Effect of Extent of White Spot Lesions on the Esthetic Outcome after Treatment by the Resin Infiltration Technique: A Clinical Trial.

Objectives: This study aimed to assess the effect of extent of white spot lesions (WSLs) on the esthetic outcome (masking effect and durability) for 6 months after treatment by the resin infiltration technique. Materials and Methods: In this clinical trial, 79 teeth with WSLs in 18 patients were selected. The lesions were assigned to localized and generalized groups, and were all treated by resin infiltration. The color of WSLs was assessed at baseline, immediately after treatment, and 1, 3, and 6 months after treatment by using Easy Shade spectrophotometer and taking standard digital photographs. The surface area of WSLs was calculated on the photographs using MIP4Student software. Repeated Measures ANOVA was used to compare color change (∆E), and the Pearson's correlation test was applied to analyze the association between the extent of lesions and ∆E (alpha=0.05). Results: A significant difference was found between the two groups in ∆E at different time points (P<0.05). Also, in both localized and generalized lesions, the pretreatment ∆E was significantly different from the ∆E values at different time points after treatment (P<0.001). However, the post-treatment ∆E values were not significantly different (P>0.05). The Pearson test showed an inverse correlation between the extent of lesions and ∆E (P<0.05). Conclusion: The resin infiltration technique is successful in masking the WSLs, with a durability of at least 6 months. Color correction by this technique is more favorable in localized lesions.

Effect of preheating nano-hybrid and bulk-fill composites with warm airstream on their microtensile bond strength to dentin.

Aims: This study assessed the effect of preheating nano-hybrid and bulk-fill composites with warm airstream on their microtensile bond strength (MTBS) to dentin. Materials and Methods: In this in vitro study, dentin was exposed in 42 extracted premolars that were assigned to two groups (n = 21) for bonding to EverX Posterior bulk-fill and Grandio nano-hybrid posterior composite. Each group was subdivided into three subgroups for preheating of composite to 50°C by a commercial composite warmer (Subgroup 1), a warm airstream by a hair dryer for 10 s (Subgroup 2), and no heating (room temperature; Subgroup 3). Composite cylinders with a 4-mm height were bonded to the tooth surface with a 5th-generation bonding agent using the incremental technique and cured (each increment for 30 s). The MTBS to dentin was measured, and the bonding interface was evaluated under a stereomicroscope and a scanning electron microscope (SEM). Data were analyzed using one-way and two-way ANOVA, Tukey's test, and independent t-test (α =0.05). Results: In both composite groups, the mean MTBS of the warm airstream subgroup was significantly higher than that of warmer (P < 0.001) and control (P < 0.001) subgroups. The mean MTBS of the warmer subgroup was significantly lower than that of control subgroup (P = 0.01). The MTBS of the EverX composite was significantly higher than that of the Grandio composite only in the warmer group (P < 0.05). Adhesive failure occurred more frequently in all groups with the highest frequency in airstream subgroup of both composite types. Conclusion: Preheating with a warm airstream significantly increased the MTBS of both composite types to dentin.

The effect of ethanol wet bonding technique on postoperative hypersensitivity of Class II composite restorations: A randomized trial.

BACKGROUND: To evaluate the effect of Ethanol Wet Bonding Technique (EWBT) on postoperative hypersensitivity (POH) of composite restorations in premolar teeth. MATERIALS AND METHODS: In this randomized trial, 24 patients with at least three proximal carious lesions with similar axial depth and position of gingival floor in their premolars were enrolled. Following cavity preparation, the teeth were randomly assigned to one of three groups: (1) Class II resin-based composite (RBC) restoration using an etch-and-rinse adhesive + wet bonding technique (Control); (2) RBC restoration using EWBT + hydrophobic adhesive; and (3) RBC restoration using EWBT + hydrophilic adhesive. Tooth hypersensitivity was evaluated before and 1, 3, 7, 14 and 30 days after treatment according to the Visual Analog Scale. Data were analyzed statistically with Kruskal-Wallis and Friedman tests (P = 0.05). RESULTS: All teeth showed similar levels of hypersensitivity after treatment (both P > 0.05). Furthermore, there was no difference between POH levels of the test and control groups at any control period (P < 0.05). Friedman test indicated that the POH significantly reduced within time in all groups (P < 0.05). CONCLUSION: Application of ethanol-wet bonding technique, either with hydrophobic or hydrophilic adhesives did not affect the POH of Class II composite restorations in premolars.

