Super high-quality SEM/FIB imaging of dentine structures without collagen fiber loss through a metal staining process.

Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) system has become valuable and popular tool for the analysis of biological materials such as dentine structures. According to physiological and anatomical studies, dentine structures are a complicated system containing collagen fibers, nanocrystalline hydroxyapatite, and numerous networks of tubular pores. During a routine FIB milling process, collagen fibers and other organic structures are vaporized, which increases the number of pores on the milled surface of the dentine. This causes the final cross-section to be more porous than the pristine sample. Unfortunately, little attention has been paid to the collagen fiber loss and how to preserve them during a FIB milling process. In this work, we present a novel and simple approach to preserve the organic portions of the dentine structure through metal staining. By using this method, the porosity of the dentine structure after the FIB milling process is significantly reduced similar to the pristine sample. This indicates that the organic portion of the dentine structure is well protected by the metal staining. This approach enables the SEM/FIB system to generate super-high quality SEM images with less ion beam damage; and the SEM images can better reflect the original condition of the dentine structure. Further, serial energy-dispersive X-ray spectroscopy (EDS) mapping of the stained dentine structure is achieved without an additional metal coating; and three-dimensional (3-D) elemental mapping of an occluded dentine is achieved with a significantly reduced data acquisition time.

Synthesis, Characterization, and Investigation of the Antimicrobial Activity of Cetylpyridinium Tetrachlorozincate.

Cetylpyridinium tetrachlorozincate (referred to herein as (CP)2ZnCl4) was synthesized and its solid-state structure was elucidated via single-crystal X-ray diffraction (SC-XRD), revealing a stoichiometry of C42H76Cl4N2Zn with two cetylpyridinium (CP) cations per [ZnCl4]2- tetrahedra. Crystal structures at 100 and 298 K exhibited a zig-zag pattern with alternating alkyl chains and zinc units. The material showed potential for application as a broad-spectrum antimicrobial agent, to reduce volatile sulfur compounds (VSCs) generated by bacteria, and in the fabrication of advanced functional materials. Minimum inhibitory concentration (MIC) of (CP)2ZnCl4 was 60, 6, and 6 µg mL-1 for Salmonella enterica, Staphylococcus aureus, and Streptococcus mutans, respectively. The MIC values of (CP)2ZnCl4 were comparable to that of pure cetylpyridinium chloride (CPC), despite the fact that approximately 16% of the bactericidal CPC is replaced with bacteriostatic ZnCl2 in the structure. A modified layer-by-layer deposition technique was implemented to synthesize mesoporous silica (i.e., SBA-15) loaded with approximately 9.0 wt % CPC and 8.9 wt % Zn.

Effect of a stannous fluoride toothpaste on dentinal hypersensitivity: In vitro and clinical evaluation.

BACKGROUND: The authors conducted an in vitro and a clinical study to assess the effect of a toothpaste containing stannous fluoride to occlude dentin tubules and reduce dentinal hypersensitivity. METHODS: For the in vitro study, the authors treated the surface of human dentin specimens with test or control toothpaste slurries and then evaluated them by using various spectroscopic techniques. For the clinical study, male and female participants who met the inclusion criteria brushed their teeth twice daily for 1 minute with test or control toothpaste. The authors assessed dentinal hypersensitivity by using tactile and air blast stimuli at baseline and after 4 and 8 weeks. All statistical tests of hypotheses were 2 sided, with a significance level of α set at .05. RESULTS: Results from in vitro studies showed that the test toothpaste effectively occluded the dentinal tubules with a deposit consisting of tin, zinc, phosphate, and silicon. The test and control toothpastes occluded the tubules 82% and 35%, respectively. Clinically, at the 4- and 8-week examinations, the test toothpaste provided statistically significant (P < .001) improvements in tactile dentinal hypersensitivity scores of 27.8% and 42.0% and in air blast hypersensitivity scores of 21.4% and 32.3%, respectively, relative to the control toothpaste. CONCLUSIONS: The in vitro results indicate the toothpaste containing 0.454% stannous fluoride effectively coated dentin surfaces and occluded patent dentin tubules. Compared with the control toothpaste, the test toothpaste provided a significant reduction in dentinal hypersensitivity after 8 weeks of product use. PRACTICAL IMPLICATIONS: A multi-benefit option for patients with dentinal hypersensitivity.

Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments.

