High-precision measurement of pH in the full toothpaste using NMR chemical shift

Effect of a 1.1% NaF toothpaste containing Sr/F-doped bioactive glass on irradiated demineralized dentin: an in vitro study

OBJECTIVE

Patients receiving head and neck radiation are at high risk for radiation caries. This study aimed to evaluate the remineralizing effects of an experimental 1.1% NaF (5000 ppmF) toothpaste containing Sr/F-doped bioactive glass nanoparticles (BAG or B) on demineralized irradiated dentin.

MATERIALS AND METHODS

Fluoride concentration and pH stability of materials upon mixing with water were assessed using a fluoride-specific electrode (n = 3) for up to 3 months. Elemental release of materials in water was determined using ICP-OES (n = 3). Fourteen extracted molars were irradiated with a cumulative dose of 70 Gy. Each tooth was sectioned into 4 specimens (n = 14/group), demineralized, and subjected to pH cycling for 14 days. Groups were treated with Prevident (PV), E5000, E5000B, and deionized water twice daily. Remineralization was assessed using ATR-FTIR (mineral-to-collagen ratio) (n = 14). Mineral precipitation was additionally examined with SEM-EDX. The in vitro cytotoxicity of the materials on L929 mouse fibrosarcoma was evaluated with the MTT test (n = 3). Kruskal-Wallis test, followed by Dunn's procedure, was used to compare the data between groups.

RESULT

PV demonstrated greater pH and fluoride release stability than the experimental materials. E5000B exhibited a slight reduction of fluoride release (p < 0.01, R²=0.656) and an increase in pH with time (p = 0.006, R²=0.233). The highest increase in mineral-to-collagen ratio at 14 days was detected with PV (p < 0.05). E5000B also showed a significantly higher ratio than E5000 (p = 0.014). SEM-EDX detected mineral precipitation on dentin treated with PV and E5000B but not in E5000 and DI. The cell viability of PV (56%) was significantly lower than that of E5000 (94%) and E5000B (89%) (p < 0.05).

CONCLUSION

The use of 5000 ppm fluoride toothpaste enhanced the remineralization of irradiated demineralized dentin, highlighting a potentially valuable strategy for preventing radiation caries. Adding bioactive glass further promoted remineralization but may require formulation adjustments to maintain toothpaste stability for clinical use.

Whitening toothpastes with hydrogen peroxide concentrations vs. at-home bleaching

OBJECTIVES

To evaluate the effect of whitening toothpastes with different hydrogen peroxide (HP) concentrations on HP permeability, color change, and physicochemical properties, compared to at-home bleaching treatment.

MATERIALS AND METHODS

Forty-nine premolars were randomized into seven groups (n = 7): untreated (control); at-home bleaching with 10% carbamide peroxide gel (AH; 10% CP) with 14 and 28 applications of 180 min each (AH [14 × 180 min] and AH [28 × 180 min]); three whitening toothpastes (3% HP; 4% HP and 5% HP) and 10% CP brushed 28 times for 90 s each (TB [28 × 90 s]). HP permeability was measured using a UV-VIS spectrophotometer and color change by a digital spectrophotometer (ΔEab, ΔE00, and ΔWID). Initial concentration, pH, and viscosity were measured through titration, digital pH meter, and rheometer, respectively. Statistical analysis included one-way ANOVA, Tukey's test, and Dunnett's test (α = 0.05).

RESULTS

4% HP group showed acidic pH, the lowest viscosity and the highest HP concentration into the pulp chamber (p < 0.05). The 10% CP groups had lower HP in the pulp chamber and greater color change than other groups (p < 0.05), except the 5% HP group in ΔEab and ΔE00. For ΔWID, the 10% CP AH groups showed greater whitening than other groups (p < 0.05).

CONCLUSIONS

Whitening toothpaste with up to 5% HP resulted in higher HP permeability and less color change compared to 10% CP. Higher HP commercial concentrations in toothpaste increased whitening effect; however, acidic pH toothpastes exhibited greater HP permeability.

CLINICAL RELEVANCE

Whitening toothpastes with high hydrogen peroxide concentrations were less effective than at-home bleaching, resulting in less color change and greater permeability of hydrogen peroxide, potentially increasing the risk of tooth sensitivity.

Effect of whitening toothpastes with different hydrogen peroxide concentrations: Penetration into the pulp chamber and color change

OBJECTIVES

This study evaluated the efficacy of simulated brushing with toothpastes containing different concentrations of hydrogen peroxide (HP) in pulp chamber penetration and color change. Also, physical-chemical properties (concentration, pH and viscosity) were evaluated.

