin shear bond strength (SBS) of universal adhesive system (UAS) applied in etch-and-rinse (ER) and self-etch (SE) strategies.

Methods. One hundred forty-four maxillary anterior sound human teeth were divided into six groups based on the types of surface contaminators: no surface contaminator (control) and experimental groups contaminated with blood, saliva, aluminium chloride (ALC), ferric sulphate (FS), and caries disclosing agent (CDA). Then, each group was further subdivided into two, based on the application strategy of UAS (ER and SE). After applying the adhesive according to the manufacturer’s instructions, and bonding cylindrical composite samples, the SBS was measured. The data were analysed using two-way ANOVA, Tukey’s HSD test and t test (P < 0.05).

Results. The SBS in all contaminated groups, except for CDA, was significantly lower in both ER and SE strategies compared to control group (P < 0.05). A comparison between the application strategies revealed that ER and SE were only significantly different in the FS contaminated group (P < 0.05).

Conclusion. All tested contaminators, except CDA, significantly decreased SBS of UAS in both ER and SE strategies.

Effect of accelerated aging and double application on the dentin bond strength of universal adhesive system

BACKGROUND

Despite the many advantages of simplified adhesive systems, there are concerns about the durability of the adhesive layer over time. The aim was to investigate the effects of various aging methods and double application of an adhesive layer on the bond strength of the universal adhesive system using etch-and-rinse (ER) and self-etch (SE) strategies.

MATERIALS AND METHODS

In this in vitro study, the occlusal enamel of 120 extracted, intact human third molars was removed to expose the dentin. Then, the samples were randomly divided into four groups of thirty according to All-Bond Universal (ABU) adhesive application strategy (ER and SE) and the number of adhesive layers (1 or 2). Then, each group was subdivided into three subgroups of ten according to aging method (control, thermal cycling, and 10% sodium hypochlorite [NaOCl]). The shear bond strength was measured at the strain rate of 0.5 mm/min. Data were analyzed using three-way ANOVA and Tukey's post hoc tests (P < 0.05).

RESULTS

The effect of adhesive application strategy (P < 0.001) and aging method (P < 0.001) on the bond strength was statistically significant, but the effect of the double application was not statistically significant (P > 0.05). In addition, the interactive effect of adhesive application strategy-aging method was significant (P = 0.005).

CONCLUSION

Using ABU with ER strategy leads to higher dentin bond strength compared to the SE method in the control and thermal cycling groups. However, no significant differences were observed between ER and SE strategies after aging with the NaOCl. Furthermore, the double application might not have any effect on the bond strength and durability.

Surface Roughness of Different Composite Resins after Application of 15% Carbamide Peroxide and Brushing with Toothpaste: An In-Vitro Study

Objectives:

This study aimed to evaluate the effect of toothbrushing after application of 15% carbamide peroxide (CP) on the surface roughness of three types of composite resins.

Materials and Methods:

Twenty samples, measuring 4 mm in height and diameter, were fabricated of three composite resins namely microfilled (MF) Heliomolar HB, nanohybrid (NH) IPS Empress Direct and microhybrid (MH) Tetric Ceram HB. After polishing, the initial surface roughness was measured with a profilometer. The tray technique was used to apply 15% CP gel for 6 hours. Then, cleaning was carried out with an Oral-B electric toothbrush for 3 minutes in a tank containing a freshly mixed toothpaste. These procedures were repeated for 21 days. Then, the surface roughness was measured again and compared with the initial values. A mixed-design ANOVA model was used for the analysis of data (P<0.05).

Results:

The baseline roughness was significantly lower in MF compared to the NH and MH composites (P<0.001). Roughness increased in all study groups during the intervention period; however, this increase was not significant in the MH group (P=0.17). Furthermore, the increase in roughness in MF was smaller than that in NH (P<0.001) and MH (P=0.02) groups.

Conclusion:

The effect of intervention was more pronounced on NH and MH groups. Surface roughness changes were minor in MF composite resin.

Effects of In-Office and Home Bleaching Gels on the Surface Mercury Levels of Dental Amalgam

Objectives: The aim of this study was to evaluate the effect of different in-office and home bleaching gels on the surface mercury levels of dental amalgam.

Methods: Sixty disk-shaped amalgam specimens (GS-80, SDI- Australia) were prepared and randomly divided into the following treatment groups: 1. Distilled water (control); 2. 15% home-bleach carbamide peroxide (Opalescence PF, Ultra dent, USA) applied for 6 h/day for 3 weeks; and 3. 35% in-office bleach carbamide peroxide (Opalescence Quick, Ultradent) applied for 30 min/week for 3 weeks. Levels of mercury were measured as weight percentages using an energy dispersive x-ray micro-analyzer detector connected to an electron microscope. Data was analyzed using one-way ANOVA and a post hoc Tukey tests (P<.05).

Results: There were no significant differences between the surface mercury levels measured following treatment with the tested home-bleach and in-office bleach products (P=0.71). However, both materials yielded significantly more mercury levels than that of the control group (P<.001).

Conclusions: The tested bleaching products significantly elevated the surface mercury levels of amalgam in vitro. (Eur J Dent 2010;4:23-27)

Manifestation of hemispheric laterality in chewing side preference and handedness

Introduction: Humans manifest a behavioral inclination towards more utility of one side of the body, in relation with the dominant hemisphere of the brain. The current investigation assessed handedness together with chewing preference which have not been evaluated in various food textures before. Methods: Nineteen young and healthy volunteers chewed hard (walnut) and soft (cake) foods, during surface electromyography recording from masseter muscles. The side of the first and all chews in the two food types were determined and compared with the side of the dominant hand. Results: Results indicated the two lateralities in the same side considerably (60%-70%), implying the solidarity in the control of the dominant hemisphere of the brain. The unilaterality was more prominent in the assessment of all chews in hard food, with higher statistical agreement and correlation. Conclusion: Thereupon masticatory preference is found with probable origins in the dominant hemisphere of the brain.

