Is home tooth bleaching gel cytotoxic?

Hydrogen Peroxide Diffusion through Dental Tissues-In Vitro Study

Whitening products commonly utilize hydrogen peroxide (HP) as an active principle, which can penetrate dental tissues with potential side effects due to its low molecular weight. This study aimed to evaluate the HP diffusion of two in-office whitening products, namely 6% VivaStyle Paint On Plus (VS) and Opalescence Boost 40% (OP), in different tooth types. Additionally, the influence of the area of exposure, dental tissue thickness and pulp chamber volume was assessed. Each group consisted of eighteen intact anterior (A), premolar (PM) and molar (M) human teeth, and a positive pulpal pressure model was employed. The samples were analyzed using spectrophotometry, and results were expressed as the mean and 95% confidence interval. Statistical tests and linear regression models were appropriately applied at α = 5%. The total HP (µg) retrieved was as follows: VS-A, 1.333 [1.214, 1.452]; OP-A, 1.538 [1.457, 1.620]; VS-PM, 1.208 [1.123, 1.291]; OP-PM, 3.628 [3.401, 3.855]; VS-M, 2.560 [2.297, 2.823]; and OP-M, 4.197 [3.997, 4.396], with statistically significant differences in diffusion kinetics between whitening products for PM and M. Several HP concentrations attained a minimum cytotoxicity value of 2.22 µg/mL. The regression model shows that OP exposed the pulp chamber to 1.421 µg of HP more than that of VS. Different whitening products can cause cytotoxic HP concentrations in the pulp chamber, with a higher risk observed in molars.

Effect of different bleaching treatment protocols on shear bond strength of bonded orthodontic brackets with no-primer adhesive resin

BACKGROUNDS:

Bleaching procedure can be companied before, during, or after orthodontic treatments. However, the risk of compromised bond strength of brackets to bleached enamels is in debate. This study tried to evaluate the shear bond strength (SBS) of bonded metal brackets to the previously bleached enamels.

MATERIALS AND METHODS:

In this in vitro study, 60 extracted, sound, human premolars were mounted vertically in cylindrical molds. The samples were randomly divided into four groups (n = 15): Control (C); at-home bleached by 20% carbamide peroxide (HB); in-office bleached by 45% carbamide peroxide (OB); and in-office bleached by 40% hydrogen peroxide activated with diode laser (L-OB). Sixty stainless steel brackets were bonded by no-primer adhesive resin (OrthoCem). Then SBS of bonded brackets was measured after 5000 thermal cycles at 5°C and 55°C. Finally, the collected data were analyzed by one-way ANOVA, and Tukey HSD tests by using SPPS software at a significant level of 0.05 (α = 0.05).

RESULTS:

Group C showed significantly higher SBS values (all P < 0.001); however, there were no significant differences in SBS compared to other tests' groups with each other (all P > 0.05).

CONCLUSION:

The SBS of bonded orthodontic brackets were compromised after bleaching with 20% and 40% of carbamide peroxide. Diode laser activation may not eliminate the negative effect of bleaching agents on SBS of bonded orthodontic brackets, neither.

Improved tooth bleaching combining ozone and hydrogen peroxide--A blinded study

OBJECTIVES

To evaluate the efficacy of tooth bleaching using ozone after hydrogen peroxide (H2O2) in comparison to the use of H2O2 alone.

METHODS

70 extracted teeth were randomly distributed into two groups. Teeth surfaces in group 1 (n=35) were treated using 38% H2O2 and then were exposed to ozone for 60s and this ozonated peroxide mixture was left on the teeth for 20 min. Meanwhile, teeth in group 2 (n=35) were treated with H2O2 38% for 20 min. The L* a* b* and Vita Classic shade values of teeth were evaluated in both groups at base line, after application of H2O2 and ozone in group 1, and after application of H2O2 and then again after another application of ozone in group 2. The statistically significant changes were set at P ≤ 0.05.

RESULTS

Baseline L* a* b* and Vita shade values were comparable between groups (P>0.05). Teeth obtained lighter shades following bleaching with both H2O2 and ozone or with H2O2 alone (P ≤ 0.05). Further bleaching with ozone for teeth already bleached with H2O2 alone showed further improvement of the shades of teeth (P<0.001). Teeth treated with H2O2 and ozone had more shade improvements than those only treated with H2O2 (P<0.001). Also, L* values were increased while b* values were decreased (teeth obtained lighter shades) following bleaching in both groups (P ≤ 0.05). More changes were obtained when both ozone and H2O2 were used (P ≤ 0.05).

