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PubMed2001

Effect of carbamide peroxide bleaching agents on the physical properties and chemical composition of enamel.

PURPOSE: To evaluate the effect of two commercially available carbamide peroxides bleaching agents, Opalescence and Nite-White, in concentrations of 10, 15 and 16%, on enamel. MATERIALS AND METHODS: Vickers hardness measurements (VH) were made at the surface and 110 microns below the surface on human enamel samples that were treated for 5 or 10 days, 6 hrs/day. Furthermore, infrared spectrophotometry (IR), Fourier transform infrared spectrophotometer (FTIR) and X-ray diffraction (XRD) measurements were performed after the VH measurements were completed. RESULTS: Using a one-way ANOVA, statistically significant differences in VH could be established between surface and subsurface VH values. For all groups, including the control group, the surface VH values were statistically significantly higher than subsurface VH. IR, FTIR and XRD established a change from hydroxyapatite to primary calcium ortho phosphate [Ca(H2PO4)2] for all experimental groups except for 10% Opalescense tested for 5 or 10 days.

Analysis of Variance↗

PubMed1994

Incidence of invasive cervical resorption in bleached root-filled teeth.

Invasive cervical resorption, a form of external root resorption, has been reported to be associated with intra-coronal bleaching of root-filled teeth and this has raised concerns about carrying out such bleaching procedures. The purpose of the present study was to examine the incidence of invasive cervical resorption in root-filled teeth which had been bleached using a standardized technique. Three observers examined records and radiographs from a total of 158 patients, whose bleaching treatment had been carried out in a specialist endodontic practice. The sample comprised 204 teeth with a review period of between 1 and 19 years. One-hundred-and-fifty-one teeth (77.94 per cent) had an associated history of traumatic injury. All teeth had been treated with a combination of thermocatalytic and 'walking bleach' procedures using 30 per cent hydrogen peroxide. In 54.41 per cent of teeth, gutta-percha and AH26 root-fillings were kept at the height of the cemento-enamel junction while 18.63 per cent were below and 26.96 per cent were above the CEJ. Sealing cement was not placed over the gutta-percha and AH26 root-fillings in any of the teeth in the study. It was found that a total of four teeth from the sample group (1.96 per cent) had developed invasive cervical resorption during the review period. All of these teeth had a history of traumatic injury and the level of gutta-percha was at the CEJ.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Post-operative bleaching: effect on microleakage.

The effect of a carbamide peroxide bleaching gel on the microleakage of Class V resin composite restorations with two dentin bonding agents was evaluated using extracted human teeth. Class V cavity preparations were placed at the cementoenamel junction of the facial and lingual surfaces of 20 teeth for a total of 40 preparations. Half of the teeth were restored with Scotchbond 2/Silux Plus and half were restored with Prisma Universal Bond 3/AP.H. Five teeth were randomly selected from each of the two groups and were stored in water at 37 degrees C to serve as controls. The remaining teeth were exposed to a carbamide peroxide gel for three 2-hour periods per day for 9 days. The specimens were stored in distilled water at 37 degrees C except during treatment periods. All teeth were then thermally stressed for 100 cycles. Microleakage was assessed by dye penetration. The results demonstrated that the carbamide peroxide agent adversely affected the marginal seal of both restorative systems.

Carbamide Peroxide↗

PubMed1995

Hydrogen peroxide: a review of its use in dentistry.

Several dentifrices that contain hydrogen peroxide are currently being marketed. The increased use of bleaching agents containing (or generating) H2O2 prompted this review of the safety of H2O2 when used in oral hygiene. Daily exposure to the low levels of H2O2 present in dentifrices is much lower than that of bleaching agents that contain or produce high levels of H2O2 for an extended period of time. Hydrogen peroxide has been used in dentistry alone or in combination with salts for over 70 years. Studies in which 3% H2O2 or less were used daily for up to 6 years showed occasional transitory irritant effects only in a small number of subjects with preexisting ulceration, or when high levels of salt solutions were concurrently administered. In contrast, bleaching agents that employ or generate high levels of H2O2 or organic peroxides can produce localized oral toxicity following sustained exposure if mishandled. Potential health concerns related to prolonged hydrogen peroxide use have been raised, based on animal studies. From a single study using the hamster cheek pouch model, 30% H2O2 was referred to as a cocarcinogen in the oral mucosa. This (and later) studies have shown that at 3% or less, no cocarcinogenic activity or adverse effects were observed in the hamster cheek pouch following lengthy exposure to H2O2. In patients, prolonged use of hydrogen peroxide decreased plaque and gingivitis indices. However, therapeutic delivery of H2O2 to prevent periodontal disease required mechanical access to subgingival pockets. Furthermore, wound healing following gingival surgery was enhanced due to the antimicrobial effects of topically administered hydrogen peroxide. For most subjects, beneficial effects were seen with H2O2 levels above 1%.