Antimicrobial Activity of Colloidal Selenium Nanoparticles in Chitosan Solution against Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans

ABSTRACT Objective: To investigate the antimicrobial activity of colloidal selenium nanoparticles in chitosan solution (Cts-Se-NPs) against Streptococcus mutans, Lactobacillus acidophilus, and Candida albicans. Material and Methods: Cts-Se-NPs solution was prepared using a simple chemical reduction method. The MIC and MBC against S. mutans, L. acidophilus, and C. albicans were determined using the broth dilution assay. Results: The Cts-Se-NPs had remarkable antimicrobial activity against S. mutans, L. acidophilus, and C. albicans. The MIC values of the Cts-Se-NPs were lowest for S. mutans (0.068 mg/ml) compared to L. acidophilus (0.137 mg/ml), and C. albicans (0.274 mg/ml). The MBC values of the Cts-Se-NPs against the microorganisms after one, two, six, and 24 hours indicated that the concentration of 0.274 mg/ml of Cts-Se-NPs completely killed S. mutans, L. acidophilus, and C. albicans after one, two, and six hours, respectively. At the concentration of 0.137 mg/ml, S. mutans and L. acidophilus were killed after six and 24 hours, respectively. Conclusion: These findings encourage the potential use of Cts-Se-NPs in dentistry, while further clinical research is required in this area.

The Effect of Fractional CO2 Laser Irradiation on Shear Bond Strength of Resin Cement to Feldspathic Porcelain.

Introduction: This study investigated the effect of fractional CO2 laser on shear bond strength (SBS) of resin cement to feldspathic porcelain. Methods: Sixty blocks of unglazed feldspathic porcelain were randomly divided into 5 groups of 12 by treatment. Group 1 and 2 underwent etching with 9.6% hydrofluoric acid (HF) and air abrasion with alumina particles, respectively. In groups 3 and 4, a fractional CO2 laser was applied for 10 seconds using 20 W/10 mJ (group 3) or 15 W/20 mJ (group 4). The specimens in group 5 were first treated by fractional CO2 laser (15 W/20 mJ) and then etched by HF acid. After silane application, a resin cement (Clearfil SA) was poured into plastic molds over the porcelain surface and light cured. SBS was assessed by a universal testing machine and the type of bond failure was determined. Results: Analysis of variance (ANOVA) indicated a significant difference in SBS among the study groups (P<0.001). Pairwise comparison demonstrated that the application of fractional CO2 laser followed by HF acid yielded SBS that was significantly greater than that of the other groups (P<0.05). The SBS of both laser groups (groups 3 and 4) were comparable to each other and significantly lower than the other groups (P<0.05). No significant difference was found in the distribution of failure modes among the groups (P=0.522) Conclusion: The application of fractional CO2 laser followed by HF acid treatment can improve SBS of resin cement to feldspathic porcelain and could be recommended when demanding extra retention.

Microtensile bond strength of resin cement primer containing nanoparticles of silver (NAg) and amorphous calcium phosphate (NACP) to human dentin.

