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At least 919 records · Page 51Linked to original sources

PubMed2003

In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time.

PURPOSE: This study evaluated the effect of two home bleaching regimens (1 h/day versus 7 h/day for a total of 21 days) on the microhardness of superficial enamel treated with 10% carbamide peroxide gel. MATERIALS AND METHODS: Rectangular enamel specimens (2.5 x 2.5 x 1 mm) were obtained from human third molars and mounted on the palatal aspect of removable orthodontic retainers. Nine enamel specimens were mounted in each of 10 retainers, used by 10 volunteers during the active phase of the study. Modified 0.089 cm thick bleaching trays were fabricated for each participant. Each bleaching tray fit a participant's arch and the retainer containing the enamel specimens. Enamel specimens were treated with a 10% carbamide peroxide bleaching gel (Nite White Excel 2Z, Discus Dental, Culver City, CA, USA) for either 1 h/day (n = 30) or 7 h/day (n = 30), both for 21 days. Three enamel specimens in each retainer were never treated and served as controls. The retainers were worn by the participants whether or not they underwent bleaching. This simulated the natural action of the saliva/oral fluids on the enamel specimens. Enamel specimens were subjected to pre- and post-treatment microhardness measurements. Post-treatment Knoop hardness numbers were compared with baseline values and analyzed statistically. RESULTS: Bleaching treatment resulted in a nonsignificant reduction in microhardness values when compared with values of the control nontreated specimens (1.7% and 2.5% reduction in hardness for 1 h/day and 7 h/day, respectively). There was no difference in microhardness between the different treatment regimens. CONCLUSION: Home bleaching with 10% carbamide peroxide for up to 7 h/day for 21 days does not significantly affect enamel microhardness. CLINICAL SIGNIFICANCE: Bleaching with 10% carbamide peroxide for 1 h/day or 7 h/day for a total of 21 days is safe for human enamel.

Adolescent↗

PubMedDate not supplied

Influence of carbamide peroxide-based bleaching agents on the bond strength of resin-enamel/dentin interfaces.

In this bond strength study, a bleaching agent containing 10% carbamide peroxide was applied over composite-teeth bonded interfaces of two adhesive systems applied to enamel and dentin. Sixteen human third molars were used for bonding procedures. Single Bond (SB) and Clearfil SE Bond (CB) were applied to enamel and dentin according to the manufacturers' instructions. A resin composite cube-like structure was incrementally built on the bonded surfaces. The restored teeth were sectioned into 0.7 mm thick slices that were trimmed at enamel or dentin bonded interfaces to an hourglass shape with a cross-sectional area of approximately 0.5 mm2. Specimens were assigned to 8 groups (n = 10) according to the following factors under study: dental substrate (enamel and dentin); adhesive system (SB and CB) and treatment (10% carbamide peroxide and not bleached/control). The bleaching gel (Opalescence) was applied at the bonded interfaces for 6 hours during 14 days and after daily treatment specimens were stored in artificial saliva. Unbleached specimens were stored in artificial saliva for 14 days. Specimens were tested for tension and the data were analyzed by three-way ANOVA and Tukey's test (p < 0.05). Enamel tensile bond strength of CB was reduced after carbamide peroxide application. The bleaching treatment did not alter dentin bond strength of both adhesives. The results suggest that bleaching significantly affects bond strength of CB to enamel, but no influence on bond strength to dentin was noted for both adhesive systems.

Analysis of Variance↗

PubMed2005

Effect of time interval between bleaching and bonding on tag formation.

The objective of this study was to assess penetration of adhesive material in enamel bleached with 35% hydrogen peroxide using optical polarized light microscopy. Extracted human teeth were randomly assigned to 5 groups, each representing a specific time interval between bleaching and the application of an adhesive material. They were designated as: (TC) the control group-restorations in unbleached teeth; (T0) comprising restorations carried out immediately after bleaching; (T7) comprising restorations 7 days after bleaching; (T14) comprising restorations 14 days after bleaching; and (T21) comprising restorations 21 days after bleaching. Length of resin tags was measured with an Axiophot photomicroscope at a x 400 magnification, and the results subjected to an ANOVA for a comparison between groups, with a p value of < 0.05. Differences between the groups were verified using a Tukey test at a confidence level of 5%. The specimens in the control group (TC) and experimental groups T7, T14 and T21 showed better penetration of adhesive material into enamel in comparison with experimental group T0. This suggests that a gap of at least 7 days should be left between bleaching enamel with 35% hydrogen peroxide and placing adhesive bonding agents and undertaking resin composite restoration work.