Animals↗

PubMed1992

Effect of bleaching agents on inorganic components of human dentin and cementum.

The effect of bleaching agents on the inorganic composition of human dentin and cementum was examined. Intact teeth were crushed, pulverized, and separated to dentin and cementum powders. The pulverized tissues were exposed to treatments with 30% H2O2, 3% H2O2, 2% sodium perborate in 30% H2O2, 2% sodium perborate in 3% H2O2, and 2% sodium perborate in bidistilled water for periods of 15 min and 1, 24, and 72 h. The degree of dissolution and the percentage of inorganic material for both dentin and cementum were measured. Thirty percent H2O2 and 2% sodium perborate in 30% H2O2 treatments significantly increased the solubility of dentin and cementum. The degree of dissolutions and the percentage of inorganic material remaining in the undissolved dentin and cementum increased with time progression. The greatest increase occurred with 30% H2O2 and 2% sodium perborate in 30% H2O2 after 24- and 72-h treatments. It is concluded that 30% hydrogen peroxide treatment may cause alteration in the chemical structure of the dentin and cementum making them more susceptible to degradation.

Borates↗

PubMed1989

Adhesion of a glass ionomer cement to bleached and unbleached bovine dentin.

Cylinders of Fuji Type II glass ionomer restorative cement were bonded to the superficial dentin layer of young bovine incisor teeth that had previously been subjected to 4 different treatments: 1) teeth immersed in 35% hydrogen peroxide for 60 min and etched with 37% phosphoric acid gel for 60 s; 2) teeth immersed in saline for 60 min and etched with 37% phosphoric acid for 60 s; 3) teeth etched with 37% phosphoric acid for 60 s and immersed in 35% hydrogen peroxide for 60 min; or 4) teeth etched with 37% phosphoric acid for 60 s and immersed in saline for 60 min. Specimens were stored in water at 37 degrees for 1 and 7 days, prior to tension and shear testing. A total of 128 teeth were tested: 8 teeth in each group for each day and for each test. Statistical analysis of the results indicated that there was a highly significant reduction in bond strength of the cement when dentin was exposed to hydrogen peroxide as compared with saline. SEM examination of randomly selected fractured test specimens indicated that bond failure was cohesive in nature, suggesting that the hydrogen peroxide treatment adversely affected the setting process of the glass ionomer cement.

Adhesiveness↗

PubMed2002

Effects of a 10% carbamide peroxide bleaching agent on rat oral epithelium proliferation.

The purpose of the present study was to evaluate the influence of short course topical application of carbamide peroxide on proliferating cell nuclear antigen (PCNA) immunohistochemical expression in the oral tongue mucosa of rats. Twelve male Wistar rats were submitted to topical application of 10% carbamide peroxide on one side of the dorsal tongue once a week for three consecutive weeks. Only distilled water was applied on the control side. The animals were killed on days 0, 10, and 20 after the last application. The tongue was fixed in buffered formalin for 24 h and embedded in paraffin. Tissue blocks (3 microns) were subjected to the biotin-streptavidin amplified system for identification of PCNA. The percentage of epithelial-positive basal cells in each side of the tongue mucosa was calculated. The results demonstrated that topical application of 10% carbamide peroxide increases PCNA immunohistochemical expression on the basal layer of the oral mucosa epithelium of rats on day 0 after treatment. In conclusion, short-course use of carbamide peroxide induces transient epithelial cell proliferation of the oral mucosa of rats.

Animals↗

PubMed1993

Adhesion of a resin composite to bleached and unbleached human enamel.

Cylinders of a visible light-cured microfil resin were formed on and bonded to the flattened enamel surface of 15 human hemisected premolar teeth which had previously been subjected to three different treatments: (a) immersion in 35% hydrogen peroxide (HP) for 60 min, (b) immersion in 35% HP for 60 min followed by storage in distilled water for 1 day prior to resin application, and (c) immersion in saline (S) for 60 min. Specimens were stored in distilled water at 37 degrees C for 7 days prior to shear bond strength testing. A total of 30 specimens were tested. Statistical analysis of the data indicated that there was a highly significant reduction in shear bond strength between HP- and saline-treated specimens. Water storage of HP-treated specimens for 1 day prior to resin application appeared to restore the adhesiveness but not to a point that was statistically significant. Scanning electron microscopic examination of randomly selected, fractured test specimens indicated that the reduction in bond strength may be related to alterations in the ability of the resin to attach itself to the HP-treated surface and to possible effects of the HP on the resin itself.