PURPOSE: The purpose of the current study was to evaluate the effect of incorporating nanoparticles of silver (NAg) and amorphous calcium phosphate (NACP) into a self-etching primer of a resin cement on the microtensile bond strength of dentin, regarding the proven antibacterial feature of NAg and remineralizing effect of NACP. MATERIALS AND METHODS: Flat, mid-coronal dentin from 20 intact extracted human third molars were prepared for cementation using Panavia F2.0 cement. The teeth were randomly divided into the four test groups (n=5) according to the experimental cement primer composition: cement primer without change (control group), primer with 1% (wt) of NACP, primer with 1% (wt) of physical mixture of NACP+Nag, and primer with 1% (wt) of chemical mixture of NACP+Nag. The resin cement was used according to the manufacturer's instructions. After storage in distilled water at 37℃ for 24 h, the bonded samples were sectioned longitudinally to produce 1.0 × 1.0 mm beams for micro-tensile bond strength testing in a universal testing machine. Failure modes at the dentin-resin interface were observed using a stereomicroscope. The data were analyzed by one-way ANOVA and Tukey's post-hoc tests and the level of significance was set at 0.05. RESULTS: The lowest mean microtensile bond strength was obtained for the NACP group. Tukey's test showed that the bond strength of the control group was significantly higher than those of the other experimental groups, except for group 4 (chemical mixture of NACP and NAg; P=.67). CONCLUSION: Novel chemical incorporation of NAg-NACP into the self-etching primer of resin cement does not compromise the dentin bond strength.

Effect of the Time of Salivary Contamination during Light Curing on Degree of Conversion and Microhardness of a Restorative Composite Resin.

Saliva contamination is a major clinical problem in restorative procedures. The purpose of this study was to evaluate the effect of the time of salivary contamination during light curing on the degree of conversion and the microhardness of a restorative composite resin. Eight groups of 10 samples for measuring the microhardness and eight groups of 5 samples for evaluating the degree of conversion were prepared. The samples of each group were contaminated with human saliva at a certain time. The first group (T0) was contaminated before light curing. The specimens in groups T2-T30 were contaminated at 2, 5, 10, 15, 20 and 30 s after the start of light curing, respectively. The samples of group T40 were contaminated after light curing. The degree of conversion and the microhardness of the specimens were measured by Fourier transform infrared (FTIR) spectroscopy and Vickers hardness testing techniques, respectively. The results of this study revealed that there were no significant differences between the groups in terms of the degree of conversion of the composite resin. Consistent with the findings for the degree of conversion, significant differences in the microhardness between the groups were not found. In conclusion, from a clinical point of view, the results of our study showed that the time of salivary contamination (before, during or after light curing of composite resin) has no significant effect on the polymerization (degree of conversion) and one of the important mechanical properties of dental composite resins (microhardness).

Effect of Non-Vital Bleaching on the Durability of Resin⁻Dentin Bond with an Ethanol-Based Etch-And-Rinse Adhesive.

To evaluate the bleaching procedure and application of sodium ascorbate on dentin bond durability, the enamel surface of intact human third molars (n = 18) were removed, and the teeth were randomly divided into two groups for immediate and six-month bond strength evaluation. The specimens were further assigned into three subgroups according to treatment procedure, as follows: subgroup A, no bleaching (positive control) was performed prior to the etch-and-rinse bonding with single bond and subsequent build-up with Z250 composite; subgroup B, the samples were bleached with 20% carbamide peroxide 6 h/day for five consecutive days prior to bonding; and subgroup C, bleaching was performed as in subgroup B, after which 10% sodium ascorbate was applied on dentin surface for 10 min before the bonding procedures. A microtensile bond strength test was performed and the failure modes were evaluated under a stereomicroscope. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey's post-hoc tests with a level of significance of 0.05. Bleaching significantly decreased the immediate and six-month bond strength. The application of sodium ascorbate had no significant effect on the immediate and six-month bond strength of bleached specimens. We conclude that the bleaching procedure may decrease the durability of the resin-dentin bond of the tested etch-and-rinse adhesive.

The effect of surface treatment with a fractional carbon dioxide laser on shear bond strength of resin cement to a lithium disilicate-based ceramic.

