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.

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.

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.

Enhanced Delivery of F-, Ca2+, K+, and Na+ Ions into Enamel by Electrokinetic Flows

As the outermost layer of the tooth crown, dental enamel is the most mineralized tissue in mammals, consisting of hydroxyapatite crystallites separated by long and narrow nanochannels. A major challenge in dentistry is how various molecules can be infiltrated into these nanopores in an efficient and controlled way. Here we show a robust method to transport various ions of interest, such as fluoride (F^-), potassium (K⁺), calcium (Ca⁺⁺), and sodium (Na⁺), into these nanopores by electrokinetic flows. It is verified by fluorescence microscopy, laser-scanning confocal microscopy, mass spectrometry, and ion selective electrode technique. Different ions are demonstrated to infiltrate through the entire depth of the enamel layer (~1 mm), which is significantly enhanced penetration compared with diffusion-based infiltration. Meanwhile, transport depth and speed can be controlled by infiltration time and applied voltage. This is the first demonstration of reliably delivering both anions and cations into the enamel nanopores. This technique opens opportunities in caries prevention, remineralization, tooth whitening, and nanomedicine delivery in clinical dentistry, as well as other delivery challenges into various biomaterials such as bones.

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.

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.

In vivo effects of a new dentifrice containing 1.5% arginine and 1450 ppm fluoride on plaque metabolism

OBJECTIVE

This paper presents the results of a clinical study assessing the in vivo effects on plaque metabolism of a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride compared to a commercially available dentifrice containing 1450 ppm fluoride alone.

METHODS

A four-week, parallel, randomized, double-blind clinical study using 54 subjects was conducted at the New York University College of Dentistry Bluestone Center for Clinical Research. Two study groups used the following products for two weeks: 1) a dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride as sodium monofluorophosphate (MFP; test); and 2) a commercial silica dentifrice with 1450 ppm fluoride as sodium fluoride (NaF; control). In the following two-week period, all subjects used the control product. The effects of product use on plaque metabolism in vivo were assessed by conducting ex vivo analyses at baseline, after two weeks of assigned product use, and after two weeks of control product use. These plaque analyses comprised pH measurements before and after an in vivo sucrose rinse, and measurements of ammonia production and lactate production.

RESULTS

The study showed that subjects using the test dentifrice, containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, had significantly higher plaque pH values before the sucrose challenge than those using the commercially available control dentifrice (p < or = 0.01). Plaque samples from subjects using the arginine-containing dentifrice also produced significantly higher levels of ammonia (p < or = 0.01). Subjects using the arginine-containing dentifrice also had a directionally higher plaque pH after the sucrose challenge, and their plaque samples produced a directionally lower level of lactate during the two-week treatment period compared to subjects using the control dentifrice. Following two weeks of subsequent use of the control product, there were no significant differences in plaque metabolism measures between groups.

CONCLUSION

A new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride has been shown in this study to modulate plaque metabolism, increasing ammonia production and decreasing lactate production, thereby increasing plaque pH to help restore a pH-neutral environment.

In situ clinical effects of new dentifrices containing 1.5% arginine and fluoride on enamel de- and remineralization and plaque metabolism

OBJECTIVE

The primary objective of the three studies reported in this paper was to evaluate the effects of new dentifrices containing 1.5% arginine, an insoluble calcium compound, and fluoride for their ability to promote remineralization of demineralized enamel, and to prevent mineral loss from sound enamel specimens. A secondary objective was to determine the effects on plaque metabolism with respect to the conversion of arginine to ammonia and sucrose to lactic acid.

METHODS

In Study 1, an intraoral remineralization/demineralization clinical model was used to assess the ability to promote remineralization of enamel of two dentifrices containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate (MFP), relative to a positive control with dicalcium phosphate dihydrate (Dical) and 1450 ppm fluoride, and a negative control with Dical and 250 ppm fluoride. One of the arginine-containing dentifrices contained Dical, and the other contained calcium carbonate as the source of insoluble calcium. Microradiography and image analysis were used to measure mineral changes. The study used a double-blind crossover design with a two-week treatment period. Each treatment period was preceded by a one-week washout period. Each product was used twice a day for two weeks. In the two other studies, the ability of dentifrices containing 1.5% arginine and fluoride to prevent demineralization of sound enamel blocks was assessed using an intraoral demineralization/remineralization clinical model and a double-blind crossover design with a five-day treatment period. A one-week minimum washout period preceded each treatment phase. Microhardness was used to assess mineral changes. Cariogenic challenges were administered by dipping each intraoral retainer into a 10% sucrose solution four times per day. Each product was used twice per day during the treatment period. Plaque was harvested from the specimens to measure the ability of the plaque to convert arginine to ammonia (Studies 2 and 3) and sucrose to lactic acid (Study 3) at the end of each treatment period. In Study 2, a dentifrice containing 1.5% arginine, Dical, and 1450 ppm fluoride as MFP was compared to a matched positive control containing 1450 ppm fluoride and to a matched negative control containing 250 ppm fluoride. In Study 3, a dentifrice containing 1.5% arginine, calcium carbonate, and 1000 ppm fluoride as MFP was compared to a matched positive control containing 1000 ppm fluoride and to a matched negative control containing 0 ppm fluoride.