Effect of Relining with Different Composite Resins on the Push-out Bond Strength of Anatomical Fiber Posts to Root Canal Dentin

Introduction

Relining fiber posts using composite resins helps the posts adapt to the anatomical space of the root canals. The aim of this study was to evaluate the effect of composite resin type on the push-out bond strength of anatomical fiber posts to intra canal dentin.

Methods and Materials

Forty-eight bovine upper incisors were prepared for post space after root canal therapy and randomly divided in to six groups. Five different types of composite resin (GrandioSO, GrandioSO Heavy Flow, X-tra Fil, X-tra base and everX Posterior) were used for relining the prepared fiber posts. In the control group, the prepared post was cemented into the post space without relining. Cervical, middle and apical cross-sections were achieved from each root and push-out test was conducted at a crosshead speed of 0.5 mm/min. One sample from each group was scanned using a micro-CT scanner which provided views from the apical, middle and coronal thirds. Data were analyzed using Kolmogorov-Smirnov test, repeated measures ANOVA and post hoc tests using SPSS 17 (P<0.05).

Results

Statistical analysis showed significant differences in terms of mean push-out bond strengths between different composite resin types and cross-sections (P<0.001). The mean push-out bond strength of the samples relined with Grandio SO composite resin (15.48±2.32) and X-tra Fil Bulk-fill composite resin (14.09±1.98) were significantly higher than that of other groups (P<0.05). The unrelined group had a mean push-out bond strength (5.94±1.45) which was significantly lower than that in other groups (P<0.05). In addition, there was a relationship between cross-sections and composite resin types (P<0.05).

Conclusion

This in vitro study showed that the composite resins used for relining can affect the push-out bond strength to intra canal dentin based on their physical and mechanical properties.

Effect of Different Intraorifice Barriers and Bleaching Agents on the Fracture Resistance of Endodontically Treated Anterior Teeth

INTRODUCTION

Intraorifice barriers (IOBs) are usually used before internal bleaching for coronal sealing and the prevention of cervical resorption. The aim of this study was to investigate the effect of different IOBs on the fracture resistance (FR) of endodontically treated anterior teeth bleached with various bleaching agents (BAs).

METHODS

After performing root canal treatment for 72 extracted bovine upper incisors, the coronal 3 mm of gutta-percha was removed, and samples were classified into 3 based on the type of IOB: calcium-enriched mixture, mineral trioxide aggregate, and resin-modified glass ionomer. After applying IOBs, samples of each group were subdivided into 4 based on the BA: carbamide peroxide 45% (CP), hydrogen peroxide 35% (HP), sodium perborate (PB), and distilled water as the control. At the end of bleaching, the access cavities were restored with composite resin. The FR was measured with a universal testing machine at a crosshead speed of 5 mm/min. The data were analyzed using 2-way analysis of variance and least significant difference post hoc tests (P < .05).

RESULTS

The effect of BAs on the FR was significant (P < .05); however, the effect of the IOB and the interactive effect of these variables were not significant (P > .05). The FR in the HP and PB groups was significantly different from the control (P < .05) but that of CP was not significantly different from the control (P > .05).

CONCLUSIONS

Mineral trioxide aggregate and calcium-enriched mixture act similarly to resin-modified glass ionomer as an IOB. CP, unlike HP and PB, did not significantly decrease the FR.

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin.

Factors affecting marginal integrity of class II bulk-fill composite resin restorations

Background. Bulk-fill composite resins are a new type of resin-based composite resins, claimed to have the capacity to be placed in thick layers, up to 4 mm. This study was carried out to evaluate factors affecting gap formation in Cl II cavities restored using the bulk-fill technique.

Methods. A total of 60 third molars were used in this study. Two Cl II cavities were prepared in each tooth, one on the mesial aspect 1 mm coronal to the CEJ and one on the distal aspect 1 mm apical to the CEJ. The teeth were divided into 4 groups: A: The cavities were restored using the bulk-fill technique with Filtek P90 composite resin and its adhesive system and light-cured with quartz tungsten halogen (QTH) light-curing unit. B: The cavities were restored similar to that in group A but light-cured with an LED light-curing unit. C: The cavities were restored using the bulk-fill technique with X-tra Fil composite resin and Clearfil SE Bond adhesive system and light-cured with a QTH curing unit. D: The cavities were restored similar to that in group C but light-cured with an LED light-curing unit. The gaps were examined under a stereomicroscope at ×60. Data were analyzed with General Linear Model test. In cases of statistical significance (P<0.05), post hoc Bonferroni test was used for further analyses.

Results. The light-curing unit type had no effect on gap formation. However, the results were significant in relation to the composite resin type and margin location (P<0.001). The cumulative effects of light-curing unit*gingival margin and light-curing unit*composite resin type were not significant; however, the cumulative effect of composite rein type*gingival margin was significant (P=0.04)

Conclusion. X-tra Fil composite exhibited smaller gaps compared with Filtek P90 composite with both light-curing units. Both composite resins exhibited smaller gaps at enamel margins.

Effect of different bleaching strategies on microhardness of a silorane-based composite resin

Background. Dentists’ awareness of the effects of bleaching agents on the surface and mechanical properties of restorative materials is of utmost importance. Therefore, this in vitro study was undertaken to investigate the effects of different bleaching strategies on the microhardness of a silorane-based composite resin.

Methods. Eighty samples of a silorane-based composite resin (measuring 4 mm in diameter and 2 mm in thickness) were prepared within acrylic molds. The samples were polished and randomly assigned to 4 groups (n=20). Group 1 (controls) were stored in distilled water for 2 weeks. The samples in group 2 underwent a bleaching procedure with 15% carbamide peroxide for two weeks two hours daily. The samples in group 3 were bleached with 35% hydrogen peroxide twice 5 days apart for 30 minutes each time. The samples in group 4 underwent a bleaching procedure with light-activated 35% hydrogen peroxide under LED light once for 40 minutes. Then the microhardness of the samples was determined using Vickers method. Data were analyzed with one-way ANOVA and post hoc Tukey tests (P < 0.05).