CONCLUSIONS

Bleaching with 38% H2O2 and ozone resulted in teeth with lighter shades than bleaching with 38% H2O2 alone.

Influence of Simulated Pulpal Pressure on Efficacy of Bleaching Gels

Aim

The aim of this study was to investigate the influence of simulated pulpal pressure on efficacy of bleaching gels.

Materials and methods

Cylindrical enamel-dentin specimens from bovine teeth (3 mm diameter, enamel and dentin layer each 1 mm thick) were divided into 4 groups, according to the bleaching treatment: negative control (non-bleached), bleached with 10% carbamide peroxide (CP), bleached with 7.5% hydrogen peroxide (HP) and bleached with 35% hydrogen peroxide. Ten percent CP gel was applied for 8 h/day and 7.5% HP for 1 h/day, during 14 days. For 35% HP treatment, two sessions of 45 minutes each were employed. In intermediate periods specimens were stored in artificial saliva. Experimental groups (n = 19) were subdivided according to the simulation of pulpal pressure (25 mm Hg) during bleaching treatment. Initial color measurement and after bleaching treatment were assessed by spectrophotometry, using CIE L*a*b* system. The data were statistically analyzed by ANOVA and Dunnett's posthoc tests (p < 0.05).

Results

There was significant difference of ∆E for all experimental groups compared to negative control group, according to Dunnett's test (p < 0.0001). There were no significant difference for total color variation (∆E) among experimental groups (p > 0.05).

Conclusion

It was concluded that all bleaching gels showed bleaching efficacy compared to non-bleached group and that the simulated pulpal pressure did not influence the bleaching outcomes of the tested gels.

Clinical significance

Although numerous in vitro studies investigating the efficacy of bleaching agents have been performed, they do not properly simulate the pulpal pressure. In order to make these studies closer to clinical conditions, it is important to reproduce these conditions in laboratory, so the results can be more reliable. This in vitro study was performed under simulated pulpal pressure, aiming to investigate its influence on dental bleaching outcomes.

How to cite this article

Borges AB, Batista GR, Arantes PT, Wiegand A, Attin T, Torres CRG. Influence of Simulated Pulpal Pressure on Efficacy of Bleaching Gels. J Contemp Dent Pract 2014;15(4):407-412.

Influence of concentration and activation on hydrogen peroxide diffusion through dental tissues in vitro

This study evaluated the effect of physical and chemical activation on the diffusion time of different concentrations of hydrogen peroxide (HP) bleaching agents through enamel and dentin. One hundred and twenty bovine cylindrical specimens were divided into six groups (n = 20): 20% HP; 20% HP with light activation; 20% HP with manganese gluconate; 35% HP; 35% HP with light activation; and 35% HP with manganese gluconate. The specimens were fixed over transparent epoxy wells with internal cavities to simulate a pulpal chamber. This chamber was filled with an enzymatic reagent to simulate pulpal fluid. The bleaching gels were applied on enamel surface and the image of the pulpal fluid was captured by a video camera to monitor the time of peroxide penetration in each specimen. ANOVA analysis showed that concentration and type of activation of bleaching gel significantly influenced the diffusion time of HP (P < 0.05). 35% HP showed the lowest diffusion times compared to the groups with 20% HP gel. The light activation of HP decreased significantly the diffusion time compared to chemical activation. The highest diffusion time was obtained with 20% HP chemically activated. The diffusion time of HP was dependent on activation and concentration of HP. The higher concentration of HP diffused through dental tissues more quickly.

Spectrophotometric evaluation of peroxide penetration into the pulp chamber from whitening strips and gel: An in vitro study

Aim:

To investigate pulp chamber penetration of different concentration of hydrogen peroxide.

Materials and Methods:

Fifty extracted human maxillary central incisor teeth were taken and grouped into five (n = 10). All teeth were cut approximately 3 mm apical to the cemento-enamel junction. Pulp was removed and the pulp chamber filled with acetate buffer. Buccal crown surfaces of teeth in the experimental groups were subjected to whitening strip and paint on whitener gel. Control group teeth were exposed to distilled water. The acetate buffer solution in each tooth was then transferred to a glass test tube after 30 min. Leuco-crystal violet dye and enzyme horse radish peroxidase were added. The optical density of resultant blue color in the tubes was measured by UV-visible spectrophotometer. The values were converted into microgram equivalents of hydrogen peroxide.

Results:

The results were evaluated statistically using nonparametric Mann–Whitney U test. Whitening strip showed the lowest pulpal peroxide penetration whereas paint on whitener gel showed highest pulpal peroxide penetration.

