Pilot clinical study to evaluate the efficacy of a professionally delivered high fluoride varnish on erosive tooth wear in an in-situ model.

OBJECTIVES: The aim for this pilot study was to investigate the effect of a sodium fluoride varnish on step height measured by a profilometer from human enamel worn by healthy volunteers with a novel in situ/ex vivo erosion design. METHOD: Healthy volunteers aged 18-70 years wore a palatal splint containing 8 human enamel samples and underwent two 3-day treatment periods for 6 h a day with a varnish containing sodium fluoride at 22,600 ppm and the control with the same ingredients but without fluoride. Each splint contained 4 polished and 4 unpolished samples. The interventions were applied to the surface of the enamel samples in randomised order, removed after 6 h, then immersed ex-vivo in 1 %, pH 2.7 citric acid for 2 min, repeated 4 times a day, over 2 days. Measurements of enamel were assessed blindly by microhardness on day 2 and by non-contact laser profilometry on day 3 for the two treatments. RESULTS: 24 volunteers, 2 males and 22 females aged 27-54 years, were screened and recruited. The delta microhardness, from polished samples removed at the end of day 2, for the control and fluoride treatment was 95.7 (22.9) kgf/mm2 and 123.7 (28.9) kgf/mm2, respectively (p < .005). The mean (SD) step height for the control polished enamel surfaces was 3.67 (2.07) µm and for the fluoride varnish was 1.79 (1.01) µm (p < .0005). The control unpolished enamel surfaces had a mean 2.09 (1.53) µm and the fluoride varnish was 2.11 (1.53) µm but no statistical difference was detected. CONCLUSIONS: The results from this pilot study, utilizing an in-situ model where enamel was exposed to acid over the course of 2 days, demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm prevented erosive wear compared to a control on the polished enamel surfaces. CLINICAL SIGNIFICANCE: Intra-oral study demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm reduced erosive tooth wear.

Xylitol associated or not with fluoride: Is the action the same on de- and remineralization?

OBJECTIVES: This study evaluated the effect of xylitol combined or not with fluoride (F) on reduction of demineralization and increase of remineralization of shallow and deep artificial enamel lesions. METHODS: Bovine enamel samples were allocated to the following solutions groups: no xylitol (negative control), 5% xylitol, 10% xylitol, 20% xylitol, 500 ppm F (as NaF), 5% xylitol+F, 10% xylitol+F or 20% xylitol+F (n = 12-15). For the demin study, a pH-cycling model (demineralization-6 h, pH 4.7/remineralization 18 h, pH 7.0) was employed for 7 days. Treatments were applied 2 × 1 min. In the remin study, specimens were pre-demineralized for 2, 5 or 10 days. Afterwards, a pH-cycling protocol was conducted (2 h demineralizing and 22 h remineralizing solution/day for 8 days) and the same treatments were done. The response variables were percentage surface hardness loss (%SHL) and transverse microradiography. Data were analyzed by RM ANOVA/Tukey or Kruskal-Wallis/Dunn (p < 0.05) RESULTS: F and Xylitol combined with F reduced the %SHL (23-30%) compared to the negative control (61.5%). The integrated mineral loss and the lesion depth were not reduced by any treatment. Surface hardness recovery was seen only for shallow lesions in case of 20% xylitol+F compared to negative control. No lesion depth recovery, but significant mineral recovery was seen for F (2-days and 10-days lesion). CONCLUSIONS: All concentrations of xylitol+F reduced enamel surface demineralization, while only 20% xylitol+F improved surface remineralization of shallow lesions in vitro. CLINICAL SIGNIFICANCE: Our results suggest that while F or any concentration of xylitol + F reduces surface demineralization, only 20% xylitol+F improves surface remineralization of shallow lesions in vitro. Therefore, xylitol may be added into oral products, combined to F, to control dental caries.

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.

Improved mineralization of dental enamel by electrokinetic delivery of F- and Ca2+ ions.

This in vitro study evaluated the effects of the infiltration of F- and Ca2+ ions into human enamel by electrokinetic flow (EKF) on the enamel microhardness and F- content. Sound human enamel ground sections of unerupted third molars were infiltrated with de-ionized water by EKF and with F- ion by EKF respectively. All samples were submitted to two successive transverse acid-etch biopsies (etching times of 30 s and 20 min) to quantify F- ion infiltrated deep into enamel. Remarkably, sound enamel showed a large increase in microhardness (MH) after infiltration of NaF (p < 0.00001) and CaCl2 (p = 0.013) by EKF. Additionally, NaF-EKF increased the remineralization in the lesion body of artificial enamel caries lesions compared to controls (p < 0.01). With the enamel biopsy technique, at both etching times, more F- ions were found in the EKF-treated group than the control group (p << 0.05), and more fluoride was extracted from deeper biopsies in the NaF-EKF group. In conclusion, our results show that EKF treatment is superior in transporting Ca2+ and F- ions into sound enamel when compared to molecular diffusion, enhancing both the mineralization of sound enamel and the remineralization of artificial enamel caries.

