Effects of bleaching agents containing fluoride and calcium on human enamel

OBJECTIVE

Since little is known about the effects of carbamide peroxide (CP) containing fluoride (F) or calcium (Ca), this study evaluated the effects of experimental and commercially available bleaching agents, with or without F and Ca, on enamel.

METHOD AND MATERIALS

Sound enamel slabs were randomly divided into six groups (n = 10): placebo gel (PLA); Whiteness (WHI-10% CP; FGM); Opalescence F (OPA-10% CP+F; Ultradent); Pola Night F (PN-10% CP+F; SDI); and experimental gels: 10% CP + F (CPF) and 10% CP + Ca (CPCa). The samples were submitted to 6-hour gel applications daily for 14 days and stored in remineralizing solution after treatment. Enamel microhardness measurements were performed at baseline and after bleaching. In addition, the analytical concentrations of F and Ca and the pH of the water used to rinse the bleached surface were analyzed by means of ion-selective electrode, atomic absorption spectroscopy, and pH meter, respectively.

RESULTS

Enamel surface microhardness significantly decreased after bleaching with nonenhanced 10% CP (WHI). The chemical analyses suggest F uptake promoted by high-concentrate F bleaching gels (CPF, OPA, and PN) and a F loss with nonenhanced 10% CP bleaching gels (PLA, WHI). CP agent enhanced with Ca (CPCa) also caused Ca enamel uptake.

CONCLUSION

Enamel was susceptible to mineral changes during bleaching treatment, but mineral loss was minimized by the addition of F and Ca to bleaching agents.

Effects of 3% sodium ascorbyl phosphate on the hardness and bond strength of human enamel bleached with 10% carbamide peroxide

For this study, 120 fragments obtained from human third molars were randomly separated into 12 groups (n = 10). Four groups were used for measuring the Knoop hardness number (KHN) of enamel, while the other eight were used for testing the microtensile bond strength (muTBS) of two adhesive systems (Single Bond and Prime & Bond NT). All groups presented statistically similar KHN values. According to bond strength results, bleached enamel without antioxidant application demonstrated the lowest values of all groups. Based on these results, it could be concluded that the bleaching agents used in the present study (with or without sodium ascorbyl phosphate) did not affect human enamel hardness and that sodium ascorbyl phosphate is able to reverse the compromised bonding in bleached human enamel.

Reversal of reduced bond strength after bleaching

This article investigated how the shear bond strength of a luting resin to dentin was affected by antioxidant treatment and delayed bonding after bleaching with carbamide peroxide. Using a lowspeed diamond saw, 40 flat dentin surfaces were prepared from freshly extracted human molars and divided into three bleaching groups (n = 10) and a control group (n = 10). Group 1 consisted of specimens bonded immediately after bleaching. Group 2 specimens were treated with an antioxidant agent (10% sodium ascorbate), while Group 3 specimens were immersed in artificial saliva for one week after bleaching. Specimens in Group 4 were not bleached but were immersed in artificial saliva for one week before bonding. Forty ceramic blocks were prepared and luted to teeth using a dual-curing resin cement. The specimens were thermocycled and the shear bond strength tests were performed using a universal testing machine. Fracture analysis was performed using a scanning electron microscope. While the Group 1 samples demonstrated the lowest shear bond strengths (11.9 +/- 3 MPa) (p < 0.05), no significant differences were found among samples in Group 2 (26.3 +/- 7.1 MPa), Group 3 (20.7 +/- 6.5 MPa), and Group 4 (22.1 +/- 2.5 MPa) (p = 0.05).

Effect of the diffusion of bleaching agents through enamel on dentin bonding at different depths

PURPOSE

To evaluate the influence of two concentrations of bleaching agents applied over enamel surfaces on the dentin bonding at different depths.