Conclusion:

This study demonstrate that peroxide is readily penetrate into the pulp chamber of teeth.

Safety controversies in tooth bleaching

Tooth bleaching using peroxide-based materials is an effective procedure in dentistry. Studies provide evidence on the safety of bleaching by dental professionals. However, concerns and controversy remain regarding the safety of bleaching systems that do not involve dental professionals, especially those available at mall kiosks, salons, spas, and cruise ships. Bleaching causes tooth sensitivity and/or gingival irritation in a significant portion of patients. Bleaching requires proper examination, diagnosis, and treatment plan, which can be performed appropriately only by dental professionals; therefore, involvement of dental professionals in bleaching is necessary to maximize the efficacy and minimize potential risks.

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).

In vitro evaluation of the cytotoxicity of a bleaching agent

Cell cultures of L929 and BHK21/C13 cells were used to evaluate the toxicity of a newly introduced bleaching agent (Colgate Platinum) compared to hydrogen peroxide, an established bleaching agent. The cell reaction was determined by a quantitative technique at 24 h and 72 h. Both bleaching materials had a dose-dependent effect on cell viability. Concentrations of hydrogen peroxide causing a 50% decrease in cell number (50% inhibition dose-ID50) were calculated as 0.00034% after 24 h and 0.00001% after 72 h in L929 cells. The ID50 of hydrogen peroxide was found to be 0.00016% after 24 h and 0.00007% after 72 h in BHK21/C13 cells. The ID50 of Colgate Platinum was 0.00074% after 24 h and 0.00045% after 72 h in L929 cells and 0.00055% after 24 h and 0.00024% after 72 h in BHK21/C13 cells. The results showed that, in vitro, both bleaching agents were cytotoxic to fibroblasts and the new bleaching agent was less toxic than hydrogen peroxide.

Toxicological considerations of tooth bleaching using peroxide-containing agents

Peroxides have been used for tooth bleaching for more than 100 years. Besides those administered in the dental office, agents for at-home bleaching have become popular. To date, there have been no published significant adverse effects caused by dentist-monitored, at-home bleaching agents. But potential risks, particularly those associated with abuses or the use of inappropriate products, need to be recognized. Using an ADA-accepted, at-home bleaching agent under a dentist's supervision is recommended to minimize risks while achieving desired benefits.

Biological properties of peroxide-containing tooth whiteners

Peroxides have been used in tooth whitening for more than 100 years. Current peroxide-containing whiteners can be classified into three categories: (1) those containing high concentrations of peroxides for professional use only; (2) materials dispensed by dentists and used by patients at home; and (3) over-the-counter products available directly to consumers for home use. Hydrogen peroxide (H2O2) and carbamide peroxide are the most commonly used active ingredients in these whiteners. Both peroxides have long been used safely in oral health products and are accepted by the US Food and Drug Administration. However, questions have been raised regarding the safety of at-home whiteners because the peroxides appear to constitute a new use. Substantial differences exist in the manner of application between at-home whiteners and oral health products. In addition, tooth whiteners are a mixture of various ingredients; possible interactions may occur because of the active nature of peroxides. Therefore, the safety evidence for peroxide-containing whiteners is considered inadequate. This paper will review the history of using peroxides for tooth whitening, the toxicology of H2O2 and carbamide peroxide, and available information on the safety of whiteners. The rationale and approaches for evaluating biological properties of peroxide containing whiteners are also discussed.

Assessing the effects of 10 percent carbamide peroxide on oral soft tissues

To examine the effects of a 10 percent carbamide peroxide bleaching gel on the oral soft tissues, the authors conducted a prospective, double-blind, placebo-controlled clinical investigation. Fifty-two patients completed a two-week treatment regimen, applying either a placebo or a 10 percent carbamide peroxide gel in a soft tray for eight hours a day. Clinicians examined the participants' oral soft tissues at baseline and one week, two weeks and six weeks after the first treatment. The examiners recorded the Silness and Löe plaque and gingival indexes, nonmarginal gingival index and nongingival oral mucosal index at each examination. The data collected at these intervals did not indicate that any soft tissue damage had occurred as a result of the bleaching regimen.

