Caries Research

ten Cate, J.M.; Duijsters, P.P.E.

doi: 10.1159/000260599pmid: 6953998

Mineral loss and uptake in artificial enamel lesions was investigated by pH cycling: samples were subjected to a sequence of de- and remineralizing solutions. The ratio between de- and remineralization per day and the presence of fluoride in the remineralizing solution were varied among different experimental groups. Calcium, phosphate and fluoride uptake and loss were measured. The lesions were also studied with a hardness tester and micro radiography. The results show a difference in remineralization mechanism between continuously remineralized and pH-cycled samples (with respect to Ca/P ratios). With fluoride present, after some time, ‘arrested’ carious lesions are formed, which can hardly be further demineralized or remineralized. This is in agreement with clinical findings of remineralization in areas with fluoridation of the drinking water.

de Rooij, J.F.; Arends, J.

doi: 10.1159/000260600pmid: 6953999

The diffusion of ³²P-labelled phosphate ions in whole bovine enamel was investigated in the pH range 5–9 at 37° C. The experiments were carried out in preequilibrated solutions (using contralateral teeth) to ensure that at the various pH values dissolution effects were absent. The diffusion profiles obtained are interpreted with a grain boundary diffusion model. The diffusion coefficients D_k and D_v for the interprismatic and intraprismatic diffusion, respectively, were found to increase with decreasing pH. The increase was most pronounced for D_v values. It is explained by the pH dependency of the fractions of the monovalent H₂PO₄^- ions and divalent HPO₄^2- ions in the enamel pores and on the enamel crystallites; at pH 7 phosphate is transported in enamel by both HPO₄^2- and H₂PO₄^-; H₂PO₄^- diffusion dominates at pH 5 whereasHPO₄^2- diffusion is dominating at pH 9.

Liem, R.S.B.; Jansen, H.W.B.

doi: 10.1159/000260601pmid: 7046938

A simple method for the preparation of partially decalcified sections of sound and carious human dental enamel for electron microscopic studies is described. Formalin-fixed human teeth are sawed in sections with a thickness of 0.5 mm. These sections are embedded in Poly Bed 812 embedding medium prior to decalcification, immersed in an aqueous solution of 1% (w/v) chromic potassium sulphate, pH 3.4 and subsequently reembedded in the same resin. The decalcification process is checked by means of transmitted light microscopy. Chromic potassium surphate fixes and contrasts the enamel matrix structures so that post-fixing of specimens and additional staining of ultrathin sections are unnecessary. The method preserves the enamel matrix well and permits the preparation of serial ultrathin sections.

Suckling, G.W.; Purdell-Lewis, D.

doi: 10.1159/000260602pmid: 6954000

Fluorotic lesions resembling those seen in human teeth were produced experimentally in the unerupted enamel of the central incisor teeth of 3 sheep by daily dosing for 21 days with 2, 4 or 6 mg fluoride/kg body weight. Opacities, both superficial and extending to the amelodentinal junction, horizontal lines and pits were seen on the specimens. A comparison between the sheep with the lowest and highest dosing showed that, at these fluoride levels and given for a relatively short period of tooth development, there was no clear correlation between fluoride intake and the type of fluorosis found. The opacities and the bases of the scattered pits showed consistently lower hardness values than the surrounding enamel and in addition, the mineral content of the opacities was significantly lower than that of the control enamel. These findings support the theory that fluorotic lesions may be both pre-eruptive or post-eruptive (traumatic) in origin.

Featherstone, J.D.B.; Cutress, T.W.; Rodgers, B.E.; Dennison, P.J.

doi: 10.1159/000260603pmid: 6954001

A mouthrinse formulated to fulfill physicochemical requirements for rapid remineralization of early carious lesions was investigated in vivo using intraoral appliances in adults. Human enamel slabs with artificially induced early lesions were embedded in the appliances. Complete rehardening of the inner 40–50 μm and twofold rehardening of the remaining body of the lesion occurred in 160-μm deep lesions with a 1-min mouthrinse on each of 14 consecutive days. Saliva alone rehardened the inner 20 μm only. At least the inner half of lesions 65 μm deep rehardened completely and the remaining body of the lesion rehardened fourfold over 14 days. Monofluorophosphate toothpastes, tested similarly remineralized to the same extent as saliva alone and increased the surface layer hardness. The remineralizing solution shows potential value as a daily mouthrinse for the prevention or reversal of early carious lesions.