Acrylic Resins↗

PubMedDate not supplied

Randomized clinical trial on the efficacy of a new bleaching lacquer for self-application.

BACKGROUND: This study evaluated the clinical efficacy and duration of effectiveness of a new bleaching lacquer for self-application without the use of mouth guards. It compared two different application times. METHODS: Forty-six adult subjects who requested bleaching treatment were selected to participate in this randomized, single-blind (examiner-blinded), single center, two-group trial. The subjects were randomly divided into two groups (n=23 each), each being instructed to bleach (8% carbamide peroxide) their six maxillary anterior teeth for two weeks. Daily contact time in Group 1 was 20 minutes once a day and, in Group 2, the time was 20 minutes twice a day. Efficacy was measured subjectively using the Chromascop Complete shade scores obtained at baseline and after one, two and three weeks, as well as after one, three, six and nine months. RESULTS: After two weeks of treatment, the teeth in the Group 1 subjects exhibited a 2.4 +/- 0.2 mean shade scores improvement compared to baseline (p < 0.001; t-test for paired samples), and the subjects' teeth in Group 2 exhibited a 3.5 +/- 0.1 mean shade scores improvement (p < 0.001). However, the difference between both groups was not statistically significant (p > 0.05). The observed effects were stable for six months. CONCLUSIONS: It can be concluded that the new bleaching lacquer is efficacious; however, a double application does not seem to be obligatory.

Adult↗

PubMed2003

Impact of Crest Night Effects bleaching gel on dental enamel, dentin and key restorative materials. In vitro studies.

PURPOSE: To examine the effects of a paint-on 19% sodium percarbonate 'overnight' bleaching gel on the structure and integrity of enamel, dentin and some common restorative materials, with a laboratory cycling model. METHODS: Enamel, root dentin and restorative materials (glass-ionomer, composite and amalgam) were prepared in methacrylate molds with surface polishing. A treatment regimen was carried out including diurnal incubation in pooled human saliva and including twice daily toothbrushing with standard fluoridated dentifrice. Test samples were treated daily with Crest Night Effects bleaching gel, which included drying of surfaces, painting of percarbonate bleaching gel, and then incubation throughout the day (8 hours) to simulate overnight wear. Treatments were carried out over 14 days, to simulate clinical exposure periods. Control and test specimens were evaluated for surface and subsurface structure and morphological integrity utilizing surface microhardness, surface profilometry, and confocal laser scanning microscopy. RESULTS: Percarbonate bleaching film treatments had no effects on enamel or root dentin surface microhardness, or on subsurface ultrastructural integrity of enamel and coronal dentin. Surface profilometry confirmed retention of small amounts of residual silicone polymers, which contributed to CLSM air objective appearance and surface roughness measures. Restoratives were generally passive to bleaching gel treatments, though composite showed a tendency to attract retained residual silicone film.

Bicuspid↗

PubMed2004

In-use comparative kinetics of professional whitening strips: peroxide recovery from strips, teeth, gingiva, and saliva.

A clinical trial was conducted to evaluate the peroxide degradation and dilution kinetics of Crest Whitestrips Supreme, a whitening strip carrying a low, fixed amount of a 14% hydrogen-peroxide bleaching gel. Crest Professional Whitestrips--a 6.5% hydrogen-peroxide strip with a well-established clinical efficacy and safety profile--served as the positive experimental control. A total of 17 healthy adults were enrolled in the crossover study (subjects used both products, and each product was used 4 times by each person). Test strips were applied to the maxillary arch, after which hydrogen-peroxide concentration was measured on the strip, teeth, gingiva, and in saliva over a 60-minute period using standard analytical methods. Treatments were compared at individual time points, and overall using the area-under-the-curve (AUC) calculation of total hydrogen-peroxide exposure (concentration over time). For the higher-concentration strip, hydrogen-peroxide concentration from the strip and teeth samples dropped initially at the 5-minute sampling point, then slowly declined over time. At 30 minutes--the nominal treatment time for these 14% hydrogen-peroxide strips--the median hydrogen-peroxide concentration was 6.2% on the strips and 4.4% on the teeth. In contrast, the gingival and salivary hydrogen-peroxide concentrations were already low and/or below the level of detection by 5 minutes, and remained low throughout the sampling period. Treatments generally differed (P < .001) with respect to hydrogen-peroxide concentrations on the strip and teeth, but not on the gingiva or in the saliva. AUC cumulative measurements through 60 minutes demonstrated 77% higher hydrogen-peroxide levels on teeth for the 14% hydrogen-peroxide strip compared to the 6.5% hydrogen-peroxide strip. This research demonstrates the feasibility of vital bleaching with an exceedingly thin layer of 14% hydrogen-peroxide gel, with little gingival or salivary hydrogen-peroxide exposure.