Results. All the bleaching agents significantly decreased microhardness compared to the control group (P < 0.05). In addition, there were significant differences in microhardness between groups 2 and 4 (P = 0.001) and between groups 3 and 4 (P<0.001). However, no significant differences were detected in microhardness between groups 2 and 3 (P > 0.05).

Conclusion. Bleaching agents decreased microhardness of silorane-based composite resin restorations, the magnitude of which depending on the bleaching strategy used.

Effect of an extra layer of hydrophobic resin on the microleakage of Cl V composite resin restorations with a universal adhesive system

AIM

The aim of the present study was to evaluate the effect of the application of a hydrophobic resin on the microleakage of Cl V composite resin restorations using a universal adhesive system applied in the self-etch (SE) and etch-and-rinse (ER) modes.

METHOD

Cl V cavities were prepared on the buccal surfaces of 64 human premolar teeth and divided into four groups (n = 16): ER, ER with hydrophobic resin (ERH), SE, and SE with hydrophobic resin (SEH). Microleakage at occlusal and gingival margins was evaluated using 0.5% methylene blue dye penetration technique under stereomicroscope at 40 × magnification. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (P < 0.05).

RESULTS

At the enamel margins, the ER group had significantly less microleakage than the SE and SEH groups (P < 0.001), but had no significant difference compared with the ERH group (P > 0.05). There was also no statistically-significant difference between the SE and SEH groups (P > 0.05). At the dentinal margins, the SE group had significantly less microleakage compared with the ER (P < 0.001) and ERH groups (P = 0.005). Furthermore, microleakage of the SEH group was significantly less than the SE group (P < 0.001).

CONCLUSION

Applying an extra layer of hydrophobic resin significantly decreased microleakage in the SE mode at the dentinal margin, but had no significant effect in the ER mode.

Mercury release of amalgams with various silver contents after exposure to bleaching agent

Background. Since it is possible for carbamide peroxide (CP) bleaching agent to contact old amalgam restorations, the present in vitro study evaluated the amount of dissolved mercury released from amalgam restorations with various percent-ages of silver content subsequent to the use of 15% CP.

Methods. Thirty ANA 2000 amalgam disks with 43.1% silver content and thirty ANA 70 amalgam disks with 69.3% silver content were prepared. In each group, 15 samples were randomly placed in glass tubes containing 15% CP (as experimental groups) and the remaining 15 samples were placed in buffered phosphate solution (as control groups) with the same 3-mL volume for 48 hours. Subsequently, the amount of mercury dissolved in each test tube was measured using Mercury Analyzing System (Cold Vapor Atomic Absorption, MASLO, Shimadzu, Japan). Data was analyzed with two-way ANOVA and a post hoc Tukey test. (α = 0.05).

Results. The amount of mercury released after exposure to CP was significantly higher than that released after exposure to buffered phosphate (P < 0.001). In addition, the amount of mercury released from dental amalgam with a silver content of 43% was significantly higher than that released from dental amalgam with a silver content of 69% (P < 0.001).

Conclusion. The amount of mercury release is inversely proportional to the silver content of dental amalgam.

Effect of Sodium Ascorbate and Delayed Bonding on the Bond Strength of Silorane and Two-step Self-etch Adhesive Systems in Bleached Enamel

Background and aims. Studies have shown decreased bond strength of composite resin to human and bovine bleached enamel. This study evaluated the effect of sodium ascorbate and delayed bonding on the bond strength of two adhesive systems to bleached enamel.

Materials and methods. The labial surfaces of 150 sound bovine incisor teeth were abraded with abrasive paper. The teeth were randomly divided into 8 groups: A: control; B: bleached with 35% hydrogen peroxide; C: bleached with 35% hydrogen peroxide + sodium ascorbate gel; and D: bleached with 35% hydrogen peroxide + delayed bonding. In groups A‒D, silorane adhesive system and Filtek silorane composite resin were used. In groups E‒H, the same preparation methods of groups A-D were used. Two-step self-etch Clearfil SE Bond adhesive systems and AP-X composite resin were administered. Shear bond strength of each group was measured. Two samples were prepared for each surface preparation for ultra-structural evaluation. Two-way ANOVA and Tukey test were used for data analysis at P<0.05.

Results. The interaction between the adhesive system type and surface preparation protocol was significant (P=0.014), withsignificant differences in shear bond strengths in terms of the adhesive systems (P<0.01). There were significant differences in shear bond strength in terms of surface preparation techniques irrespective of the adhesive system (P<0.01).

Conclusion. The results showed that bleaching with 35% hydrogen peroxide decreased the shear bond strength values with both adhesive systems, and a one-week delay in bonding and 10% sodium ascorbate for10 minutes restored the bond strength in both adhesive systems.

Shear bond strength of calcium enriched mixture cement and mineral trioxide aggregate to composite resin with two different adhesive systems

OBJECTIVE

Immediate restoration after vital pulp therapy is essential in order to create and maintain effective coronal seal.

PURPOSE OF STUDY

The aim of this study was to evaluate the shear bond strength of recently used pulp capping materials: white mineral trioxide aggregate (MTA), and calcium enriched mixture cement (CEM) to composite resin with the use of etch-and-rinse and self-etch adhesive systems and compare them with the bond strength of commonly used resin modified glass ionomer (RMGI) cement.

MATERIALS AND METHODS

Forty specimens from each test material were fabricated, measuring 4 mm in diameter and 2 mm in depth. The specimens of each material were divided into 2 groups of 20 specimens according to the adhesive system (Single Bond vs. Clearfil SE Bond) used for bonding of resin composite. The shear bond strength values were measured at a crosshead speed of 1.0 mm/min and fractured surfaces were examined. Data were analyzed using two-way ANOVA and a post hoc Tukey's test (P<0.05).