An aqueous suspension of nanogibbsite was synthesized via the titration of aluminum aqua acid [Al(H2O)6]3+ with L-arginine to pH 4.6. Since the hydrolysis of aqueous aluminum salts is known to produce a wide array of products with a wide range of size distributions, a variety of state-of-the-art instruments (i.e., 27Al/1H NMR, FTIR, ICP-OES, TEM-EDX, XPS, XRD, and BET) were used to characterize the synthesis products and identification of byproducts. The product, which was comprised of nanoparticles (10-30 nm), was isolated using gel permeation chromatography (GPC) column technique. Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (PXRD) identified the purified material as the gibbsite polymorph of aluminum hydroxide. The addition of inorganic salts (e.g., NaCl) induced electrostatic destabilization of the suspension, thereby agglomerating the nanoparticles to yield Al(OH)3 precipitate with large particle sizes. By utilizing the novel synthetic method described here, Al(OH)3 was partially loaded inside the highly ordered mesoporous framework of MCM-41, with average pore dimensions of 2.7 nm, producing an aluminosilicate material with both octahedral and tetrahedral Al (Oh/Td = 1.4). The total Al content, measured using energy-dispersive X-ray spectrometry (EDX), was 11% w/w with a Si/Al molar ratio of 2.9. A comparison of bulk EDX with surface X-ray photoelectron spectroscopy (XPS) elemental analysis provided insight into the distribution of Al within the aluminosilicate material. Furthermore, a higher ratio of Si/Al was observed on the external surface (3.6) as compared to the bulk (2.9). Approximations of O/Al ratios suggest a higher concentration of Al(O)3 and Al(O)4 groups near the core and external surface, respectively. The newly developed synthesis of Al-MCM-41 yields a relatively high Al content while maintaining the integrity of the ordered silica framework and can be used for applications where hydrated or anhydrous Al2O3 nanoparticles are advantageous.

A Water-Soluble Cationic Zinc Lysine Precursor for Coating ZnO on Biomaterial Surfaces.

A novel water-soluble cationic zinc lysine coordination compound, [Zn[(C6H14N2O2)]2Cl]Cl·2H2O (1), has been designed and synthesized and its crystal structure determined. The aqueous solution of this coordination compound is not only transparent and stable at room temperature but it is also nearly neutral (pH ∼ 7). It is worth noting that zinc oxide (ZnO) forms in situ upon dilution of a solution of the compound. The bioactivity of ZnO has been confirmed using an Alarma Blue assay. These unique properties allow the coordination compound to gently grow ZnO coating with excellent antibacterial benefits onto biomaterial surfaces in a facile and safe manner.

In vitro study of the effect of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate on acid-softened enamel.

OBJECTIVE: To investigate the possible mode of action of a dentifrice containing 8% arginine and calcium carbonate (Pro-Argin Technology), and sodium monofluorophosphate in delivering the benefits of preventing acid erosion and rehardening acid-softened enamel. METHODS: The surfaces of acid-softened bovine enamel specimens were evaluated after application of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate in vitro. Scanning Electron Microscopy (SEM), Electronic Spectrometry for Chemical Analysis (ESCA), and Secondary Ion Mass Spectrometry (SIMS) were used to characterize the enamel surfaces. RESULTS: Exposure of pristine enamel surfaces to citric acid resulted in clear roughening of the surface. Multiple applications of a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate to the surface of the enamel resulted in the disappearance of the microscopic voids observed by SEM as a function of treatment applications. The ESCA analysis demonstrated that both the nitrogen and carbonate levels increased as the number of treatments increased, which provides evidence that arginine and calcium carbonate were bound to the surface. Observance of arginine's signature mass fragmentation pattern by SIMS analysis confirmed the identity of arginine on the enamel surface. CONCLUSION: A series of in vitro experiments has demonstrated a possible mode of action by which a dentifrice containing 8% arginine, calcium carbonate, and sodium monofluorophosphate delivers the benefits of preventing acid erosion and rehardening acid-softened enamel. The combination of arginine and calcium carbonate adheres to the enamel surface and helps to fill the microscopic gaps created by acid, which in turn helps repair the enamel and provides a protective coating against future acid attacks.

Mode of action studies of a new desensitizing mouthwash containing 0.8% arginine, PVM/MA copolymer, pyrophosphates, and 0.05% sodium fluoride.