Characterization of white spot lesions formed on human enamel under microcosm biofilm for different experimental periods.

The initial characteristics of white spot lesion (WSLs), such as the degree of integrated mineral loss (ΔZ), depth and pattern of mineral distribution, have an impact on further demineralization and remineralization. However, these lesion parameters have not been evaluated in WSLs produced from microcosm biofilms. OBJECTIVE: This study characterized artificial white spot lesions produced on human enamel under microcosm biofilm for different experimental periods. METHODOLOGY: In total, 100 human enamel specimens (4x4mm) were assigned to 5 distinct groups (n=20/group) differing according to the period of biofilm formation (2, 4, 6, 8 or 10 days). Microcosm biofilm was produced on the specimens from a mixture of human and McBain saliva at the first 8h. Enamel samples were then exposed to McBain saliva containing 0.2% sucrose. WSLs formed were characterized by quantitative light-induced fluorescence (QLF) and transverse microradiography (TMR). Data were analyzed by ANOVA/Tukey or Kruskal-Wallis/Dunn tests (p<0.05). RESULTS: A clear time-response pattern was observed for both analyses, but TMR was able to better discriminate among the lesions. Regarding QLF analysis, median (95%CI; %) changes in fluorescence ∆Z were -7.74(-7.74:-6.45)a, -8.52(-8.75:-8.00)ab, -9.17(-10.00:-8.71)bc, -9.58(-10.53:-8.99)bc and -10.01(-11.44:-9.72)c for 2, 4, 6, 8, and 10 days, respectively. For TMR, median (95%CI; vol%.µm) ∆Z were 1410(1299-1479)a, 2420(2327-2604)ab, 2775(2573-2899)bc, 3305(3192-3406)cd and 4330(3972-4465)d, whereas mean (SD; µm) lesion depth were 53.7(12.3)a, 71.4(12.0)a, 103.8(24.8)b, 130.5(27.2)bc, 167.2(39.3)c for 2, 4, 6, 8 and 10 days, respectively. CONCLUSION: The progression of WSLs formed on human enamel under microcosm biofilm can be characterized over 2-10 days, both by QLF and TMR analyses, although the latter provides better discrimination among the lesions.

Characterization of white spot lesions formed on human enamel under microcosm biofilm for different experimental periods

Abstract The initial characteristics of white spot lesion (WSLs), such as the degree of integrated mineral loss (ΔZ), depth and pattern of mineral distribution, have an impact on further demineralization and remineralization. However, these lesion parameters have not been evaluated in WSLs produced from microcosm biofilms. Objective: This study characterized artificial white spot lesions produced on human enamel under microcosm biofilm for different experimental periods. Methodology: In total, 100 human enamel specimens (4x4mm) were assigned to 5 distinct groups (n=20/group) differing according to the period of biofilm formation (2, 4, 6, 8 or 10 days). Microcosm biofilm was produced on the specimens from a mixture of human and McBain saliva at the first 8h. Enamel samples were then exposed to McBain saliva containing 0.2% sucrose. WSLs formed were characterized by quantitative light-induced fluorescence (QLF) and transverse microradiography (TMR). Data were analyzed by ANOVA/Tukey or Kruskal-Wallis/Dunn tests (p<0.05). Results: A clear time-response pattern was observed for both analyses, but TMR was able to better discriminate among the lesions. Regarding QLF analysis, median (95%CI; %) changes in fluorescence ∆Z were -7.74(-7.74:-6.45)a, -8.52(-8.75:-8.00)ab, -9.17(-10.00:-8.71)bc, -9.58(-10.53:-8.99)bc and -10.01(-11.44:-9.72)c for 2, 4, 6, 8, and 10 days, respectively. For TMR, median (95%CI; vol%.µm) ∆Z were 1410(1299-1479)a, 2420(2327-2604)ab, 2775(2573-2899)bc, 3305(3192-3406)cd and 4330(3972-4465)d, whereas mean (SD; µm) lesion depth were 53.7(12.3)a, 71.4(12.0)a, 103.8(24.8)b, 130.5(27.2)bc, 167.2(39.3)c for 2, 4, 6, 8 and 10 days, respectively. Conclusion: The progression of WSLs formed on human enamel under microcosm biofilm can be characterized over 2-10 days, both by QLF and TMR analyses, although the latter provides better discrimination among the lesions.

Deformation behavior of normal human enamel: A study by nanoindentation.