RESULTS

Analysis of data showed a significantly higher bond strength for RMGI compared to MTA and CEM (P<0.001); however, no significant differences were observed in the bond strength values of MTA and CEM (P=0.9). Furthermore, there were no significant differences in relation to the type of the adhesive system irrespective of the type of the material used (P=0.95) All the failures were of cohesive type in RMGI, MTA and CEM.

CONCLUSION

Bond strength of RMGI cement to composite resin was higher than that of MTA or CEM cement irrespective of the type of the adhesive system.

Effect of Casein Phosphopeptide-amorphous Calcium Phosphate Treatment on Microtensile Bond Strength to Carious Affected Dentin Using Two Adhesive Strategies

Background and aims. The aim was to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on microtensile bond strength (μTBS) to carious affected dentin (CAD) using etch-and-rinse and self-etch adhesive systems.

Materials and methods. The occlusal surface of 32 human molars with moderate occlusal caries was removed. Infected dentin was removed until reaching CAD and the teeth were randomly divided into two groups based on the Single Bond (SB) and Clearfil SE Bond (CSE) adhesive systems. Before composite resin bonding, each group was subdivided into three subgroups of ND, CAD and CPP-ACP-treated CAD (CAD-CPP) based on the dentin substrate. After dissecting samples to l-mm-thick cross-sections (each subgroup: n = 13), μTBS was measured at a strain rate of 0.5 mm/min. Data was analyzed using two-way ANOVA, independent samples t-test and post-hoc Tukey tests (α=0.05).

Results. Bond strength of both adhesive systems to ND was significantly higher than that to CAD (P <0.001) and CAD/CPP (P < 0.001). There were no significant differences between the μTBS of SB to CAD and CAD-CPP (P > 0.05).μTBS of CSE to CAD-CPP was higher than that to CAD; however, the difference was not significant (P > 0.05). Significant differences were found between SB and CSE systems only with CAD substrate (P < 0.001).

Conclusion. Regardless of the adhesive system used, surface treatment of CAD with CPP-ACP did not have a significant effect on bond strength. However, bond strength to CAD was higher with SB rather than with CSE.

Effect of Light Intensity on the Degree of Conversion of Dual-cured Resin Cement at Different Depths with the use of Translucent Fiber Posts

OBJECTIVES

To evaluate the effect of different light intensities on the degree of conversion (DC) of dual-cured resin cement at different depths of translucent fiber posts.

MATERIALS AND METHODS

Thirty translucent fiber posts were randomly assigned into three (n=10) groups. They were cemented in the simulated canal spaces using Duo-Link dual-cured resin cement. The cement was light-cured under 600, 800 and 1100 mW/cm(2) light intensities for 40 seconds. DC of the resin cement was calculated at cervical, middle and apical thirds using the spectra of FT-Raman spectrometer. Data were analyzed by repeated measurement ANOVA and Tukey's post hoc tests (α=0.05).

RESULTS

In all the groups, the least DC was obtained at the apical region. There were no significant differences in the DC with different light intensities between the cervical and middle regions (p>0.05). However, in the apical region, the DC in both 800 and 1100 mw/cm(2) was similar (p>0.05), but greater with 600 mW/cm(2) light intensity (p=0.02 and p<0.001, respectively).

CONCLUSION

In comparison with the light intensity of 600 mW/cm(2), the light intensity of 800 mW/cm(2) significantly increased the DC of dual-cured resin cement in the apical region. However, DC was not significantly different between 800 and 1100 mw/cm(2) light intensities. If the resin cement, especially in the apical areas is not sufficiently cured, microleakage might increase and post retention might be jeopardized. In comparison with 600 mW/cm(2) light intensity, 800 mW/cm(2) significantly increases DC at the apical third that might be clinically beneficial.

Effect of Nd:YAG laser pulse energy on mercury vapor release from the dental amalgam

OBJECTIVE

The aim of this study was to evaluate the effect of different pulse energies of Nd:YAG laser on the amalgam ablation, and its effect on the amount of mercury vapor release from amalgam.

BACKGROUND DATA

Toxic vapor release from amalgam restorations at the laser focus site is possible.

MATERIALS AND METHODS

Forty-five amalgam samples (4 mm in diameter and 5 mm in height) were placed in sealed containers and underwent Nd:YAG laser irradiation with pulse energies of 50, 150, and 250 mJ at a distance of 1 mm from the amalgam surface for 4 sec. Subsequently, 150 mL of air was collected from the inside of the container using an Apex Pump to analyze the amount of mercury vapor in the air samples using a mercury vapor analyzer. Data were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p<0.05).

RESULTS

The amount of mercury vapor release significantly increased with an increase in the pulse energy of Nd:YAG laser (p<0.001). In addition, the amount of mercury vapor release with 250 mJ pulse energy was significantly higher compared with the standard mercury vapor concentration (50 μg/m(3)) (p<0.001). Nd:YAG laser produced cavities on the amalgam surface, which increased in size with an increase in the energy of the laser beam.

CONCLUSIONS

The amount of mercury vapor significantly increased with an increase in the pulse energy of the laser beam, and was significantly higher than the standard mercury vapor concentration with 250 mJ pulse energy.

Comparison of shear bond strength of resin-modified glass ionomer and composite resin to three pulp capping agents

Background and aims. Present study was designed to compare the bonding strength of resin-modified glass ionomer (RMGI) and composite resin to mineral trioxide aggregate (MTA), MTA mixed with Na2HPO4 (NAMTA), and calcium-enriched mixture (CEM).

Materials and methods. Thirty specimens of each CEM, NAMTA, and MTA were prepared. Composite and RMGI restorations were then placed on the samples (15 samples in six subgroups). Shear bond strength was assessed using universal testing machine. Data were analyzed with two-way ANOVA and post-hoc Tukey test. To compare the bond strength in subgroups, one-away ANOVA was applied. Significance level was set at P < 0.05.