Adult↗

PubMed1997

A review of esthetic alternatives for the restoration of anterior teeth.

PURPOSE: This article describes different options for the esthetic treatment of anterior teeth, starting with minimally invasive procedures, such as facial surface bleaching and bonding with composites. METHODS: The importance of metal ceramic restorations, porcelain shoulder techniques, and metal free ceramics are also emphasized. The options are carefully demonstrated to identify advantages and limitations of each technique.

Composite Resins↗

PubMed2003

Can previously bleached teeth be bonded safely?

The purpose of our study was to determine the effect of a 35% hydrogen peroxide bleaching agent on the shear bond strength of metallic orthodontic brackets. Sixty premolars were randomly divided into 3 groups of 20 each. Teeth in group A were etched with 37% phosphoric acid before bonding metallic premolar brackets. Teeth in the other 2 groups were bleached with a 35% hydrogen peroxide in-office bleaching agent according to the manufacturer's recommendations. Twenty bleached teeth (group B) were bonded immediately, and the other 20 (group C) were stored in artificial saliva for 30 days before bonding. Shear bond strength of these brackets was measured on a universal testing machine and recorded in MPa. Adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance (ANOVA) and chi-square tests. The shear bond strength values of groups A, B, and C were 12.9 +/- 3.4, 12.0 +/- 4.6, and 14.8 +/- 4.0 MPa, respectively. Results of ANOVA showed no statistically significant differences in shear bond strengths between groups (P >.05). ARI scores were significantly different in all groups. The unbleached group's failures were primarily at the bracket/adhesive interface, whereas the bleached groups either showed cohesive failures within the adhesive or failed at the adhesive/enamel interface. The results of this study suggest that office bleaching with hydrogen peroxide does not adversely affect the bond strengths of brackets bonded immediately after bleaching or 30 days after bleaching, even though bleaching can result in differences in the failure site.

Acid Etching, Dental↗

PubMed2005

Effects of a 10% carbamide peroxide bleaching agent on roughness and microhardness of packable composite resins.

PURPOSE: Bleaching agents containing 10% carbamide peroxide may be applied to the surface of preexisting packable resin-based composite restorations. The aim of this in vitro study was to evaluate the effect of a 10% carbamide peroxide bleaching agent (Review, SS White, Rio de Janeiro, Brazil) on surface roughness and microhardness of three packable resin-based composites (Fill Magic condensable, Vigodent, Rio de Janeiro, Brazil; Alert, Jeneric Pentron, Wallingford, CT, USA; Definite, Degussa, Hanau, Germany). MATERIALS AND METHODS: For the control (no bleaching) and experimental (bleaching treatment) groups, 12 specimens of each material were prepared in cylindrical acrylic molds. The experimental specimens were exposed to the bleaching agent for 6 hours a day for 3 weeks. During the remaining time (18 h), they were stored in artificial saliva. The control specimens remained immersed in artificial saliva throughout the experiment. Surface roughness and microhardness measurements were performed on the top surface of each specimen. RESULTS: Analysis of variance and the Tukey test showed no significant differences in roughness among the packable composites evaluated (p = .18), but those submitted to the treatment with a 10% carbamide peroxide bleaching agent displayed significantly higher mean surface roughness than did the corresponding control group for each material. For the microhardness tests, there were significant differences among materials (p < .0001). Alert showed the highest microhardness values followed by Definite and Fill Magic condensable. CONCLUSIONS: Ten percent carbamide peroxide bleaching agents may change the surface roughness of packable composites, but they do not alter their microhardness. CLINICAL SIGNIFICANCE: Under the conditions of this study, a 3-week bleaching regimen with 10% carbamide peroxide agents affected the roughness of packable composites. Nevertheless, the surface microhardness was not affected, although there were differences among the materials evaluated inherent to their composition.

Carbamide Peroxide↗

PubMed2005

Effect on enamel microhardness of two consumer-available bleaching solutions when compared with a dentist-prescribed, home-applied bleaching solution and a control.

