Ex vivo study of molecular changes of stained teeth following hydrogen peroxide and peroxymonosulfate treatments.

White teeth can give confidence and tend to be associated with a healthier lifestyle in modern society. Therefore, tooth-bleaching strategies have been developed, including the use of hydrogen peroxide. Recently, peroxymonosulfate has been introduced as an alternative bleaching method to hydrogen peroxide. Although both chemicals are oxidizing agents, their effects on the molecular composition of the stained teeth are yet unknown. In this study, the molecular profiles of teeth bleached with hydrogen peroxide and peroxymonosulfate were compared using Liquid Chromatography-Tandem Mass Spectrometry. Statistical analyses were used to assess the samples. In addition, reference spectral libraries and in silico tools were used to perform metabolite annotation. Overall, principal component analysis showed a strong separation between control and hydrogen peroxide and peroxymonosulfate samples (p < 0.001). The analysis of molecular changes revealed amino acids and dipeptides in stained teeth samples after hydrogen peroxide and peroxymonosulfate treatments. Noteworthy, the two bleaching methods led to distinct molecular profiles. For example, diterpenoids were more prevalent after peroxymonosulfate treatment, while a greater abundance of alkaloids was detected after hydrogen peroxide treatment. Whereas non-bleached samples (controls) showed mainly lipids. Therefore, this study shows how two different tooth-whitening peroxides could affect the molecular profiles of human teeth.

Enhanced In Vitro Zinc Bioavailability through Rational Design of a Dual Zinc plus Arginine Dentifrice.

OBJECTIVES: To investigate bioavailability enhancement of zinc on model oral surfaces and in oral biofilms in vitro through strategic formulation with two sources of zinc and L-arginine. METHODS: To modulate the bioavailability of active zinc ions in a zinc citrate dentifrice, an additive research strategy was pursued. A series of zinc citrate dentifrice formulations were prepared with increasing replacement of zinc citrate with zinc oxide (a water insoluble source of zinc ions) to generate a Dual Zinc active system. A screening of isolated zinc and amino acid effects in simple solutions using zeta potential and uptake to model oral surfaces was performed in an effort to determine the effect of particle charge on zinc bioavailability. Zinc delivery and antibacterial efficacy of the Dual Zinc plus Arginine dentifrice formula were tested using in vitro oral epithelial tissue and saliva-derived biofilm models. Furthermore, zinc penetration and retention were determined by subjecting in vitro biofilms to dynamic flow after treatment with the Dual Zinc plus Arginine dentifrice with treated biofilms evaluated for zinc using imaging mass spectrometry (I-MS). Bacterial adhesion to gingival epithelial cells treated with the Dual Zinc plus Arginine dentifrice was imaged upon challenging with Streptococcus gordonii. RESULTS: Addition of zinc oxide into a zinc citrate dentifrice formula enhanced the efficacy of the system against anaerobic biofilms in a concentration- dependent manner. L-arginine further provided a significant positive charge (+36 mV) to the zinc oxide suspension (+16 mV) as measured by zeta potential. Simple solutions of the Dual Zinc active showed increased zinc uptake on model oral surfaces as a direct function of L-arginine concentration. Antibacterial efficacy of a Dual Zinc plus Arginine dentifrice was evaluated through multiple mechanisms. Enhanced antibacterial performance was observed through significant reductions in metabolic activity as measured through bacterial glycolytic function (p = 0.0001) and total oxygen consumption (p = 0.0001). Greater penetration and retention of zinc was observed in bacterial biofilms treated with the Dual Zinc plus Arginine dentifrice in comparison to treatment with a Dual Zinc dentifrice after twelve hours of dynamic flow (10 mL/hour) in an in vitro drip flow biofilm culture. Confocal microscopy showed adherent bacteria on cheek cells treated with the Dual Zinc plus Arginine dentifrice formula. CONCLUSIONS: The combination of zinc citrate, zinc oxide, and the amino acid L-arginine in a dentifrice formula enhances the bioavailability of zinc to model oral tissue surfaces, resulting in unique physicochemical effects. The significant antimicrobial control associated with the Dual Zinc plus Arginine dentifrice provides a unique vehicle toward achieving whole mouth health.

Cortical activity changes as related to oral irritation-an fNIRS study.

We present the first investigation of how the cortical regions of the brain respond to the sensations related to oral irritation, using functional near-infrared spectroscopy (fNIRS). fNIRS is used to record irritant-induced activities in the prefrontal and somatosensory regions of nine healthy individuals. Two types of solutions, irritant-free and soft tissue-irritant-contained, are adopted as the stimuli for the control and task experiments, respectively. Our findings reveal that both somatosensory and prefrontal regions show activity as a result of oral irritation. Furthermore, using moving window analysis, we identify the time interval during which the largest number of channels (indicative of high involvement of cortical regions) show irritant-induced activity. Our results indicate that fNIRS can be used to study brain activities related to oral irritation.

Laboratory evaluation of extrinsic stain removal by a specially engineered sonic powered toothbrush with unique sensing and control technologies.

OBJECTIVE: The purpose of this laboratory study was to evaluate extrinsic stain removal from teeth by a specially engineered sonic powered toothbrush with unique sensing and control technologies, using the Triple Clean and the Sensitive refill brush heads, in comparison to a manual flat-trim toothbrush. METHODS: Twelve (12) artificially stained bovine teeth were tested with each product. The percentage of stain removed by each product was calculated by taking the ratio of the amount of stain removed by brushing for 800 strokes to the total amount of stain removed by subsequent application of a dental prophylaxis. The stain was quantified by measuring the light reflected by the stained teeth with a spectrophotometer. Data were reported as L*, lightness of the stain, and as W*, a whiteness index comprising the lightness, hue, and chroma of reflected light. Statistical analyses were performed separately for the AL* and AW* scores. Comparisons of the toothbrushes with respect to baseline-adjusted deltaL* and deltaW* scores were performed using an analysis of covariance (ANCOVA). Post-ANCOVA pair-wise comparisons of the study toothbrushes were performed using Tukey's test for multiple comparisons. All statistical tests of hypotheses were two-sided, and employed a minimum level of significance of 0.05. RESULTS: The percentage of stain removed by the sonic powered toothbrush, using either the Triple Clean brush head or the Sensitive brush head under laboratory test conditions, is superior (p < 0.05) to the percentage of stain removed by the manual flat-trim toothbrush when analyzed for both the deltaL* and deltaW* scores. The mean percentage of stain removed was 62.10 for the power toothbrush with the Triple Clean brush head, 49.01 for the power toothbrush with the Sensitive brush head, and 30.56 for the manual flat-trim toothbrush when calculated using deltaL* scores. The mean percentage of stain removed was 59.89 for the power toothbrush with the Triple Clean brush head, 46.83 for the power toothbrush with the Sensitive brush head, and 29.25 for the manual flat-trim toothbrush when calculated using deltaW* scores. CONCLUSIONS: This new specially engineered sonic powered toothbrush with unique sensing and control technologies effectively removes extrinsic stains from the surface of teeth under laboratory test conditions with both the Triple Clean and the Sensitive brush heads. The effectiveness of stain removal with either brush head is significantly greater than the effectiveness of stain removal of a manual flat-trim toothbrush under these conditions.