The in-situ remineralization effect of hard cheese was compared with that of saliva on tooth enamel in man. The intra-oral test of softening enamel surfaces by a cola type drink followed by rehardening by chewing hard cheese and/or parafilm was assessed by microhardness and SEM measurements. Cheese consumption significantly increased the enamel hardness, whereas stimulated saliva did not have this effect. The remineralizing effects are presumably due to uptake of calcium and phosphate salts by the surface enamel. Morphologically, the enamel surfaces did not return to their original state.

The effectiveness of topical 2% sodium fluoride applied with and without 10% strontium chloride pretreatment was compared in patients complaining of tooth hypersensitivity. In addition the radiopacity of 2% sodium fluoride and 25% strontium chloride treated dentin was studied in vitro. Reduction of sensitivity to cold and mechanical stimuli was evaluated during a period of 3 months by pain scoring in the exposed cervical dentin of homologous teeth on the two sides of the jaws. There was a significant decrease in the sensitivity of the exposed cervical dentin after treatment with sodium fluoride solution with or without pretreatment with strontium chloride solution. At the end of the experimental period the combined strontium and fluoride treatment was found to be more effective than that of fluoride alone in reducing sensitivity to cold. The increase in radiodensity of dentin samples immersed in strontium chloride was statistically significant, while there was no significant increase in density for the samples immersed in sodium fluoride solutions. A mineralization process is possibly the effective means by which fluoride or strontium diminishes sensitivity of dentin.

Immersion in fluoride solution increased fluoride concentration in three root layers of extracted monkey incisors. Replantation of the teeth resulted in fluoride uptake by adjacent bone.The immersion of teeth in concentrated fluoride solutions before delayed replantation1-3 and allogenic transplantation4 in monkeys and rats has been found to effectively inhibit the rate of subsequent root resorption. In vitro experiments with root surfaces of human teeth immersed in concentrated fluoride solutions have shown a high fluoride uptake. The subsequent immersion of these fluoride-treated teeth for 24 hours (a period known to release almost all labile fluoride) in saline resulted in a decrease in the fluoride concentration by about half.5This investigation deals with fluoride uptake by the root surfaces of extracted monkey incisors immersed in 2°%-, NaF * 0.1 M H3PO4 (pH 5.5) for 20 minutes5; residual fluoride in the root cementum after a period of replantation; and uptake by the adjacent alveolar bone of fluoride released from the cementum. Materials and MethodsThe mandibular right and left lateral incisors of five rhesus monkeys were extracted, and biopsy specimens of the lingual plate of the left lateral incisor were obtained and air-dried. The pulps of the two extracted teeth were extirpated and the teeth were immersed in 2% phosphate-acidulated sodium fluoride (pH, 5.5) for 20 minutes. After fluoride immersion the teeth were dipped in saline for ten seconds to remove excess fluoride solution on the tooth. The left lateral incisor then was air-dried and the right lateral incisor root canal was filled, replanted and sprinted. After three weeks the replanted incisor was extracted, biopsy specimens of the lingual plate of alveolus (experimental) were obtained, and the tooth and bone samples were air-dried.Extracted incisors and alveolar bone chips of 11 other rhesus monkeys were used as controls.Examination of three consecutive root layers of the extracted untreated incisors and the fluoride-immersed and replanted fluorideimmersed incisors was carried out by immersion of the roots in 1 ml 0.25 N HCl for three two-minute periods. Weighing of the root layers removed by HCl was carried out under standardized conditions. The amount removed from each root varied between 1.5 and 2 mg. Fluoride analysis of the removed root layers and ashed bone samples was conducted with an electrodes according to the method of Singer and Armstrong.6 The statistical significance of fluoride analysis differences was calculated by the t test. The criterion for statistical significance was P < 0.05. ResultsThe results of this experiment are shown in the table. Teeth immersed in 2% NaF-0.1 M H3PO4 for 20 minutes showed a significant increase in the amount of fluoride a Union Research, Cambridge, Mass.

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