Caries Research

doi: 10.1159/000259850pmid: N/A

Carlsson, J.; Johansson, T.

doi: 10.1159/000259851pmid: 4518083

The aim of this study was to elucidate if sugar is a limiting substrate for the growth of the oral microflora. Six subjects were used. Water, glucose solution or peptone yeast extract broth were pumped into the mouth during 4-hour periods and all oral fluid was collected. The number of viable bacteria and the contents of RNA and DNA were estimated in the fluid. There was no obvious difference in the amount of microbial biomass shed into oral fluid during the water period and the glucose period, while an increased amount of biomass could be shown in the fluid during the broth period. Sugar does not appear to be the primary growth-limiting substrate of the oral microflora.

Loesche, W.J.; Murray, R.J.; Mellberg, J.R.

doi: 10.1159/000259852pmid: 4518084

The percentage of Streptococcus mutans and Streptococcus sanguis in interproximal plaque following 5–10 daily applications of either an acidulated phosphate fluoride (APF) gel or a placebo gel was determined. Institutionalized boys, 14–16 years of age, residing in a rehabilitation center and who had detectable levels of S. mutans and S. sanguis in their plaque served as subjects. The APF gel increased the fluoride levels in the enamel surface from 1,889+403 to 3,284 ± 1,737 ppm, whereas the placebo gel had no effect on the enamel fluoride, i.e. approximately 1,950 ppm pre and post treatment. Six days after treatment, the percentage of S. mutans had decreased in 15 of 17 APF subjects but in only 4 of 10 placebo subjects. Six weeks after treatment, 13 of 17 APF subjects still had decreased percentages of S. mutans, whereas only 2 of 9 placebo subjects showed decreased levels. These differences were significant by χ²-analysis. S. mutans and S. sanguis each comprised about 5–7% of the plaque colony-forming units prior to treatment. Six days after APF treatment, S. mutans was reduced by about 75%, and remained at these low levels for at least 12 weeks. No change in S. mutans levels were seen in the placebo group. When the APF and placebo groups were compared using a paired t-test, a significant reduction in the S. mutans at 6 days post treatment was found. Fluoride or placebo treatment had no effect on plaque levels of S. sanguis. This study suggests that a topical APF gel may have a direct antibacterial effect on S. mutans.

Driessens, F.C.M.

doi: 10.1159/000259853pmid: 4518085

The classical theory on the solubility of ionic compounds has been extended to solid solutions and deviations from stoichiometry by combination of thermodynamical and solid state chemical principles. Theory predicts that the incorporation of foreign ions in enamel apatite can change its solubility product over several orders of magnitude in several ways. Experimental data on the composition of enamel indicate that the incorporation of F^- ions will stabilize the enamel crystals by the apparent diminution of Na⁺ and CO₃^2- incorporation. The additional effect may be that a change in the type of the main ternary apatite in enamel apatite crystals, carbonatoapatite into hydroxyapatite, is induced by incorporation of a relatively small amount of F^- ions. It is estimated that these effects in combination lower the solubility product of enamel apatite, calculated as Koha, by 5–10 orders of magnitude. The present theory can be used to screen other single or combined substitutions for their possible anticariogenic effect. Kinetic factors determining the success of prevention by ion incorporation are discussed.

Ingram, G.S.

doi: 10.1159/000259854pmid: 4518086

The reaction between hydroxyapatite and sodium monofluorophosphate has been studied under conditions pertinent to the use of a sodium monofluorophosphate dentifrice. Salivary o-phosphate and bicarbonate both inhibit the reaction. As the flow of saliva is stimulated the bicarbonate level rises and the inhibition becomes more marked. The reaction between monofluorophosphate and hydroxyapatite is favoured by a decrease in pH and the inhibition caused by saliva can be partially overcome by raising the concentration of sodium monofluorophosphate in the dentifrice. The results of these experiments indicate that the content of sodium monofluorophosphate in a dentifrice should be increased from 0.8 to 2.0%. It is preferable that the dentifrice gives a pH of below 7.0 in the mouth and that the other components of the dentifrice be chosen so that they do not add to the soluble o-phosphate in the saliva.

Mellberg, J.R.; Nicholson, C.R.; Packer, M.W.; Laswell, H.R.

doi: 10.1159/000259855pmid: 4518087

Analysis of exfoliated deciduous teeth from children living in both fluoridated and non-fluoridated areas and who used a 0.02% F rinse 5 times per week or a 0.1% F rinse one time per week revealed that significant fluoride was acquired only at a depth of 5 μm from the surface. Children who used the dilute F rinse in the non-fluoridated area acquired approximately one-third as much fluoride as teeth from the other groups. Enamel was not found to increase in fluoride concentration as more rinses were received but maintained the increase initially obtained.

Nixon, G.S.; Helsby, Christine A.

doi: 10.1159/000259856pmid: 4518088

A number of investigations have been carried out into the physiological relationship occurring between copper and molybdenum in differing animal species. The present study investigates this relationship in the hard dental tissues of the rat. Rats were fed varying amounts of either molybdenum, molybdenum and sulphate, molybdenum and copper, or molybdenum and sulphate. After 45 days the rats were killed and the teeth analysed by atomic absorption. The copper and molybdenum were complexed with ammonium pyrrolidine dithiocarbamate and extracted into methyl isobutyl ketone. Interference by other trace elements and macro-elements in the teeth was assessed. This study indicated that molybdenum retention in hard dental tissues of the rats was influenced only by the dietary molybdenum levels and not by dietary copper or sulphate. Similarly, the copper level was independent of the molybdenum and sulphate dietary levels but was influenced by the combined levels of copper and sulphate and also by the dietary copper level. However, the increased retention of both copper and molybdenum in the hard dental tissues due to increased levels of these elements in the diet occurs to a greater extent for molybdenum than for copper.

Hallsworth, A.S.; Weatherell, J.A.; Robinson, C.

doi: 10.1159/000259857pmid: 4518089

The changes in carbonate concentration of enamel associated with the first visible stages of carious attack have been investigated. Samples of translucent-zone enamel and adjacent samples of sound enamel have been dissected from small carious lesions and their carbonate content determined. The resuits indicate that a selective loss of carbonate occurs during the early stages of carious attack.

Davidson, C.L.; Boom, G.; Arends, J.

doi: 10.1159/000259858pmid: 4583438

In this investigation, the calcium content of sound decalcified and etched enamel was measured with an electron microprobe. The results show that calcium content, as a function of depth, decreases only a few percent as a result of decalcification in gelatin solutions of pH 4 and 5 within 1–8 days. Subsurface lesions (with a relatively low Ca concentration) could be observed. These lesions penetrated under the enamel surface at a rate proportional to the square root of the decalcification time. In etched enamel, however, the Ca decrease observed (also a few percent) was uniform over the whole penetrated area.

Rowles, S.L.; Levine, R.S.

doi: 10.1159/000259859pmid: 4518090

Surface material removed with an excavator from 23 lesions diagnosed clinically as arrested dentine caries has been analysed by X-ray powder diffraction. While hydroxyapatite was present in all samples analysed, crystalline non-apatitic phases were detected in six of the samples. These were weddellite, whewellite, calcite, brushite, whitlockite and octocalcium phosphate. In only one sample, however, was a non-phosphatic phase, weddellite, predominant. In the remainder the non-apatitic phases were minor components although the results indicate that the distribution may be heterogeneous.