Effect of energy drinks on microhardness of silorane and dimethacrylate-based composite resins

Introduction: Increased consumption of energy drinks has raised concerns about their effects on dental restorations. This study assessed the effects of two energy drinks on the surface microhardness of methacrylate and silorane-based composites after 1-week and 1-month periods. Materials & Methods: In this in-vitro study, 90 cubic samples were prepared from Filtek P90, Filtek Z250 and Filtek Z350 XT composite resins. Vickers hardness test was performed to measure the baseline surface microhardness for each specimen. Ten randomly selected samples from each composite material were then immersed in one of the two sports drinks (Red Bull and Hype) or artificial saliva (control). Surface microhardness was re-evaluated after 1 week and 1 month of immersion. The data were evaluated using ANOVA via post-hoc Tukey tests and repeated measure test (α=0.05). Results: Surface microhardness of all composites were significantly decreased in energy drinks in both evaluation periods (P<0.001). In artificial saliva, microhardness was significantly increased after 1 week and decreased after 1 month of immersion (P< 0.001). After 1 month, the lowest microhardness changes were observed in Filtek Z350 XT composite. (18% and 14% reduction in Hype and Redbull respectively). Differences between energy drinks were significant for Z350 XT composite only after 1 week (P=0.01) and for Z250 composite after 1 week and 1 month (P=0.020 and P< 0.001 respectively). Conclusion: Hype and Red Bull energy drinks can affect the surface hardness of composite resins depending on their characteristics and exposure time

Effect of expiration date of universal adhesives on the alterations of microtensile bond strength of composite resin to dentin

Introduction: One of the factors affecting the success of bonded restoration is the use of appropriate adhesives and attention to their maintenance time. The aim of this study was to investigate the effect of three time periods related to the expiration date of two universal adhesives on the bond strength of resin composite to dentin. Materials & Methods: In this in-vitro study, 30 intact third human molars were selected. The roots of the teeth were cut and the crown part was mounted in acrylic resin in such a way that the enamel of the buccal surface was clearly visible. Using abrasive disks, the enamel of the buccal surface of the teeth was abraded to create a flat dentin area with dimensions of 25 mm2. The samples were randomly divided into 2 groups based on adhesive type (All Bond (Bisco, Fchaumburg,IL, USA) G-Permio and each group was divided into 3 subgroups based on expiration date. After the bonding process and fabrication of composite samples, microtensile bond strength (TBS) was measured at a speed of 1 mm/min. The data were analyzed using the Kruskal-Wallis test and post hoc Tukey's test. P<0.05 was considered as significant level. Results: Significant differences were found among samples with different expiration dates in both All-Bond Universal (p=0.0001) and G-Premio (p=0.0001) groups in terms of micro TBS (μTBS). In both adhesive groups, a significant difference was found between 2 months after expiration with expiration time and 2 months before expiration, but there was no significant difference between expiration time and 2 months before expiration. Conclusion: The end of the expiration date has a reducing effect on the μTBS of universal adhesives investigated in this study. However, the amount of this effect varies depending on the type of adhesive

The effect of powder/liquid ratio on microleakage of resin-modified glass-ionomer

Introduction: Resin modified glass-ionomer cement (RMGI) is prepared by manual mixing of powder and liquid. Different mixing ratios influence on the RMGI properties. The aim was to compare the effect of different mixing ratios on the microleakage of RMGI. Materials &Methods: In this in vitro study, 60 Class V cavities (3×2×1.5 mm) with the gingival margin of 1 mm apical to the cement-enamel junction were prepared on the buccal and lingual surfaces of 30 sound premolars. The teeth were randomly divided into 6 groups. Group 1: The manufacturer’s recommended ratio, without conditioning; Group2: The manufacturer’s recommended ratio with conditioning; Group 3: 20% lower than the manufacturer’s ratio without conditioning; Group4: 20% lower than the manufacturer’s ratio with conditioning; Group 5: 20% higher than the manufacturer’s ratio without conditioning; Group6: 20% higher than the manufacturer’s ratio with conditioning. After thermocycling, the microleakage was evaluated using silver nitrate staining. The teeth were cut into two mesial and distal halves, and the microleakage at occlusal and gingival margins was recorded based on a 0‒3 scoring system under a stereomicroscope. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests with significance level at P<0.05. Results: The maximum microleakage at gingival margins was recorded for group 4, which was significantly higher than that of group 2 and 6 (P=0.043 and P=0.043, respectively). No significant differences were observed in the microleakage between occlusal and gingival margins. Conclusion: A 20% reduction in P/L ratio of RMGI increases the gingival microleakage when surface conditioning was applied