METHODS

Twenty-four bovine incisors were sectioned, obtaining three fragments per tooth (4x4 mm). Each fragment presented a 0.7 mm enamel thickness; and the dentin thickness varied according to the experimental group: 0.5 mm, 1 mm or 1.5 mm. Fragments from each dentin-thickness were allocated into three groups (n=8): G1: Control (no bleaching); G2: 16% carbamide peroxide (6 hours/14 days); G3: 35% hydrogen peroxide (three 15-minute treatments). 24 hours after enamel bleaching, the adhesive system was applied and dentin surfaces were restored with resin composite cylinders (2 mm diameter and 1 mm height). The micro-shear testing was performed immediately after restorative procedures, at a speed of 0.5 mm/minute until failure. Bond strength values, in MPa, were statistically analyzed (split-plot ANOVA/Tukey alpha=0.05).

RESULTS

Means obtained were: G1-0.5 mm: 13.5, G1-1 mm: 9.48, G1-1.5 mm: 9.01; G2-0.5 mm: 9.64, G2-1 mm: 9.44, G2-1.5 mm: 9.27; G3-0.5 mm: 11.68, G3-1 mm: 11.64, G3-1.5 mm: 7.63. Regardless of the dentin thickness, bleached groups presented bond strengths similar to that of control groups. Nevertheless, significant differences among dentin depths were detected (P=0.02); and the lowest bond strength was observed on the deepest dentin (1.5 mm). The diffusion of bleaching agents through enamel surfaces did not affect the bond strength to dentin, which is highly dependent on the morphology/depth of the substrate.

Effect of fluoride therapies on the surface roughness of human enamel exposed to bleaching agents

OBJECTIVES

To evaluate in vitro the effect of fluoride therapies on the surface roughness of human dental enamel exposed to bleaching agents.

METHOD AND MATERIALS

Sixty-six specimens obtained from 33 third molars were centrally cut, mounted on acrylic resin supports, polished, and submitted to baseline surface roughness readings (RaB). Next, the specimens were distributed into 11 groups and exposed to one of the bleaching agents-16% carbamide peroxide (CP) or 35% hydrogen peroxide (HP)-and one of the fluoride therapies-0.05% NaF daily (DF); 0.2% NaF weekly (WF); 2% final topical fluoride (FTF); or 2% initial and final topical fluoride (IFTF). The positive control group specimens were exposed to neither bleaching agents nor fluoride therapies. The negative control group specimens were exposed to the bleaching agents but none of the fluoride therapies. After storage in artificial saliva for 7 days, final surface roughness readings (RaF) were taken. Percentage differences between RaB and RaF were analyzed by ANOVA and Tukey HSD tests at a P value of .05.

RESULTS

The bleaching agents CP and HP increased the surface roughness compared with the control group; FTF and IFTF reduced the surface roughness of enamel exposed to CP and HP; DF and WF did not reduce the surface roughness of enamel exposed to CP and HP.

CONCLUSION

Both bleaching agents tested increased the surface roughness of dental enamel, and both topical fluoride therapies were effective at reducing the increase in enamel surface roughness after bleaching.

Effect of postoperative bleaching on marginal leakage of resin composite and resin-modified glass ionomer restorations at different delayed periods of exposure to carbamide peroxide

AIM

To evaluate the effect of dental bleaching with carbamide peroxide at different exposure times on the microleakage of resin composite and resin-modified glass ionomer restorations after placement in extracted human teeth.

METHODS AND MATERIALS

120 Class V cavity preparations were placed at the cementoenamel junction (CEJ) of human teeth. Half of the cavities were restored with Filtek P60 resin composite (C) and the other half were restored with Fuji II LC resin-modified glass ionomer (G). Each group was randomly divided into four subgroups (n=15). Groups C1 and G1 were not bleached and stored in artificial saliva at 37 degrees C to serve as control groups, while in Groups C2 and G2, C3 and G3, and C4 and G4 specimens were exposed to a 15% carbamide peroxide gel for one day, one week, and two weeks, respectively, following the placement of restorations. Microleakage was assessed using the dye penetration method. Data were analyzed using the Kruskal-Wallis and Wilcoxon tests (p=0.05).

