Tooth-Bleaching: A Review of the Efficacy and Adverse Effects of Various Tooth Whitening Products.

Tooth bleaching (whitening) is one of the most common and inexpensive method for treating discolouration of teeth. Dental aesthetics, especially tooth colour, is of great importance to majority of the people; and discolouration of even a single tooth can negatively influence the quality of life. Therefore, a review of the literature was carried out (limited to aesthetic tooth-bleaching) to provide a broad overview of the efficacy and adverse effects of various tooth whitening products on soft and hard oral tissues.

In vitro evaluation of variances between real and declared concentration of hydrogen peroxide in various tooth-whitening products.

OBJECTIVES: The aim of this in vitro study was to analyze the real hydrogen peroxide (HP) concentration in various commercially available tooth-whitening products containing HP and/or carbamide peroxide (CP). MATERIALS AND METHODS: Sixteen commercially available tooth-whitening products containing various concentrations of CP or HP were investigated. The products were divided into four groups: dentist-supervised home bleaching products (Group 1, n = 5), in-office bleaching products (Group 2, n = 4), over-the-counter bleaching products (Group 3, n = 3) and whitening toothpastes and rinses (Group 4, n = 4). The peroxide concentration was determined using the oxy-reduction titration method. All the reagents used in the study were of analytic grade and freshly prepared before the experiment. RESULTS: The HP concentration in various dentist-supervised home bleaching products and in-office bleaching products ranged from 3.02-37.08% (expected range = 3-38%). The HP concentration of over-the-counter whitening products ranged from 1.24-5.57% (expected range cannot be estimated as no concentration of active ingredient was provided). Among whitening toothpastes and rinses, Colgate Plax whitening rinse showed more than 1% HP concentration, whereas it was lower than 0.05% in other whitening toothpastes and oral rinses (expected range cannot be estimated as no active ingredient was mentioned). CONCLUSIONS: HP concentration of most of the professional tooth-whitening products was different from the expected concentrations, although the deviations were small and most of the products were close to the expected concentration. No concentration of active ingredient was provided for over-the-counter whitening products and no active ingredient was mentioned for whitening toothpastes and rinses.

IPNs from Cyclodextrin:Chitosan Antioxidants: Bonding, Bio-Adhesion, Antioxidant Capacity and Drug Release.

IPNs are unique "alloys" of cross-linked polymers in which at least one network is synthesized and/or cross-linked in the presence of the other. IPNs are also known as entanglements of polymer networks that are ideally held together only by permanent topological interactions. The objectives of this study are to evaluate novel chitosan-based functional drug delivery systems that can be successfully incorporated into "dual action bioactive tooth restorative materials". These materials should be capable of inducing an improved wound healing prototype. The novel hydrogels will be investigated with respect to the antioxidant capacity of conventional antioxidants, such as resveratrol, b-carotene and propolis, as a designer drug delivery system, with the use of SEM imaging for the characterization of the surfaces, bio-adhesive property, antioxidant capacity, free radical defence, antioxidant, active ingredient stability and reactive features of novel materials. The additional benefit of the site-specific "functional restorative material" for use in dressings to deliver antibiotics to wound sites can provide tissue compatibility and reduced interference with wound healing. The materials were tested using an effective in vitro free radical generation model as functional additive prototypes for further development of "dual function restorative wound healing materials". We quantified the effects of functional designer biomaterials on the dentin bond strength of a composite and evaluated the bio-adhesive capacity of the materials in the two separate "in vitro" systems. The added benefits of the chitosan/vitamin C/cyclodextrin (CD) host:guest complex-treated hydrogels involved a positive influence on the tetracycline release, increased dentin bond strength, as well as a demonstrated in vitro "built-in" free radical defence mechanism and, therefore, acting as a "proof of concept" for functional multi-dimensional restorative wound healing materials with a built-in free radical defence mechanism. Based on our results, we can conclude that the CD:chitosan-antioxidant-containing hydrogels are a suitable carrier for tetracycline to be slow-released. Within the limitations of the study design, chitosan-based hydrogels are suitable materials for functional restorative and wound healing applications in vitro. Cytotoxicity data are currently being evaluated in our laboratory.

