Carbamide Peroxide Bleaching Gel Research Articles

In vitro evaluation of the effect of addition of biomaterials to carbamide peroxide on the bleaching efficacy and microhardness of enamel.

Teeth bleaching, although considered safe and conservative, cause microscopic changes in the tooth structure. The aim of this study is to evaluate the bleaching efficacy of carbamide peroxide (CP) bleaching gel when modified with the incorporation of bioactive glass (BG) and hydroxyapatite (HA) and its effect on enamel microhardness. Forty-five maxillary incisors were decoronated, artificially stained and mounted in acrylic. The samples were divided into three groups of 15 each and subjected to the following bleaching protocol for 8 h/day at 37°C for 2 weeks: Group 1 - 16% CP, Group 2 - CP modified with BG, and Group 3 - CP modified with hydroxyapatite (HA). Spectrophotometric color assessment using CIE L*a*b* system and Vickers microhardness were assessed before and after bleaching. Data were analyzed using Student's paired t-test and one-way ANOVA followed by Tukey's post hoc analysis. There was a significant change in color (L*a*b*) in all the three groups when compared to the baseline values. However, no significant difference in the total color change (ΔE) was observed between the three groups. Enamel microhardness reduced significantly in the CP group, whereas it increased in the BG and HA group after bleaching. Scanning electron microscopy images of BG and HA groups showed crystalline deposits suggesting mineral deposition. Addition of biomaterials can be a beneficial alternative to bleaching with CP alone, considering the increase in microhardness without hindering the bleaching action.

Efficacy of Tooth Bleaching With Prior Application of Two Different Desensitizing Agents: An In Vitro Study.

Objective To compare and evaluate the efficacy of tooth bleachingwith prior application of two different desensitizing agents such assodium fluoride and5% potassium nitrate. Materials and methods A total of 108 extracted human maxillary central incisors were stained in black coffee solution and stored in artificial saliva for colour stabilization. The specimens were randomly divided into three groups (n = 36) according to the following protocols: (a) bleaching without desensitizer, (b) bleaching with prior application of sodium fluoride, and (c) bleaching with prior application of 5% potassium nitrate. After fabricating customized trays,desensitizers were applied for 10 minutes followed by 16% carbamide peroxide bleachinggel, which was in contact with the teeth for three hours. The bleaching efficacy was evaluatedat baseline (after staining), 3rd day, 7th day, and 14th day using a digital spectrophotometer. Results There was an increase in the overall colour change (∆E)from baseline to 14th day, which was statistically significant at cervical, middle, and incisal thirds of the teeth between the three groups with the sodium fluoride group showing decreased ∆E. Conclusions Carbamide peroxide (16%) showed improved whitening efficacy from baseline to the 14th day with increasing median values at all time periods. The sodium fluoride group showed decreased ∆E value when compared to other groups.

Influence of violet LED and fluoride-containing carbamide peroxide bleaching gels on early-stage eroded/abraded teeth

PurposeThis study evaluated enamel with early-stage erosion/abrasion following bleaching with 20% and 45% carbamide peroxide (CP) gels containing fluoride (F) and irradiated with violet LED (LED). MethodsEnamel blocks were immersed in 1% citric acid (5 min) and artificial saliva (120 min) three times to produce early-stage enamel erosion. Simulated toothbrushing was performed only after the first saliva immersion, to provoke enamel abrasion. The erosive/abraded enamel samples were submitted to (n=10): LED/CP20, CP20, LED/CP20_F, CP20_F, LED/CP45, CP45, LED/CP45_F, CP45_F, LED, and control (without treatment). The pH of the gels was assessed, and color (ΔE00) and whiteness index (ΔWID) changes were calculated after cycling (T1), and 7 days from bleaching (T2). Enamel surface roughness average (Ra) and Knoop microhardness (kg/mm2, %SHR) were evaluated at baseline (T0) at T1 and T2. Scanning electron microscopy evaluated the enamel surface morphology at T2. ResultsThe gels’ pH was neutral and CP20 and CP45 exhibited no differences in ΔE00 and ΔWID (p>0.05) but LED increased these parameters for CP20_F and CP45. Erosion/abrasion significantly decreased mean kg/mm2, and the LED group was the only one not increasing microhardness after bleaching (p>0.05). None of the groups fully recovered the initial microhardness. All groups exhibited %SHR similar to the control (p>0.05) and the increase in Ra was detected only after erosion/abrasion. CP20_F groups exhibited a more preserved enamel morphology. ConclusionLight irradiation combined with low-concentrated CP gel promoted a bleaching effect comparable to the high-concentrated CP. The bleaching protocols did not adversely impact the surface of early-stage eroded/abraded enamel.