Role of saliva and salivary components as modulators of bleaching agent toxicity to human gingival fibroblasts in vitro

Mild oxygenating agents generating H2O2 are used for effective at-home tooth bleaching, but can cause gingival ulcers in some patients. There are concerns about the possible pathological effects of relatively long-term exposure of oral tissues to bleaching agents. Previous work in our laboratory showed that a bleaching agent, which generates approximately 3% H2O2 from carbamide peroxide, was toxic to human gingival fibroblasts in vitro, but that the toxicity was abolished by treatment with the H2O2-destroying enzyme catalase. The purpose of the present study was to determine if whole saliva, the salivary enzyme lactoperoxidase (LP) (which, like catalase, removes H2O2), or salivary mucin protected fibroblasts from bleaching agent toxicity. The cells were exposed to 0.05% agent with or without saliva, LP, mucin or catalase (as a positive control based on our previous study) and assessed for effect on viability/morphology (by microscopic observation), proliferation (by [3H]-thymidine incorporation), and the production of fibronectin (FN) and type I collagen (by ELISA). While the bleaching agent at 0.05% caused cell death, the cells appeared viable and morphologically normal when treated with the bleaching agent and LP (> or = 0.1 microM), saliva LP, and catalase from agent inhibition of proliferation (P < or = 0.04) and FN production (P < or = 0.01). Mucin had statistically insignificant or no protective effect as assessed by the above parameters. Treatment with saliva, LP, mucin, and catalase gave complete or partial protection from agent-inhibition of collagen production (P < or = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Oxidative stress aspects of the cytotoxicity of carbamide peroxide: in vitro studies

Carbamide peroxide is the active ingredient in many at-home patient-applied tooth whiteners. The cytotoxicity of carbamide peroxide, as related to oxidative stress, was evaluated in vitro with several human cell lines, including Smulow-Glickman (S-G) gingival epithelial cells. The potency of carbamide peroxide was related to its hydrogen peroxide component rather than to carbamide, was eliminated in the presence of exogenous catalase, and was enhanced in the presence of aminotriazole, an inhibitor of cellular catalase. The intracellular level of glutathione, a scavanger of toxic oxygen metabolites, was decreased in cells exposed to carbamide peroxide; at higher concentrations of carbamide peroxide, leakage of lactic acid dehydrogenase was also evident. Cells pretreated with the glutathione-depleting agents, buthionine sulfoximine, chlorodinitrobenzene, and bis(chloroethyl) nitrosourea, were hypersensitive to subsequent challenge with carbamide peroxide. Conversely, pretreatment with the iron chelator, deferoxamine, protected the cells against subsequent exposure to carbamide peroxide.

Effect of enamel bleaching on the bonding strength of orthodontic brackets

Various whitening/bleaching systems have been introduced on the market, including an over-the-counter external bleaching material, containing carbamide peroxide. It has been suggested that the process might alter the enamel surface structure in a manner similar to acid etching. Orthodontists are interested in determining whether the process will alter the adhesive characteristics of orthodontic bonding systems. The results of this study indicate that the use of 10% carbamide peroxide did not result in significant changes in the shear debonding strength of orthodontic brackets.

Cytotoxicity and dentin permeability of carbamide peroxide and hydrogen peroxide vital bleaching materials, in vitro

There has been recent concern about the inadvertent exposure of dentin with patent tubules as well as gingiva to bleaching systems containing 10-15% carbamide peroxide or 2-10% hydrogen peroxide for more than a few minutes. The aims of the present study were: (1) to determine the cytotoxicity of dilutions of hydrogen peroxide in cell culture; (2) to measure hydrogen peroxide diffusion from bleaching agents through dentin in vitro; and (3) to determine the risk of hydrogen peroxide-induced cytotoxicity from exposure of dentin to these vital bleaching agents. The 50% inhibitory dose (ID50) of hydrogen peroxide to succinyl dehydrogenase activity in cultured cells was found to be 0.58 mmol/L after 1 h. All bleaching materials demonstrated diffusion of hydrogen peroxide through dentin in an "in vitro pulp chamber" device. The one- and six-hour diffusates of all bleaching agents through 0.5-mm dentin exceeded the ID50 in monolayer cultures. Inhibition of succinyl dehydrogenase activity corresponded to the amount of hydrogen peroxide that can rapidly diffuse through dentin in vitro and reach concentrations which are toxic to cultured cells in less than 1 h.

Vital bleaching agents and oral antiseptic: effect on anaerobic bacteria

This in vitro study compared the antimicrobial effect of several at-home bleaching agents and an oral antiseptic against anaerobic bacteria that are commonly found in the oral cavity. Zones of inhibition produced by Rembrandt Lighten Bleaching Gel, Opalescence, and Peroxyl were measured and compared. All the materials produced zones of inhibition with the five bacteria used in the study.