Michael A. Cochran

Review of the Effectiveness of Various Tooth Whitening Systems

This review compares nine published studies conducted at the Indiana University School of Dentistry. Twenty-five products in four different systems were evaluated using the Trubyte Bioform Color Ordered Shade Guide and a Chroma Meter. The dentist-prescribed overnight bleaching delta mean shade guide value (DSGV) 10 weeks post-bleaching was 13.2 and delta E value (DEV) 4.7; dentist-prescribed daytime bleaching DSGV 10 weeks post-bleaching was 10.5 and DEV 3.4; in-office bleaching DSGV 10 weeks post-bleaching was 6.7 and DEV was 2.1; over-the-counter bleaching DSGV two weeks post-bleaching was 7.2 and DEV was 4.1. A color difference of Delta E 2.6 is perceivable. Tooth whitening is observable with all methods of bleaching. Dentist-prescribed overnight bleaching was shown to be the most effective method of bleaching.

Eight in-office tooth whitening systems evaluated in vivo: a pilot study.

This in vivo pilot study evaluated eight products with hydrogen peroxide (HP) concentrations ranging from 15% to 35%. The treatment contact time varied from 15 minutes to 60 minutes. Patients were evaluated for color at baseline, immediately after treatment and at one, two, four and six weeks after treatment using a colorimeter, shade guide and photos. All eight products were effective in bleaching teeth. Colorimeter data for deltaE immediately after treatment was 6.77. At one and six weeks after bleaching, there were 51% and 65% reductions in deltaE, respectively.

Clinical evaluation of 15% carbamide peroxide on the surface microhardness and shear bond strength of human enamel.

PURPOSE This clinical evaluation compared a neutral sodium fluoridated whitening product to a neutral non-fluoridated whitening product in terms their effects on human enamel surface microhardness (SMH) and human enamel/resin composite shear bond strength (SBS) following various treatment times. MATERIALS AND METHODS Subjects were evaluated for enamel SMH and enamel/resin SBS following 15% carbamide peroxide (CP) with and without potassium nitrate and fluoride (PF). Twenty subjects (80 first or second premolars), who were treatment-planned for premolar extraction due to orthodontic therapy, were allocated into two groups, A and B. Group A received 15% CP, while Group B received 15% CP with PF. Each patient had a control tooth, a 14-day treatment + 14-day recovery tooth, a 14-day treatment + no recovery tooth and a 4-day + no recovery tooth. Each tooth was further divided into two testing surfaces; the facial surface was used for SMH, while the lingual surface was used for SBS. RESULTS The results of this study determined that there was no statistically significant difference between the effects of the two products on SMH and enamel/resin SBS. Additionally, there was no statistically significant difference between the treatment specimens compared to the controls in terms of SMH. However, there was a significant difference between the treatment groups compared to the controls in terms of enamel/resin SBS. CONCLUSION Within the limitations of this clinical study, 15% CP with and without PF does not seem to alter the SMH of human enamel. However, 15% CP with and without PF significantly reduced enamel/resin SBS immediately following tooth whitening therapy, up to 14 days post-treatment.

In vivo study of two carbamide peroxide gels with different desensitizing agents.

This study evaluated tooth whitening and sensitivity that occurred during and after 14 days of overnight bleaching with 15% carbamide peroxide gel with potassium nitrate and fluoride (Opalescence 15% PF, OP) and 16% carbamide peroxide with amorphous calcium phosphate (Nite White 16%, NW). Thirty-two subjects bleached their teeth using custom trays. The subjects had a baseline evaluation and returned after 7, 14, 21, 35 and 90 days for subjective and objective color evaluations. The subjects also recorded daily tooth and gingival sensitivity. The treatments were compared for differences in mean L*, a*, b* and shade guide rank order at baseline and each appointment thereafter, using repeated measures analysis of variance (ANOVA). OP and NW showed significant tooth whitening. Subjects using OP were significantly lighter in b* and E* than those using NW, while exhibiting no difference in tooth or gingival sensitivity overall or during any evaluation.

Extended Bleaching of Tetracycline-Stained Teeth: A 5-Year Study

Bleaching tetracycline-stained teeth is the most challenging form of tooth lightening. This article reports on 44 subjects who bleached their tetracycline-stained teeth for 6 months using trays with reservoirs overnight in a half-mouth designed study and 2 of 3 different concentrations of carbamide peroxide (10%, 15% or 20%). The subjects were followed for 5 years. The area evaluated was the middle third of the teeth. More than 55% of tooth lightening occurred within 1 month; after 5 years, more than 65% of the maximum tooth whitening remained for all 3 gel concentrations. Tooth whitening can be accomplished with any of the 3 concentrations used.