Chemical behavior of 20%-22% carbamide peroxide gels in at-home bleaching: Randomized crossover in situ trial.

To evaluate if distinct 20%-22% carbamide peroxide bleaching gels present similar decomposition pattern and pH during the clinical use in both arches, as well as gels viscosity. Participants randomly received treatments with carbamide peroxide gels (n=10): OPF (OpalescencePF-20%); PNT (Polanight-22%); and WPC (Whiteness Perfect-22%) in three different days, with 2-day washout. Decomposition pattern was assessed by peroxide concentration. Both PC and pH of bleaching gels were measured in different time points in upper and lower trays during a total of 120 min of clinical use. Viscosity of bleaching gels was measured in triplicate. ANOVA and Tukey's test were applied (α=0.05). Regarding decomposition pattern, no significant differences were observed for the interaction between gel, time, and tray position factors. The peroxide concentration progressively reduced until 120 min of trays use (p < 0.001), being overall more notable in lower trays (p < 0.001). Regarding pH, the lowest values were verified in WPC within time. At 120 min, an increase of pH was observed for both WPC and OPF (p < 0.001) compared to baseline means. PNT exhibited constant pH values over time. The values of viscosity were: OPF (1.682.000 ± 19 cP)a, WPC (1.388.667 ± 172.63 cP)ab, PNT (579.567 ± 0.98 cP)b. The bleaching gels presented overall decomposition pattern clinically equivalent, being more notable in lower trays over time. Nevertheless, distinct pH and viscosities were observed among the products. Although the manufacturers recommend different times of use for bleaching gels with similar peroxide concentrations, the commercial products tested did not exhibit clinically relevant difference in the decomposition pattern during the 120 min of clinical procedure.

At-home Bleaching with a Novel Carbamide Peroxide Polymeric Nanoparticle Gel: A Multicenter Randomized Controlled Trial.

To compare the risk and intensity of tooth sensitivity (TS) as well the effectiveness of at-home bleaching using two carbamide peroxide bleaching gels, specifically a novel polymeric nanoparticle gel (experimental) and a commercial gel (Opalescence PF, Ultradent, South Jordan, Utah, USA), applied at two application times. This multicenter, triple-blind, and split-mouth randomized controlled trial was conducted on 80 healthy adults with canine teeth that were shade A2 or darker. The participants all used the experimental and the control gels on one side of a tray, depending on the group to which they were allocated, for 30 or 60 minutes per day over four weeks. The absolute risk and intensity of TS were assessed daily using the five-point Numeric Rating Scale and the 0-10 Visual Analogue Scale. Color change was evaluated with shade guide units (ΔSGU) and a digital spectrophotometer (ΔEab, ΔE00, and ΔWid) at baseline and 30 days postbleaching. The risk and intensity of TS was evaluated by the McNemar and the Wilcoxon signed-rank tests, respectively. Color change (ΔSGU, ΔEab, ΔE00, and ΔWid) was evaluated by Mann-Whitney and paired t-tests (α=0.05). No differences in the risk and intensity of TS were observed based on the bleaching gels used and the times of application (p>0.05). Thirty days after bleaching, there was no significant difference in color change, in terms of the bleaching gels used or the application times (p>0.05). The novel carbamide peroxide polymeric nanoparticles gel, when applied for 30 or 60 minutes, produced effective color change and a low rate of tooth sensitivity, as compared to the control group.