Tooth enamel has an important mechanical function for human dental health, yet characterizing its mechanical properties is not trivial due to its complex nanoporous structures. We examined the distribution of hardness and modulus across the lingual-buccal enamel cross-section by nanoindentation. At the occlusal surface, the hardness and modulus of enamel were found to be 5.00 ± 0.22 GPa and 97.12 ± 2.95 GPa, respectively. At the area close to the enamel-dentine-junction (EDJ), the hardness and modulus were 3.72 ± 0.35 GPa and 76.83 ± 5.71 GPa, respectively. At the middle region in between the EDJ and the outer enamel layer, the hardness and modulus were found to be 4.23 ± 0.18 GPa and 87.62 ± 2.50 GPa, respectively. The surface and area underneath the nanoindent were analyzed using the following microscopy tools: Scanning Electron Microscopy, Focused Ion Beam imaging, and Transmission Electron Microscopy. The deformation mechanisms of enamel were found to be location dependent and influenced by changes in the chemical composition within enamel. The EDJ forms the interface between enamel and dentin. The deformation behavior differed at the EDJ, due to the increased organic phase at the interface. Within the intermediate enamel region, intra-rod cracks were formed at the center of enamel rods and propagated into the neighboring inter-rod region at deviated directions along the orientation of the local crystallites. At the outer enamel layer, crack propagation was constrained by the rigid structure surrounding the indented site. Most of the cracks were formed close to the surface. A significant amount of material was also pushed upwards and delaminated from the enamel surface of the indentation area.

Enhanced teeth whitening by nanofluidic transport of hydrogen peroxide into enamel with electrokinetic flows.

Tooth whitening, a routine procedure in dentistry, is one of the examples of medical procedures that are limited by the challenge of delivering molecules into various types of nanoporous tissues. Current bleaching methods rely on simple diffusion of peroxides into enamel nano channels, therefore requires sufficient contact time with peroxides. In-office treatments often involve enamel etching or light activation which often results in patient sensitivity and potential soft tissue damage. OBJECTIVE: To demonstrate a robust method to transport hydrogen peroxide to greater depths into enamel nanopores through nanofluidic flows driven by electrokinetics, with the intention to increase efficacy while reducing treatment time. METHODS: Freshly extracted human teeth were subjected to electrokinetic flow treatment with hydrogen peroxide under different electric fields with varying operation times. Pre- and post-operative shade matching was done using a photospectrometer. RESULTS: It is demonstrated that the operation time for the same concentration of hydrogen peroxide can be shortened by 10 times. The proposed method showed significant improvements in whitening effects over control groups and thus offers promising clinically-viable chairside applications with efficacy. SIGNIFICANCE: The demonstrated nanofluidic transport of hydrogen peroxide into enamel has a potential to be applied for enhancing tooth whitening, compared to simple diffusion, without heating the hard dental tissues.

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.

A 12-week clinical study assessing the clinical effects on plaque metabolism of a dentifrice containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm fluoride.

PURPOSE: To evaluate the clinical effect on plaque metabolism of a dentifrice containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm fluoride compared to a commercially available dentifrice containing 1,450 ppm fluoride in a silica base. METHODS: A 12-week, parallel, randomized, double-blind study using 48 subjects was conducted at the Colgate-Palmolive Technology Center (Piscataway, NJ, USA). One group used a test dentifrice containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm fluoride as sodium monofluorophosphate (MFP), and the other group used a commercial silica dentifrice with 1,450 ppm fluoride as sodium fluoride (NaF) as a control. Plaque metabolism analyses were conducted at baseline and after 2, 4, 6, 8, and 12 weeks of assigned product use. The plaque analyses included pH measurements before and after a sucrose rinse, ammonia production and lactic acid production. RESULTS: Subjects using the test dentifrice had significantly higher plaque pH values before (P< or = 0.01) and after (P< or = 0.045) a sucrose challenge than those using the commercially available control dentifrice. Subjects using the test dentifrice also produced higher levels of ammonia and lower levels of lactic acid compared to subjects using the control dentifrice.

Nanoscale characterization of effect of L-arginine on Streptococcus mutans biofilm adhesion by atomic force microscopy.

A major aetiological factor of dental caries is the pathology of the dental plaque biofilms. The amino acid L-arginine (Arg) is found naturally in saliva as a free molecule or as a part of salivary peptides and proteins. Plaque bacteria metabolize Arg to produce alkali and neutralize glycolytic acids, promoting a less cariogenous oral microbiome. Here, we explored an alternative and complementary mechanism of action of Arg using atomic force microscopy. The nanomechanical properties of Streptococcus mutans biofilm extracellular matrix were characterized under physiological buffer conditions. We report the effect of Arg on the adhesive behaviour and structural properties of extracellular polysaccharides in S. mutans biofilms. High-resolution imaging of biofilm surfaces can reveal additional structural information on bacterial cells embedded within the surrounding extracellular matrix. A dense extracellular matrix was observed in biofilms without Arg compared to those grown in the presence of Arg. S. mutans biofilms grown in the presence of Arg could influence the production and/or composition of extracellular membrane glucans and thereby affect their adhesion properties. Our results suggest that the presence of Arg in the oral cavity could influence the adhesion properties of S. mutans to the tooth surface.

