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.

Effect of a triclosan/PVM/MA copolymer/fluoride dentifrice on volatile sulfur compounds in vitro.

OBJECTIVE: The objective of the investigation was to document the in vitro efficacy of a triclosan/PVM/MA copolymer/fluoride (TCF) dentifrice against the formation of volatile sulfur compounds (VSC) as well as the growth of H2S-producing bacteria. Clinical studies using organoleptic judges, gas chromatography, or a portable sulfide monitor have generally been employed in the assessment of treatments for the control of oral malodor. However, these studies are not appropriate for screening purposes because of the expense and time required. METHODS: An in vitro method was developed for the purpose of screening new compounds, agents or formulations for their ability to control VSC formation and for determining bio-equivalence of efficacy when implementing changes in existing formulations. The method combines basic microbiological methods, dynamic flow cell techniques and head space analysis. The in vitro VSC method was validated by comparing the efficacy of two dentifrices containing TCF with a control fluoride dentifrice as the TCF products have been clinically proven to control oral malodor. RESULTS: In the validation studies, the TCF-containing dentifrices were significantly better (P < 0.05) than the control dentifrice in inhibiting VSC formation and reducing H(2)S-producing bacteria. For example, when compared with baseline, the TCF dentifrices reduced VSC formation between 42 and 49% compared with the control dentifrice which reduced VSC formation 3%. There was no significant difference (P > 0.05) between the two TCF dentifrice formulations. CONCLUSION: Using an in vitro breath VSC model, it has been demonstrated that two variants of a dentifrice containing triclosan, PVM/MA copolymer and fluoride have efficacy that is significantly better than a control fluoridated dentifrice and that there is no significant difference between the triclosan/PVM/MA copolymer/fluoride dentifrice variants.

Clinical efficacy of a triclosan/copolymer/NaF dentifrice and a commercially available breath-freshening dentifrice on hydrogen sulfide-forming bacteria.

OBJECTIVE: The objective of this randomized, cross-over clinical study was to compare the 4-h and overnight effects of a triclosan/copolymer/fluoride (TCF-AF) dentifrice and a commercially available breath freshening (CBF) dentifrice containing fluoride for their ability to control H(2)S-forming bacteria. METHODS: Following a 1 week washout period of brushing with a regular fluoride dentifrice, subjects reported to the clinical site without performing oral hygiene, eating or drinking in preparation for baseline saliva sampling. After providing a baseline saliva sample, subjects were randomly assigned a test dentifrice and instructed to brush their teeth for 1 min, twice a day for 1 week. On the morning of the eighth day, subjects returned to the test site having refrained from oral hygiene, eating and drinking for overnight sampling. Subjects then brushed for 1 min with the assigned dentifrice, and returned for 2 and 4 h postbrushing evaluations. Following a second 1 week washout, subjects repeated the same regimen, but now using the other dentifrice. Oral micro-flora samples were collected by subjects rinsing with 10 ml of sterile water for 10 s. Each collected sample was serially diluted and plated in duplicate onto lead acetate agar. After incubating for 72 h, dark colonies were counted, expressed as log colony-forming units/ml, and reductions from baseline were calculated. RESULTS: Compared with baseline, the TCF-AF dentifrice reduced H2S-forming bacteria 0.82, 0.80 and 0.22 log units at the 2 and 4 h and overnight time points compared with 0.60, 0.43 and 0.07 log units for the CBF dentifrice. The TCFAF dentifrice was statistically significantly better (P < 0.05) than the CBF dentifrice at 4 h and overnight after brushing the teeth. CONCLUSION: The results of this randomized study indicate that the TCF-AF dentifrice is effective in controlling H2S-producing bacteria.

New directions in dietary studies in cancer: the National Cancer Institute.

Through an orderly sequence incorporating epidemiologic and laboratory research, human clinical/metabolic studies, and clinical intervention trials, the NCI develops and maintains cancer prevention and control programs that are directed toward the overall goal to reduce cancer incidence, morbidity, and mortality. Epidemiologic studies have shown correlations between consumption of numerous dietary constituents and cancer risk. Results of in vitro and animal studies have reinforced many of these epidemiologic associations and data from clinical/metabolic studies are being used to evaluate the relevance of these associations in humans. Although much remains to be learned about the influence of specific dietary constituents and dietary patterns on cancer risk, it is clear that diet can have a significant impact in cancer prevention and control. Investigations on the cellular and molecular effects of dietary constituents, as well as their metabolic and physiologic effects should provide better insight on the mechanisms of action of these dietary constituents. There also is a need to develop biomarkers of dietary intake that could be used to monitor compliance in intervention studies, as well as biomarkers as clinical trial endpoints that can be used to predict the emergence and progression of cancer. Working with other agencies and the private sector, the NCI will continue to design and implement information programs that translate the knowledge gained from these diet and cancer prevention studies to help Americans adopt dietary patterns that may reduce cancer risk. Continued emphasis will be placed on intervention programs targeted toward high-risk and underserved segments of the U.S. population in an effort to reduce the high incidence of cancers in these groups.

Analysis of vitamin A data from the health and nutrition examination surveys.

An Expert Panel on Vitamin A Nutriture assessed serum vitamin A values and related data collected during the first and second National Health and Nutrition Examination Surveys (NHANES I and NHANES II) and the southwest component of the Hispanic Health and Nutrition Examination Survey (SW HHANES). The appropriateness of the analytical methodologies and adequacy of the quality-control procedures used to obtain the serum vitamin A values were evaluated. Age-specific guidelines for the interpretation of serum vitamin A values in selected low ranges (less than 20, 20-24 and 25-29 micrograms/dl) were developed, and estimates of the prevalence of serum vitamin A values in these ranges were presented for each of the three surveys.