RESULTS

The Kruskal-Wallis test showed no significant difference among all groups of composite or glass ionomer restorations with either enamel or dentinal margins with regard to microleakage (p>0.05). The Wilcoxon test revealed more marginal leakage in the enamel/glass ionomer margins than the enamel/composite margins (p<0.05). In comparisons within each group, the Wilcoxon test showed there was more microleakage in dentinal margins of composite restorations than in the enamel margins in the test groups (p<0.05). The dentinal margins of the glass ionomer in control groups showed more leakage than the enamel margins, but after the bleaching procedure all experimental groups showed statistically similar microleakage in both the enamel and dentinal margins (p>0.05).

CONCLUSION

Postoperative bleaching with carbamide peroxide could increase microleakage in the dentinal margins of composite and the enamel margins of resin-modified glass ionomer restorations.

CLINICAL SIGNIFICANCE

Rebonding of resin composite restorations should be considered following bleaching with 15% carbamide peroxide in order to reseal the margins. Resin-modified glass ionomer is not suitable as a filling material before bleaching because of its susceptibility to increased microleakage.

Dentine hypersensitivity in dental bleaching: case report

Hydrogen and carbamide peroxides used for in-office and at-home whitening treatments are potentially harmful to pulp causing various alterations. Also characteristic and quite frequent is the presence of dental sensitivity. The aim of this paper is to review the appearance of post-whitening tooth hypersensitivity in clinical cases treated with different techniques. A study of patients (N = 56) with 5 different dental whitening techniques was managed: in-office light activated, with 35% hydrogen peroxide (N1 = 10); in-office chemical activated, also with 35% hydrogen peroxide (N2 = 10); in-office with custom-formed trays using 35% carbamide peroxide (N3 = 10); at-home with custom-formed trays (N4 = 16, 8 with 10% carbamide peroxide and 8 with 3.5% hydrogen peroxide); and at-home with a 6% carbamide peroxide varnish (N5 = 10). For the set of cases, sensitivity was 55% and varied between slight and intense. All whitening procedures can cause hypersensitivity, although it does not always occur. When present (31-55% of all the patients treated), hypersensitivity is not usually very intense and affects only a few teeth in each patient. Greater sensitivity was observed with in-office chemical activated (70%) and light-activated (100%) whitening techniques. So, after dental whitening treatment, dental hypersensitivity is to be expected, independently of technique and product used, in at least one out of two patients.

Evaluation of 30% carbamide peroxide at-home bleaching gels with and without potassium nitrate--a pilot study

OBJECTIVES

This double-blind study examined the bleaching effectiveness of two 30% carbamide peroxide bleaching gels: one with 5% potassium nitrate (treatment A) and one without (treatment B). The treatment time was reduced for this pilot study to one hour per day for 10 days to determine whether the higher concentration would whiten teeth and to ascertain the tooth sensitivity and gingival effects of the 30% solution.

METHOD AND MATERIALS

Forty subjects were selected with an initial tooth shade corresponding to Bioform shade guide B65 or darker. After obtaining consent, subjects were randomly divided into two groups (n = 20). Custom-fabricated bleaching trays were made for each subject. Trays did not extend onto the gingiva. Each subject was instructed in the placement and wear of the tray and bleach and supplied with one of the two bleaching gels. Subjects had 10 hours of treatment time with the bleaching gel. Photographs and shades (using a standardized Bioform shade guide) were taken at baseline and at final recall to determine bleaching effectiveness. Tooth sensitivity was measured at baseline and final recall by applying a pellet saturated with skin refrigerant to the tooth for 2 seconds. The sensitivity was recorded on a scale ranging from 1 to 10. Gingival index was also measured at baseline and at final recall. Data was analyzed with Wilcoxon rank-sum and Wilcoxon signed rank tests.