Adolescent↗

PubMed2006

Visual whiteness ranking of a Vitapan 3D Master shade guide by untrained assessors.

OBJECTIVE: This study was conducted to obtain the ranking order of a 29-tab (including three "bleaching tabs") Vita Shade Guide for perceived "whiteness" by untrained assessors, and to compare this ranking with both the shade guide manufacturer's rank order and a colorimetrically derived rank order. METHODOLOGY: A total of 85 people, not trained in color assessment by shade guides, were asked to rank order the tabs of a Vitapan 3D Master shade guide for perceived "whiteness" under standardized lighting conditions. A whiteness ranking was also obtained colorimetrically using a Minolta CM-2600d spectrophotometer calibrated to give CIE whiteness values. The data were analysed using means, standard deviations, and standard errors. RESULTS: The assessors varied more in their rankings for darker shades than the lighter ones. The order derived by the assessors and the colorimetry order did not match well with the manufacturer's order, especially toward the darker shades. CONCLUSION: For use in studies of whitening products, a new order of the Vitapan 3D Master shade guide tabs has been developed in relation to whiteness.

Adult↗

PubMed2001

Color and optical properties of resin-based composites for bleached teeth after polymerization and accelerated aging.

PURPOSE: To determine changes in color and optical properties after polymerization and accelerated aging of white resin-based composites (RBCs) used to restore bleached teeth and compare them with those of conventional shades. MATERIALS AND METHODS: Four white shades and two conventional shades (A2, A3) of two different brands of RBCs (Vitalescence, Synergy) were measured before and after polymerization and after accelerated aging for 150 kJ/m2. Color was measured according to CIE L*a*b* color scale on a reflection spectrophotometer, and scattering coefficient, absorption coefficient, contrast ratio and translucency parameter were calculated. RESULTS: After curing, the color change ( E*) of white RBC was not significantly higher than that of conventional shade (P= 0.05). Color change after curing was positively influenced by the change of K (beta = 0.55), and negatively influenced by the changes of L*, b* and S (beta = -0.34, -0.95 and -0.70, respectively). After aging for 150 kJ/m2, the color changes of white RBCs were 2.4 and 5.8, and those of conventional shade were 1.7 and 2.9, respectively. Higher a* and b* values had a negative influence on the color change for both polymerization and aging.

Color↗

PubMed1988

Adhesion of composite resin to bleached and unbleached bovine enamel.

Cylinders of microfil and small-particle light-cured composite resin were bonded to the flattened labial enamel surface of young bovine incisor teeth which had previously been subjected to four different treatments: (1) teeth immersed in 35% hydrogen peroxide (HP) for 60 min and etched (E) with 37% phosphoric acid gel for 60 sec; (2) teeth immersed in saline (S) for 60 min and E for 60 sec; (3) teeth E for 60 sec and immersed in HP for 60 min; and (4) teeth E for 60 sec, immersed in S for 60 min. Specimens were stored in water at 37 degrees for one and seven days prior to tension- and shear-testing. A total of 256 teeth was tested--eight teeth in each group for each day, for each resin, and for each test. Statistical analysis of the results indicated that there was a highly significant reduction in adhesive bond strength of the resins when the enamel was exposed to HP as compared with S. SEM examination of randomly selected fractured test specimens indicated that this reduction in adhesive bond strength occurred primarily at the bonding resin-enamel interface. Less significant differences in bond strength were noted in the control specimens, with regard to resin type, time of storage, and the etching order.

Adhesiveness↗

PubMed1991

Scanning electron microscopy observations on the penetration and structure of resin tags in bleached and unbleached bovine enamel.

The purpose of this study was to determine the effect of hydrogen peroxide on the ability of composite resin to penetrate bovine enamel etched with phosphoric acid. In a previous investigation, the flattened enamel surfaces of extracted bovine incisors were immersed in either saline (control) or 35% hydrogen peroxide (experimental) for 5 or 30 min before or after acid etching with 37% phosphoric acid gel for 60 s. A standard-sized light-cured resin cylinder was then bonded to the enamel surface. The specimens were stored in a water bath at 37 degrees C for 1 day or 7 days, after which the enamel-resin bond was tensile tested to failure. Sixteen of the failed specimens (eight control and eight experimental) were randomly selected for the present scanning electron microscopic study to evaluate the appearance of the resin tags at the resin-enamel interface. In the control specimens, the tags were well defined and contiguous with resin which was uniformly adherent to the enamel surface. In the experimental specimens, large areas of the enamel surface were free of resin. When tags were present, they were fragmented, poorly defined, and penetrated to a lesser depth than in the saline controls. The changes observed suggest that there may be interaction between resin and residual peroxide at or near the enamel surface.