The Effect of Carbamide Peroxide Bleaching Gel Containing Remineralization Agents on the Bond Strength of Universal Adhesives to Enamel

The Effect of Carbamide Peroxide Bleaching Gel Containing Remineralization Agents on the Bond Strength of Universal Adhesives to Enamel

Novel in-office peroxide-free tooth-whitening gels: bleaching effectiveness, enamel surface alterations, and cell viability

To evaluate the bleaching ability, the effect on enamel surface and cytotoxicity of novel tooth-whitening formulations containing papain, ficin, or bromelain. Forty bovine dental discs (6 cm ×4 cm) were pigmentated and randomly allocated into the following groups (n = 10): Group 1, 20 wt% carbamide peroxide (control); group 2, 1% papain-based whitening; group 3, 1% ficin-based whitening; and group 4, 1% bromelain-based whitening. The whitening gels were prepared and applied on the enamel three times per day once a week, for 4 weeks. Color measurement was obtained by CIEDE2000. Enamel Knoop microhardness and roughness were evaluated. The WST-1 assay was used to evaluate the cell viability of mouse fibroblast cells (L929). Data were statistically analyzed by one-way analysis of variance (ANOVA) and Student Newman Keuls’s post hoc test at α = 0.05 significance level. Bromelain, ficin-based, and carbamide peroxide bleaching gels showed a similar color change (p < 0.001). Higher enamel hardness decrease and higher enamel roughness were caused by the carbamide peroxide (p < 0.05). The experimental whitening gels did not affect cell viability. Tooth bleaching gels containing bromelain, papain, or ficin have substantial clinical potential to be used in the development of peroxide-free tooth whitening gels.

Effect of 10% carbamide peroxide bleaching gels on surface hardness of nano filled composite resin

Introduction: Home bleaching is the whitening treatment of vital teeth applied by patients themselves at home under dentist supervision. In clinical condition, several patients who need bleaching treatment already had nano filled composite resin restoration on their teeth. The purpose of this study was to investigate the contact time difference of 10% carbamide peroxide bleaching gels application for home bleaching on the surface hardness of nano filled composite resin activated by Light Emitting Diode (LED). Methods: Total sample in this study was 30 samples, divided into 3 groups. The samples used were nano filled composite resin cylindrical shape with a diameter of 6 mm and a thickness of 2 mm. Group I as the control group was immersed in distilled water, group II was treated with immersion in 10% carbamide peroxide for 4 hours per day, and group III was immersed in 10% carbamide peroxide for 6 hours per day. The duration of treatment was 14 days for all groups. Data were analysed using Kruskal-Wallis with Mann-Whitney test and the p-value = 0.05. Results: The result of one-way Kruskal-Wallis with Mann-Whitney test showed that there were significant difference between the control group and the groups applied with 10% carbamide peroxide for 4 hours and 6 hours per day with the p-value 0.00 (p &lt; 0.05). Conclusion: Application of 10% carbamide peroxide decreasing the surface hardness of nano filled composite resins activated by LED.Keywords: Nano filled composite resin, carbamide peroxide, composite resin hardness, Light Emitting diode (LED).

Effect of 15% carbamide peroxide bleaching gel on color of Class V resin composite restoration

