Depth profile analysis of non-specific fluorescence and color of tooth tissues after peroxide bleaching.

PURPOSE: To examine laboratory changes of endogenous non-specific fluorescence and color throughout subsurface of tooth structures prior to and following peroxide bleaching. METHODS: Extracted human teeth were cross sectioned and mounted on glass slides. Cross sections were examined for internal color (digital camera) and nonspecific fluorescence (microRaman spectroscopy) throughout the tooth structure at specified locations. Surfaces of sections were then saturation bleached for 70 hours with a gel containing 6% hydrogen peroxide. Cross sections were reexamined for color and non-specific fluorescence changes. RESULTS: Unbleached enamel, dentin-enamel junction and dentin exhibit different CIELab color and non-specific fluorescence properties. Bleaching of teeth produced significant changes in color of internal cross sections and substantial reductions of non-specific fluorescence levels within enamel dentin and DEJ. Enamel and dentin non-specific fluorescence were reduced to common values with bleaching with enamel and the DEJ showing larger reductions than dentin.

Effects of hydrogen peroxide bleaching strips on tooth surface color, surface microhardness, surface and subsurface ultrastructure, and microchemical (Raman spectroscopic) composition.

OBJECTIVE: This study examined the effects of hydrogen peroxide tooth bleaching strips on the surface hardness and morphology of enamel and the ultrastructure and chemical composition of enamel and dentin in vitro. METHODOLOGY: Sound human molars were ground and polished to prepare a uniform substrate for bleaching treatments. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching strips, which utilize hydrogen peroxide in a gel as the in situ bleaching source at 6.0 and 6.5% concentrations of H2O2. Control treatments included an untreated group. Crest Whitestrips bleaching included treatment exposures simulating 2x the recommended clinical exposures (28 hours bleaching). Surface color measurements were taken prior to and following bleaching to ensure tooth bleaching activity. The effects of bleach on physical properties of enamel were assessed with microhardness measures. Ultrastructural effects were classified by surface and subsurface confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) techniques. In addition, the effects of bleaching on tooth microchemical composition was studied in different tooth regions by coincident assessment of Raman spectroscopic signature. RESULTS: Color assessments confirmed significant ex vivo tooth bleaching by Whitestrips. Surface microhardness and SEM measures revealed no deleterious effects on the enamel surfaces. CLSM micromorphological assessments supported the safety of hydrogen peroxide bleaching strips both on surface and subsurface enamel, DEJ, and dentin ultrastructure. Raman spectroscopy analysis demonstrated no obvious effects of bleaching treatments on the microchemical composition of enamel and dentin. CONCLUSION: These results confirm that tooth bleaching with hydrogen peroxide whitening strips does not produce changes in surface/subsurface histomorphology or in surface microhardness and ultrastructure of treated teeth. In addition, for the first time, these results confirm the safety of hydrogen peroxide bleaching strips to tooth microchemical composition as measured by Raman spectroscopy.

Effects of Crest Whitestrips bleaching on subsurface microhardness and ultrastructure of tooth enamel and coronal dentin.

PURPOSE: To describe the complementary subsurface analysis of structural and ultrastructural effects of bleaching with Crest Whitestrips on enamel and coronal dentin METHODS: Human tooth enamel specimens were cycled through a daily regimen including salivary immersions and treatments with commercial tooth whitening gels containing hydrogen peroxide or carbamide peroxide. Treatments with hydrogen peroxide in Crest Whitestrips gel base were carried out for up to 70 hours bleaching (some five fold to the clinical exposure required to produce satisfactory whitening in bleaching strip systems as established by double blind placebo controlled clinical studies) [correction]. Following in vitro laboratory cycling, the teeth were cross sectioned and remounted for observation of microhardness and ultrastructural characteristics in subsurface regions. Ultrastructure was assessed by application of confocal laser scanning microscopy (reflection mode). RESULTS: Peroxide whitening compositions had no effects on subsurface microhardness of enamel or dentin, even under conditions of five fold overbleaching. Crest Whitestrips gel containing up to 6.5% hydrogen peroxide applied for periods up to 70 hours (five kit) overbleaching was found to produce no changes (at a lateral resolution of 200-300 nm) in observed subsurface enamel and dentin ultrastructure or architecture.