BACKGROUND: There exists limited data in the literature regarding the efficacy and safety of consumer-available, paint-on bleaching solutions. PURPOSE: The purpose of this in vitro study was to evaluate the effect of two consumer-available, paint-on bleaching products on enamel microhardness against a control and a dentist-prescribed, home-applied (DPHA) bleaching product. MATERIALS AND METHODS: Eighty enamel slabs were obtained from extracted human teeth and randomly divided into four treatment groups: (1) control; (2) Opalescence (Ultradent Products, Inc., South Jordan, UT, USA); (3) Crest Night Effects (Procter & Gamble, Cincinnati, OH, USA); and (4) Colgate Simply White Night (Colgate-Palmolive Co., Piscataway, NJ, USA). Opalescence is a carbamide peroxide DPHA product, whereas Crest Night Effects and Colgate Simply White Night are consumer-available products. The specimens in groups 2 to 4 underwent 2 weeks of treatment for 8 h/d. Specimens were maintained in artificial saliva at 37 degrees C between treatments. Subsequently, one-half of the specimens in groups 2 to 4 (n=10) underwent an additional seven treatments for 8 h/d, while the other half were stored in artificial saliva, receiving no further treatment. Microhardness was measured as Knoop hardness numbers (KHNs) at baseline and after 1, 7, 14, and 21 treatment days. The results were analyzed for statistical significance both intra- and intergroups using analysis of variance (p=.05). RESULTS: A statistically significant reduction in mean KHN was observed compared with baseline at 1, 7, 14, and 21 treatment days for group 4 and at 7 treatment days for group 3. When compared with the control or DPHA product, group 4 was the only treatment that resulted in significantly lower mean KHNs at 7, 14, and 21 treatment days. CONCLUSION: When evaluating enamel microhardness, consumer available, paint-on bleaching solutions may adversely affect enamel microhardness compared to a control and 10% carbamide peroxide DPHA bleaching solution. CLINICAL SIGNIFICANCE: With numerous consumer-available bleaching products on the market, it is crucial to be judicious in their selection and use. The results of this in vitro study showed that the consumer-available, paint-on bleaching solutions adversely affected enamel microhardness at some time during the study. Consumers should be made aware of this effect on enamel.

Carbamide Peroxide↗

PubMed2002

Effects of two 10% peroxide carbamide bleaching agents on dentin microhardness at different time intervals.

OBJECTIVE: The purpose of this in vitro study was to evaluate the microhardness of human dentin exposed to two 10% carbamide peroxide agents at different bleaching times. METHOD AND MATERIALS: Opalescence 10% and Rembrandt 10% were tested. A placebo agent was used as a control group. The bleaching and placebo agents were applied to the surface of human dentin fragments for 8 hours and then stored in individual receptacles with artificial saliva for the remaining 16 hours each day. Microhardness testing was performed at baseline, after 8 hours, 7, 14, 21, 28, 35, and 42 days of treatment, and 7 and 14 days posttreatment. RESULTS: Analysis of Variance and the Tukey test revealed significant differences in microhardness values for dentin treated with the agents within each time interval. There was a decrease in the microhardness values of dentin for both bleaching agents after 8 hours of treatment. Fourteen days after the completion of treatment, the microhardness values for dentinal surfaces treated with either Opalescence or Rembrandt reached the baseline values; the dentinal surfaces treated with a placebo exhibited an increase in microhardness values posttreatment. CONCLUSION: Ten percent carbamide peroxide bleaching agents decreased dentinal microhardness over time, but after 14 days in artificial saliva storage at the completion of treatment, the baseline microhardness values were recovered.

Analysis of Variance↗

PubMed2006

Effect of an antioxidizing agent on the shear bond strength of brackets bonded to bleached human enamel.

INTRODUCTION: The purpose of this study was to investigate the effect of antioxidant treatment and delayed bonding on the shear bond strength of metal brackets bonded with composite resin to human enamel after bleaching with carbamide peroxide (CP). METHODS: Eighty recently extracted premolars were divided into an experimental group (n = 60), which was bleached with 10% CP, and a control group (n = 20), which was not bleached. The experimental group was further divided into 3 groups. Specimens in group 1 (n = 20) were bonded immediately after bleaching; specimens in group 2 (n = 20) were bleached, then treated with 10% sodium ascorbate, an antioxidant agent, and then bonded; group 3 specimens (n = 20) were bleached, then immersed in artificial saliva and held for 1 week before bonding. The specimens were debonded, and the enamel surfaces and bracket bases were examined with a stereomicroscope. The adhesive remnant index was used to assess the amount of resin left on the enamel surfaces after debonding. The shear bond strength data were subjected to 1-way analysis of variance. Multiple comparisons were performed with the Bonferroni test. The level of significance was established at P < .05 for all statistical tests. RESULTS: Shear bond strength of brackets bonded immediately after bleaching with 10% CP was significantly lower than that of brackets bonded to unbleached enamel (P < .05). No statistically significant differences in shear bond strength were noted when the antioxidant-treated and delayed bonding groups were compared with the control group (P > .05). CONCLUSIONS: Bleaching with 10% CP immediately before bonding reduces the bond strength of composite resin to enamel. Treating the bleached enamel surface with 10% sodium ascorbate or waiting 1 week reverses the reduction.