Results. Bond strength was significantly higher to composite samples compared to RMGI samples (p<0.001). The difference in bond strength of composite samples between MTA and CEM subgroups (P=0.026) as well as MTA and NAMTA subgroups (P= 0.019) was significant, but the difference between NAMTA and CEM subgroups (P=0.56) was not significant. The differences in bond strength in subgroups of RMGI group were not significant (P>0.05).

Conclusion. Regarding shear bond strength to the tested substrates, composite was shown to be superior to RMGI. The bond of resin composite to MTA was weaker than that to CEM and NAMTA.

Comparison of the Effect of Nd:YAG and Diode Lasers and Photodynamic Therapy on Microleakage of Class V Composite Resin Restorations

Background and aims

Considering the importance of disinfecting dentin after cavity preparation and the possible effect of disinfection methods on induction of various reactions between the tooth structure and the adhesive restorative material, the aim of the present study was to evaluate microleakage of composite resin restorations after disinfecting the prepared dentin surface with Nd:YAG and Diode lasers and photodynamic therapy.

Materials and methods

Standard Class V cavities were prepared on buccal surfaces of 96 sound bovine teeth. The samples were randomly divided into 4 groups based on the disinfection method: Group 1: Nd:YAG laser; Group 2: Diode laser; Group 3: photodynamic therapy; and Group 4: the control. Self-etch bonding agent (Clearfil SE Bond) was applied and all the cavities were restored with composite resin (Z100). After thermocycling and immersing in 0.5% basic fuchsin, the samples were prepared for microleakage evaluation under a stereomicroscope. Data was analyzed with Kruskal-Wallis and Wilcoxon signed-rank tests at P<0.05.

Results

There were no significant differences in the microleakage of occlusal and gingival margins between the study groups (P>0.05). There were no significant differences in microleakage between the occlusal and gingival margins in the Nd:YAG laser group (P>0.05). In the other groups, microleakage at gingival margins was significantly higher than that at the occlusal margins (P<0.05).

Conclusion

Nd:YAG and Diode lasers and photodynamic therapy can be used to disinfect cavity preparations before composite resin restorations.

Effect of three different contamination removal methods on bond strength of a self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent

AIM

This study evaluated the effect of three different contamination removal methods on bond strength of one-step self-etching adhesive to dentin contaminated with an aluminum chloride hemostatic agent.

MATERIALS AND METHODS

One hundred noncarious adult molars were used in this study; 2-mm-thick dentin disks were prepared and randomly assigned to 5 groups (n = 20). Group I: control; group II: hemostatic agent-contaminated; group III: hemostatic agent-contaminated and rinsing with water; group IV: hemostatic agent-contaminated and ethylene diamine tetraacetic acid (EDTA) application; and group V: hemostatic agent-contaminated and phosphoric acid application. Clearfil S3 Bond was used to bond composite to dentin surfaces. Subsequent to adding composite cylinders the shear bond strength test was performed. Data were analyzed by one-way ANOVA and Tukey test. Two additional specimens from each group were prepared and evaluated under scanning electron microscope (SEM).

RESULTS

There were statistically significant differences in bond strength among the groups (p < 0.001). In two-by-two comparisons statistically significant differences were observed in bond strength values between all the groups (p < 0.001) except for groups I and IV (p = 0.933).

CONCLUSION

Aluminum chloride hemostatic agent adversely affected the bond strength of self-etch adhesive to dentin. However, application of EDTA increased the bond strength to the level of normal dentin.

CLINICAL SIGNIFICANCE

EDTA and phosphoric acid removed aluminum chloride hemostatic agent contamination of dentin surfaces. However, unlike EDTA phosphoric acid failed to increase the bond strength of self-etch adhesive to dentin to the level of the control group.

Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

Background and aims

Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS) of silica- (Spectrum TPH) and zirconia-filled (Filtek Z250) composite resins.

Materials and methods

Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05).

Results

Analysis of data showed that the effect of composite resin type was not significant (p > 0.05), but the effects of the type of surface treatment (p = 0.01) and the type of adhesive system (p = 0.01) were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05). However, the cumulative effects of the adhesive system-surface treatment (p = 0.03) and the composite type-the adhesive system-surface treatments (p = 0.002) were significant.

Conclusion

Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently.

The effect of composite fiber insertion along with low-shrinking composite resin on cuspal deflection of root-filled maxillary premolars

AIM

The aim of the present study was to evaluate the effect of three methods of composite fiber placement along with siloranebased composite resin on cuspal deflection and fracture strength of root-filled maxillary premolars.

MATERIALS AND METHODS

Mesio-occluso-distal cavities were prepared in 60 extracted premolars subsequent to endodontic treatment. The remaining thickness of buccal and lingual walls at height of contour was 2.5 ± 0.2 mm and the gingival cavosurface margin was 1.5 mm coronal to cementoenamel junction. Subsequent to measurement of primary intercuspal distances, the teeth were randomly divided into four groups. In group 1, the cavities were only filled with Filtek Silorane composite resin. In the other three groups, preimpregnated glass fibers were placed at gingival, middle and occlusal thirds respectively, and the cavities were restored similar to the group 1. Cuspal deflection was recorded in micrometer using a stereomicroscope. Fracture strength of the samples was measured in Newton subsequent to thermocycling. Data was analyzed using Kruskal-Wallis, Mann-Whitney U, one-way ANOVA and post-hoc Tukey tests at a significance level of p < 0.05.

RESULTS

The highest cuspal deflection was recorded in the group 1, and the difference between group 1 and other groups was significant (p < 0.001). Fracture resistance in group 4 was significantly higher than that in other groups (p < 0.001).

CONCLUSION

In restoring root-filled premolars with siloranebased composite resins, cuspal deflection decreased with the use of preimpregnated glass fibers.

CLINICAL SIGNIFICANCE

Using preimpregnated glass fibers along with silorane-based composite resin may lead to better results in cuspal deflection and fracture resistance of endodonticallytreated maxillary premolars.

