Tooth bleaching: its effect on oral tissues

Biomaterials based on advanced oxidation processes in tooth whitening: fundamentals, progress, and models

The increasing desire for aesthetically pleasing teeth has resulted in the widespread use of tooth whitening treatments. Clinical tooth whitening products currently rely on hydrogen peroxide formulations to degrade dental pigments through oxidative processes. However, they usually cause side effects such as tooth sensitivity and gingival irritation due to the use of high concentrations of hydrogen peroxide or long-time contact. In recent years, various novel materials and reaction patterns have been developed to tackle the issues related to H2O2-based tooth whitening. These can be broadly classified as advanced oxidation processes (AOPs). AOPs generate free radicals that have potent oxidizing properties, which can thereby increase the oxidation power and/or reduce the exposure time and can probably minimize the side effects of tooth bleaching. While there have been several reviews on clinical tooth whitening and the application of novel nanomaterials, a review based on the concept of AOPs in tooth bleaching application has not yet been conducted. This review describes the common types and mechanisms of AOPs, summarizes the latest research progress of new tooth bleaching materials based on AOPs, and proposes a model for tooth bleaching and a rate control step at the molecular level. The paper also reviews the shortcomings and suggests future development directions.

Prognosis in home dental bleaching: a systematic review

OBJECTIVES

The aim of this systematic review was to evaluate the prognosis of at-home dental bleaching using low concentration bleaching products.

MATERIALS AND METHODS

This review was conducted was performed following the recommendations of the 2020 PRISMA statement and was registered in the International Prospective Register of Systematic Reviews (PROSPERO-CRD42022360530). The PICO question was "What is the prognosis of home teeth whitening treatment?". An advanced electronic search was made in three databases: PubMed, Web of Science, and Embase.

RESULTS

The database search led to the retrieval of 225 articles. After elimination of duplicate references, the titles and abstracts of the articles were analyzed with respect to the eligibility criteria, and 24 studies were included for the development of the systematic review.

CONCLUSIONS

Most authors state that the color remains stable between 1 and 2.5 years regardless of the type of bleaching agent or the forms of administration, and color stability in cases of severe discolorations presents a higher degree of recurrence.

CLINICAL RELEVANCE

Given the growing demand for dental cosmetic treatments, the following systematic review may aid the clinician's continuing education and evidence-based practice by providing knowledge on the field of at-home dental bleaching agents and their long-term effects.

Effects of Hypochlorous Acid and Hydrogen Peroxide Treatment on Bacterial Disinfection Treatments in Implantoplasty Procedures

One of the main problems in oral implantology today is peri-implantitis, which affects almost 20% of dental implants placed in patients. One of the most commonly used techniques to eliminate bacterial biofilm is the implantoplasty, that consists of the mechanical modification of the implant surface topography followed by treatments with chemical reagents for decontamination. In this study, the main aim is to evaluate the use of two different chemical treatments based on hypochlorous acid (HClO) and hydrogen peroxide (H₂O₂). For this purpose, 75 titanium grade 3 discs were treated with implantoplasty according to established protocols. Twenty-five discs were used as controls, 25 were treated with concentrated HClO and 25 were treated with concentrated HClO followed by treatment with 6% H₂O₂. The roughness of the discs was determined using the interferometric process. Cytotoxicity with SaOs-2 osteoblastic cells was quantified at 24 and 72 h, whereas bacteria proliferation using S. gordonii and S. oralis bacteria was quantified at 5 s and 1 min of treatment. The results showed an increase in the roughness values, the control discs had an Ra of 0.33 μm and those treated with HClO and H₂O₂ reached 0.68 μm. Cytotoxicity was present at 72 h, together with a significant proliferation of bacteria. These biological and microbiological results can be attributed to the roughness produced by the chemical agents that triggered bacterial adsorption while inhibiting osteoblast adhesion. The results indicate that even if this treatment can decontaminate the titanium surface after implantation, the produced topography will generate an environment that will not favor long-term performance.