Insights into and relative effect of chitosan-H, chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin on dentine bond strength.

OBJECTIVE: The purpose of the study was to design and evaluate novel functional chitosan hydrogels (chitosan-H-propolis, chitosan-H-propolis-nystatin and chitosan-H-nystatin) by using the chitosan-H polymer as "dual function restorative materials". MATERIALS AND METHODS: The nystatin/antioxidant carrier gel was prepared by dispersion of the corresponding component in glycerol and 3% acetic acid with 5% chitosan gelling agent was then added to the dispersion with continuous mixing. The natural bio-adhesive functionalized chitosan hydrogels were combined with built in drug delivery system and bio-actives such as propolis in order to increase the dentin bond strength capacity and maintain therapeutic properties of the alternative drug delivery system. The surface morphology, release behaviors (physiological pH and also in acidic conditions), stability of nystatin:antioxidant:chitosan and the effect of the hydrogels on the shear bond strength of dentin were also evaluated. STATISTICAL ANALYSIS USED: Non-parametric ANOVA test was used to asses significance of higher shear bond values than dentine treated or not treated with phosphoric acid. RESULTS: The release of both nystatin and propolis confer the added benefit of dual action of a functional therapeutic delivery when comparing the newly designed chitosan-based hydrogel restorative materials to commercially available nystatin alone. Neither the release of nystatin nor the antioxidant stability was affected by storage. Chitosan-H, chitosan-propolis, chitosan-nystatin and chitosan-nystatin-propolis treated dentine gives significantly (P < 0.05) higher shear bond values (P < 0.05) than dentine treated or not treated with phosphoric acid. CONCLUSION: The added benefits of their unique functionality involve increased dentin adhesive bond strengths (after 24 h and after 6 months) and positive influence on the nystatin release. Nystatin was a model therapeutic agent, evaluating the concept of using functional materials as carriers for pro-drugs as well as displaying a certain degree of defence mechanism for free radical damage of the novel functional drug delivery. Overall, there was an insignificant relapse in the shear bond strength after 6 months.

A clinical study of the effectiveness of a light emitting diode system on tooth bleaching.

UNLABELLED: The purpose of this study was to evaluate the efficacy of a Light Emitting Diode (LED) System (BriteWhite) on tooth bleaching. METHOD: eeth 11 and 21 of twenty one subjects were treated in the chair with a LED light and 44% carbamide peroxide gel, followed by an at-home treatment period of 14 days with 35% carbamide peroxide. The color of the teeth was measured with a spectrophotometer (L*; a*; b*) before treatment (control) and after the above mentioned two stages. The subjects were also instructed to note tooth and gingival sensitivity. RESULTS: For the L* component a statistically significant difference (p<0.05) between base-line and directly after the LED treatment stage (whiter) was found and a complete relapse was found after the 14 day at-home treatment period. The b* component showed statistically significant differences (p<0.05) between base-line and the LED stage (less yellow more blue), with a further significant color improvement after the 14 day treatment period. For the a* component (green to red) no statistically significant change was (p>0.05) found throughout the study (Wilcox on Signed Rank Sum Test). A major color change of 1.8 units (ΔE(ab)) was found after the LED treatment stage with only a further small 0.2 unit improvement after the 14 day at-home treatment stage. Tooth and gingival sensitivity scores were low (below mild) throughout the treatment stages. CONCLUSION: A major tooth color increase was found after the in-office LED/gel treatment stage and only an insignificant further improvement was noted after the additional 14 day at-home treatment period. Only low tooth and gingival sensitivity scores were found. A slight increase in both the sensitivity and gingival scores after the LED/gel activated stage could be observed. Overall the total color increase was low.

The pH Levels of Different Methamphetamine Drug Samples on the Street Market in Cape Town.