Impact of Crest Night Effects bleaching gel on dental enamel, dentin and key restorative materials. In vitro studies.

PURPOSE: To examine the effects of a paint-on 19% sodium percarbonate 'overnight' bleaching gel on the structure and integrity of enamel, dentin and some common restorative materials, with a laboratory cycling model. METHODS: Enamel, root dentin and restorative materials (glass-ionomer, composite and amalgam) were prepared in methacrylate molds with surface polishing. A treatment regimen was carried out including diurnal incubation in pooled human saliva and including twice daily toothbrushing with standard fluoridated dentifrice. Test samples were treated daily with Crest Night Effects bleaching gel, which included drying of surfaces, painting of percarbonate bleaching gel, and then incubation throughout the day (8 hours) to simulate overnight wear. Treatments were carried out over 14 days, to simulate clinical exposure periods. Control and test specimens were evaluated for surface and subsurface structure and morphological integrity utilizing surface microhardness, surface profilometry, and confocal laser scanning microscopy. RESULTS: Percarbonate bleaching film treatments had no effects on enamel or root dentin surface microhardness, or on subsurface ultrastructural integrity of enamel and coronal dentin. Surface profilometry confirmed retention of small amounts of residual silicone polymers, which contributed to CLSM air objective appearance and surface roughness measures. Restoratives were generally passive to bleaching gel treatments, though composite showed a tendency to attract retained residual silicone film.

Peroxide interactions with hard tissues: effects on surface hardness and surface/subsurface ultrastructural properties.

Laboratory studies were performed to assess the impact of peroxide bleaching on enamel surface and subsurface physical and ultrastructural properties. Human enamel blocks were prepared, polished, and measured for native color. Cyclic bleaching treatments were carried out with soaks in whole stimulated saliva interspersed with bleaching treatments using bulk bleaching gels from commercial bleaching systems including Opalescence (20% and 10% carbamide peroxide systems) and Crest Whitestrips, a hydrogen peroxide gel formula, at doses of 5.3% and 6.5% hydrogen peroxide. Treatments ranged from conditions of normal use (14 hours as recommended for Crest Whitestrips) to excessive bleaching (70 hours). Controls included nontreated as well as treatments with placebo (not containing peroxide) gels. Surface hardness and confocal laser scanning microscopy (CLSM) techniques were used to characterize the effects of bleaching on the physical properties and ultrastructure of the teeth. Tooth color measurements revealed dose-response bleaching in vitro with the increases in L* and decreases in b* normally expected with effective bleaching. Placebo control treatments did not bleach. Surface hardness measurements showed no decreases associated with tooth bleaching. CLSM measurements also showed no effects from tooth bleaches on the surface or subsurface prism architecture of enamel. This was opposed to significant changes seen with even moderate levels of demineralization associated with the caries process. These studies support: (1) the safety of Crest Whitestrips formulas for enamel surfaces and tooth subsurfaces; and (2) the generic safety of peroxide bleaching of hard tissues associated with conditions of both recommended use and overuse.

Effects of hydrogen peroxide bleaching strip gels on dental restorative materials in vitro: surface microhardness and surface morphology.