METHODS

Forty-nine premolars were divided into seven groups (n = 7): untreated (control); whitening gel (White Class 6 %, 6 %BG) with one 90  min application (6 %BG 90  min) and 14 applications of 90  min (6 %BG 14×90 min); toothpastes (Colgate Luminous White Glow 3 %, 3 %TP; Crest 3D White Brilliance 4 %, 4 %TP; Colgate Optic White Pro-Series 5 %, 5 %TP) and 6 %BG toothbrushing for 14 applications of 90 s. HP penetration into the pulp chamber was measured through UV-Vis spectrophotometry and color change with a spectrophotometer (ΔEab, ΔE00, and ΔWID). Initial concentration, pH, and viscosity were measured through Titration, Digital pH-meter, and Rheometer, respectively. Statistical analysis used one-way ANOVA and Tukey's test (α = 0.05).

RESULTS

6 %BG (14×90 min) and 4 %TP groups showed acidic pH and higher concentrations of HP in the pulp chamber compared to the other groups (p < 0.05). On the other side, 3 %TP and 5 %TP groups showed alkaline pH, higher viscosity between the toothpastes and lower HP penetration (p < 0.05). The 6 %BG AH (14×90 min) group exhibited the most significant color change (ΔEab, ΔE00, and ΔWID) (p < 0.05).

CONCLUSIONS

Brushing with whitening toothpaste with an acidic pH leads to greater HP penetration into pulp chamber; but, even when a high concentrated HP whitening toothpaste was used, a lower whitening effect was observed when compared to a two-week at-home bleaching.

CLINICAL SIGNIFICANCE

Whitening toothpastes containing up to 5 % HP produced lower whitening effect than two-week at-home bleaching. Additionally, HP was detected within the pulp chamber which can potentially impact in tooth sensitivity.

Clinically Translatable Hyperpolarized 13C Bicarbonate pH Imaging Method for Use in Prostate Cancer

Solid tumors such as prostate cancer (PCa) commonly develop an acidic microenvironment with pH 6.5-7.2, owing to heterogeneous perfusion, high metabolic activity, and rapid cell proliferation. In preclinical prostate cancer models, disease progression is associated with a decrease in tumor extracellular pH, suggesting that pH imaging may reflect an imaging biomarker to detect aggressive and high-risk disease. Therefore, we developed a hyperpolarized carbon-13 MRI method to image the tumor extracellular pH (pHe) and prepared it for clinical translation for detection and risk stratification of PCa. This method relies on the rapid breakdown of hyperpolarized (HP) 1,2-glycerol carbonate (carbonyl-13C) via base-catalyzed hydrolysis to produce HP 13CO32-, which is neutralized and converted to HP H13CO3-. After injection, HP H13CO3- equilibrates with HP 13CO2 in vivo and enables the imaging of pHe. Using insights gleaned from mechanistic studies performed in the hyperpolarized state, we solved issues of polarization loss during preparation in a clinical polarizer system. We successfully customized a reaction apparatus suitable for clinical application, developed clinical standard operating procedures, and validated the radiofrequency pulse sequence and imaging data acquisition with a wide range of animal models. The results demonstrated that we can routinely produce a highly polarized and safe HP H13CO3- contrast agent suitable for human injection. Preclinical imaging studies validated the reliability and accuracy of measuring acidification in healthy kidney and prostate tumor tissue. These methods were used to support an Investigational New Drug application to the U.S. Food and Drug Administration. This methodology is now ready to be implemented in human trials, with the ultimate goal of improving the management of PCa.

Modified Lactoperoxidase System as a Promising Anticaries Agent: In Vitro Studies on Streptococcus mutans Biofilms

The lactoperoxidase (LPO) system shows promise in the prevention of dental caries, a common chronic disease. This system has antimicrobial properties and is part of the non-specific antimicrobial immune system. Understanding the efficacy of the LPO system in the fight against biofilms could provide information on alternative strategies for the prevention and treatment of caries. In this study, the enzymatic system was modified using four different (pseudo)halide substrates (thiocyanate, thiocyanate-iodide mixture, selenocyanate, and iodide). The study evaluated the metabolic effects of applying such modifications to Streptococcus mutans; in particular: (1) biofilm formation, (2) synthesis of insoluble polysaccharides, (3) lactate synthesis, (4) glucose and sucrose consumption, (5) intracellular NAD+ and NADH concentrations, and (6) transmembrane glucose transport efficiency (PTS activity). The results showed that the LPO-iodide system had the strongest inhibitory effect on biofilm growth and lactate synthesis (complete inhibition). This was associated with an increase in the NAD+/NADH ratio and an inhibition of glucose PTS activity. The LPO-selenocyanate system showed a moderate inhibitory effect on biofilm biomass growth and lactate synthesis. The other systems showed relatively small inhibition of lactate synthesis and glucose PTS but no effect on the growth of biofilm biomass. This study provides a basis for further research on the use of alternative substrates with the LPO system, particularly the LPO-iodide system, in the prevention and control of biofilm-related diseases.