The purpose of this study was to determine the pH levels of 29 different samples of methamphetamine on the street market in Cape Town. The sample was dissolved in water and the pH of each sample determined. The pH levels varied from 3.02 to 7.03 with an average of 5.0. Seventy-two percent (21) of the samples had a pH level below the saliva "critical pH point of 5.6" and therefore should cause significant damage to enamel, especially in hyposalivation subjects without a saliva flow. However, about 26% of the samples had a pH level close to the neutral point and should cause minor damage to enamel. To lessen enamel damage, subjects should exercise good oral hygiene practice, rinse with a fluoride-containing mouth rinse, drink artificially sweetened drinks, and eat cheese. It is concluded that most of the methamphetamine samples have a low enough pH to cause direct damage to enamel especially in hyposalivation subjects.

In vivo Spectrophotometric Assessment of the Tooth Whitening Effectiveness of Nite White 10% with Amorphous Calcium Phosphate, Potassium Nitrate and Fluoride, Over a 6-month Period.

UNLABELLED: To clinically evaluate the effectiveness of Nite White 10% carbamide peroxide with amorphous calcium phosphate, potassium nitrate and fluoride over a 6-month follow-up period. Nite White was applied nightly for 14 days, according to the manufacturer's instructions. The color of teeth 11 and 21 of twenty one subjects was measured with a spectrophotometer (L(*); a(*); b(*)). Subjects were instructed to take note of any tooth sensitivity and gingival irritation. For all three components (L(*), a(*) and b(*)) statistical significant differences (p<0.05) in the values between base-line (pre-bleaching) and; after treatment, after 1-month, after 3-months as well as after 6-months were found (Wilcoxon Signed Rank Sum Test). Significant differences were also found amongst the ΔE(*) (ab) (0-14days) values and; ΔE(*) (ab) (0-1 month), ΔE*(ab) (0-3 months) and ΔE(*) (ab) (0-6 months). However, no significant differences were found between pairs of ΔE(*) (ab) (0-1 month), ΔE(*) (ab) (0-3 months) and ΔE(*) (ab) (0-6months). The decrease in ΔE(*) (ab) was the highest after 1 month (~30%). The highest decrease in L(*) was about 58% after 1 month. Over the 14-day treatment period tooth sensitivity was 24.5%. CONCLUSIONS: Nite White ACP demonstrated significant tooth-whitening (unit increase = 5.29) with a low tooth sensitivity (25%) probably due to the presence of amorphous calcium phosphate, potassium nitrate, and fluoride. The whitening effect decreased the most after one month and then maintained well even after a 6 month period (units 3.89). CLINICAL IMPLICATIONS: The product is a good tooth whitener with a color increase of about 5 units accompanied with a low sensitivity.

Orthodontic molar brackets: the effect of three different base designs on shear bond strength.

The purpose of the study was to assess the relative base designs of three different maxillary molar stainless steel brackets with reference to the shear bond strength of three different adhesive resins. The molar brackets used were Victory series (3M Unitek), Upper Molar (GAC) and Optimesh XRT (Ormco). The adhesives used were Transbond XT (3M Unitek), Enlight (Ormco) and Sure Ortho Light Bond (Sure Orthodontics). The human enamel specimens (144) were randomly divided into nine groups and each group (n=16) was allocated to a bracket/adhesive combination. The contact surface of each of the bracket bases was measured three dimensionally using a reflex microscope. The base designs were also subjected to further microscopic investigations. The brackets were bonded to the enamel, temperature cycled and the shear bond strength was measured. The size and design of each of the brackets was different. The base size, surface treatment, mesh strand diameter and aperture size of the bracket base mesh have a significant effect on the shear bond strength at the bracket/adhesive interface. The shear bond strengths of all three Ormco bracket/adhesive resin combinations (5.8-6.8 MPa) were significantly lower (p<0.05; Kruskal-Wallis) than the other six bracket/adhesive combinations (9.4-12.1 MPa). The different adhesive types (3 types) could not be mainly responsible for the low shear bond values found for the Ormco bracket. The 3M Unitek combination of the Victory series bracket and Transbond XT adhesive proved to have a high shear bond strength without enamel damage.