Brudevold, F.; Aasenden, R.; Bakhos, Y.

doi: 10.1159/000260604pmid: 6954002

A method for in vivo measurements of the permeability of surface enamel was applied to the central maxillary incisor of two groups of children ranging in age from 7 to 9 and 13 to 14 years, respectively. The method involved exposure of a standard area of the surface enamel to 2 M KI, removal of the iodide present on the surface, and determination of back diffusion of the imbibed iodide. The mean ( ± SE) of recovered iodide, expressed in mole equivalents × 10¹⁰, was 34.0 (5.9) for the younger group (n = 27) and 4.1 (1.3) for the older group (n = 32). The difference was statistically significant (p < 0.01). It is concluded that posteruptive maturation of enamel involves a decrease in permeability to iodide. The drinking water was fluoridated 4 years before the study was undertaken and possible effects of the waterborne fluoride on the findings are discussed.

Spak, C.J.; Ekstrand, J.; Zylberstein, D.

doi: 10.1159/000260605pmid: 6954003

The aim of the present study was to examine the bioavailability of fluoride (F) from some infant food products containing considerable amounts of F. Three different solutions containing 5 mg F were administered on three separate occasions to 4 young volunteers. They consisted of 500 ml of a 10 ppm F water solution, 500 ml milk containing 10 ppm F and 500 ml of a baby formula prepared with a 10 ppm F solution. Plasma F and urinary F levels were subsequently monitored for 15 h. Pharmacokinetic analysis of the data was performed and F bioavailability calculated. The results show that 72% of all F in the milk- and 65% of all F in the water-diluted baby formula were absorbed. Results from in vitro recovery studies demonstrated a 100% F recovery from milk and a 90% F recovery from baby formula. An explanation for the contradictory findings in the in vivo experiments is discussed.

Andlaw, R.J.; Burchell, C.K.; Tucker, G.J.

doi: 10.1159/000260606pmid: 6954004

The purpose of the study was to compare the dental health of 11-year-old and 14-year-old children in three Bristol schools with that of children of the same ages who attended the same schools and participated in a clinical trial from 1970 to 1973. The children were examined by the same two clinicians who conducted the clinical trial. The results showed marked reductions in dental caries experience. The reductions of mean DMFT and DMFS of 11-year-old children from 1970 to 1979 were 36 and 41%, respectively, and of 14-year-old children from 1973 to 1979, 30 and 36%, respectively. The reason for these reductions is unknown, but it is noted that they occurred during a period when the use of toothpastes containing fluoride increased markedly.

Katz, Ralph V.; Hazen, Stanley P.; Chilton, Neal W.; Mumma, Richard D., Jr.

doi: 10.1159/000260607pmid: 6980052

A descriptive epidemiologic survey of root caries in 473 20- to 64-year-olds revealed an age- and sex-adjusted overall root caries index (RCI) rate of 11.4% indicating that approximately one in nine surfaces with recession exhibited root caries. Although age-adjusted RCI rates for males and females were similar, the sex-adjusted RCI rates for each decade of life between 20 and 60 increased from 1.1% to 4.7% to 13.0% to 22.0%. Intraoral distribution patterns for root caries revealed that the most frequently attacked tooth types were mandibular molars (RCI = 40%), mandibular premolars (RCI = 25%) and maxillary canines (RCI = 23%). The least frequently attacked tooth types were the mandibular incisors (RCI = 2%). The interproximal surfaces exhibited the highest RCI rates in the maxillary arch while the buccal surfaces showed the highest RCI rates in the mandibular arch.

Künzel, W.

doi: 10.1159/000260608pmid: 6954005

A study on 614 children (aged 6–13) showed caries reduction in La Salud, Cuba, after 7 years of water fluoridation (0.7 ± 0.1 ppm F). Despite this relatively low fluoride level the caries-inhibiting effect was comparable with a similar study carried out in a temperate climate. The low incidence of mottling in artificially fluoridated and naturally high F areas would seem to justify an increase in the fluoride concentration of water supplies to 0.9 ± 0.1 ppmF.