Present status and future directions - Managing discoloured teeth

Managing tooth discolouration involves a range of different protocols for clinicians and patients in order to achieve an aesthetic result. There is an increasing public awareness in the appearance of their teeth and management of tooth discolouration may be inter-disciplinary and involve both vital and nonvital teeth. Vital teeth can be easily treated with low concentration hydrogen peroxide products safely and effectively using an external approach and trays. For endodontically treated teeth, the walking bleach technique with hydrogen releasing peroxide products is popular. However, there is an association with external cervical root resorption with higher concentrations of hydrogen peroxide of 30%-35%. There are also regulatory considerations for the use of hydrogen peroxide in certain jurisdictions internationally. Prosthodontic treatments are more invasive and involve loss of tooth structure as well as a life cycle of further treatment in the future. This narrative review is based on searches on PubMed and the Cochrane library. Bleaching endodontically treated teeth can be considered a safe and effective protocol in the management of discoloured teeth. However, the association between bleaching and resorption remains unclear although there is likely to be a relation to prior trauma. It is prudent to avoid thermocatalytic approaches and to use a base/sealer to cover the root filling. An awareness expectations of patients and multidisciplinary treatment considerations is important in achieving the aesthetic result for the patient. It is likely that there will be an increasing demand for aesthetic whitening treatments. Bleaching of teeth has also become increasingly regulated although there are international differences in the use and concentration of bleaching agents.

Hamster Cheek Pouch Bioassay of Dentifrices Containing Hydrogen Peroxide and Baking Soda

The objective of this study was to determine the effects of hydrogen peroxide alone and in combination with 7,12-dimethylbenza[a]anthracene (DMBA) in the oral cavity because H2o2, has been implicated as a complete carcinogen or cocarcinogen in two animal models. In the two independent studies, golden Syrian hamsters were used to evaluate the carcinogenic and cocarcinogenic potential of dentifrices containing H2o2 and NaHCO3. In the first study, the cocarcinogenic potential of a dentifrice containing 0.75% H2O2/ 5% baking soda was compared with that of a commercial dentifrice with similar ingredients except baking soda and H2O2. In the second study, the cocarcinogenic potential of a dentifrice formulated with 1.5% H, sb>2O2/7.5% baking soda was compared with a mixture of 3% H2O2/baking soda. All materials were applied to the right cheek pouches of experimental animals, and the left cheek pouches were untreated. In the first study. 0.5% DMBA was administered five times weekly for 20 weeks, and the dentifrices were applied immediately after the DMBA. Dentifrices or mineral oil alone were also applied five times weekly. In the second study. 0.5% DMBA or 0.25% DMBA were applied three times weekly for 16 weeks; dentifrices (or 3% H2O2/baking soda) were applied five times weekly for 16 weeks. The dual-phase dentifrice containing 0.75% H2O2/5% baking soda was not carcinogenic, and in combination with DMBA resulted in no observable acceleration of tumor onset, compared with DMBA alone. In fact, animals treated with 0.5% DMBA and the H2O2/baking soda dentifrice had a significantly delayed onset of tumor formation than did animals treated with DMBA alone. In the second bioassay, an increased latency period for tumor formation was observed with 0.5% DMBA and a dual-phase dentifrice containing 1.5% H2O2/7.5% baking soda, compared with 0.5% DMBA alone. With 0.25% DMBA, latency was not affected by addition of the dual-phase dentifrice. In contrast, animals receiving 0.25% DMBA and 3% H2O2/ NaHCO3 had a significantly lower rate of tumor formation and overall mass incidence. Croton oil also reduced the rate of tumor formation when applied with 0.25% DMBA. Histopathologic examination of cheek pouches revealed squamous cell carcinomas in the majority of DMBA-treated animals. Cheek pouches of DMBA-treated animals killed at interim times indicated a progression from keratotic changes and/or dyskeratosis at 6 weeks with the occurrence of carcinomas in approximately half the animals examined at 12 weeks. No significant histopathologic abnormalities were observed in animals not receiving DMB A other than slight keratosis in the oral mucosa of one or two animals per group. These results demonstrated that an oral product containing baking soda and hydrogen peroxide was not carcinogenic, and that baking soda and H2O2 did not enhance the tumorigenicity of DMB A. Furthermore, the tumor-igenic response of DMBA was reduced by coadministration of 3% H2O2 and sodium bicarbonate.