Cytotoxicity of recent dentin bonding agents on mouse fibroblast cells.

OBJECTIVES: To compare the cytotoxicity of the polymerized bonding agents Scotchbond 1 (3M ESPE), Prime and Bond NT (Dentsply DeTrey), Xeno III (Dentsply DeTrey), and Clearfil Protect Bond (primer and bond parts; Kuraray) on mouse fibroblast cells. Xeno III was also tested through thin dentin disks. METHOD AND MATERIALS: Near-confluent 3T3 cells were exposed to Dulbecco modified eagle's medium extractions from the above-mentioned agents, and the cell viability (survival rate) was measured using the standard MTT assay and related to the nonexposed controls. RESULTS: All bonding agents were found to be cytotoxic toward the 3T3 cells. Scotchbond 1 (59% survival rate) and Prime and Bond NT (62% survival rate) were not statistically different (Kruskal-Wallis test, P> > .05). However, the survival rates of Xeno III (25% through membrane and dentin disks) and Clearfil Protect Bond (35%) were significantly lower than those of the other 2 bonding agents, with Xeno III significantly the most toxic (Kruskal-Wallis test, P> .05). Of the 2 parts from Clearfil Protect Bond, the bond part was the least toxic (91% survival rate), but the primer part was very toxic (30% survival rate). CONCLUSION: In an in vitro culture, all 4 dentin bonding agents were cytotoxic. Xeno III was the most toxic, even through dentin disks. It seems that the cytotoxicities depend on the compositions of the materials tested. The most toxic part of Clearfil Protect Bond was the primer, which contains the antibacterial pyridinium molecule.

Antimicrobial activity of two South African honeys produced from indigenous Leucospermum cordifolium and Erica species on selected micro-organisms.

BACKGROUND: Honey has been shown to have wound healing properties which can be ascribed to its antimicrobial activity. The antimicrobial activity can be effective against a broad spectrum of bacterial species especially those of medical importance. It has also been shown that there is considerable variation in the antimicrobial potency of different types of honey, which is impossible to predict. With this in mind we tested the antimicrobial activity of honeys produced from plants grown in South Africa for their antibacterial properties on selected standard strains of oral micro-organisms. METHODS: The honeys used were produced from the blossoms of Eucalyptus cladocalyx (Bluegum) trees, an indigenous South African plant Leucospermum cordifolium (Pincushion), a mixture of wild heather shrubs, mainly Erica species (Fynbos) and a Leptospermum scoparium (Manuka) honey. Only pure honey which had not been heated was used. The honeys were tested for their antimicrobial properties with a broth dilution method. RESULTS: Although the honeys produced some inhibitory effect on the growth of the micro-organisms, no exceptionally high activity occurred in the South African honeys. The carbohydrate concentration plays a key role in the antimicrobial activity of the honeys above 25%. However, these honeys do contain other antimicrobial properties that are effective against certain bacterial species at concentrations well below the hypertonic sugar concentration. The yeast C. albicans was more resistant to the honeys than the bacteria. The species S. anginosus and S. oralis were more sensitive to the honeys than the other test bacteria. CONCLUSION: The honeys produced from indigenous wild flowers from South Africa had no exceptionally high activity that could afford medical grade status.

Microleakage and confocal laser studies of 2 single-step self-etching bonding agents/systems.