OBJECTIVE: The mode of action of an arginine mouthwash using the Pro-Argin™ Mouthwash Technology, containing 0.8% arginine, PVM/MA copolymer, pyrophosphates and 0.05% sodium fluoride, has been proposed and confirmed as occlusion using a variety of in vitro techniques. METHODS: Quantitative and qualitative laboratory techniques were employed to investigate the mode of action of the new arginine mouthwash. Confocal laser scanning microscopy (CSLM) and atomic force microscopy (AFM) investigated a hydrated layer on dentine surface. Electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectroscopy (SIMS) and near-infrared spectroscopy (NIR) provided information about its chemical nature. RESULTS: CLSM was used to observe the formation of a hydrated layer on exposed dentine tubules upon application of the arginine mouthwash. Fluorescence studies confirmed penetration of the hydrated layer in the inner walls of the dentinal tubules. The AFM investigation confirmed the affinity of the arginine mouthwash for the dentine surface, supporting its adhesive nature. NIR showed the deposition of arginine after several mouthwash applications, and ESCA/SIMS detected the presence of phosphate groups and organic acid groups, indicating the deposition of copolymer and pyrophosphates along with arginine. CONCLUSION: The studies presented in this paper support occlusion of the dentine surface upon the deposition of an arginine-rich layer together with copolymer and phosphate ions from an alcohol-free mouthwash containing 0.8% arginine, PVM/MA copolymer, pyrophosphates and 0.05% sodium fluoride.

Anti-hypersensitivity mechanism of action for a dentifrice containing 0.3% triclosan, 2.0% PVM/MA copolymer, 0.243% NaF and specially-designed silica.

PURPOSE: To evaluate the laboratory dentin occlusion efficacy and effects on dentin permeability of a new multi-benefit dentifrice in order to gain insight into the mechanism of action of a novel technology for dentin hypersensitivity relief based on a specially-designed silica and copolymer system. METHODS: Acid-etched human dentin was evaluated with confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) after treatment with one of the following: (1) a dentifrice containing 0.3% triclosan, 2.0% PVM/MA copolymer, 0.243% sodium fluoride with specially designed silica (Test Dentifrice 1); (2) a dentifrice containing 0.3% triclosan and the same overall silica loading as Test Dentifrice 1 but without copolymer and the specially-designed silica (Placebo Dentifrice); (3) a commercially-available dentifrice containing 0.454% stannous fluoride in a silica base with sodium hexametaphosphate and zinc lactate (Test Dentifrice 2); and (4) a commercially-available non-sensitive dentifrice containing 0.243% sodium fluoride in a silica base (Negative Control Dentifrice). The composition of dentin treated with either Test Dentifrice 1 or Negative Control Dentifrice was analyzed using energy dispersive x-ray (EDX) and electron spectroscopy for chemical analysis (ESCA). To highlight dentin occluding efficacy of the specially-designed silica, dentin was treated with Test Dentifrice 1 formulated with fluorescently-tagged specially-designed silica and resulting occlusion followed with CLSM. The dentin occluding abilities of Test Dentifrices 1 and 2 were compared with the Negative Control dentifrice using CLSM after a 4-day cycling model consisting of twice daily dentifrice treatment and four acid challenges. Effects of treatment with Test Dentifrices 1 or 2 on dentin permeability and subsequent resistance of occluding deposits to acid dissolution and dislodgement by pulpal pressure were assessed using hydraulic conductance. RESULTS: Dentin specimens treated with Test Dentifrices 1 and 2 were significantly occluded compared to Placebo Dentifrice and Negative Control Dentifrice when visualized with CLSM. The level of occlusion remaining after challenge with cola was highest for dentin treated with Test Dentifrice 1 in CLSM xz views. Test Dentifrice 1 produced dentin surface deposits and tubule plugs containing silicon in addition to calcium and phosphorus as indicated by ESCA and EDX. CLSM visualization of fluorescently-tagged material confirmed occlusion by the specially-designed silica which was localized at the dentin tubule openings. Imaging of dentin by CLSM after the 4-day cycling model revealed a significantly higher amount of occluded tubules for dentin treated with Test Dentifrice 1 compared to the Negative Control Dentifrice or Test Dentifrice 2. Etched dentin treated with the Test Dentifrice 1 was significantly less permeable compared to that treated with the Negative Control Dentifrice, exhibiting over 80% reduction in dentin permeability. The occlusion provided by the Test Dentifrice 1 was maintained and provided significantly better reduction in permeability after extended pulpal pressure and acid challenge compared to dentin treated with Test Dentifrice 2.