ObjectiveTo investigate effect of 15% carbamide peroxide bleaching gel on color of Class V resin composite restoration. Materials and methods60 class V cavities were made in maxillary premolars Teeth were randomly divided into four groups of 15 specimens each (2 control and 2 experimental or bleached groups). Group A to be restored with light nanocomposite resin (Filtek Z350 XT) with no post-restoration bleaching procedure (control). Group B to be restored with light nanocomposite resin (Filtek Z350 XT, with post-restoration bleaching procedure (Experimental). Group C to be restored with microhybrid resin (Filtek 250 XT) with no post-restoration bleaching procedure (control). Group D to be restored with microhybrid resin (Filtek 250 XT), with post-restoration bleaching procedure (Experimental). The bleaching was made with 15% at home bleaching agent (Opalescence PF). Color, opacity and fluorescence were analyzed by taking digital photos for the specimens at baseline and 24 h after completion of the bleaching procedure. The color pattern was evaluated according to the CIE - L*, a* and b* color system. Bleaching according to the following equation (25) ΔE = [(ΔL) 2+(Δa) 2+(Δb) 2] 1/2 For optical analysis, the specimens were subjected to the color measurements on white and black patterns, considering only the L* coordinate, which was calculated according to the formula: Opacity = L*b/L*w, where L*b corresponds to the reading of the L* coordinate against a black background and L*w against a white background. This procedure was performed before after bleaching, and the difference in opacity between the two periods was calculated in percentage. While for fluorescence comparison, the Fluorescence parameter (FL) was calculated, at baseline and post bleaching procedure, as the difference in color (ΔE) depending on the inclusion or exclusion of the UV component according to the equation: FL = [(CIE L*100 – CIE L*0) 2 + (CIE a*100 – CIE a*0) 2 + (CIE b*100 – CIE b*0) 2] 1/2, where subscripts 100 and 0 denote the 100% UV-included and the UV-excluded conditions respectively. The recorded data for the tested materials' color, opacity and fluorescence were collected and statically analyzed with IBM® SPSS® statistical version 20 with the significance level set at P ≤ 0.05. ResultsThere was no statistically significantly different between the two materials before as well as after bleaching.Conclusion: the color change of the nanofilled and microhybride light activated composite after bleaching (home-bleaching) was not perceptible or significant.

Influence of tooth bleaching on dental enamel microhardness: a systematic review and meta-analysis.

Several studies have investigated the effect of bleaching on dental tissues. The evaluation of the effect of home bleaching with 10% carbamide peroxide is important for assessing alterations in enamel microhardness that may affect dental health in terms of resistance to masticatory forces. This meta-analysis was performed in order to determine scientific evidence regarding the effects of home vital bleaching with 10% carbamide peroxide gel on the microhardness of human dental enamel. A systematic electronic literature search was conducted in the PubMed and Web of Science databases using search terms. Two independent researchers evaluated the information and methodological quality of the studies. Inclusion and exclusion criteria were established for article selection; further, only studies published in English were selected. Thirteen studies that metall of the inclusion and exclusion criteria were selected and underwent statistical analysis. The results of this meta-analysis showed no significant changes in enamel microhardness when using the 10% carbamide peroxide bleaching gel over periods of 7, 14 and 21days.

Effect of varying concentrations of home bleaching agents on hardness of a resin composite: An in vitro study

Aim: To evaluate the effect of 10%, 20% and 35% Carbamide Peroxide home bleaching agent on hardness of a microfilled resin composite. Materials and Methods: Forty specimens of micro filled resin composite(Z250, 3M ESPE) were prepared using moulds with dimensions of 4mm diameter x 2mm thickness and cured with a LED polymerization unit (LEDition - Ivoclar Vivadent). The specimens were polished with coarse, medium, fine and super fine polishing discs (Sof-lex, 3M ESPE) and were stored in distilled water at 37?C in an incubator for 24 hours. Specimens were then divided into four groups of 10 specimens each. One group was selected as the control group (not treated with bleaching agents) and was stored in artificial saliva for 7 days at 37?C. The other three groups were treated with 10%, 20% and 35% carbamide peroxide gels respectively (Opalesence PF 10%, Opalesence PF 20% and Opalesence PF 35%, Ultradent) as per the manufacturer’s instructions over a period of 7 days. The specimens were subjected to Shore Durometer for 15 seconds and checked for hardness. The results were analyzed using ANOVA and Post hoc Bonferroni tests. Results: There was no significant difference in the hardness of the specimens belonging to Group A, Group B or Group C when compared with the Control Group. Conclusion: It can be confirmed based on the results of this study that the hardness of the Micro filled Composite resin was not affected by10%, 20 % or 35% carbamide peroxide bleaching gels when used as per the manufacturer’s instructions. Restorations done using microfilled composite resins can be retained after bleaching procedures.