OBJECTIVES: This study investigated the microleakage, etching ability, and dentin-restorative interface of 2 different single-step self-etching bonding agents with compomers as restoratives. METHOD AND MATERIALS: Fifteen extracted noncarious human premolars were used for each dental material system. The bonding agent Xeno III was used with their compomer Dyract AP (Dentsply) and Adper Prompt L-Pop with their compomer Z2000 (3M Espe). Cylindrical cavities were prepared in enamel and dentin on the buccal surface at the cementoenamel junction and restored. The specimens were thermocycled and cut into slices, and the depth of dye penetration scored. The dentine-restorative interface was examined through a confocal scanning laser microscope. RESULTS: Microleakages between the enamel and dentin sides differed significantly for Xeno (Wilcoxon rank sum test; P = .0058) as well as for Prompt (P = .0106), while the microleakages between the dentin sides of Xeno and Prompt did not differ significantly. However, between the enamel sides, a significant difference was found (P = .000), with the highest value for Prompt. The confocal laser studies showed tag formation, penetration of the bonding agents deep into the tubules, and hybrid layer formation for both bonding agents. CONCLUSIONS: It can be concluded that both adhesives gave microleakage values for dentin that are on the lower side. However, careful inspection of the enamel side indicated that both cannot be recommended for enamel sealing.

Effect of power density on shrinkage of dental resin materials.

This study compares volumetric changes and rates of shrinkage during different stages of polymerization of dental resin composites and compomers exposed to the same total energy by using two different combinations of power density and exposure duration. A hybrid composite and its equivalent flowable and a compomer and its equivalent flowable were exposed using a halogen curing unit set at 400 mW/cm2 for 40 seconds and 800 mW/cm2 for 20 seconds: delivering 16 J/cm2 in both cases. Volumetric changes were recorded every 0.5 seconds using a mercury dilatometer. Ten replications per test condition were performed and the data were subjected to ANOVA. Statistically significant differences in shrinkage values and rates among different power densities were determined by means of paired t-tests at a 95% confidence level. Significantly more shrinkage (p<0.05) was found for the higher filled materials, Z250 and Dyract AP, when higher power density was used. However, no significant differences were found between their flowable counterparts when exposed to various power densities. Of the four materials, only Dyract AP exhibited no significant difference in shrinkage rate when various power densities were used. All the other materials exhibited significantly higher rates (p<0.05) at the higher power density.

The effects of light intensity and method of exposure on the hardness of four light-cured dental restorative materials.

AIM: To determine the microhardness of several light-curing dental restorative materials at the top surface as well as at a depth of 2mm. METHODS: Comparisons were made using different light sources. Four groups of five specimens each (3mm diameter, 2mm thick) of Z250 (composite), Filtek Flow (flowable composite), Dyract AP (compomer) and Dyract Flow (flowable compomer) were cured using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 mW/cm2 and 400 mW/cm2 and an Optilux 501 ramping light. Vickers microhardness tests were performed at the top surface and at the bottom surface. RESULTS: Significant differences in microhardness between the top and bottom surfaces were demonstrated for all materials and with all light sources (p<0.05). The different exposures also produced significant differences (p<0.05). The light source used had less of an effect on the hardness of the compomers than the composites. CONCLUSIONS: Effective hardness ratios between the top and bottom surfaces were achieved with all three curing protocols. The effect of total energy application must be taken into account before assumptions can be made as to the effect on hardness using different exposure methods.

The effect of an additional flowable compomer layer on microleakage of Class V compomer restorations.

BACKGROUND: Polymerisation shrinkage and the associated stress on composite resins and surrounding structures have been regarded as a major cause of leakage and clinical failures in modern polymer restorations. The purpose of this study was to investigate the effect of an additional flowable compomer layer on the microleakage of Class V dental cavities, which were further filled with a compomer. METHOD: Cavities (32) were prepared in human premolars, conditioned with a non-rinsing agent (Prime & Bond NRC) and treated with the bonding agent (Prime & Bond NT). Sixteen of these cavities were then lined with a layer of flowable compomer (Dyract Flow, approximately 0.5 mm) and further filled with Dyract AP. The other 16 cavities were filled without the flowable compomer. The specimens were thermo-cycled in a 0.5% basic fuchsin solution, sectioned and evaluated for dye penetration using a scoring system of 0 to 4. RESULTS: Lower microleakage values were found at the enamel as well as at the dentine sides when a layer of Dyract Flow was used as a liner. Furthermore, significantly (p < 0.05) lower microleakage was found in enamel than in dentine for both layered and unlayered restorations. CONCLUSION: It can be concluded that a layer of flowable compomer (i.e. Dyract Flow) in a cavity under a compomer may be recommended to improve the marginal seal of a restoration.