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.

A breakthrough therapy for dentin hypersensitivity: how dental products containing 8% arginine and calcium carbonate work to deliver effective relief of sensitive teeth.

OBJECTIVE: These studies have utilized a range of state-of-the-art surface techniques to gain insight into the mechanism of action of a new technology for dentin hypersensitivity relief based upon arginine and calcium carbonate and, in particular, to address important questions regarding the nature and extent of dentin tubule occlusion. METHODS: Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) have been used to assess tubule occlusion. Energy dispersive x-ray (EDX) and electron spectroscopy for chemical analysis (ESCA) have been used to identify the composition of the dentin plug. CLSM has also been used to compare the mechanism of action of the toothpaste and the desensitizing prophylaxis paste, to address whether both the arginine and the calcium carbonate components are essential to occlusion, to identify the location of the arginine within the occluded dentin, and to demonstrate resistance of the occlusion to acid challenge. Hydraulic conductance has been used to assess the effectiveness of the arginine-calcium carbonate technology in arresting dentin fluid movement, to evaluate the effects of pulpal pressure on the robustness of the occlusion, and to confirm the resistance of the occlusion to an acid challenge. RESULTS: The CLSM, SEM, and AFM studies demonstrate that the arginine-calcium carbonate technology is highly effective in rapidly and completely occluding dentin tubules. The EDX and ESCA studies show that the dentin surface deposit and occluded tubule plug contain high levels of calcium and phosphate, as well as carbonate. CLSM has confirmed that the toothpaste and the desensitizing prophylaxis paste have the same mechanism of action, that the arginine and calcium carbonate components are both essential to the effectiveness of these products, and that the arginine becomes incorporated into the dentin plug. The hydraulic conductance studies demonstrate that the occlusion provided by the arginine-calcium carbonate technology results in highly significant reductions in dentin fluid flow, and that the tubule plug is resistant to normal pulpal pressure and acid challenge. CONCLUSION: A breakthrough technology based upon arginine and calcium carbonate provides clinically proven benefits with respect to rapid and lasting relief of dentin hypersensitivity. It is unique in that two of its key components, arginine and calcium, are found naturally in saliva, and that the arginine and calcium carbonate work together to accelerate the natural mechanisms of occlusion to deposit a dentin-like mineral, containing calcium and phosphate, within the dentin tubules and in a protective layer on the dentin surface.

Fluorescence correlation spectroscopic study of serpin depolymerization by computationally designed peptides.

Members of the serine proteinase inhibitor (serpin) family play important roles in the inflammatory and coagulation cascades. Interaction of a serpin with its target proteinase induces a large conformational change, resulting in insertion of its reactive center loop (RCL) into the main body of the protein as a new strand within beta-sheet A. Intermolecular insertion of the RCL of one serpin molecule into the beta-sheet A of another leads to polymerization, a widespread phenomenon associated with a general class of diseases known as serpinopathies. Small peptides are known to modulate the polymerization process by binding within beta-sheet A. Here, we use fluorescence correlation spectroscopy (FCS) to probe the mechanism of peptide modulation of alpha(1)-antitrypsin (alpha(1)-AT) polymerization and depolymerization, and employ a statistical computationally-assisted design strategy (SCADS) to identify new tetrapeptides that modulate polymerization. Our results demonstrate that peptide-induced depolymerization takes place via a heterogeneous, multi-step process that begins with internal fragmentation of the polymer chain. One of the designed tetrapeptides is the most potent antitrypsin depolymerizer yet found.

Alpha 1-antitrypsin polymerization: a fluorescence correlation spectroscopic study.

Alpha(1)-antitrypsin (AT) is the most abundantly circulating human proteinase inhibitor in the serpin family. The polymerization of AT, leading to alpha(1)-antitrypsin deficiency, has been studied extensively in vitro by a variety of ensemble methods. Here we report the use of fluorescence correlation spectroscopy to gain further insight into this process. Measurements of the distributions of diffusion times of polymerizing AT, carried out at 45, 50, and 55 degrees C, clearly show the existence of a kinetic lag phase, during which short oligomers are formed, prior to the formation of heterogeneous mixtures of longer polymers, and suggest that long polymers, which appear to be metastable, are produced through the condensation of shorter oligomers.