RESULTS

In Study 1, the percent mineral changes were +18.64, +16.77, +4.08, and -24.95 for the 1.5% arginine/Dical/1450 ppm fluoride, the 1.5% arginine/calcium carbonate/1450 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better that the negative control in promoting remineralization (p = 0.0001). The two arginine-containing test products were statistically significantly better than the positive control (p < 0.05). No significant difference was observed in efficacy between the two arginine-containing products, indicating that efficacy in promoting remineralization was independent of the choice of Dical or calcium carbonate as the source of insoluble calcium. In Study 2, the percent demineralization values were -8.50, +1.67, and +12.64 for the 1.5% arginine/Dical/1450 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better at preventing demineralization than the negative control (p < 0.0001). The arginine-containing dentifrice was shown to be statistically significantly better at preventing enamel demineralization than the positive control (p < 0.0001). Plaque metabolism measures for plaque exposed to the three treatments gave the following values for ammonia production after an arginine-sucrose challenge, expressed in nanomoles per milligram plaque: 162.7; 105.4; and 115.9 for the 1.5% arginine/Dical/1450 ppm fluoride, positive control, and negative control dentifrices, respectively. No statistically significant differences were observed between the three treatments, but the arginine-based dentifrice showed directionally higher ammonia production than both the positive and negative controls In Study 3, the percent demineralization values were +1.16, +4.96, and +15.34, for the 1.5% arginine/calcium carbonate/1 000 ppm fluoride, the positive control, and negative control dentifrices, respectively. Study validation was successfully achieved by showing that the positive control was statistically significantly better at preventing demineralization than the negative control (p < 0.0001). The arginine-containing dentifrice was shown to be statistically significantly better at preventing enamel demineralization than the positive control (p < 0.05). Plaque metabolism measures for plaque exposed to the three treatments gave the following values for ammonia production after an arginine-sucrose challenge, expressed in nanomoles per milligram plaque: 99.6; 56.2; and 42.2 for the 1.5% arginine/calcium carbonate/1000 ppm fluoride, the positive control, and negative control dentifrices, respectively. Plaque treated with the arginine- containing dentifrice produced significantly more ammonia than the positive and negative control dentifrices (p < 0.05). No significant difference in ammonia production was observed between the two controls. Lactic acid production after a sucrose challenge gave the following values, expressed as nanomoles per milligram plaque: 4.06; 5.12; and 4.64 for the 1.5% arginine/calcium carbonate/1000 ppm fluoride, the positive control, and negative control dentifrices, respectively. No significant difference was observed between the three treatments, but the arginine-based treatment showed directionally lower lactic acid production.

RESULTS

The results of these three studies show that dentifrices containing 1.5% arginine, an insoluble calcium compound, and fluoride have a significantly improved ability to promote remineralization and prevent demineralization of enamel relative to dentifrices containing the same level of fluoride alone. Two different sources of insoluble calcium were evaluated, Dical and calcium carbonate. Dentifrices with Dical and with calcium carbonate, each in combination with 1.5% arginine and fluoride, provided superior efficacy as compared to matched dentifrices with fluoride alone, and the two products demonstrated comparable efficacy in promoting remineralization. The results of these studies demonstrate that the addition of 1.5% arginine to Dical-and calcium carbonate-based fluoride dentifrices provides superior efficacy in preventing demineralization and promoting remineralization, and, further, indicate that he arginine-containing dentifrices enhance the ability of plaque to metabolize arginine to ammonia.

Clinical efficacy of a specifically targeted antimicrobial peptide mouth rinse: targeted elimination of Streptococcus mutans and prevention of demineralization

BACKGROUND/AIMS

Streptococcus mutans, the major etiological agent of dental caries, has a measurable impact on domestic and global health care costs. Though persistent in the oral cavity despite conventional oral hygiene, S. mutans can be excluded from intact oral biofilms through competitive exclusion by other microorganisms. This suggests that therapies capable of selectively eliminating S. mutans while limiting the damage to the normal oral flora might be effective long-term interventions to fight cariogenesis. To meet this challenge, we designed C16G2, a novel synthetic specifically targeted antimicrobial peptide with specificity for S. mutans. C16G2 consists of a S. mutans-selective 'targeting region' comprised of a fragment from S. mutans competence stimulation peptide (CSP) conjoined to a 'killing region' consisting of a broad-spectrum antimicrobial peptide (G2). In vitro studies have indicated that C16G2 has robust efficacy and selectivity for S. mutans, and not other oral bacteria, and affects targeted bacteria within seconds of contact.

METHODS

In the present study, we evaluated C16G2 for clinical utility in vitro, followed by a pilot efficacy study to examine the impact of a 0.04% (w/v) C16G2 rinse in an intra-oral remineralization/demineralization model.