Does at-home bleaching induce systemic oxidative stress in healthy subjects?

BACKGROUND

At-home bleaching is a technique characterized by the use of carbamide peroxide or hydrogen peroxide as a tooth-whitening agent. However, no data exist regarding systemic safety of this technique. The aim of this study was to investigate the effect of at-home bleaching on serum redox homeostasis.

METHODS

Twenty-nine healthy volunteers who requested tooth-whitening participated in this study. Specified bleaching trays were fabricated for the maxilla and mandible arches. Each participant was given two syringes containing 9% hydrogen peroxide gel to use for 30 min/night for 14 nights consecutively. To evaluate the redox status, the serum concentrations of malondialdehyde (MDA), total antioxidant capacity (TAC) and pro-oxidant-antioxidant balance (PAB) were measured. Blood samples were obtained in the morning prior to initiation of study and the morning after expiration of the bleaching period. The collected data were analyzed using Student's t-test with 95% confidence interval.

RESULTS

Twenty-three subjects completed the study. MDA, PAB and TAC were significantly increased after the bleaching period (P = 0.001, 0.001 and 0.002, respectively).

CONCLUSIONS

At-home bleaching revealed the potential to disturb oxidant-antioxidant balance and induce oxidative stress. Its clinical relevance is unfavourable and potential side-effects of at-home bleaching should be considered.

Tooth-bleaching procedures and their controversial effects: A literature review

AIM

This review article will help clinicians improve their understanding of the history of bleaching procedures, bleaching types, components, mechanisms, and their effects on soft tissue, tooth structures, resin composite, and bonding.

METHODS

The controversial issues about bleaching procedures and their effects are reviewed. Additionally, the consequences of pre- and post-bleaching on the bonding potential of composite resin restorations to tooth structure are discussed.

CONCLUSION

The overall goal of the paper is to help reduce risks for patients.

Effect of intracoronal bleaching agents on ultrastructure and mineral content of dentin

Aim:

The purpose of this in vitro study was to evaluate the ultrastructural changes of dentin induced after exposure to different intracoronal tooth bleaching agents.

Materials and Methods:

Dental discs of 1 mm thickness were prepared from coronal dentin of sixty-four human maxillary premolars. Experimental specimens were divided into four subgroups: 45% carbamide peroxide, 35% hydrogen peroxide, sodium perborate + 30% hydrogen peroxide, sodium perborate + water. The specimens were then evaluated under scanning electron microscope to determine diameter of dentinal tubules and chemical analysis.

Results:

There was significant difference between dentinal tubule diameter of all test and control groups with the exception of sodium perborate + water. Chemical analysis revealed that there was no significant difference between experimental subgroups regarding calcium and sulfur wt%.

Conclusions:

All bleaching agents increased dentinal tubule diameter and promote alterations in mineral content of dentin with the exception of Sodium perborate mixed with water.

Influence of the light source and bleaching gel on the efficacy of the tooth whitening process

OBJECTIVE

To examine the whitening efficacy of three whitening agents in combination with six different photoactivation systems.

BACKGROUND

Bleaching techniques have achieved significant advances using photoactivation with coherent or incoherent radiation sources.

METHODS

Quick White, Ena White Power, and Opalescence Endo bleaching agents, all containing 35% hydrogen peroxide, were stimulated with halogen lamp, light-emitting diode (LED), low-power diode laser, and neodymium: yttrium-aluminum-garnet (Nd:YAG), second harmonic of Nd:YAG, and Er:YAG lasers. One hundred twenty-six extracted human incisors were treated, and color change, pulpal temperature, and enamel morphological alterations were evaluated.

