Silica as a reference for laboratory dentifrice assessment methods: multiple site collaborative study.

OBJECTIVE: This collaborative study was designed to collect data from multiple laboratories, using recognized abrasion and cleaning power methods, to assess the functionality, stability, and suitability of three Sident silica abrasives for consideration as references for ISO (International Standards Organization) abrasion and other dentifrice assessment methods. METHODOLOGY: This study included ISO and other physicochemical methods to characterize the abrasive powders, as well as ISO and related abrasion methods--Radioactive Dentin Method, Profilometry, and Copper Gravimetric, and two Cleaning Power methods--to test the functionality of the silica abrasives with the current ISO abrasion reference calcium pyrophosphate. RESULTS: The outcomes demonstrated that the collaborative study to measure the physicochemical characteristics of three Sident silica abrasive materials, stored at ISO and tropical conditions, found no change in the functionality as measured by these methods over the two-year test period. CONCLUSION: The three Sident silica abrasives demonstrated suitability to be considered as references for use with calcium pyrophosphate in the ISO 11609 Toothpaste Specification.

Evaluation of dentin abrasion during professional tooth cleaning in an in vitro model.

OBJECTIVES: Professional tooth cleaning (PTC) may lead to loss of exposed dentin. The aim of the present study was to determine the absolute loss of dentin during PTC using various product combinations with an in vitro model. MATERIAL AND METHODS: Dentin specimens (72) were randomly assigned to nine groups. In four groups each, prophy brushes and prophy cups were used in combination with four different abrasives (calcium pyrophosphate, pumice, Hawe cleanic, Nupro coarse). In the ninth group, a rubber cup with embedded fluoride and abrasives was used (pasteless prophy cup). The treatment time was 37 s. Surface loss was determined by profilometry. RESULTS: The surface loss in the nine groups was as following: (1) brush/calcium pyrophosphate: 6.18 microm (a); (2) brush/pumice: 5.51 microm; (3) brush/Nupro coarse: 10.10 microm (b); (4) brush/Hawe cleanic: 1.88 (a, b); (5) prophy cup/calcium pyrophosphate 2.07 (c); (6) prophy cup/pumice: 6.07 microm; (7) prophy cup/Nupro coarse: 5.93 microm (c); (8) prophy cup/Hawe cleanic: 4.93 microm (c); (9) pasteless prophy cup: 11.86 microm (c). Groups with the same letter in parentheses are statistically significant different at p<0.05. In a pooled analysis, no statistically significant difference between brushes and prophy cups was found. CONCLUSION: In the present study, the surface loss of about eight PTC procedures was simulated. Hence, the dentin loss ranged between 0.24 and 1.48 microm per PTC. Therefore, PTC does not seem to be a main factor in dentin loss.

Modern methods for assessing the cariogenic and erosive potential of foods.

Assessment of the acidogenic and cariogenic erosive potential of foods requires the use of reproducible and standardised methods. The methodology laid down at the San Antonio conference in 1985 remain today the basis for research on and the testing of foods. The 1999 workshop has updated the appropriate methodology and introduced guidelines on the testing of erosive potential of foods. It is to be hoped that researchers wishing to evaluate foods and their effect on the teeth will continue to use these methods.

Assessment methods and clinical outcomes: chemical and microbial composition, formation, and maturation dynamics of pellicle, plaque, and calculus.

Understanding the functional dynamics of the oral cavity helps researchers design methods to predict clinical outcomes. Most information about the oral cavities of companion animals must be drawn from animal studies designed to understand human oral disease and from human studies. Based upon functional criteria for any animal or experimental research study, supragingival plaque and calculus can be assessed within four to six weeks. Although longer studies may be more appealing, such study designs may compromise the oral soft tissue health of the animals and are complicated by oral cavity dynamics. Thus, they are less sensitive and predictive of longer term clinical outcomes. Additional research is necessary to relate tooth surface accumulation phenomena with oral soft tissue health.

Modification of food cariogenicity in rats by mineral-rich concentrates from milk.