Gingival microleakage in class II composite restorations using different flowable composites as liner: an in vitro evaluation

Introduction: One of the main disadvantages of composites is marginal microleakage; using flowable composites as a liner beneath composite restorations has been recommended to reduce microleakage. The aim of this study was to assess the microleakage of class II restorations with different flowable composites liners. Materials &Methods: 45 extracted premolars teeth with class II cavity preparation (90 cavities) were divided into five groups and filled as follows: 1.control group: hybrid composite (Z250) 2. Z250+surefil SDR flow 3.Z250+filtek supreme xt flow composite 4.Z250+Grandio flow 5.Z250+Tetric flow. Mesial and distal cavities were filled using snowplow and layering technique, respectively. After that, the samples were immersed in 0.5% fuchsin solution and sectioned. Gingival microleakage was then graded. Data were analyzed using Kruskal Wallis and Mann Whitney U test. Results: There was no significant difference between the snowplow and layering methods. Microleakage of Tetric flow and Grandio flow liners was significantly higher than the control group. Other flowable composites showed no significant difference in comparison with the control group. Conclusion: In the present study, the results indicated that the flowable composites were not effective on reducing gingival microleakage

Effect of different curing modes on the Vickers hardness number and curing depth of bulk fill composites

Introduction: The purpose of this study was to compare the Vickers hardness number (VHN) and depth of cure of two types of bulk fill composites in high, low and soft light curing modes. Materials & Methods: In this experimental study, 60 cylindrical samples were fabricated from two types of bulk fill composites (Tetric N-Ceram and X-tra fil) in a Teflon mold with one semi-circular notch. Then, the samples were randomly divided into the following three subgroups based on the curing modes (high, low and soft) and were light-cured. The samples were removed from the molds, and their VHN and depth of cure were measured. Data were analyzed using One-way ANOVA and Tukey’s post hoc test at the significance level of P<0.05. Results: The mean VHN of the X-tra fil composite was significantly higher than that of Tetric N-Ceram composite (P<0.001). The depth of cure of X-tra fil composite was also significantly higher than that of Tetric N-Ceram composite in high and soft curing modes (P<0.001). Conclusion: According to the current results, X-tra fil composite is a convenient material for the restoration of deep cavity in posterior teeth compared with Tetric N-Ceram

Effect of three veneering techniques on fracture resistance and marginal adaptation of zirconia-based crowns

Introduction: The aim of this study was to evaluate the fracture resistance (FR) of zirconia-based crowns veneered with different methods and to assess marginal gap before and after veneering. Materials & Methods: Thirty zirconia copings fabricated by Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) were divided into three groups. In the porcelain layering (PL) group, the copings were manually veneered with VM9 feldspathic porcelain. In the indirect composite (IC) group, the Gradia indirect composite was veneered on zirconia copings, and for the CAD-on (CO) group, the CAD/CAM-fabricated Vita Mark II veneer was cemented onto the copings. For each sample, the marginal gap values at four points (buccal, lingual, mesial and distal) were measured using stereomicroscope and computer software (Motic Images plus 2.0 ML) before and after veneering process. All crowns were cemented on their dies with resin cement and then were loaded by a universal testing machine for failure. Data were analyzed using one-way ANOVA and post-hoc Tukey tests at significant level of 0.05. Results: Mean FR was statistically higher in PL group (3005 N) than IC (2026 N) and CO (1605 N) groups (P=0.000). Before and after veneering, mean marginal gap was 43.42μm and 48.47μm for PL group, 44.69μm and 51.06μm for IC group as well as 53.03μm and 56.08μm for CO group, respectively. Marginal gap had no significant difference in study groups before and after veneering (P=0.56 and 0.18, respectively). The lowest change in marginal gap was observed in CO group. Conclusion: The PL technique might increase the failure resistance of Zirconia-based crowns compared to IC and CO techniques. The marginal gap rate following veneering in all three techniques was within acceptable clinical limits