RESULTS

Only the groups that were photoactivated using a diode laser, halogen lamp, and LED showed statistically significant differences (p < 0.005) in color change when compared with the control group (without photoactivation). All whitening protocols were safe with regard to the increase in pulpal temperature. Scanning electron microscopy showed no evidence of effects on the integrity of enamel.

CONCLUSIONS

The source of irradiation is more relevant than the bleaching agent for efficient tooth whitening. In addition, photoactivation with LED was found to be the best choice: it yielded significant change in color with only a minor increase in pulpal temperature.

Diffusion of peroxides through dentine in vitro with and without prior use of a desensitizing varnish

Different bleaching regimens are used in dentistry possibly penetrating the dentine and affecting the pulp. The aim of the present study was to investigate peroxide diffusion through dentine pre-treated with a desensitizing varnish (Vivasens®) in a standardized in vitro setup during application of different bleaching materials. The penetration was tested using 1.3-mm-thick bovine dentine slabs. The following bleaching materials were tested with and without prior application of the desensitizing varnish on the external side of the dentine slabs: Vivastyle, Whitestrips, Simply White, Opalescence (external bleaching), and sodium perborate (internal bleaching, only tested without varnish; n = 8 samples per subgroup). The penetration of peroxides was measured photometrically using 4-aminoantipyrin as a substrate, the penetration of peroxides was monitored over 240 min. All bleaching agents yielded a diffusion of peroxides through the dentine, the kinetics of penetration were approximately linear for all materials tested. The significantly highest diffusion of peroxides was observed with Opalescence, the lowest with sodium perborate. The adoption of the desensitizing varnish reduced the diffusion of peroxides significantly for all external bleaching materials. Peroxides penetrated the dentine during application of bleaching materials; the penetration of peroxides can be reduced by application of a desensitizing agent.

In Situ Study of In-office Bleaching Procedures Using Light Sources on Human Enamel Microhardness

Regardless of the light sources used, the microhardness of human dental enamel did not present significant changes 14 days after in-office bleaching.

Nonvital tooth bleaching: a review of the literature and clinical procedures

Tooth discoloration varies in etiology, appearance, localization, severity, and adhesion to tooth structure. It can be defined as being extrinsic or intrinsic on the basis of localization and etiology. In this review of the literature, various causes of tooth discoloration, different bleaching materials, and their applications to endodontically treated teeth have been described. In the walking bleach technique the root filling should be completed first, and a cervical seal must be established. The bleaching agent should be changed every 3-7 days. The thermocatalytic technique involves placement of a bleaching agent in the pulp chamber followed by heat application. At the end of each visit the bleaching agent is left in the tooth so that it can function as a walking bleach until the next visit. External bleaching of endodontically treated teeth with an in-office technique requires a high concentration gel. It might be a supplement to the walking bleach technique, if the results are not satisfactory after 3-4 visits. These treatments require a bonded temporary filling or a bonded resin composite to seal the access cavity. There is a deficiency of evidence-based science in the literature that addresses the prognosis of bleached nonvital teeth. Therefore, it is important to always be aware of the possible complications and risks that are associated with the different bleaching techniques.

External bleaching therapy with activation by heat, light or laser—A systematic review

OBJECTIVE

External bleaching procedures utilizing highly concentrated 30-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures.

SOURCES

Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review.

DATA

Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 degrees C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation.

CONCLUSION

Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.

In vitro evaluation of a novel 6% hydrogen peroxide tooth whitening product

OBJECTIVES

The aims of this study were to evaluate the in vitro tooth whitening effects of a novel 6% hydrogen peroxide containing tooth whitener Xtra White (XW) on extrinsic stain and intrinsic tooth colour and the effects on enamel and dentine microhardness. In addition, to determine the levels of peroxide found in tooth pulp chambers after treatment with XW in vitro.