The effect of different power densities and method of exposure on the marginal adaptation of four light-cured dental restorative materials.

PURPOSE: To determine whether marginal adhesion is sensitive to different irradiation parameters, we investigated the in vitro adhesion values of four dental resins on metal surfaces. METHODS: Four groups of eight specimens each of Z250, Filtek flow, Dyract AP and Dyract flow were placed in pre-treated stainless steel cavities and irradiated using different methods of exposure. The curing lights used were a Spectrum 800 halogen curing light at settings of 800 and 450 mW/cm(2) and an Optilux 501 ramping light. The maximum amount of push-out force required to displace the resin from the metal cavity was equated with adhesive value (shear bond strength). Comparisons (ANOVA, p<0.0001) were made within the same material and between the different materials when using different curing protocols. RESULTS: Significant lower bond strengths were recorded when curing was done by gradually increasing the intensity (ramping method) compared to curing with the fixed intensities (p>0.0001) Comparing the fixed intensities, significant lower bond strength values were obtained at 800 mW/cm(2) compared to 450 mW/cm(2) (p<0.0001). For all exposures, the two flowable materials demonstrated weaker values when compared to the higher filled materials. CLINICAL SIGNIFICANCE: The advantage of initial slow polymerization (more elasticity and less tension) obtained by the so-called "soft start" method, was offset by a rise in total polymerization shrinkage, when final curing was completed at 1130 mW/cm(2). These tests demonstrated that using halogen units, exposure for 40s with an intensity of 450 mW/cm(2) appeared to be the most promising for light-curing dental resin composites.

Compomers: adhesion and setting reactions.

The term compomer is misleading as it suggests a combination of glass-ionomer and composite technology. This has led to confusion as to its clinical uses as well as the way it bonds to tooth structure. However, the properties and adhesion of compomers to tooth structure suggest a closer link to composites than to glass-ionomers. The clinical significance of this is that compomers lack direct chemical adhesion to any tooth structure and therefore needs to be bonded to tooth structure similar to composites via a separate bonding agent. Their closeness to composites however, does not make them composite substitutes or replacements. Dentists should strictly follow instructions by the manufacturers because failure of materials can mostly be blamed on the clinician rather than on the material.

A 3-year clinical evaluation of a compomer, a composite and a compomer/composite (sandwich) in class II restorations.

PURPOSE: To compare the clinical performance of Dyract, Spectrum-TPH and Dyract layered with Spectrum-TPH (sandwich) in Class II restorations of permanent dentitions. MATERIALS AND METHODS: 23 adult patients aged 25-62 were selected at random in a general dental practice. Each patient had 3 bicuspid teeth restored with Dyract, Spectrum-TPH and a "sandwiched" combination where Dyract was covered by the composite resin TPH. During the entire study, three patients were lost. Restorations were clinically evaluated using a modified Ryge/USPHS system. RESULTS: Over 36 months all three types of restorations performed well clinically. No post-operative sensitivity was reported by any patient indicating proper bonding and sealing. Only one Dyract/TPH sandwich restoration had to be replaced after 2.5 years due to root caries. The Dyract restorations exhibited significantly higher (P = 0.0039) occlusal wear than the TPH and the Dyract/TPH sandwiched restorations. The marginal integrity was also found to be significantly better (P = 0.001) for the TPH and Dyract/TPH restorations compared to Dyract alone, while no significant difference (P > 0.05) could be demonstrated between TPH and Dyract/TPH restorations. The low rate of failure in the three different restorative systems suggests that they are reliable restorative materials in permanent bicuspids over a 3-year period.