RESULTS

No significant differences were found for changes in color, tooth sensitivity, and gingival condition between the two bleaching gels (P = .899, P = .375, and P = .056, respectively). Within each group, bleaching gel A and B significantly whitened teeth (P < .0001 for both groups). There were no significant changes in tooth sensitivity and gingival condition for gel A (P = .057 and .063, respectively) or gel B (P = .911 and .510, respectively).

CONCLUSION

Thirty percent carbamide bleaching gels effectively whiten teeth without causing a significant increase in tooth sensitivity or changes in gingival condition. Potassium nitrate has little effect in sensitivity when treatment time is short.

Effect of reservoirs on gingival inflammation after home dental bleaching

OBJECTIVE

To evaluate the influence of reservoirs on the gingival mucosa of patients submitted to at-home bleaching with 16% carbamide peroxide.

METHOD AND MATERIALS

Nineteen nonsmoking male patients, 18 to 25 years of age, were submitted to home bleaching with a 16% carbamide peroxide gel for 2 consecutive hours for 21 days. The custom-made mouth trays were made with a reservoir on only the left side and cut anatomically 1 mm beyond the gingival margin. Smears of the gingival mucosa were obtained by the exfoliation cytology in liquid media technique before (control), immediately after, and 30 and 45 days after treatment. The samples were processed in the laboratory and evaluated according to Papanicolaou's criteria of malignity. Statistical analysis was carried out by McNemar test, 2 proportions test, and Wilcoxon test with a level of significance of 1%.

RESULTS

The presence of a reservoir in the custom tray resulted in an increase of inflammation only immediately after the bleaching procedure. After 30 and 45 days, the difference between inflammation on the sides with and without a reservoir was not statistically significant. Significant differences were found in the degree of inflammation, classified as predominantly mild on the nonreservoir side and moderate on the reservoir side (P < .01).

CONCLUSIONS

A 16% carbamide peroxide bleaching gel caused gingival inflammation immediately after the procedure and persisted until 45 days after the bleaching treatment. The use of a reservoir in the custom tray for home bleaching resulted in higher rates and higher intensity of gingival inflammation.

Fungal nail infections: diagnosis and management

1) Fungal nail infection, or onychomycosis, mainly affects toenails. Infections are generally asymptomatic. Spontaneous regressions, but also complications, appear to be rare. Discomfort and cosmetic complaint are occasionally reported; 2) After a review of the literature based on the standard Prescrire procedure, we examined the diagnosis and management of fungal nail infections; 3) Clinical signs of fungal nail infections are non-specific. Alternative diagnoses include psoriasis and nail microtrauma. Nail hyperkeratosis and leukonychia are useful diagnostic pointers. Matrix involvement has important implications in the choice of treatment; 4) Detection of fungal structures by direct examination of a nail sample is strongly suggestive of fungal nail infection. In contrast, cases of negative direct examination with positive culture must be interpreted with caution, as contamination is frequent; 5) Antifungal lacquers (5% amorolfine and 8% ciclopirox) applied to the nails cure about 30% of fungal infections and sometimes cause mild irritation. There is no firm evidence that these solutions are any more effective than other topical antifungals applied daily to the affected nail. Trimming, filing or grinding the nail, in addition to these drug treatments, is likely to be beneficial, but these measures have not been evaluated; 6) Chemical nail destruction with a combination of urea and bifonazole, followed by treatment with an antifungal ointment, can be used when the nail is markedly thickened. Non-comparative trials have shown cure rates close to 70% at three months when the matrix is not involved, and 40% with matrix involvement. Drug application is inconvenient and local reactions are frequent. Surgical nail avulsion carries a risk of local infection and permanent nail dystrophy; 7) Oral terbinafine is effective in more than 50% of cases but its cutaneous, hepatic and haematological adverse effects are severe in about 1 in 2000 patients and can be life-threatening; 8) It is better to treat Candida nail infections with oral azoles (ketonazole, itraconazole) than with terbinafine. These treatments carry a risk of serious adverse effects and numerous drug interactions; 9) Fungal nail infections are usually mild. Treatments with potentially severe adverse effects must therefore be used with caution. It is better not to treat fungal nail infections if the risks outweigh the expected benefits.