BACKGROUND: This study investigated the impact of different surface treatments, including fractional carbon dioxide (CO2) laser on shear bond strength (SBS) of resin cement to lithium disilicate ceramic. MATERIALS AND METHODS: In this in vitro study, 72 blocks of IPS e.max CAD ceramic were randomly divided into six groups in terms of treatment (n = 12). Group 1 underwent etching with 9.6% hydrofluoric (HF) acid, whereas group 2 was subjected to air abrasion with aluminum oxide particles. Groups 3 and 4 were treated with a fractional CO2 laser for 10 s using 10 W/14 mJ (group 3) or 20 W/10 mJ (group 4). In groups 5 and 6, the CO2 laser was applied similar to that in groups 3 and 4, respectively; then, the specimens were etched by HF acid. After silane application, luting cement was bonded to the specimens. The SBS was assessed with a universal testing machine, and the type of bond failure was determined. Data were analyzed by ANOVA, Duncan, and Fisher's exact tests. RESULTS: Surface conditioning with fractional CO2 laser alone resulted in significantly lower SBS than HF acid treatment (P < 0.05). Bond strengths of the specimens treated with a combination of laser irradiation and acid etching were significantly greater than all the other groups (P < 0.05). No significant difference was found in the distribution of failure modes among the groups (P = 0.337). CONCLUSION: The combination of fractional CO2 laser irradiation and HF acid etching could be recommended when extra retention is required for lithium disilicate-based restorations, whereas laser treatment alone cannot produce sufficient SBS.

Synergistic effects of sodium ascorbate and acetone to restore compromised bond strength after enamel bleaching.

AIM: To evaluate the effect of a new experimental solution containing sodium ascorbate (SA) and acetone on reversing compromised bonding to enamel immediately after bleaching. MATERIALS AND METHODS: The buccal surface of intact, extracted human premolars (n = 60) was bleached. The teeth were then randomly assigned to 6 groups according to the type of pretreatment applied prior to adhesive procedures: 10% SA in acetone-water solution applied for 1 and 5 min (groups 1 and 2, respectively); aqueous solution of 10% SA applied for 10 min (group 3); 100% acetone applied for 10 min (group 4); no pretreatment (negative control; group 5). An additional group (positive control; group 6) comprised unbleached teeth (n = 12). Two composite microcylinders were bonded on each specimen for evaluation of microshear bond strength (MBS) and failure modes. Data were analyzed using the one-way ANOVA and Tukey's post-hoc and chi-square tests at P = 0.05. RESULTS: Groups 1 and 2 yielded similar MBS values to groups 4 and 6 (positive control). The mean MBS of groups 3 and 5 (negative control) were similar, and significantly lower than that of the positive control group. CONCLUSION: The application of 10% SA in an acetone-water solution prior to bonding procedures can restore compromised enamel bond strength to its unbleached state within a clinically acceptable time of 1 min.

Surface treatment with a fractional CO2 laser enhances shear bond strength of resin cement to zirconia.

AIMS: The present study investigated the effect of different surface treatments on shear bond strength (SBS) of resin cement to zirconia. MATERIALS AND METHODS: Ninety zirconia blocks were prepared and divided into 6 groups of 15 by treatment. Group 1 served as the control group, whereas groups 2 and 3 were treated with air abrasion and a universal primer (Monobond plus), respectively. The remaining zirconia copings were treated with a fractional CO2 laser for 10 seconds using 10 W/10 mJ (group 4), 10 w/14 mJ (group 5) or 20 W/10 mJ (group 6). A luting cement (Clearfil SA) was bonded to the treated zirconia surfaces and cured for 40 seconds. SBS was measured with a universal testing machine and the type of bond failure was determined. RESULTS: There was a statistically significant difference in SBS among the study groups (p<0.001). The highest SBS values were observed in the groups treated with the fractional CO2 laser at settings of 20 W/10 mJ (28.1 MPa) or 10 W/14 mJ (27.4 MPa), followed by the specimens treated with the universal primer (22.8 MPa). The control specimens exhibited the lowest SBS (9.4 MPa) among the study groups (p<0.05). There was no significant difference in the distribution of failure modes among the groups (p=0.871). CONCLUSIONS: The application of fractional CO2 laser can improve bond strength of resin cement to zirconia ceramic, and thus it could be considered as an appropriate alternative to conventional methods of zirconia surface treatment.