Acid Etching, Dental↗

PubMed2002

Effects of a bleaching agent containing 35% carbamide peroxide on the immunolocalization of cyclin D and p16.

The evidences that p16 and cyclin D alterations occur in the earlier stages of many human cancers and that its immunolocalization can be used to study the cell cycle regulation, coupled with the possibility that chronic use of carbamide peroxide would induce DNA damage and cell cycle alteration, prompted us to analyse the effect of carbamide peroxide on the immunolocalization of these proteins in rat oral mucosa. Ten male Wistar rats were selected and submitted to topical application of 35% carbamide peroxide over buccal mucosa. The procedures were carried out twice a week for 3 months consecutively. The animals were killed after the last treatment and the buccal mucosa was removed and stored at -70 degrees C. Only distilled water was applied over the buccal mucosa of the control animals. The biotin-streptavidin amplified system was used for identification of cyclin D and p16 antigens and the percentage of basal and suprabasal cells positive for each one were obtained. The results did not show any difference between the experimental and control groups regarding the immunolocalization of cyclin D and p16. In conclusion, the present study showed that chronic use of carbamide peroxide does not induce cell cycle alteration in the oral mucosa of rats.

Animals↗

PubMed1995

Effects of a bleaching agent on human gingival fibroblasts.

Mild oxygenating agents generating low concentrations of hydrogen peroxide (H2O2) are effective alternatives to heat-activated 30% H2O2 in bleaching discolored, vital teeth. There are concerns about possible pathological effects of long-term exposure to bleaching agents, and irritation and ulceration of the gingiva and other oral soft tissues can occur. The objective of this study was to determine the effect of one of these agents on gingival fibroblasts in vitro. Microscopic examination revealed that concentrations of 0.05% to 0.025% of the agent appeared to kill most of the cells. At concentrations of 0.025% to 0.017% some morphological changes were noted; the cells appeared normal at concentrations of < or = 0.0125%. The agent significantly (P < or = 0.002) decreased proliferation (measured by incorporation of [3H]-thymidine into cellular DNA) at concentrations as low as 0.006%. The agent also had a dose-dependent effect on fibronectin production, measured by ELISA, causing significant (P < or = 0.03) decreases at concentrations as low as 0.017%. The agent significantly decreased the production of types I (P < or = 0.01) and III (P < or = 0.04) collagens (measured by ELISA) at concentrations as low as 0.0125%. Type V collagen was not detected under any conditions. Catalase, which catalizes the breakdown of H2O2, abolished toxic effects of a 0.05% solution. The results show that in vitro, the agent is toxic to human gingival fibroblasts, inhibiting several cellular functions.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbamide Peroxide↗

PubMed1992

Enamel shear bond strengths after vital bleaching.

This study examined the shear bond strengths of enamel bond formed at specific time intervals after the termination of vital bleaching. A total of 160 extracted human anterior teeth were divided into three bleaching treatment (BTx) groups (Superoxol, Proxigel, White & Brite), two bonding agent (BA) subgroups (Scotchbond Dual Cure, Scotchbond 2) and two BA control groups. After BTx for 30 days, bonds were formed at 1, 6 and 24 hours; 3 and 7 days (time interval, TI) post-termination of BTx. A total of 32 groups of n = 5 were used. Bonds were formed in nylon tubes with selected BA and Silux Plus, and ruptured 24 hours later with Instron and cable/loop to measure enamel shear bond strength (SBS). A 3 x 2 x 5 factorial ANOVA and Tukey 95% confidence interval (TCI) detected significant differences between BTx (F = 3.54; TCI = 2.7 MPa), BA (F = 9.73; TCI = 1.8 MPa) and TI (F = 9.39; TCI = 4.1 MPa). The interaction between BTx and TI was slightly significant (F = 2.02); other interactions were not significant. Post-hoc analysis showed 80% of bonds failed at the interface or by mixed cohesive composite/interfacial failure. Scanning electron microscope observations suggested association of increased density of voids in bond area at TI with lowest mean bond strengths. SBS ranged from 42.3 to 106.8% of control.