Adhesives↗

PubMed2006

Study of DNA damage induced by dental bleaching agents in vitro.

Dental bleaching is a simple and conservative procedure for aesthetic restoration of vital and non-vital discolored teeth. Nevertheless, a number of studies have demonstrated the risk of tissue damage from the contact of these agents with the oral mucosa. In the current study, the genotoxic potential associated with exposure to dental bleaching agents was assessed by the single cell gel (comet) assay in vitro. Chinese hamster ovary (CHO) cells in vitro were exposed to six commercial dental bleaching agents (Clarigel Gold - Dentsply; Whitespeed - Discus Dental; Nite White - Discus Dental; Magic Bleaching - Vigodent; Whiteness HP - FGM and Lase Peroxide - DMC). The results pointed out that all dental bleaching agents tested contributed to DNA damage as depicted by the mean tail moment, being the strongest effect observed with the highest dose of hydrogen peroxide (Whiteness HP and Lase Peroxide, at a 35% concentration). On the other hand, Magic Bleaching (Vigodent) induced the lowest level of DNA breakage. Negative and positive controls displayed absence and presence of DNA-damaging, respectively. Taken together, these results suggest that dental bleaching agents may be a factor that increases the level of DNA damage. A higher concentration of hydrogen peroxide produced higher noxious activities in the genome as detected by single cell gel (comet) assay.

Animals↗

PubMed2004

Efficacy of different whitening modalities on bovine enamel and dentin.

Previous studies have shown that bleaching treatment may be efficient in both enamel and dentin, but it is still unknown how much the subsurface dentin contributes to the color change of teeth. This in vitro study evaluated the whitening effect of different external bleaching agents on enamel-dentin slabs and subsurface dentin. Ninety bovine teeth were distributed among six groups (A, Opalescence 10%; B, Opalescence PF 15%; C, Opalescence Quick; D, Opalescence Extra Boost; E, Rapid White; F, Whitestrips). Two enamel-dentin specimens were prepared from the labial surface of each teeth. In one of the specimens enamel was removed, resulting in a dentin (CD) disc of 1 mm high. The labial and the pulpal sides of the second specimen were ground until the remaining enamel and dentin layers of the enamel-dentin sample (ED) were 1 mm each. Whitening treatment of the ED specimens was performed according to manufacturers' instructions. Pre- and posttreatment Lab values of ED samples were analyzed using CIE-Lab. Baseline Lab values of dentin were analyzed by evaluation of the CD specimen. Finally, enamel of the ED specimens was removed and color change of the exposed dentin (D) was recorded. For all treatment agents significant color changes (DeltaE) were observed for enamel-dentin samples and subsurface dentin specimens compared to controls. In groups A-D DeltaE was significantly higher in dentin than enamel-dentin. Furthermore, L and b values of bleached enamel-dentin and subsurface dentin samples differed significantly from baseline. Treatment with the tested external whitening bleaching agents resulted in color change of both enamel-dentin and subsurface dentin samples. The results indicate that color change of treated teeth might be highly influenced by color change of the subsurface dentin.

Animals↗

PubMed2004

Effect of 10% sodium ascorbate on the shear bond strength of composite resin to bleached bovine enamel.

The purpose of this study was to comparatively investigate the effect of antioxidant treatment and delayed bonding after bleaching with three different concentrations of carbamide peroxide (CP) on the shear bond strength of composite resin to enamel. One hundred flat buccal enamel surfaces obtained from bovine incisors were divided into three bleaching groups of 10, 16 and 22% CP (n = 30) and a control group. Each bleaching group was then divided into three subgroups (n = 10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with antioxidant agent, 10% sodium ascorbate, while Group 3 specimens were immersed in artificial saliva for 1 week after bleaching. Specimens in the control group were not bleached. After the specimens were bonded with Clearfil SE Bond and Clearfil AP-X, they were thermocycled and tested in shear until failure. Fracture analysis of the bonded enamel surface was performed using scanning electron microscope. The shear bond strength data was subjected to one-way analysis of variance followed by Duncan's multiple range test at a significance level of P < 0.05. Shear bond strength of composite resin to enamel that was bonded immediately after bleaching with 10, 16 and 22% CP was significantly lower than that of unbleached enamel (P < 0.05). For all three bleaching groups, when the antioxidant-treated and delayed bonding (1 week) subgroups were compared with the control group, no statistically significant differences in shear bond strength were noted (P < 0.05).