OBJECTIVE: This study examined the effects of peroxide tooth bleaching, including Crest Whitestrips hydrogen peroxide gel treatments, on the surface hardness and morphology of common dental restorative treatments. METHODOLOGY: American Dental Association (ADA) recommended dental restorative materials, including amalgam, dental gold, porcelain, glass ionomer, and composites, were prepared according to manufacturers' instructions. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching gels, which utilize hydrogen peroxide as the in situ bleaching source, and several commercial carbamide peroxide bleaching gels. Control treatments included placebo gels and an untreated group. Crest Whitestrips bleaching included treatment exposures simulating recommended clinical exposures (14 hours), along with excess bleaching simulating exposure to five times suggested Crest Whitestrips use. At the conclusion of treatments, surface microhardness measures and surface morphological assessments with standard and variable pressure (VP-) SEMs were conducted to assess the effects of bleaching exposure on the surface morphology and structural integrity of the restoratives. RESULTS: Surface microhardness and SEM measures revealed no significant deleterious effects on the restoration surfaces from Whitestrips gels. CONCLUSION: These results confirm that tooth bleaching from the selected commercial hydrogen peroxide or carbamide peroxide bleaching systems does not produce changes in surface morphology or microhardness of common dental restorative materials. These results support the clinical safety of the selected commercial bleaching systems to the oral environment, matching results obtained from long-term use of these ingredients applied in dental offices and available in commercial formulations.

Effects of Crest Whitestrips bleaching on surface morphology and fracture susceptibility of teeth in vitro.

OBJECTIVE: This study examined the effects of peroxide tooth bleaching, including Crest Whitestrips hydrogen peroxide treatments, on the fracture susceptibility and surface morphology of human tooth enamel in vitro. METHODOLOGY: Extracted human molars were ground and polished to prepare a uniform substrate for bleaching treatments. A cycling treatment methodology was employed which alternated ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching treatments included commercial Crest Whitestrips bleaching gels, which utilize hydrogen peroxide as the in situ bleaching source, and several commercial carbamide peroxide bleaching gels. Control treatments included placebo gels and an untreated group. Crest Whitestrips bleaching included treatment exposures simulating recommended clinical exposures (14 hours of bleaching), along with excess bleaching simulating exposure to five times the suggested Crest Whitestrips use. At the conclusion of treatments, surface color measurements were taken to ensure tooth bleaching. Surface microhardness measures and surface morphological assessments with SEM were conducted to assess the effects of bleaching exposure on the surface morphology and mineral integrity of the teeth. These latter measures were then complemented with assessments of fracture susceptibility utilizing detailed analyses of crack propagation resulting from post-treatment microhardness indentations. RESULTS: Surface microhardness and SEM measures revealed no deleterious effects on the enamel surfaces from any of the bleaching products assessed. This included conditions of excess bleaching exposure or "overbleaching." The analysis of fracture susceptibility similarly revealed no significant effects from tooth bleaching, regardless of the peroxide source. CONCLUSIONS: These results confirm that tooth bleaching from the selected commercial hydrogen peroxide or carbamide peroxide bleaching systems do not produce changes in surface morphology, microhardness or fracture susceptibility of human tooth enamel under in vitro cycling conditions of treatment matching clinical bleaching exposures. These results support the clinical safety of the selected commercial bleaching systems to vital dentition, matching results obtained from the long-term use of these ingredients applied in dental offices and available in commercial formulations.

Laboratory studies on the chemical whitening effects of a sodium hexametaphosphate dentifrice.

Laboratory studies were developed to permit the evaluation of chemical actions of toothpaste components in the non-abrasive prevention and removal of tea stains. Powdered hydroxyapatites were used as substrates for adsorption of tea chromogens. Pre-treatment with a sodium hexametaphosphate dentifrice (Crest Dual Action Whitening) reduced tea adsorption to powdered apatite, while post-treatments of pre-stained powder resulted in desorption of tea components. These results exemplified the chemical actions of condensed calcium phosphate surface active builders toward dental stain removal and prevention. A cycling synamel chip model permitted the study of stain prevention, including salivary pellicle formation and chlorhexidine enhancement of dental staining by tea chromogens. Staining was evaluated by image analysis of color development. Under these conditions, condensed phosphate dentifrices were observed to produce superior prevention of stain accumulations, with Crest Dual Action Whitening dentifrice providing stain prevention superior to a variety of commercial dentifrices, including Colgate Total, Aquafresh Whitening, Colgate Tartar Control Whitening, Mentadent Baking Soda and Peroxide Whitening, Close-Up Whitening, Crest Tartar Control and Crest Regular Cavity Protection.