Effects of Carbamide Peroxide Bleaching Gel on Color of Silorane- and Methacrylate-based Resin Composites

Effects of Carbamide Peroxide Bleaching Gel on Color of Silorane- and Methacrylate-based Resin Composites

Enamel Surface Changes After Exposure to Bleaching Gels Containing Carbamide Peroxide or Hydrogen Peroxide.

This study evaluated the differences in enamel color change, surface hardness, elastic modulus, and surface roughness between treatments with four bleaching gels containing carbamide peroxide (two at 10% and one each at 35%, and 45%) and two bleaching gels containing hydrogen peroxide (two at 40%). Enamel specimens were bleached and color changes were measured. Color change was calculated using either ΔE or the Bleaching Index (BI). Then, surface hardness, elastic modulus, and surface roughness of the enamel specimens were evaluated. All measurements were performed at baseline and directly after the first bleaching treatment for all carbamide peroxide- and hydrogen peroxide-containing bleaching gels. In addition, final measurements were made 24 hours after each of a total of 10 bleaching treatments for carbamide peroxide bleaching gels, and 1 week after each of a total of three bleaching treatments for hydrogen peroxide bleaching gels. After the last bleaching treatment, respective ΔE scores were 17.6 and 8.2 for the two 10% carbamide peroxide gels, 12.9 and 5.6 for the 45% and 35% carbamide peroxide gels, and 9.6 and 13.9 for the two 40% hydrogen peroxide gels. The respective BI scores were -2.0 and -2.0 for the two 10% carbamide peroxide gels, -3.5 and -1.5 for the 45% and 35% carbamide peroxide gels, and -2.0 and -3.0 for the two 40% hydrogen peroxide gels. Each bleaching gel treatment resulted in significant whitening; however, no significant difference was found among the gels after the last bleaching. Whitening occurred within the first bleaching treatments and did not increase significantly during the remaining treatments. Surface hardness significantly decreased after the last bleaching treatment, when 10% carbamide peroxide was used. Furthermore, significant changes in the elastic modulus or surface roughness occurred only after treatment with 10% carbamide peroxide. All six bleaching gels effectively bleached the enamel specimens independent of their concentration of peroxide. Gels with low peroxide concentration and longer contact time negatively affected the enamel surface.

In Vitro Evaluation of the Efficacy of Different Over-the-Counter Products on Tooth Whitening

This in vitro study evaluated the whitening effect of four different over-the-counter products compared with a 10% carbamide peroxide (CP) bleaching gel. Specimens obtained from bovine incisors were stained in a tea solution and randomly divided into six groups according to the product used (n=10): CT: conventional toothpaste (negative control); CWT: Crest 3D White toothpaste; CWR: Crest 3D White mouth rinse; CWS: Crest 3D White strips; DW: Dazzling White (paint-on gel); and OP: Opalescence PF 10% CP (at-home bleaching gel, positive control). Over-the-counter products and 10% CP were used according to the manufacturer's recommendations. Color measurements were performed according to the CIELab system using spectrophotometer after staining, and after 4 and 8 weeks of the treatment procedure. The ∆E, ∆L, ∆a, and ∆b values were calculated. The data obtained were analyzed by repeated-measures ANOVA. Tukey's test for multiple comparisons was applied (p<0.05). All groups, except CWT, were effective in tooth whitening in comparison with conventional toothpaste. There was no significant difference in tooth whitening between CWT and CT (p=0.93). CWS, DW and OP groups presented significantly higher color changes than the CWR group. DW and CWS showed similar tooth whitening to OP.

Role of fluoridated carbamide peroxide whitening gel in the remineralization of demineralized enamel: An in vitro study.

