Dj Purdelllewis

Monobacterial and Mixed Bacterial Plaques of Streptococcus mutans and Veillonella alcalescens in an Artificial Mouth: Development, Metabolism, and Effect on Human Dental Enamel

To gain greater understanding of the role of Streptococcus mutans and Veillonella in the caries process, studies of both aerobically and anaerobically grown plaques of S. mutans C67-1 and V. alcalescens V-1 on human enamel slabs were carried out in an artificial mouth. Plaque development, acid production, and demineralization were measured. Early plaque development of monobacterial and mixed bacterial plaques started from randomly adhering cells on day 1 to confluent multilayered microcolonies on day 4. Differences were observed in viable cell counts, total cell mass, and in acid production. In most cases CFU, DNA and acid production were higher in the mixed bacterial plaque, especially in the anaerobic mixed plaque. Lactic acid was the predominant acid in all cases following the supply of sucrose to the plaque. No decisive role could be found for acetic, formic, and propionic acid. No inhibition of demineralization was observed in the enamel slabs inoculated with both aerobic and anaerobic mixed plaques. Demineralization ranged from the more classical picture of lesion development in the aerobic monobacterial plaque-treated samples to an aggressive etching of the enamel surface in the anaerobically mixed treated slabs.

HARDNESS TESTS ON SOUND ENAMEL AND ARTIFICIALLY DEMINERALIZED WHITE SPOT LESIONS

The accuracy and reproducability of hardness measurements have been investigated in this study. Sound and demineralized enamel were used as the main test materials. The reproducability of hardness measurements on artificial white spot lesions produced by a hydroxyethyl cellulose/lactic acid demineralizing solution was also investigated on embedded cross-sections. The operator error was found to be less than 5% when reading both steel and enamel indentations. The maximum hardness of the surface layer and the minimum hardness of the subsurface lesion were measured in three positions in each of 10 artificial white spot lesions. An analysis of the results showed that: (a) the hardness values at the same distance from the surface but in different areas of the same lesion were very similar; (b) hardness values between lesions were also very even; (c) the drop in hardness after demineralization was related to the initial hardness of the enamel.

Influence of the Mineral Content of Enamel on Caries-Like Lesions Produced in Hydroxyethyl Cellulose Buffer Solutions

The influence of the original mineral content on the effect of one and two periods of acid attack was studied using quantitative microradiography. The maximum mineral content and the thickness of the surface layer, the minimum mineral content and the depth of the lesion were depicted as a function of the original mineral content. A linear relationship was found in all cases except in those groups with the highest original mineral content, where a flattening of the curve was seen. It may be concluded from the correlation between the lesion depth and the thickness of the surface layer that, when more material is dissolved in the lesion, more precipitation can take place near the intact surface, thus increasing the thickness of the surface layer.

0.25% and 0.4% Amine Fluoride Gel for Weekly Topical Application

In a double-blind crossover study the remineralizing effects of the combinations: placebo toothpaste, placebo gel; amine fluoride toothpaste, placebo gel; amine fluoride toothpaste, 0.25% F–– amine fluoride gel and amine fluoride toothpaste, 0.4% F–– amine fluoride gel were investigated in vivo. Artificially demineralized flattened enamel slabs were placed in the buccal flanges of partial dentures. It was found during the 3-week experimental periods that there was a significantly higher increase in remineralization in the 2 fluoride gel groups. This occurred in both the surface layer and subsurface lesion and resulted in a significant decrease in lesion depth and increase in hardness. It is suggested that the weekly use of these gels should be considered in patients with early enamel lesions if they are formed during, or fail to remineralize under, a normal preventive regime.In a double-blind crossover study the remineralizing effects of the combinations: placebo toothpaste, placebo gel; amine fluoride toothpaste, placebo gel; amine fluoride toothpaste, 0.25% F–– amine fluoride gel and amine fluoride toothpaste, 0.4% F–– amine fluoride gel were investigated in vivo. Artificially demineralized flattened enamel slabs were placed in the buccal flanges of partial dentures. It was found during the 3-week experimental periods that there was a significantly higher increase in remineralization in the 2 fluoride gel groups. This occurred in both the surface layer and subsurface lesion and resulted in a significant decrease in lesion depth and increase in hardness. It is suggested that the weekly use of these gels should be considered in patients with early enamel lesions if they are formed during, or fail to remineralize under, a normal preventive regime.