Novel Sterically Crowded and Conformationally Constrained α-Aminophosphonates with a Near-Neutral pKa as Highly Accurate 31P NMR pH Probes. Application to Subtle pH Gradients Determination in Dictyostelium discoideum Cells

In order to discover new 31P NMR markers for probing subtle pH changes (<0.2 pH unit) in biological environments, fifteen new conformationally constrained or sterically hindered α-aminophosphonates derived from diethyl(2-methylpyrrolidin-2-yl)phosphonate were synthesized and tested for their pH reporting and cytotoxic properties in vitro. All compounds showed near-neutral pKas (ranging 6.28−6.97), chemical shifts not overlapping those of phosphorus metabolites, and spectroscopic sensitivities (i.e., chemical shifts variation Δδab between the acidic and basic forms) ranging from 9.2−10.7 ppm, being fourfold larger than conventional endogenous markers such as inorganic phosphate. X-ray crystallographic studies combined with predictive empirical relationships and ab initio calculations addressed the inductive and stereochemical effects of substituents linked to the protonated amine function. Satisfactory correlations were established between pKas and both the 2D structure and pyramidalization at phosphorus, showing that steric crowding around the phosphorus is crucial for modulating Δδab. Finally, the hit 31P NMR pH probe 1b bearing an unsubstituted 1,3,2-dioxaphosphorinane ring, which is moderately lipophilic, nontoxic on A549 and NHLF cells, and showing pKa = 6.45 with Δδab = 10.64 ppm, allowed the first clear-cut evidence of trans-sarcolemmal pH gradients in normoxic Dictyostelium discoideum cells with an accuracy of <0.05 pH units.

A novel near-infrared colorimetric and fluorescent probe based on a piperidine-substituted aza-BODIPY photosensitizer for detection of extreme acidity

In this paper, a novel near-infrared (NIR) colorimetric and turn-on fluorescent pH probe (denoted as Probe 1) has been designed and synthesized based on piperidine-substituted aza-BODIPY, and its ability for sensing pH under extremely acidic conditions has been studied. The maximum absorption band of Probe 1 locates at 811 nm in the NIR region in CH₂Cl₂ with an intense molar absorption coefficient of the order of 10⁴ M^-1 cm^-1, which is highly important for biological application. An approximately 156 nm red shift was observed in the absorption of the aza-BODIPY dyes from BDP to Probe 1 (from 655 nm to 811 nm). Dramatic pH responsive absorption and fluorescence changes can be observed under extreme acidity, in conjunction with a visible colorimetric change from purple to blue. Therefore, the detection of pH can be visualized through the color change. Probe 1 with a pK_a value of 2.17 could be used in the detection of pH in the range 0.84 to 3.15. Remarkably, this developed fluorescent probe exhibits extraordinary performances including rapid response time, good stability, high specificity and excellent recyclability. This work will provide a new research platform for detecting strong acidity.

The Biocompatibility of a New Erythritol-and Xyltol-Containing Fluoride Toothpaste

The basic function of toothpastes is biofilm removal in order to prevent caries and gingivitis. Toothpastes should provide maximal fluoride availability, optimal abrasivity, and ingredients that do not interfere with fluoride release but should have additional beneficial effects. Further, the effect on cells of the oral cavity is of the utmost importance. We investigated several biological parameters of a new toothpaste (AirFlow-AF) that contains fluoride, xylitol and erythritol but no sodium lauryl sulfate and compared them to commercially available toothpastes (Zendium-Ze, Sensodyne-Se, OdolMed-OM, OralB-OB). The half lethal concentration (LC50) as well as the proliferation behavior on gingival (GF), periodontal ligament (PDL), and mouse fibroblast cells (L929) were was tested. The mean LC50 values of AF on GF, PDL, and L929 were 16.2, 10.9, and 9.3, respectively. In comparison, the four other toothpastes showed mean LC50 values of 1.5 (OB), 1.2 (OM), 1.4 (Se), and 27.7 (Ze) on GF. Mean LC50 values on PDL and L929 were 1.0 and 0.2 (OB), 3.7 and 0.9 (OM), 1.2 and 0.6 (Se), and 25.4 and 5.6 (Ze), respectively. Proliferation behavior mainly confirmed the LC50 values. While cells after stimulation with AF returned to almost unimpaired proliferation behavior at 6%, cells were still strongly impaired after stimulation with all tested commercially toothpastes. AF showed high biocompatibility with different cell types.