Dairy products, including milk, cheese, and casein, can reduce the caries-causing potential of cariogenic substrates as measured in various animal, plaque acidity, and in vitro systems. Although the mechanisms responsible for protection are not completely identified, substances containing Ca and P may contribute to the protective potential by reducing demineralization and/or promoting remineralization of enamel. Casein may reduce demineralization by forming a protective coat on the enamel surface. By means of a rat model, this study evaluated the ability of three casein-free milk mineral concentrates with various levels of whey protein, calcium, and phosphate to modify the cariogenicity of a powdered diet containing 20% sucrose. Analysis of these data indicates that there were no significant differences among groups for weight gain, total food consumption, or feeding frequency, as monitored by a computer-based infrared activity monitor. All three mineral concentrates significantly reduced buccal caries, and two of the three reduced sulcal caries by from 10 to 30%. The analysis further shows that casein-free milk mineral fractions can modify the cariogenicity of sucrose-containing foods in a rat model.

Dental cariogenic evaluation of foods using human plaque pH and an experimental rat-caries model.

Five well-characterized foods were used to compare two systems for estimating the cariogenic potential of food: human plaque-acidity using interdental metallic touch electrodes, and cariogenicity testing in rats. Both systems identified the same food as the least cariogenic or acidogenic food and identified the same three foods as being both cariogenic in rats and acidogenic in man, although the ranking of these foods differed. The systems differed in their assessment of potato chips, a food high in cooked starch and low in free sugars. The results confirmed that non-acidogenic foods are non-cariogenic, but that foods acidogenic in man may exhibit a greater range of cariogenicity in rats. Data from both human plaque pH studies and rat caries models may permit better assessment of cariogenic potential of foods containing fermentable carbohydrates.

An international collaborative study of laboratory methods for assessing abrasivity to dentin.

An International Collaborative Study was conducted in which one surface profile and two radiotracer methods for assessing abrasivity of dentifrices on human dentin were compared. The study consisted of two phases: an open phase in which participating laboratories used the method they routinely practiced; and a controlled phase in which an expert team for each method performed the abrasion tests using all three methods. Four test pastes of known abrasivity were evaluated by each method. Similar abrasivity values for the test pastes were obtained with the radiotracer methods, whereas the surface profile method produced significantly different values. The precision levels of the radiotracer methods were similar, and both were superior to those obtained by the surface profile method. The time needed to perform the tests by the ADA radiotracer method was significantly less than that needed by the other methods. These findings suggest that the ADA radiotracer method will be useful in assessing abrasivity of dentifrices.

Solution activity product (KFAP) and simultaneous demineralization-remineralization in bovine tooth enamel and hydroxyapatite pellets.

The effects of changing the ion activity product of the remineralization solution at pH 4.5 (pKFAP 108-118) on the remineralization behavior of demineralized bovine tooth enamel and hydroxyapatite pellets have been studied. Solutions containing calcium-4.5, phosphate, and fluoride in acetate buffers were used. The 45Ca/F molar ratios indicated the formation of fluoridated hydroxyapatite in the enamel or the pellet when the pKFAP values for remineralizing solutions were less than 112. When the pKFAP values were greater than 112, the 45Ca/F ratios were found to be much less than 5. Also, when the pKFAP values were large (greater than 112), the remineralization patterns based on the fluoride distribution in the tooth (or pellet) were found to be different than when the pKFAP values were small (less than 112). The hypothesis that a pKFAP value of 112 is the demarcation between remineralization only and simultaneous dissolution-remineralization has been proposed based on these results.

Fluoride remineralization of demineralized bovine tooth enamel and hydroxyapatite pellets.

Both bovine enamel and hydroxyapatite pellets were remineralized in a fluoride-containing remineralization solution after prior demineralization for various lengths of time. In both the enamel and pellet systems, the degree of remineralization attainable was directly related to the extent of prior demineralization, although the demineralized material was never 100% recovered in remineralization. In some cases, fluoride levels up to several thousand parts per million were found at depths as great as 50 micrometers from the surface. The stoichiometry of the remineralized material and electron microprobe examination were consistent with the formation of fluoridated hydroxyapatite rather than calcium fluoride.

Novel topical fluoride delivery system I: remineralization of ground bovine teeth.

Laboratory studies were carried out on a newly conceived fluoride-containing remineralizing system with bovine teeth. The prototype fluoride delivery device involved micronized calcium fluoride maintained at the tooth surface with a cellulose film. Together with salivary calcium and phosphate (or simulated saliva), this system was able to generate and maintain the appropriate thermodynamic activity driving force for significant fluorapatite deposition in a reasonably short time (approximately 48 hr).