RESULTS AND CONCLUSIONS

C16G2 rinse usage was associated with reductions in plaque and salivary S. mutans, lactic acid production, and enamel demineralization. The impact on total plaque bacteria was minimal. These results suggest that C16G2 is effective against S. mutans in vivo and should be evaluated further in the clinic.

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.

Relevance of postmortem radiology to the diagnosis of fatal cerebral gas embolism from compressed air diving

AIMS

To test the hypothesis that artefact caused by postmortem off-gassing is at least partly responsible for the presence of gas within the vascular system and tissues of the cadaver following death associated with compressed air diving.

METHODS

Controlled experiment sacrificing sheep after a period of simulated diving in a hyperbaric chamber and carrying out sequential postmortem computed tomography (CT) on the cadavers.

RESULTS

All the subject sheep developed significant quantities of gas in the vascular system within 24 hours, as demonstrated by CT and necropsy, while the control animals did not.

CONCLUSIONS

The presence of gas in the vascular system of human cadavers following diving associated fatalities is to be expected, and is not necessarily connected with gas embolism following pulmonary barotrauma, as has previously been claimed.

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.

Trunk muscle activation. The effects of torso flexion, moment direction, and moment magnitude

OBJECTIVES

This study was performed to quantify the electromyographic trunk muscle activities in response to variations in moment magnitude and direction while in forward-flexed postures.

METHODS

Recordings were made over eight trunk muscles in 19 subjects who maintained forward-flexed postures of 30 degrees and 60 degrees. In each of the two flexed postures, external moments of 20 Nm and 40 Nm were applied via a chest harness. The moment directions were varied in seven 30 degrees increments to a subject's right side, such that the direction of the applied load ranged from the upper body's anterior midsagittal plane (0 degree) to the posterior midsagittal plane (180 degrees).

RESULTS

Statistical analyses yielded significant moment magnitude by moment-direction interaction effects for the EMG output from six of the eight muscles. Trunk flexion by moment-direction interactions were observed in the responses from three muscles.

CONCLUSIONS

In general, the primary muscle supporting the torso and the applied load was the contralateral (left) erector spinae. The level of electromyographic activity in the anterior muscles was quite low, even with the posterior moment directions.

Delayed left ventricular rupture secondary to transatrial left ventricular vent

The cases of 2 patients with delayed ventricular rupture secondary to ventricular venting through the left atrium during myocardial revascularization are reported. Both patients were weaned from cardiopulmonary bypass without difficulty and were transported to the intensive care unit in good condition. Rupture occurred in one patient two hours later and in the other, approximately twelve hours postoperatively; both patients died. Both patients were short in stature, and it is possible that advancing the catheter to the first guide mark left the tip unusually close to the ventricular apex. As the catheter cooled and hardened and as the heart was retracted, the catheter may have been pushed against the apical endocardium, thereby producing undetectable subendocardial damage. Our experience with these 2 patients has led us to become more selective in venting for coronary bypass operations. When venting is necessary, we insert the catheter so that its tip barely enters the ventricle.

Albumin and creatinine clearances in renal disease

1. The ratio of albumin clearance to creatinine clearance (CA/CC) was determined on 129 occasions in forty patients with a wide variety of renal diseases, both 24 h collections of urine and random mid-morning samples being used. The clearance ratios derived from 24 h urine (24 h CA/CC) and random urine (R CA/CC) were compared with random urine protein concentration, 24 h urine protein excretion and 24 h urine albumin excretion.

2. From these measurements 24 h CA/CC could only be predicted accurately by R CA/CC, particularly when patients with postural proteinuria were excluded.

3. The diurnal variation of CA/CC was investigated in twelve patients with renal disease. The individual values for CA/CC obtained throughout the day were within the limits of prediction of 24 h CA/CC already established. The diurnal variation of CA/CC was considerably less than that of CA or CC alone and also less than that of the rates of protein and albumin excretion.

4. It is suggested that CA/CC is the best readily available measure of ‘glomerular leakiness’ and examples are given of its clinical value. In patients with renal disease 24 h CA/CC could be predicted, in this study, from the clearance ratio based on simultaneous random urine and blood samples.

Nonketotic hyperosmolar coma and frusemide therapy

Nonketotic hyperosmolar diabetic coma developed in a patient with congestive cardiac failure who was treated with frusemide. With the introduction of large doses of frusemide for resistant edema the authors suggest that particular care be taken to exclude the development of diabetes mellitus. Hyperglycemia in a patient with an already established diuresis may lead to lethal hyperosmolar coma.

Acute renal failure and lithium intoxication

A case of acute renal failure is reported in a patient with severe lithium intoxication. Renal biopsy showed damage in the proximal tubules with less marked changes in the glomeruli and interlobular arteries.

Lithium was withdrawn, and after treatment with peritoneal dialysis the patient regained normal renal function.

The accumulation of lithium is known to lead to acute renal failure in the rat and the dog, and this report provides further evidence that it may do so in man.

Retroperitoneal fibrosis causing localized portal hypertension

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