METHODS

Extrinsic stain changes were determined by measuring colour changes of tea stained hydroxyapatite discs after treatment with water, placebo gel, XW or Colgate Simply White (CSW). Intrinsic tooth colour changes were determined by treating extracted human teeth in vitro with a placebo gel, XW or CSW for a simulated two weeks use and measuring colour differences with a chroma meter. Teeth treated with placebo gel and XW were cross-sectioned and the subsurface enamel and dentine was polished and the microhardness determined. The peroxide concentration found in extracted tooth pulp chambers was determined spectrophotometrically.

RESULTS

XW gave significantly more extrinsic stain removal (p<0.0001) and an increase in tooth whiteness (p<0.05) than a placebo gel, but was not significantly different to CSW. There were no significant differences in subsurface enamel and dentine microhardness values for the placebo and XW treated teeth. The mean concentration of peroxide found in the tooth pulp chambers was 0.44 mM, which is over 3000 times below the concentration reported to cause pulpal enzyme damage.

CONCLUSIONS

XW has been shown to be an effective tooth whitening product in vitro with support for its safety on subsurface enamel and dentine together with its safety on tooth pulp tissue.

Determination of peroxides in saliva--kinetics of peroxide release into saliva during home-bleaching with Whitestrips and Vivastyle

Aim of the study was to determine peroxides in saliva, released during bleaching procedures. Upper incisors of five subjects were bleached with Whitestrips (5% H2O2) and Vivastyle (10% carbamide peroxide, tray charged with 225mg) for 30min, each on different days. Saliva was collected before and during the whole period of bleaching at different intervals. The amount of peroxide in the salivary samples was assessed with peroxidase, phenol and 4-aminoantipyrin in a photometric assay. Additionally the amount of peroxides in the bleaching material was determined before and after the bleaching, so that the peroxide release into saliva could be balanced. The amount of peroxides released into saliva was related to the bleaching system and only partially influenced by the individual salivary flow rate. Bleaching with Vivastyle led to lower release of peroxides into saliva compared to Whitestrips (Vivastyle: 0.8+/-0.17mg; Whitestrips: 1.5+/-0.84mg). Salivary flow rate was not correlated to release of peroxides from the bleaching products. It can be concluded that the enzymatic method adopting 4-aminoantipyrin and peroxidase is valid for the determination of peroxides in saliva. Furthermore distinctly more peroxides are released into the oral cavity from Whitestrips than from trays charged with Vivastyle .

Effect of bleaching agents on the fluoride release and microhardness of dental materials

The use of bleaching agents has become a popular procedure for whitening teeth. Recently introduced polyacid-modified composite resins (compomers) have several favorable features, such as improved physical properties and fluoride release. Because these two materials have many possibilities to interact in the oral cavity during dental treatment, it is necessary to understand such interaction. To evaluate the effect of a bleaching agent on dental restoratives, three compomers were photopolymerized and then bleached for 1, 2, 3 and 5 days with the use of 30% hydrogen peroxide. Fluoride release, surface microhardness, and surface modifications were evaluated. It was found that the cumulative fluoride release was found to be linearly correlated to the tested periods of bleaching in all compomers. Among the tested compomers, F2000 showed the highest cumulative fluoride release. Bleached compomers became soft because of surface degradation, so the surface microhardness decreased. F2000 showed an apparent crack formation that was not observed in other compomers. The nearly linear correlation between the filler content and microhardness was found in the control samples. However, the same correlation was not observed after the compomers were stored in a bleaching agent or distilled water.

Safety and stability of nightguard vital bleaching: 9 to 12 years post-treatment

PURPOSE

The purposes of this retrospective case series study were to evaluate safety issues and determine participants' perceptions of a nightguard vital bleaching (NGVB) technique approximately 10 years post-treatment (average, 118 mo; range, 108-144 mo).

MATERIALS AND METHODS

The study sample included 30 (79%) of 38 participants who had completed a previous NGVB study using a 10% carbamide peroxide solution (Proxigel or Gly-Oxide) in a custom tray for 6 weeks. Participants were asked whether there had been any change in the shade of their teeth post-treatment and, if so, to quantify the change on a verbal scale. In addition, 19 participants had gingival index and tooth vitality evaluated clinically, external cervical root anatomy evaluated radiographically, and enamel surface changes evaluated microscopically.