Mode of action studies on a new desensitizing dentifrice containing 8.0% arginine, a high cleaning calcium carbonate system and 1450 ppm fluoride.

PURPOSE: To ascertain the mode of action of a new Pro-Argin formula desensitizing dentifrice with a gentle whitening benefit containing 8.0% arginine, a high cleaning calcium carbonate system and sodium monofluorophosphate, utilizing a range of state-of-the-art surface techniques. METHODS: Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were used to assess tubule occlusion. Electron spectroscopy for chemical analysis (ESCA) was used to identify the composition of the occlusive material. CLSM was also used to identify the location of the arginine within the occluded dentin tubule and to demonstrate the resistance of the occlusion to an acid challenge. RESULTS: The CLSM and SEM studies demonstrated that the arginine-calcium carbonate technology in this new Pro-Argin formula sensitivity dentifrice was highly effective in occluding dentin tubules. ESCA showed that the dentin surface deposit contained high levels of calcium, phosphorous, oxygen and carbonate. CLSM also confirmed that the arginine incorporated into the dentin plug, and the dentin plug resisted an acid challenge.

High levels of hydrogen peroxide in overnight tooth-whitening formulas: effects on enamel and pulp.

PURPOSE: Limited data are available to assess the safety of high levels of hydrogen peroxide in overnight tooth-whitening formulas. The purpose of this study was to assess the effects of hydrogen peroxide on enamel microhardness, pulp penetration, and enamel morphology. MATERIALS AND METHODS: Colgate Platinum Professional Overnight Whitening System (Colgate Oral Pharmaceuticals, Inc., Canton, MA, USA) (10% carbamide peroxide, equivalent to 3.5% hydrogen peroxide) was compared with two prototype formulations containing either 7.0% or 12.0% hydrogen peroxide. In the pulp chamber studies, human extracted teeth were exposed to 3.5%, 7.0%, or 12.0% hydrogen peroxide for 30 minutes, 4 hours, or 7 hours. Microhardness, electron spectroscopy for chemical analysis, and atomic force microscopy evaluations were made from enamel blocks cut from human extracted molars. The enamel blocks were evaluated following 14 7-hour treatments (98 h total). RESULTS: At 7 hours' post-treatment, hydrogen peroxide penetrated the pulp chamber at 23.12 +/- 10.09, 24.58 +/- 6.90, and 26.39 +/- 5.43 microg for 3.5%, 7.0%, and 12.0% hydrogen peroxide, respectively. With regard to enamel morphology, pulp penetration, microhardness, and elemental composition, no statistically significant differences were observed between treatment groups following 98 hours of treatment. CONCLUSIONS: Hydrogen peroxide does not adversely affect enamel morphology or microhardness. The levels recovered in pulp indicate that hydrogen peroxide is not expected to inhibit pulpal enzymes. CLINICAL SIGNIFICANCE: Overnight tray products containing levels of hydrogen peroxide of 3.5%, 7.0%, and 12.0% are not expected to adversely affect the enamel or pulpal enzymes. Additional safety studies are needed to assess the potential for tooth sensitivity and gingival irritation.

Safety profile of a new liquid whitening gel.

Colgate Simply White Clear Whitening Gel, an at-home tooth-whitening product purchased over the counter, contains 18% carbamide peroxide (equivalent to 6.5% hydrogen peroxide) as the active ingredient in a brush-applied liquid gel. The excipients include ingredients commonly used in dentifrices. The potential for effects on the tooth pulp, oral soft tissue irritation, enamel damage, and tooth sensitivity with this peroxide-containing product have been evaluated. An in vitro study demonstrated that pulpal chamber hydrogen peroxide levels are well below those considered to cause an effect on pulpal tissue. An exaggerated-use (4 applications per day for 3 weeks) clinical study showed that no oral irritation occurred during 3 weeks of use. A study measuring peroxide salivary concentration after use of Colgate Simply White Clear Whitening Gel showed that the concentration of peroxide in the saliva after use of the product was extremely low, further supporting the position that this product has a low potential for causing oral irritation. Additional studies demonstrate that Colgate Simply White Clear Whitening Gel does not harm the enamel surface or produce demineralization after exposure equivalent to 3 weeks of normal use and over 6 weeks of exaggerated use. Colgate Simply White Clear Whitening Gel has not produced oral irritation (hard and soft tissues) or tooth hypersensitivity in a clinical subject population of 141 individuals using varying treatment regimens. These studies prove that Colgate Simply White Clear Whitening Gel is safe for daily use as directed.