Evaluation of the efficacy of flowable composite as lining material on microleakage of composite resin restorations: A systematic review and meta-analysis.

OBJECTIVE: The efficacy of flowable composite in improving marginal adaptation or reducing microleakage is not fully understood. The purpose of this study was to systematically evaluate existing evidence to verify whether an application of flowable composite as a liner provided less microleakage in Class 2 composite restorations. METHOD AND MATERIALS: PubMed, ISI (Web of Science), and Scopus databases were searched according to the selected keywords, up to 15 Feb 2015, without any restriction on date or language. Full texts of published articles that seemed to meet primary criteria for inclusion in this research were obtained. Data of studies were extracted if they were assessed as high or moderate level of evidence. Due to the variation of methods used in different studies, they were divided into five groups: groups 1 and 2, studies that evaluated the effect of flowable composite as a liner on dentinal or enamel margins and applied flowable composite on all of the cavity wall margins; groups 3 and 4, studies that evaluated the effect of flowable composite as a liner on dentinal and enamel margins and applied flowable composite only on gingival margin; and group 5, clinical studies. RESULTS: The initial search yielded 1,370 publications. After hand searching, six extra studies were included in the review. The abstracts of all were read independently by AB and SG. After methodologic assessment and evaluation of the level of evidence, 18 studies were selected for this study. The results of this study indicate that flowable composite liners have no significant effect on microleakage of composite restorations in all of five groups. CONCLUSION: Application of flowable composite as a liner in composite restorations cannot reduce microleakage or improve clinical performance.

Evaluation of bond strength of orthodontic brackets without enamel etching.

BACKGROUND: To compare the shear bond strength of brackets with and without enamel etching. MATERIAL AND METHODS: In this study, 60 sound premolars were randomly divided into four different groups: 1- TXE group: Enamel etching+Transbond XT adhesive+ Transbond XT composite. 2- TXS group: Transbond plus self-etch adhesive+ Transbond XT composite. 3- PQ1E group: Enamel etching+ PQ1 adhesive+ Transbond XT composite. 4- PQ1 group: PQ1 adhesive+ Transbond XT composite. The shear bond strengths of brackets were evaluated using universal testing machine at cross head speed of 0.5 mm/min. The Adhesive Remnant Index (ARI) was also measured. One-way ANOVA, Tukey's post hoc, Kruskal-wallis and Mann-Witney U test were used for data analysis. RESULTS: There was a significant difference between etched and unetched groups respect to SBS and ARI (p<0.05), however; no significant difference was observed between unetched group and self-etch adhesive group (p>> 0.05). The shear bond strength of PQ1 group was the least but in acceptable range and its ARI was less than other groups. CONCLUSIONS: PQ1 adhesive can be used for bracket bonding without enamel etching with adequate bond strength and minimal ARI. KEY WORDS: Bracket, shear bond strength, filled-adhesive, self-etch adhesive.

Bond strength between composite resin and resin modified glass ionomer using different adhesive systems and curing techniques.

AIM: To evaluate bond strength between RMGI and composite using different adhesive systems and curing techniques. MATERIALS AND METHODS: Sixty prepared samples of RMGI were randomly divided into six groups according to adhesive systems (total-etch, two-step self-etch and all-in-one) and curing techniques (co-curing and pre-curing). In co-curing technique, the adhesive systems were applied on uncured RMGI samples and co-cured together. In the pre-curing technique, before application of adhesive systems, the RMGI samples were cured. Composite layers were applied and shear bond strength was measured. Two samples of each group were evaluated by SEM. Failure mode was determined by streomicroscope. RESULTS: Both curing methods and adhesive systems had significant effect on bond strength (P-value < 0.05). There was an interaction between two factors (P-value <0.05). Both self-etch adhesives had significantly higher shear bond strength than the total-etch adhesive (P-value <0.05). The co-curing technique improved the bond strength in self-etch adhesives, but decreased the bond strength in total-etch adhesive (P-value<0.05). CONCLUSION: The application of self-etch adhesive systems and co-curing technique can improve the bond strength between the RMGI and composite.