DEVELOPMENTAL AND METABOLIC ASPECTS OF A MONOBACTERIAL PLAQUE OF STREPTOCOCCUS-MUTANS C 67-1 GROWN ON HUMAN-ENAMEL SLABS IN AN ARTIFICIAL MOUTH MODEL .1. PLAQUE DATA

Development and metabolic aspects of a monobacterial plaque of Streptococcus mutans C 67-1, inoculated on flattened human enamel slabs, were studied using an artificial mouth model.

MICROHARDNESS AND DENSITOMETRIC MEASUREMENTS OF EFFECT OF 4 PERCENT SNF2 SOLUTION ON ARTIFICIAL WHITE SPOT LESIONS

The effect of differing periods of 4% stannous fluoride treatment at 50 °C on artificial white spot lesions was investigated on cross-sections. Microhardness, densitometric and microprobe measurements were made through the same place on the sections. Both hardness and radiodensity increased significantly after half an hour and reached a maximum after 6h treatment with SnF2 solution. The rate of hardness increase, even in heavily demineralized sections, appears to be superior to that so far achieved using remineralizing solutions. The microprobe results indicated that the increase in radiodensity was linked to the tin uptake. There was, however, no such correlation with the hardness increase, which appears to be due to an alteration in structure.

The Pattern of Mineralization of Traumatically-induced Developmental Defects of Sheep Enamel Assessed by Microhardness and Microradiography

An earlier study showed that some of the variation in appearance of defects of enamel in sheep incisor teeth induced by trauma during tooth development was related to the phase of activity of the ameloblasts at the time of injury. In the present study, sixteen selected defects were examined by microhardness and microradiography. It was found that in some of the fully formed teeth, the defects had retained the pattern of mineralization present at the time of trauma, i.e., mineralization had ceased. In other teeth, further mineralization of the defects occurred after trauma, resulting in well-mineralized enamel, although sometimes of incomplete thickness. It was concluded that the trauma, depending on its severity, leads to either permanent or temporary dysfunction of the ameloblasts, which also influences the appearance of the resulting lesions.

LOWER FLUORIDE CONCENTRATIONS FOR TOPICAL APPLICATION - INVITRO STUDY ON HUMAN DENTAL ENAMEL

The potential toxicity of fluoride application can be reduced by using lower fluoride concentrations. A previous study has shown that 0.4% F–– and 1.2% F–– organic fluoride gels were equally effective in preventing demineralization in both sound and primed human enamel. In this study 0.4, 0.1 and 0.01 % F–– amine fluoride and acidulated phosphate fluoride (APF) solutions were tested to see whether a further reduction in concentration was possible. All amine fluoride groups and 0.4% F–– APF showed significantly shallower lesions than controls. Lesion depth in both amine fluoride and APF groups increased with decreasing F–– concentration. APF groups showed a tendency for deeper lesions than amine fluoride groups. All fluoride groups showed significantly higher minimum vol% mineral in the subsurface lesion than the controls; these values decreased with decreasing F–– concentration. It can be concluded that under these experimental conditions adequate protection against further acid attack was provided by 0.4% F–– amine fluoride followed by 0.4% F–– APF.

The Effect of Demineralization on SnF2-Treated White Spot Enamel Lesions

It has been shown that the application of stannous fluoride (SnF2) solution increases the resistance of sound enamel to demineralization. The effect of SnF2 on demineral

Plasma Fluoride Levels in 9 Children with Acute Lymphatic Leukaemia Using Daily Self-Applied Fluoride Gels

Many patients with acute lymphatic leukaemia apply 1% NaF gel daily. Plasma fluoride levels and urinary excretion of 9 children using this regimen were followed in this study. Patients with a high dai