Wear and surface roughness of bovine enamel submitted to bleaching

The present study evaluated surface roughness and wear of bovine enamel following three different bleaching techniques and simulated brushing. Initial surface roughness (Ra) was evaluated and teeth were randomly divided into 4 groups (n = 10): Group 1, control; Group 2, 35% hydrogen peroxide (HP) activated by a hybrid light; Group 3, 35% HP activated by a halogen light; and Group 4, 16% carbamide peroxide. After bleaching, surface roughness was measured and teeth were subjected to 100,000 cycles of simulated brushing. After brushing, the final roughness and wear was determined. Data were statistically analyzed by ANOVA and Tukey test (P < 0.05). There were no significant differences among groups comparing initial and postbleaching roughness. After brushing, significant differences were found between the control and experimental groups. Group 4 showed a significant increase in roughness values compared with Group 2. The control group showed significantly less wear than other groups. Bleaching techniques promoted increased roughness and wear of bovine enamel, when submitted to simulated brushing. Tooth enamel after bleaching can present a larger alteration in the amount of roughness due to brushing.

Effects of 10% carbamide peroxide treatment and sodium fluoride therapies on human enamel surface microhardness

This study sought to evaluate the microhardness of enamel submitted to 10% carbamide peroxide treatment and different methods of remineralization involving sodium fluoride (NaF). Non-erupted third molars were used and 75 enamel blocks with standardized dimensions (4.0 x 4.0 x 2.0 mm) were obtained. Enamel blocks were randomly divided into five groups (n = 15): one control (no bleaching and no fluoride treatment), one receiving a 10% carbamide peroxide treatment, one receiving 10% carbamide peroxide plus acidulated phosphate fluoride, one receiving 10% carbamide peroxide with 0.2% NaF, and one receiving 10% carbamide peroxide and 0.05% NaF. There were no differences among four of the groups (p > 0.05); the group receiving 10% carbamide peroxide only was different from all other groups (p < 0.05). Based on these results, NaF therapies are recommended during carbamide peroxide bleaching treatments.

Effectiveness of nightguard vital bleaching with 10% carbamide peroxide -- a clinical study

OBJECTIVE

To use the criteria set by the American Dental Association to evaluate the effectiveness of nightguard vital bleaching with 10% carbamide peroxide through a controlled randomized clinical trial.

MATERIALS AND METHODS

Fifty volunteers allocated to either an experimental group(Opalescence PF 10%; OPA) or a control group (placebo; PLA) used a gel for 21 days. Observations of tooth colour were recorded at baseline, immediately after 3 weeks of use(day 21), and 30 days (day 30) and 6 months (day 180) after the treatment was finished. Colour was evaluated with the Vitapan classical shade guide and from the volunteers' degree of satisfaction. Tooth sensitivity and gingival bleeding were also assessed.

RESULTS

The median increase in the lightness of the teeth in the OPA group was 3 units,based on the value-ordered Vitapan shade guide. This improvement in lightness was maintained for 6 months in 88% of this group. In the PLA group, 8% had a 2-unit reduction in tooth colour at day 21. Tooth sensitivity occurred in the OPA (36%) and PLA (8%)groups. Gingival bleeding was not associated with gel use. Volunteers' satisfaction was 92% for the OPA and 8% for the PLA group.

CONCLUSIONS

With the protocol used, nightguard vital bleaching was an effective technique that had minimal and transient side effects that disappeared after treatment without causing sequelae or complications.