RESULTS

Thirty-five (92%) of the original 38 participants had successful lightening of their teeth. At approximately 10 years post-treatment (average, 118 mo; range, 108-144 mo), external cervical resorption was not diagnosed and gingival index and tooth vitality findings were considered within the normal expectations for the sample studied, suggesting minimal clinical post-NGVB side effects at approximately 10 years. Scanning electron microscopic observations did not reveal substantial differences between treated and nontreated surfaces. Color stability, as perceived by 43% of the participants, may last approximately 10 years (average, 118 mo; range, 108-144 mo) post-treatment.

CLINICAL SIGNIFICANCE

Nightguard vital bleaching using 10% carbamide peroxide is safe and effective, with no noticeable side effects, at approximately 10 years (average, 118 mo; range, 108-144 mo) post-treatment. Color stability, as perceived by 43% of the participants, may last 108 to 144 months post-whitening.

Sensitivity and tooth whitening agents

PURPOSE

Three commercially available dentist-prescribed home-applied bleaching systems were evaluated to identify the incidence of sensitivity and to compare the efficacy of whitening the maxillary anterior teeth of 18 patients.

METHODS

NiteWhite Excel 2Z (Discus Dental), fx (Challenge Products), and Rembrandt Xtra-Comfort (DenMat Corp.) were randomly assigned to six patients each. The fx product was used as a control since it was not advertised as a zero sensitivity product. The manufacturers' instructions for tray fabrication and use were followed while the patients bleached for 2 weeks. The patients kept a diary and were recalled at 1 week, 2 weeks, and 4 weeks. The shade change and the presence or absence of any sensitivity were evaluated at each recall.

RESULTS

NiteWhite Excel 2Z was used for 83 days of treatment with the following percentage of positive sensitivity reported: 0% hot and cold, 2.4% throat sensitivity, 2.4% tongue sensitivity, and 25.3% gingival sensitivity. Rembrandt Xtra-Comfort was used for 84 days with 0% hot and cold, 0% throat, 11.9% tongue, and 27.4% gingival sensitivity reported. The fx product was used for 83 days and resulted in 14.5% hot and cold, 3.6% throat, 1.2% tongue, and 16.9% gingival sensitivity. All products lightened the teeth an average of eight shade tabs on the Vita guide. There was a statistically significant difference between the groups when comparing the presence of sensitivity (chi-squared test, p < .001) but not when comparing the shade tab change.

CLINICAL SIGNIFICANCE

Of the products tested, all produced similar change in shade tab value, none were sensitivity free, but NiteWhite Excel 2Z and Rembrandt Xtra-Comfort did not produce thermal sensitivity.

Nightguard vital bleaching and its effect on enamel surface morphology

BACKGROUND

The effect that nightguard vital bleaching (NGVB) has on enamel surface morphology is a subject of debate. Previous studies that have evaluated the effect of NGVB on the enamel surface report minimal changes to changes that appear to worsen post-treatment. The purpose of this in vivo NGVB study was to evaluate by scanning electron microscopy (SEM) the effects that 10% carbamide peroxide has on enamel morphology after 2 weeks of treatment and at 6 months post-treatment.

MATERIALS AND METHODS

Ten patients participated in the study. Each participant wore a guard filled with an active whitening solution for 8 to 10 hours per day for 14 treatment days. An impression of the study teeth (maxillary incisors) was taken at baseline, after 14 days of treatment, and at 6 months post-treatment, and an epoxy cast made. The epoxy casts were prepared for viewing under the SEM and photographs were taken at 200 times and 2,000 times magnification. Six examiners evaluated changes in enamel surface morphology by comparing the SEM photographs taken at baseline, on treatment day 14, and at 6 months post-treatment. Still masked, the examiners also compared each patient's baseline:treatment day 14 and baseline:6 months post-treatment photographs with photographs of a known standard.