Analysis of Variance↗

PubMed2004

Bleaching efficacy of whitening agents activated by xenon lamp and 960-nm diode radiation.

OBJECTIVE: This in vitro study examines the efficacy of two different dental whitening agents, Opalescence Xtra and Opus White, by analyzing the change in color achieved by the treatment and the temperature increase induced in the pulpal chamber. BACKGROUND DATA: Bleaching techniques achieved significant advances with the use of coherent or incoherent radiation sources to activate the bleaching chemicals. METHODS: The bleaching agents, containing 35% of hydrogen peroxide, were stimulated with 0.9 W of xenon arc lamp and 0.9 W or 2 W of a 960-nm diode laser during 60 sec (0.9 W) and 30 sec (2 W) on 33 extracted human teeth. During irradiation, the temperature in the pulpal cavity was monitored. The color change was evaluated using the CIE L*a*b* color space measurement system. RESULTS: The treated groups showed an increase in color saturation (DeltaC*) of 3-32% and a change in whiteness (DeltaL*) of 0-8%. This study found that only some of the irradiated groups show statistically significant difference (p < 0.05) in the effectiveness of their treatment when compared to the control, whereas no significant statistical difference was obtained in between the irradiated groups. Temperature increase was 2-4 degrees C when using the xenon arc lamp, 2-8 degrees C and 4-12 degrees C when using the diode laser at 0.9 W and 2 W, respectively. CONCLUSIONS: The results of this study suggest that Opalescence Extra and Opus White are both effective to provide brighter teeth. However, according to the conditions used in this study, only the xenon arc lamp induced a safer temperature increase.

Body Temperature↗

PubMed1990

The influence of time of hydrogen peroxide exposure on the adhesion of composite resin to bleached bovine enamel.

Standard sized cylinders of a small particle light-cured resin were bonded to the flattened labial surface of young bovine incisor teeth which had been previously subjected to four different treatments: (a) immersion in 35% hydrogen peroxide and etched with 37% phosphoric acid gel for 60 s, (b) immersion in saline and etched for 60 s, (c) etched for 60 s and immersion in hydrogen peroxide, and (d) etched for 60 s and immersion in saline. Two hydrogen peroxide and saline immersion periods were used, 5 and 30 min. Specimens were stored in water at 37 degrees C for 1 and 7 days before tensile and shear testing. A total of 256 teeth were used, 8 for each treatment group, each immersion period, and each water storage period for each test. Statistical analysis of the results indicated that there was a highly significant reduction in the adhesive bond strength of the resin when the enamel was exposed to hydrogen peroxide and that the reduction was, within the limits of this study, time dependent. The bond strength was unaffected by the etching order and the period of water storage. Scanning electron microscopic examination of randomly selected fractured peroxide-treated specimens indicated that the failure occurred primarily at the bonding resin-enamel interface and that it was associated with areas of resin nonattachment and an alteration in resin quality. It is suspected that these changes were caused by the presence of residual peroxide or peroxide-related substances at or near the enamel surface.

Adhesiveness↗

PubMed2003

In vitro effects of bleaching agents on FM3A cell line.

OBJECTIVE: There are concerns about the possible pathologic effects of relatively long-term exposure of oral tissues to bleaching agents. The purpose of the present study was to investigate the cytotoxic effects of various bleaching agents on mouse mammary carcinoma FM3A cell line. METHOD AND MATERIALS: FM3A cell line obtained from European Collection of Animal Cell Cultures was used in cell culture assay. Exponentially growing cells were seeded in 1 x 105 cells/mL in 5 mL of RPMI 1640 medium supplemented with 10% fetal calf serum and antibiotics in each well of a six-well plate. PowerGel was applied onto the cell culture medium and incubated for 24 hours at 37 degrees C in a 5% carbon dioxide atmosphere after light curing. Opalescence PF gel was left on cell culture medium for 24 hours at the same conditions. After 24-hour incubation, the cells were collected by trypsinization and counted with a hemocytometer. For cell viability, trypane blue exclusion assay was used. The cytotoxicity of PowerGel and Opalescence PF were determined by evaluation of cell growth and viability in comparison to untreated controls (cell growth = 100%). The data were submitted to statistical analysis (One-way analysis of variance, Dunnett's t test). RESULTS: Cell growth after 24 hours was significantly reduced (P = .000) in comparison to the control group. The cell growth in the Opalescence PF gel group also was reduced (P < .05). It was found that both gels affected cell viability. CONCLUSION: PowerGel and Opalescence PF showed a cytotoxic effect on cell growth in FM3A cell line.

Analysis of Variance↗