Chewing side preference in first and all mastication cycles for hard and soft morsels

Preferred chewing side is a still controversial matter and various methods used have yielded some inconsistencies. The aim of this study is to compare the preference determined in different conditions. Nineteen healthy subjects were offered hard (walnut) and soft (cake) foods, while the electromyography was recorded from their masseter muscles, in 2009 in the Research Center of Physical Medicine and Rehabilitation, Tabriz University of Medical Sciences, Tabriz, Iran. Four occurrences were determined as the side of the first chews/all chews in the two food types, and then analyzed for correlations and agreements. For hard food 73.68% and for soft food 57.89% of the subjects showed preference. The comparison of all chews showed a highly significant preference towards the right side in both food types (p=0.000 & 0.003). There was both correlation and agreement between the first chew preferences in both food types, and an agreement between the first and all chew preferences in the hard food. Therefore, there seems to exist some laterality in mastication, which is more explicit when using hard food and assessing all chews.

Shear bond strength of self-etching adhesive systems with different pH values to bleached and/or CPP-ACP-treated enamel

PURPOSE

To compare shear bond strengths of three different self-etching adhesive systems of different pH values to enamel bleached with carbamide peroxide, treated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), or treated with CPP-ACP subsequent to bleaching with carbamide peroxide.

MATERIALS AND METHODS

Thirty-six human third molars were cut into 4 sections and randomly assigned to 4 groups (n = 36): group I: no treatment; group II: bleaching; group III: CPP-ACP; group IV: bleaching and CPP-ACP. After surface treatments, the samples of each group were further divided into three subgroups (n = 12) based on the adhesive used. The adhesives Clearfil SE Bond (CSE), AdhesE (ADE), and Adper SE Plus (ADP) were applied, and resin composite cylinders with a diameter of 2 mm and a height of 4 mm were bonded to the enamel. Then the specimens were subjected to shear bond strength testing. Two-way ANOVA and a post-hoc Tukey's test were used for statistical analysis (α = 0.05).

RESULTS

There were significant differences between the adhesive systems (p < 0.001) and surface treatments (p < 0.001), but no significant interactions were observed between these variables (p = 0.78). The CSE adhesive system showed the highest bond strength, and the bleaching procedure reduced bond strengths (p = 0.001). Furthermore, there were no significant differences in shear bond strength values between the control and CPP groups. However, the differences between other groups were statistically significant (p < 0.05).

CONCLUSION

Bleaching reduced shear bond strength to enamel, but CPP-ACP application did not affect the bond strength to intact and previously bleached enamel. The bond strength of adhesives with different pH values to enamel was material dependent.

Effect of composite resin contamination with powdered and unpowdered latex gloves on its shear bond strength to bovine dentin

The aim of the present study was to evaluate the effect of composite resin contamination with powdered and unpowdered latex gloves on the shear bond strength of etch-and-rinse and two-step self-etch adhesive systems. Standard flat dentin surfaces were prepared on the facial aspect of 120 bovine incisors and randomly assigned into two (n=60) groups: group 1: Single Bond (SB), group 2: Clearfil SE Bond (CSE). Furthermore, each group was randomly subdivided into three (n=20) based on the type of composite contamination (without contamination, contamination with powdered latex gloves, and contamination with unpowdered latex gloves). The adhesives were applied and resin composite bonded to the dentin. After thermocycling, the specimens were subjected to a shear bond strength test. Two-way analysis of variance (ANOVA) and a post hoc Bonferroni test were used for statistical analysis. One-way ANOVA was used to compare shear bond strength values in each group. Statistical significance was set at p < 0.02. Two-way ANOVA showed that the shear bond strength was significantly influenced by the type of composite surface contamination (p=0.001). In the SB group there were no significant differences between different surface treatments (p=0.08). In the CSE group a significant difference was observed between the subgroup without contamination and the subgroup with powdered latex glove contamination (p=0.01); however, no significant differences were observed between the other subgroups.

Effect of three different mouthrinses on microleakage of composite resin restorations with two adhesive systems after bleaching with 10% carbamide peroxide

AIM

The aim was to evaluate the effects of Oral-B (OB), Listerine (LN) and Rembrandt Plus (RM) mouthrinses on microleakage of composite resin restorations bonded with two adhesive systems after bleaching with 10% carbamide peroxide.

MATERIALS AND METHODS

A total of 60 Cl V cavities were prepared on human premolars. The occlusal and gingival margins were placed 1 mm occlusal to and apical to CEJ respectively. The teeth were randomly divided into two groups based on the adhesive system used: Excite (EX) and Clearfil SE Bond (CSE) groups. After composite resin restoration of cavities, thermocycling and bleaching with 10% carbamide peroxide for 2 hours daily for 14 days, the teeth in each adhesive group were further subdivided into three subgroups and were immersed for 12 hours in the three OB, RM and LN mouthrinses. The teeth were then placed in 2% basic fuschin for 24 hours. After dissecting the teeth, microleakage was evaluated under a stereomicroscope at 16×. Data was analyzed with multifactor ANOVA and Bonferroni test at p < 0.05.

RESULTS

Microleakage with EX was significantly higher than that with CSE (p = 0.009). Microleakage at gingival margins was significantly higher than that at occlusal margins (p = 0.15). Microleakage with OB was higher than that with LN (p = 0.02). However, there were no significant differences in microleakage between LN and RM (p = 1) and between RM and OB (p = 0.15). In addition, with the EX adhesive system, microleakage with OB was higher than that with LN and RM (p = 0.02).

CONCLUSION

In the present study, microleakage of composite resin restorations was influenced by the type of the adhesive system, mouthrinse type and the location of the cavity margin.

CLINICAL SIGNIFICANCE

Use of some mouthrinses, such as OB after bleaching can increase postrestoration microleakage of resin composite restorations bonded with etch-and-rinse adhesive systems.