Tensile strength of dentin after bleaching treatment

The mechanical properties of dentin are changed after bleaching, although the effects of the bleaching conditions on the tensile strength of dentin have not been determined. In the current study, a tensile test of bovine dentin was conducted after bleaching and the effects of the bleaching conditions were investigated, including the number of bleaching times, the location where the bleaching agent was applied, and the kind of illumination. The weight of organic content in dentin before and after application of the agent was also measured. The results showed that the tensile strengths did not change after three times office bleaching procedure, and the location where the bleaching agent was applied, the kind of bleaching agent and the kind of illumination did not have influence on the tensile strength. On the other hand, organic component in dentin significantly decreased after application of the agent (p<0.05). Since the bleaching agent would potentially affect tensile strength with deterioration of collagen matrix, the frequency of bleaching treatment should be minimized in clinical use.

Subjective intensities of pain and contentment with treatment outcomes during tray bleaching of vital teeth employing different carbamide peroxide concentrations

OBJECTIVES

It has been suggested that tooth whitening might cause considerable pain. The aim of this study was to evaluate subjective intensities of pain during bleaching of vital teeth and to assess the patients' contentment with the treatment outcome.

METHOD AND MATERIALS

Thirty patients were treated for 1 week in a double-blind study design. Employing gels containing 17%, 10%, or 0% (control group) carbamide peroxide, patients wore bleaching trays for 2 hours per day and described subjective intensities of pain while wearing the trays by means of a visual analog scale. The patients' subjective contentment with the bleaching outcome was measured with an intermodal intensity comparison.

RESULTS

For the 17% gel, a median value of 3.5 U (max: 10; min: 1) for pain intensity was observed; this was statistically different from the value seen with the 10% group (2.0 U; max: 7; min: 0) (P < .05). Both test groups differed significantly from the control group, which had a median value of 0.0 U (max: 3; min: 0) (P < .05). Patients' contentment with the treatment outcome did not differ between the test groups (P > .05), although statistical differences were observed between the control and the test groups (P < .05) after bleaching for 1 week.

CONCLUSION

Application of carbamide peroxide-containing bleaching agents to vital teeth causes pain correlated with the agent's concentration. Since both highly and less concentrated gels might result in a similar contentment with the treatment outcome, the use of highly concentrated agents appears not to be justified to improve vital tooth color.

PET analysis of the 5-HT2A receptor inverse agonist ACP-103 in human brain

The mechanisms underlying the clinical properties of atypical antipsychotics have been postulated to be mediated, in part, by interactions with the 5-HT2A receptor. Recently, it has been recognized that clinically effective antipsychotic drugs are 5-HT2A receptor inverse agonists rather than neutral antagonists. In the present study, which is part of the clinical development of the novel, selective 5-HT2A receptor inverse agonist ACP-103, we applied positron emission tomography (PET) with the radioligand [11C]N-methylspiperone ([11C]NMSP) to study the relationship between oral dose, plasma level, and uptake of ACP-103 in living human brain. The safety of drug administration was also assessed. Four healthy volunteers were examined by PET at baseline, and after the oral administration of various single doses of ACP-103. Two subjects each received 1, 5, and 20 mg doses, and two subjects each received 2, 10, and 100 mg doses, respectively. ACP-103 was well tolerated. Detectable receptor binding was observed at very low ACP-103 serum levels. Cortical [11C]NMSP binding was found to be dose-dependent and fitted well to the law of mass action. A reduction in binding was detectable after an oral dose of ACP-103 as low as 1 mg, and reached near maximal displacement following the 10-20 mg dose. In conclusion, administration of ACP-103 to healthy volunteers was found to be safe and well tolerated, and single oral doses as low as 10 mg were found to fully saturate 5-HT2A receptors in human brain as determined by PET.

Comparison of two low sensitivity whiteners

PURPOSE

To evaluate two commercially available doctor-supplied, patient-applied, bleaching systems for their ability to whiten the maxillary anterior teeth while at the same time not causing sensitivity.