RESULTS

This in vivo study demonstrated that a 14-day regimen of NGVB using a 10% carbamide peroxide solution had minimal effect on the surface morphology of enamel and that the effects did not worsen over time.

Safety issues relating to the use of hydrogen peroxide in dentistry

Hydrogen peroxide is used widely in professionally and self-administered products. Hydrogen peroxide is a highly reactive substance which can damage oral soft tissues and hard tissues when present in high concentrations and with exposures of prolonged duration. This report provides an overview of health issues relating to the use of hydrogen peroxide, with an emphasis on safety with prolonged exposure to low concentrations of peroxide products. There is good evidence for the safety of hydrogen peroxide when used at low concentrations on a daily basis over extended periods of time, in self-administered oral health care products such as dentifrices and mouthrinses. These low concentrations neither damage oral hard or soft tissues, nor do they pose a significant risk of adverse long-term effects. Caution should be exercised with the increasingly higher concentration peroxide products used for 'walking' or 'power' bleaching due to the possibility of chemical irritation of oral soft tissues with injudicious use. The volumes of material and application times should be controlled carefully. Thorough education of patients is particularly important with self-applied gels because of the lack of professional supervision with such products. Such education is part of the duty of care of the dentist who supplies bleaching gels for at-home use.

Nightguard vital bleaching of tetracycline-stained teeth: 54 months post treatment

PURPOSE

The purpose of this longitudinal whitening study was to determine the stability, post-treatment side effects, and patient satisfaction after 6 months of active treatment of tetracycline-stained teeth with 10% carbamide peroxide at 0 and 54 months post treatment.

MATERIALS AND METHODS

Twelve patients who completed the study (80%) were contacted and asked to participate in a survey concerning their whitening experience. Subjects were asked whether there had been any change in the shade of their teeth after treatment, and if they had experienced any side effects that they believed were treatment-related. Eight of the twelve patients underwent clinical examination.

RESULTS

Ten patients (83%) reported no obvious shade change or only a slight darkening not noticed by others. Two (17%) reported a slight darkening that is probably noticeable by other people, but no one reported moderate darkening or significant darkening back to original shade. All respondents (n = 12) denied having to have a crown or root canal that they believed was treatment-related. Examiners who compared preoperative and post-treatment photographs and Vita shade values were in agreement with the patient's perceptions of shade change. The degree of improvement was significant for both the immediate (0 mo) and the 54-month post-treatment comparison with the pretreatment shade (p < .005 and p < .01 respectively).

CLINICAL SIGNIFICANCE

Results of this nightguard vital bleaching study indicate that tetracycline-stained teeth can be whitened successfully using extended treatment time, and that shade stability may last at least 54 months after treatment. Patients who participated in this study were overwhelmingly positive about the procedure in terms of shade retention and lack of post-treatment side effects.

Bleaching effect of sodium percarbonate on discolored pulpless teeth in vitro

The purpose of this study was to evaluate the bleaching effect of sodium percarbonate on artificially stained pulpless teeth. Twenty extracted human mandibular premolars were stained by immersing them in human blood mixed with iron sulfide, and divided into three test groups and one control group. The following bleaching agents were used: sodium perborate mixed with 30% hydrogen peroxide (WB), sodium percarbonate mixed with distilled water (PW) or 30% hydrogen peroxide (PH). On days 5, 10, and 15, each pulp chamber was refilled with fresh bleaching paste. The L* (average lightness) of the midbuccal area of specimens was measured before and after staining, and on days 5, 10, 15, and 20 by colorimeter. The bleaching effect was evaluated by the lightness recovery rate (LRR) calculated from L*. WB showed the highest LRR among all groups, and PW and PH showed significantly higher LRR when compared with the control group. PW and PH were not significantly different. Results showed that sodium percarbonate had an obvious bleaching effect without hydrogen peroxide and indicated that it could be a safe intracoronal bleaching agent.

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%.