Comparison of shear bond strength of calcium-enriched mixture cement and mineral trioxide aggregate to composite resin

AIM

Adhesion of composite resin and pulp capping biomaterials remarkably influences treatment outcomes. This in vitro study aimed to compare the shear bond strength of composite resin to calcium enriched mixture (CEM) cement, mineral trioxide aggregate (MTA) and resin modified glass ionomer (RMGI) with or without acid etching.

MATERIALS AND METHODS

A total of 90 cylindrical acrylic blocks containing a central hole, measuring 4 mm diameter and 2 mm height were prepared. The blocks were randomly divided into three experimental groups based on being filled with CEM, MTA or RMGI. Samples in each group were then randomly divided into two subgroups, i.e. with or without phosphoric acid etching. Placing composite resin cylinders on the samples, shear bond strengths were measured using a universal testing machine. Failure modes of the samples were evaluated under a stereomicroscope. Data were analyzed using two-way ANOVA and Tukey tests.

RESULTS

Shear bond strengths in the etched and nonetched samples were not significantly different (p = 0.60). There was a significant difference in shear bond strength values of the three experimental materials (p < 0.001) and RMGI showed the highest strength values (p < 0.001); no significant difference was observed between MTA and CEM (p = 0.51). The interaction of the type of material and surface etching was statistically significant (p < 0.001). All of the samples showed cohesive failure mode.

CONCLUSION

Acid etching of MTA, CEM and RMGI do not improve the shear bond strength of these materials to composite resin. Besides, shear bond strength values of MTA and CEM to composite resin, are favorable due to their cohesive mode of failure.

CLINICAL SIGNIFICANCE

When MTA and CEM biomaterials are used in vital pulp therapy, it is advisable to cover these materials with RMGI. In addition, if it is not possible to use RMGI, the surface etching of MTA and CEM biomaterials is not necessary prior to composite restoration using total-etch adhesive resin.

Effect of 10% sodium ascorbate on bleached bovine enamel surface morphology and microhardness

Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces. The aim of present study was to evaluate the effect of 10% sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics. A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin. Subsequent to polishing, they were randomly divided into 3 groups of 23 specimens each; 3 for Scanning Electron Microscopy (SEM) analysis and 20 for hardness test. In group 1 the specimens were immersed in distilled water as control group; in group 2 the specimens were bleached with 35% carbamide peroxide for 30 min a week for 3 consecutive weeks; and in group 3 the specimens were exposed to 10% sodium ascorbate for 30 min subsequent to bleaching similar to group 1. After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA (P < 0.05). The highest and lowest microhardness values were observed in group 1 and group 2, respectively. However, there were no statistically significant differences in microhardness between the groups (P = 0.12). The use of 35% carbamide peroxide alone or with 10% sodium ascorbate does not affect bovine enamel hardness. SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface.

Comparison of the effect of hydrogel and solution forms of sodium ascorbate on orthodontic bracket-enamel shear bond strength immediately after bleaching: an in vitro study

AIM

This study compared the effects of hydrogel and solution forms of sodium ascorbate (SA) with two different application times on bracket bond strength subsequent to bleaching.

MATERIALS AND METHODS

A total of 72 sound premolars were randomly divided into six groups (n = 12): An unbleached control group (group one) and five experimental groups of carbamide peroxide. Specimens in group two were bonded immediately after bleaching; specimens in groups three and four were bleached, then treated with SA solution for ten minutes and three hours, respectively, and then bonded. In groups five and six, SA hydrogel was used and the specimens were prepared similar to groups three and four, respectively. Following debonding, bond strengths were recorded in MPa. To evaluate the amount of resin left on the enamel surfaces, adhesive remnant index (ARI) scores were used.

STATISTICAL ANALYSIS

The bond strength data were analyzed with ANOVA and pairwise comparisons were made by Tukey test. The ARI data were subjected to Kruskal-Wallis test and two-by-two comparisons were made by the Mann-Whitney U test.

RESULTS

There were significant differences in bond strengths between the groups ( P < 0.0005). However, the differences between groups three, four, five and six were not significant. Furthermore, there were no significant differences between group one and groups four and six, whereas the differences between the other groups were significant ( P < 0.05). Regarding ARI, there were significant differences among the groups ( P = 0.004).

CONCLUSION

Bleaching significantly decreased the bracket bond strength. Compromised bonding was reversed with a three-hour application of both forms of SA.

Effects of in-office and home bleaching gels on the surface mercury levels of dental amalgam

OBJECTIVES

The aim of this study was to evaluate the effect of different in-office and home bleaching gels on the surface mercury levels of dental amalgam.

METHODS

Sixty disk-shaped amalgam specimens (GS-80, SDI- Australia) were prepared and randomly divided into the following treatment groups: 1. Distilled water (control); 2. 15% home-bleach carbamide peroxide (Opalescence PF, Ultra dent, USA) applied for 6 h/day for 3 weeks; and 3. 35% in-office bleach carbamide peroxide (Opalescence Quick, Ultradent) applied for 30 min/week for 3 weeks. Levels of mercury were measured as weight percentages using an energy dispersive x-ray micro-analyzer detector connected to an electron microscope. Data was analyzed using one-way ANOVA and a post hoc Tukey tests (P<.05).

RESULTS

There were no significant differences between the surface mercury levels measured following treatment with the tested home-bleach and in-office bleach products (P=0.71). However, both materials yielded significantly more mercury levels than that of the control group (P<.001).

CONCLUSIONS

The tested bleaching products significantly elevated the surface mercury levels of amalgam in vitro.

Evaluation of Radiation-induced Class V Dental Caries in Patients with Head and Neck Cancers Undergoing Radiotherapy

Background and aims

Salivary glands are very susceptible to radiation and any disturbances in their function are detrimental to the hard tissues in the oral cavity. The aim of this study was to evaluate posterior class V dental caries in patients with head and neck cancers undergoing radiotherapy.