METHODS

46 participants were randomly assigned to one of two groups: One group received Rembrandt Xtra-Comfort and the other group Nite White Excel 2Z. Bleaching stents were fabricated and the bleaching systems were used following manufacturers' instructions. Participants recorded tray use and any sensitivity on a daily basis. Participants bleached for 2 weeks followed by 2 weeks of no bleaching. Color was evaluated at the first, second and fourth week following the initial delivery of bleaching trays. Color change was measured using the Vita Classic Shade Guide arranged by value.

RESULTS

As a group, participants in the NW2Z group bleached for 302 days with a total of 48 days (16%) of sensitivity recorded. The Rembrandt Xtra Comfort group bleached for 313 total days with 97 days (31%) of sensitivity recorded. The difference in sensitivity between the two products proved to be statistically significant (Chi-square analysis, P < or = 0.0001). The median shade change for both products following 2 weeks of active treatment was six tabs. At the 4-week evaluation, the median shade change was 5.5 and 6.0 tabs respectively for Rembrandt and Nite White. There was no statistical difference between the products in respect to shade change.

Comparison of the effect of hydrogel and a solution of sodium ascorbate on dentin-composite bond strength after bleaching

AIM

The aim of this study was to compare the effects of solution and different sodium ascorbate hydrogels on dentin-resin composite shear bond strength subsequent to a bleaching procedure with 10% carbamide peroxide.

METHODS AND MATERIALS

Sixty buccal dentin surfaces obtained from intact human third molars were randomly divided into five groups (n=12). Dentin surfaces received different treatments: (1) no treatment; (2) bleaching (10% carbamide peroxide gel); (3) bleaching + 10% sodium ascorbate solution; (4) bleaching + 10% sodium ascorbate hydrogel, and (5) bleaching + 20% sodium ascorbate hydrogel. Dentin surfaces were bonded with Single Bond and restored with a composite (Z100). The samples were tested for shear bond strengths. Data was analyzed using analysis of variance (ANOVA) and Tukey tests.

RESULTS

Significantly higher bond strengths were observed subsequent to treatment with hydrogel and solution forms of sodium ascorbate (p<0.05). No significant differences were demonstrated between different forms of sodium ascorbate preparations. In addition, no significant differences were observed among groups with antioxidant treatment (Groups 3, 4, and 5) and Group 1 (no treatment).

CONCLUSION

Reduced bond strength to bleached dentin can be amended by the use of sodium ascorbate as an antioxidant.

CLINICAL SIGNIFICANCE

Both hydrogel and solution forms of sodium ascorbate can significantly improve the reduced bond strength of resin composite to dentin subsequent to a bleaching procedure with 10% carbamide peroxide.

The effects of high concentration tooth whitening bleaches on microleakage of Class V composite restorations

OBJECTIVE

To explore the effects of high-concentration hydrogen peroxide bleaching agents on the microleakage of composite restorations.

METHODS

In 60 extracted human molars, Class V restorations were prepared with Scotchbond 1/Filtek Z250 composite. Teeth were randomly divided into four groups: (1) no bleaching; (2) bleaching with 14% hydrogen peroxide gel from Crest Whitestrips; (3) bleaching with 20% carbamide peroxide gel from Opalescence PF 20; and (4) bleaching with 38% hydrogen peroxide gel Opalescence Xtra Boost. Bleaching procedures were carried out at 37 degrees C for 21 days/42 hours (2); seven days/42 hours (3); one day/45 minutes (4). Varnish was applied on the apical portion of the teeth only, excluding the restoration, prior to immersion in a 0.1% rhodamin-B-isothiocyanate solution for 24 hours at 37 degrees C. After rinsing, specimens were embedded in methacrylate blocks, and sectioned with a water-cooled microtome with three restoration cuts positioned centrally parallel to the long axis of the tooth. Microleakage was evaluated at the occlusal margins of the Class V restorations using a stereo microscope, separate for dentin and enamel margins.