Introduction:The use of self-administered carbamide peroxide bleaching gels has become increasingly popular for whitening of discolored vital teeth. Studies have reported that its use may induce increased levels of sensitivity and surface roughness of the tooth due to demineralization. This study evaluates the effect of fluoride addition to the bleaching agent – its remineralizing capacity and alterations in the whitening properties.Materials and Methods:Twenty-four extracted lower third molar teeth, with the pretreatment shade determined, were taken up in the study. Each tooth was sectioned into four and labeled as groups A, B, C, and D. The tooth quadrants in group A-C were demineralized; groups A and B were treated with 10% carbamide peroxide gel (group-A without fluoride and group-B with 0.463% fluoride addition) (no further treatment was carried out for group c) group-D remained as the control. The post-treatment shade was determined. The tooth samples were sectioned (approximately 200 μm) for evaluation under a light microscope. The depth of demineralization was analyzed at five different equidistant points. Statistical analysis was carried out with t-tests, accepting ≤0.05 as significant.Results and Conclusion:Addition of fluoride caused remineralization of demineralized enamel. The tooth whitening system showed that the remineralization properties did not affect the whitening properties.

Mineral Loss and Morphological Changes in Dental Enamel Induced by a 16% Carbamide Peroxide Bleaching Gel

The aim of this study was to compare the effect of a 16% carbamide peroxide (CP) gel and a 10% CP gel on mineralized enamel content and morphology. Enamel blocks from bovine incisors were subjected to a 14-day treatment (8 h/day) with 10% or 16% CP gels. Knoop microhardness was evaluated before bleaching and at 1, 7 or 14 days after this treatment (50 g/15 s). Mineral content (energy-dispersive x-ray spectroscopy), surface roughness and topography (atomic force microscopy) were evaluated at the 14-day period. Data were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05). Significant microhardness reduction was observed at the 7 th and 14 th days for 10% CP gel, and for all bleaching times for 16% CP gel (p<0.05). At the 14-day period, a significant decrease in Ca and P content, increase on surface roughness (p<0.05) as well as on picks and valleys distance were observed when both bleaching gels were used. These enamel alterations were more intense for 16% CP gel. It was concluded that both CP-based gels promoted loss of mineral structure from enamel, resulting in a rough and porous surface. However, 16% CP gel caused the most intense adverse effects on enamel.

Effect of Carbamide Peroxide Bleaching Gel on Composite Resin Flexural Strength and Microhardness

This study investigated the effect of 16% carbamide peroxide (Whiteness Perfect/FGM) on the Vickers microhardness and flexural strength of the restorative composites Filtek Z100 (hybrid), Filtek Z350 (nanofill), Brilliant (micro-hybrid) and Opallis (micro-hybrid). Disc-shaped (4x2 mm; n=5) and bar-shaped (12x2x1 mm; n=10) specimens of each restorative material were randomly divided into 2 groups: (G1) 16 weeks stored in distilled water; (G2) 16 weeks stored in distilled water, with 16% carbamide peroxide application during 6 h per day for the last 4 weeks. The mechanical properties were evaluated using a Vickers microhardness tester and a mechanical testing machine. Data were analyzed by two-way ANOVA and Tukey's (HSD) post-hoc test (α=0.05). Filtek Z100 presented the highest microhardness value, followed by Filtek Z350 and finally by Brilliant and Opallis (p=0.00). Filtek Z100 and Brilliant exhibited the highest flexural strength value, followed by Filtek Z350 and Opallis (p=0.00). Bleaching treatment decreased significantly microhardness of Brilliant and Opallis (p=0.00). The flexural strength of all studied materials was not affected by the home bleaching (p=0.28).