Materials and methods

In this study, twenty seven patients undergoing conventional radiotherapy were included. Class V dental caries of posterior teeth in these patients were evaluated in three intervals: before treatment, 3 weeks after the initiation of the treatment, and at the end of the treatment. Differences of mean caries activity between intervals were evaluated using paired sample t-test.

Results

There were no class V decays prior to radiotherapy. Mean percentage of class V caries three weeks after radiotherapy and at the end of radiotherapy were 28.42% ± 14.41 and 67.05% ± 19.02, respectively. There were statistically signifi-cant differences in mean values among three stages (P = 0.00025).

Conclusion

The results of the present study re-vealed that radiotherapy in patients with head and neck cancers causes class V dental caries on posteri-or teeth.

Evaluation of Radiation-induced Xerostomia in Patients with Nasopharyngeal Carcinomas

BACKGROUND AND AIMS

Salivary glands are extremely susceptible to radiation injuries. The aim of this study was to evaluate radiation-induced xerostomia in patients with nasopharyngeal carcinomas, referring to Tabriz Imam Khomeini Hospital in 2005-2006.

MATERIALS AND METHODS

Thirty patients with nasopharyngeal carcinomas, who received conventional radiotherapy, were included in the present study. The patients' unstimulated saliva samples were collected at three intervals, i.e. before treatment, 3 weeks after the initiation of treatment and at the end of treatment by spitting, and measured with a graduated pipette.

RESULTS

The differences in the mean values of the patients' salivary flow rates at three afore-mentioned intervals were statistically significant (p<0.001). Two-by-two comparison of the mean values of salivary flow rates of all the patients and of males and females, carried out separately, demonstrated statistically significant differences (p<0.0025). However, there were no statistically significant differences between males and females before treatment (p = 0.723), 3 weeks after the initiation of treatment (p = 0.724) and at the end of treatment (p = 0.595). There were no statistically significant relationships between age and a decrease in salivary flow rate in the total sample (p = 0.76, r = -0.057), in males (p = 0.96, r = 0.011) and in females (p = 0.539, r = -0.208).

CONCLUSION

Conventional radiotherapy results in severe xerostomia in 3 weeks in patients with nasopharyngeal carcinomas. Age and sex do not influence radiotherapy-induced xerostomia.

In Vitro Fracture Resistance of Endodontically-treated Maxillary Premolars

Horizontal pins alone, or with flowable composite, have no effect on the fracture resistance of endodontically-treated maxillary premolars restored with resin composite.

Reasons for Retreatment of Amalgam and Composite Restorations among the Patients Referring to Tabriz Faculty of Dentistry

Background and aims

Retreatment of existing restorations not only requires a lot of money and time but also there is a danger of weakening tooth structure and irritating the pulp. Since awareness of the reasons for the retreatment of teeth will save the teeth from possible future failure, the aim of this study was to assess the reasons for retreatment of amalgam and composite restorations in patients referring to Tabriz Faculty of Dentistry.

Materials and methods

In this descriptive study, the subjects had previously received an amalgam or a composite restoration in the Operative Department by dental students and were judged to need retreatment in their second visit. A total of 300 defective teeth were selected by simple random sampling method. The data was collected through examination and questionnaires and analyzed using chi-square test.

Results

There was a statistically significant association between the type of the restorative material and the reason for retreatment (p=0.001).

Conclusion

Although the reasons for the retreatment of amalgam and composite restorations were different, recurrent caries was the main reason for the retreatment for both restorative materials.

Contamination of dental unit water and air outlets following use of clean head system and conventional handpieces

Background and aims

Dental handpiece is a source of contamination because it is in constant touch with the oral cavity. Sterilization does not seem to be sufficient to prevent penetration of microorganisms into air and water lines of the unit, because negative pressure developed by valves (which are placed in water outlets) and post shut-off inertial rotation of handpiece result in water and debris being sucked into air and water outlets of dental unit. The aim of this study was to compare dental unit contamination following use of clean head system handpieces and conventional handpieces.

Materials and methods

Twenty-two dental units in the Department of Pediatric Dentistry in Shahid Beheshti Faculty of Dentistry were used for the purpose of this study. A 1.5×108 cfu/mm3 concentration of Staphylococcus epidermis (SE) was used to contaminate the air and water outlets of dental units. Ten clean head system handpieces and 10 conventional handpieces were used for 30 seconds in the above-mentioned suspension. Microbial samples were collected from the air and water lines. Culturing and colony counting procedures were carried out. Data was analyzed by t-test; a value of p<0.01 was considered significant.

Results

Results demonstrated a significantly lower SE contamination in water outlets following the use of clean head system (p<0.01).

Conclusion

A lower tendency of clean head system handpieces to transmit SE compared to conventional system makes them a better choice for infection control.

Effect of 1-bottle light-cured adhesive acidity on microleakage of a self-cured composite

This in vitro study examined the effect of 1-bottle light-cured adhesives with different acidities on the microleakage of a self-cured composite in Class II restorations. Forty-five Class II cavities were prepared on the proximal surfaces of extracted human intact third molars that were randomly assigned to 3 groups (15 cavities in each group). The following adhesives were applied according to the manufacturer's instructions: Single Bond (Group 1), Excite (Group 2) and One-Step (Group 3). The teeth were restored with a combination of a self-cured resin composite (Concise) and a light-cured resin composite (Filtek P60). After thermocycling (500 cycles at 5 degrees C/55 degrees C) and immersion in 2% basic Fushin, the teeth were sectioned and evaluated for microleakage using a stereomicroscope (16x). Microleakage was scored on a scale of 0 to 3. Kruskal-Wallis analysis showed that there was a significant-difference in microleakage values of 3 adhesives with a self-cured composite, and low pH may have contributed to high microleakage values. Also, 2 by 2 comparisons with the Mann-Whitney U-test revealed a significant difference at the p<0.05 level between Groups 1 and 2 and between Groups 2 and 3. However, there was no statistically significant difference between Groups 1 and 3.