RESULTS

Over 90% of enamel margins exhibited no microleakage following cycling. Bleaching agents had almost no effect on numerical averages. Eighty-eight percent of the dentin margins were free of microleakage for the non-treated control group. Bleaching treatments collectively had slight numerical reductions to around 80%. The statistical evaluation (Kruskal-Wallis-test) showed no significant difference in microleakage between groups for enamel or dentin.

CONCLUSION

Bleaching with the materials tested had no influence on microleakage of Filtek Z250 composite bonded with Scotchbond 1.

Effect of bleaching treatments on microleakage of Class I restorations

OBJECTIVE

To test the effect of bleaching agents on microleakage of composite restorations.

METHODS

Sixty extracted human molar class I cavities were restored using Scotchbond 1 and Filtek Z250 composite according to the manufacturer's instructions. The teeth were randomly divided into four groups (n = 15 each). Group 1 was the control group, which was not bleached. Group 2 had a once-daily bleaching treatment with 20% carbamide peroxide gel for eight hours. Group 3 had a bleaching of 6% H2O2 for 30 minutes twice a day. Group 4 had a bleaching treatment once per day with 19% percarbonate gel for eight hours. The bleaching was carried out at 37 degrees C for 14 days. Nail varnish was applied on the apical portion of the teeth only, and the specimens were immersed in a 0.1% rhodamin-B-isothiocyanate for 24 hours at 37 degrees C. After thorough rinsing with tap water, the specimens were embedded in self-curing methacrylate resin. The blocks were sectioned with a water-cooled microtome saw into three to five slices. The cuts were positioned centrally through the restorations and approximately parallel to the long axis of the tooth in the mesiodistal direction. Microleakage was evaluated at the occlusal margins of the class I restorations using a stereo microscope.

RESULTS

Microleakage occurred in all groups. The percentage of sections showing leakage was 20% (Group 1), 11% (Group 2), 15% (Group 3), and 18% (Group 4). The statistical evaluation (Kruskal-Wallis test) showed no significant difference between groups (p = 0.537).

CONCLUSION

Bleaching with the materials tested has no influence on microleakage of Filtek composite bonded with Scotchbond I.

[Questions and answers to possible side effects of external bleaching therapies]

There are several questions with regard to the application and possible side effects of external bleaching therapies. The following short review gives answers to some questions regarding this topic. It might be concluded that every bleaching therapy should be preceded by a meticulous intraoral examination. To reduce the risk of adverse effects, it is mandatory to have knowledge about the mode of action of bleaching agents.

Duration and timing of sensitivity related to bleaching

PROBLEM

Reports of sensitivity vary greatly from one study to another, probably because studies are small. Generally, only the percentage of subjects is reported.

PURPOSE

This study reports sensitivity using a large database. We investigated the source, duration, and timing of sensitivity during 14 days of active bleaching.

MATERIALS AND METHODS

One hundred and seventy-two people recorded sensitivity from any of the five sources on a daily basis.

RESULTS

No one withdrew from the study because of sensitivity. Forty-seven percent of participants experienced sensitivity. Seventy-seven percent had sensitivity of 3 or fewer days. Temperature sensitivity tended to occur later in the 14-day bleaching cycle, and hot and cold sensitivity tended to occur together.

CONCLUSIONS

There was great variability in sensitivity levels from person to person. Temperature sensitivity tended to occur later in the active phase of bleaching, whereas irritation of the tongue tended to occur earlier.

CLINICAL SIGNIFICANCE

The results from a large group of people are more likely to include a wide cross-section of the population sampled. This data provides practitioners with a better estimate of what their patients are likely to experience. It is estimated that, during 2 weeks of active bleaching, 77% of people will experience 3 or fewer days of sensitivity. On average, sensitivity is short-lived, thus making it is easy to underestimate the importance of discussing sensitivity with patients considering bleaching. However, for some, the duration of sensitivity is much greater and has a very negative impact on satisfaction.