A Clinical Evaluation of Two In-office Bleaching Regimens With and Without Tray Bleaching

This study evaluated the degree of color change of teeth, the rebound effect and the sensitivities of teeth and gingiva associated with the use of an in-office bleaching agent followed by an at-home bleaching agent to lighten stained teeth in an in vivo study. Thirty-seven subjects who met the Inclusion/Exclusion criteria were divided into two cells. Twenty-five subjects received three 15-minute in-office bleaching treatments in succession with 36% hydrogen peroxide (HP) on the maxillary anterior teeth, followed by at-home overnight bleaching with 15% carbamide peroxide (CP) for seven days on one side of the dental arch. Twelve other subjects received a 40-minute in-office bleaching treatment on their maxillary anterior teeth, followed by at-home overnight bleaching for seven days on one side of the dental arch with the same product. The cells of teeth on the other side of the dental arch received the same in-office treatment but were not bleached overnight for seven days. Color was subjectively evaluated using the Vitapan Classical Shade Guide and was objectively evaluated using the Chroma Meter at the baseline appointment, immediately after in-office bleaching and at 4, 7 and 14 days and 3 months after the in-office treatment. For two weeks, the subjects completed sensitivity evaluations of gingival tissues and hard tooth tissues. The cells that did not receive the at-home bleaching had significantly less color change than the cells that received at-home bleaching. The cell that was bleached for 40 minutes and received the at-home treatment had significantly less overall change (deltaE) at 14 days and 3 months than the cell that received three 15-minute treatments with the at-home treatment. Throughout the study, the subjects in the three 15-minute treatment cells had less gingival and tooth sensitivity than the other cells.

Microtensile Bond Strength of Glass Ionomer Cements to Artificially Created Carious Dentin

In this laboratory study, the microtensile bond strengths of a conventional glass ionomer cement (GIC) and a resin modified glass ionomer cement (CRMGIC) to artificially created carious dentin and sound dentin were compared, and the ultrastructural morphology of the fractured interface was examined with a low-vacuum scanning electron microscope (SEM). The specimens were divided into 4 groups: 1) a conventional GIC (Ketac-Fil Plus Aplicap) placed on sound dentin; 2) a conventional GIC placed on artificially created carious dentin; 3) an RMGIC (Photac-Fil Aplicap) placed on sound dentin and 4) an RMGIC placed on artificially created carious dentin. Artificial carious lesions were created using a chemical demineralizing solution of 0.1 M/L lactic acid and 0.2% carbopol. GIC buildups were made on the dentin surfaces according to the manufacturers directions. After storage in distilled water at 37 degrees C for 24 hours, the teeth were sectioned vertically into 1 x 1 x 8-mm beams for the microtensile bond strength test. The microtensile bond strength of each specimen was measured, and failure mode was determined using an optical microscope (40x). The fractured surfaces were further examined with SEM. Two-way analysis of variance showed that the mean microtensile bond strengths of a GIC and an RMGIC to carious dentin were significantly lower than those to sound dentin, and the mean microtensile bond strengths of Photac-Fil to both sound and carious dentin were significantly higher than those of Ketac-Fil Plus. Chi-square tests indicated that there was a significant difference in failure mode between the sound dentin and carious dentin groups. In sound dentin groups, cohesive failure in GIC was pre- dominant; whereas, mixed failure was predominant in carious dentin groups. SEM examination showed that the specimens determined to be cohesive failures under light microscopy in the Photac-Fil/Sound Dentin group were actually mixed failures under high magnification of SEM.

Quantitative Comparison of the Water Permeable Zone Among Four Types of Dental Adhesives Used with a Dual-cured Composite

This study compared silver penetration in the adhesive interface among four versions of adhesives from the same manufacturer: OptiBond FL, OptiBond Solo Plus, OptiBond Solo Plus Dual Cure, and OptiBond Solo Plus Self-Etch, when coupled with dual-cured composite, CoreRestore 2 (Kerr). Twenty flat dentin surfaces were prepared using one of the adhesives and bonded with the composite, following the manufacturers instructions. The surfaces were sectioned into 2-mm slabs and immersed in ammoniacal silver nitrate for 24 hours. Each specimen was exposed to a photodeveloping solution for eight hours and examined with a scanning electron microscope (SEM). The water permeable area occupied by the silver nitrate tracer was determined, and the relative weight of silver was analyzed by wavelength dispersive spectrometry (WDS). The OptiBond FL group had a significantly lower silver content than the other groups (p < 0.0001). Each group demonstrated different patterns of silver deposition within the adhesive layer and within various features of artifactual fracture from dehydration stress of the SEM. This may be indicative of weak links in the bonded interfaces. Simplified-step adhesives showed increased permeability, which can lead to disruption of coupling with composites.

Color stability of composite resins.

The color stability of seven visible light-cured and three chemically-cured composite resins was investigated while being subjected to UV light irradiation and storage in an aqueous environment at elevated temperatures. Color shift was evaluated visually and by colorimetric measurements. Significant correlation was found between visual scoring and colorimetric readings. When subjected to UV light, a wide deviation in color change existed from brand to brand in photocured composite resins. The color shift of chemically-cured composite resins was less than but fell within the range of photocured composite resins. When stored in water at elevated temperatures, photocured resins exhibited better color stability than the chemically-cured composite resins.

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