Effect of Energy Drinks on Discoloration of Silorane- and Dimethacrylate-Based Composite Resins

Objectives: This study aimed to assess the effects of two energy drinks on color change (∆E) of two methacrylate-based and a silorane-based composite resin after one week and one month. Materials and Methods: Thirty cubic samples were fabricated from Filtek P90, Filtek Z250 and Filtek Z350XT composite resins. All the specimens were stored in distilled water at 37°C for 24 hours. Baseline color values (L*a*b*) of each specimen were measured using a spectrophotometer according to the CIEL*a*b* color system. Ten randomly selected specimens from each composite were then immersed in the two energy drinks (Hype, Red Bull) and artificial saliva (control) for one week and one month. Color was re-assessed after each storage period and ∆E values were calculated. The data were analyzed using the Kruskal Wallis and Mann–Whitney U tests. Results: Filtek Z250 composite showed the highest ∆E irrespective of the solutions at both time points. After seven days and one month, the lowest ∆E values were observed in Filtek Z350XT and Filtek P90 composites immersed in artificial saliva, respectively. The ∆E values of Filtek Z250 and Z350XT composites induced by Red Bull and Hype energy drinks were not significantly different. Discoloration of Filtek P90 was higher in Red Bull energy drink at both time points. Conclusions: Prolonged immersion time in all three solutions increased ∆E values of all composites. However, the ∆E values were within the clinically acceptable range (<3.3) at both time points.

Effect of different surface treatments on the shear bond strength of nanofilled composite repairs

Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS) of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-μm aluminum oxide particles (group 2); irradiation with Er:YAG laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). Another group of Filtek Z350XT composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05). Results. One-way ANOVA indicated significant differences between the groups (P < 0.05). SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used

Effects of surface treatments of conventional glass-ionomer on shear bond strength to giomer

Background : An appropriate bond between glass-ionomer and the superficial resin materials is very important for the success of sandwich technique. The aim of the present in vitro study was to evaluate the effect of three surface treatments of conventional glass-ionomer on its shear bond strength to giomer. Materials and Methods: Sixty cylindrical specimens of a conventional glass-ionomer (GC Fuji II) were prepared and randomly divided into three groups (n = 20). The specimens in groups 1 and 2 were treated with total-etch adhesive resin (Single Bond) along with acid etching, and self-etch adhesive resin (FL-Bond II) on the set glass-ionomer, respectively. Specimens in group 3 were treated with self-etch adhesive resin (FL-Bond II) before initial setting of the glass-ionomer was complete. Then a giomer restorative (Beautifil II) was added to the specimens. Subsequent to thermocycling, the specimens were subjected to shear bond strength test. Failure modes were evaluated under a stereomicroscope. Data were analyzed by one-way analysis of variance and a post hoc Tukey test at a significance level of P < 0.05. Results: There were statistically significant differences in bond strengths between the groups (P < 0.0005). Differences in bond strengths between group 2 and other groups were significant (P < 0.0005) while the differences between groups 1 and 3 were not significant. Failures were predominantly of the cohesive type in all the groups. Conclusion: Based on the results of this study, the use of self-etch adhesive resin (FL-Bond II) on the set glass-ionomer yielded the highest bond strength in the glass-ionomer/giomer sandwich technique