Animals↗

PubMed2000

Protective effect of Copalite surface coating on mercury release from dental amalgam following treatment with carbamide peroxide.

The effect of Copalite coating on mercury release from dental amalgam following treatment with 10%, 20%, 30% and 40% carbamide peroxide was assessed in vitro, using a cold-vapour atomic absorption Mercury Analyzer System. Eighty samples of dental amalgam were automatically mixed in a dental amalgamator and condensed into silicon embedding molds. Forty amalgam samples were coated with three uniform layers of Copalite intermediary varnish and the other 40 samples were left uncoated. The coated and non-coated amalgam samples were exposed for 24 h to 10%, 20%, 30% or 40% carbamide peroxide preparations and compared with samples exposed to phosphate buffer. In the non-coated samples a significant increase of mercury concentration in solution was found following exposure to all carbamide peroxide preparations tested. Mercury concentration was directly related to carbamide peroxide concentration. In the Copalite-coated samples, significantly lower concentrations of mercury in solution were found as compared to the non-coated samples (P < 0.01). In conclusion, exposure of amalgam restorations to 10%-40% carbamide peroxide-based bleaching agents increased the mercury release. Pre-coating of the external amalgam surfaces with Copalite significantly reduced the release of mercury.

Analysis of Variance↗

PubMed2004

Peroxide penetration into the pulp from whitening strips.

It was observed that externally applied bleaching gels may penetrate into the pulp chamber. This study was conducted to evaluate the peroxide diffusion from two whitening strips into the pulp chamber. Twenty-four, human, extracted, maxillary central teeth were separated into three groups (n = 8). All teeth were sectioned 3-mm apical to CEJ, the intracoronal pulp tissue was removed, and the pulp chamber was filled with acetate buffer. Vestibuler crown surfaces of teeth in the experimental groups were subjected to whitening strips; the teeth in the control group were exposed only to distilled water. The acetate buffer solution in each tooth was transferred to the tube. Leuco-crystal violet and enzyme horseradish peroxidase also were added to the tube. The pulpal peroxide was determined spectrophotometrically. The results indicated that the whitening strip containing 14% hydrogen peroxide presented a higher pulpal peroxide penetration than 6.5 % hydrogen peroxide (p < 0.001).

Dental Devices, Home Care↗

PubMed2005

Dental effects of home bleaching gels and whitening strips on the surface hardness of resin composites.

PURPOSE: To evaluate the effects of two bleaching gels and two whitening strips on surface hardness of four resin composites in vitro. METHODS: 60 cylindrical samples of each composite (Surefil, Charisma, Admira, Flowline) were prepared (4 mm thickness and 6 mm diameter) and stored in distilled water at 37 degrees C for 24 hours. These samples were randomly divided into six test groups (n=10). One group was selected for baseline and Vickers microhardness measurements (load= 100 g, dwell time 20 seconds) were taken immediately. The other groups were treated for 21 days with one of the following: distilled water (control), containing 10% carbamide peroxide bleaching gel (Perfect Bleach), 16% carbamide peroxide bleaching gel (Viva Style), 5.3% hydrogen peroxide whitening strips (Crest Whitestrips) and 14% hydrogen peroxide whitening strips (Crest Whitestrips Supreme). The treated samples were also subsequently subjected to the same microhardness testing by using the same method as applied to the baseline measurements. Data were analyzed statistically (alpha = 0.05). RESULTS: Overall, the lowest surface hardness value was observed in baseline measurements. An increase in surface hardness was noted in all of the other groups. The higher surface hardness values were found in control, whitening strip (5.3% HP) and bleaching gel (10% CP) groups than whitening strip (14% HP) group. Bleaching gel (16% CP) was statistically different from only baseline measurements. In addition, regardless of the tested groups, statistically significant differences in surface hardness were observed between composite materials. Surefil showed the highest hardness values while Flowline presented the lowest hardness values.

Acrylic Resins↗