Effect of Fluoride-Treated Enamel on Indirect Cytotoxicity of a 16% Carbamide Peroxide Bleaching Gel to Pulp Cells

The aim of this study was to evaluate the possibility of fluoride solutions applied to enamel to protect pulp cells against the trans-enamel and transdentinal cytotoxicity of a 16% carbamide peroxide (CP) bleaching gel. The CP gel was applied to enamel/dentin discs adapted to aicial pulp chambers (8 h/day) during 1, 7 or 14 days, followed by fluoride (0.05% or 0.2%) application for 1 min. The extracts (culture medium in contact with dentin) were applied to MDPC-23 cells for 1 h, and cell metabolism (MTT assay), alkaline phosphatase (ALP) activity and cell membrane damage (flow cytometry) were analyzed. Knoop microhardness of enamel was also evaluated. Data were analyzed statistically by ANOVA and Kruskal-Wallis tests (α=0.05). For the MTT assay and ALP activity, significant reductions between the control and the bleached groups were observed (p<0.05). No statistically significant difference occurred among bleached groups (p>0.05), regardless of fluoride application or treatment days. Flow cytometry analysis demonstrated 30% of cell membrane damage in all bleached groups. After 14 days of treatment, the fluoride-treated enamel presented significantly higher microhardness values than the bleached-only group (p<0.05). It was concluded that, regardless of the increase in enamel hardness due to the application of fluoride solutions, the treated enamel surface did not prevent the toxic effects caused by the 16% CP gel to odontoblast-like cells.

Effect of Postoperative Peroxide Bleaching on the Stability of Composite to Enamel and Dentin Bonds

This study investigated the effect of peroxide bleaching gel on the durability of the adhesive bond between composite material, enamel, and dentin created with the etch-and-rinse adhesive Gluma Comfort Bond (GLU) and with the self-etch adhesives Clearfil SE Bond (CLE), Adper Prompt (ADP), and iBond (IBO). The adhesives were applied to flattened enamel and dentin of extracted human molars and built up with a microhybrid composite (Charisma). After 25 eight-hour cycles of bleaching with a 20% carbamide peroxide bleaching gel (Opalescence PF 20), the shear bond strength was measured and compared with one-day and two-month control specimens stored in water. The data were analyzed using nonparametric Mann-Whitney and Kruskal-Wallis statistics (p<0.05). Detailed fractographic analysis was performed using scanning electron microscopy. The bleaching gel significantly decreased the bond strength on both enamel and dentin for the simplified single-step self-etch adhesives ADP and IBO and markedly affected a fracture pattern of ADP specimens at the periphery of their bonded area. The results of our study indicate that the durability of adhesive restorations can be detrimentally influenced by carbamide peroxide bleaching and that different adhesives show varying sensitivity levels to the bleaching gel.

The Effect of Bleaching Agents on the Color Stability of Ceromer and Porcelain Restorative Materials In Vitro

The aim of this in vitro study was to determine the color changes of five different restorative materials after exposing these materials to two different home bleaching agents. This study applied bleaching agents to an ultralow-fusing porcelain, a low-fusing porcelain, two types of heat-pressed glass ceramics, and a ceromer. A total of 24 disc-shaped specimens were fabricated (with a diameter of 10 mm and a thickness of 2 mm) from each material (n=12). The initial color measurements were taken with a spectrophotometer. The first set of specimens were bleached with 10% hydrogen peroxide (HP) for one hour daily for 10 days. The other set of specimens were bleached with 10% carbamide peroxide (CP) bleaching gel for eight hours daily for 14 days. Data were analyzed with the one-way analysis of variance and Kruskal-Wallis statistical test. The difference in the prebleaching and postbleaching color of each material was considered to be statistically significant at p < 0.05. The study found a statistically significant difference among the color changes of the test groups after exposing them to both bleaching agents (p<0.05). Appreciable color change was observed in the Estenia (ΔE=3.99) specimens that were bleached with the HP, and noticeable color changes were observed in the Estenia (ΔE=1.89) and IPS Empress 2 (ΔE=1.66) groups when they were treated with the CP. Restorations (especially polymer-containing restorative materials) should be protected before any bleaching procedure due to the high risk of color change.