ABSTRACT
The effect of pulpal cavity pressure on structures present on etched and unetched dentine was determined in 24 human premolars in vitro. The dentine was exposed in vivo. After extraction, the pulp was removed and the crown stored in 2.5 N sodium hydroxide for 3 days to remove the odontoblasts. The pulp cavity was filled with Ringer's solution at atmospheric pressure, +30 or -5 mmHg. After 30s-5 min a silicone-rubber impression was taken of the cavity floor and a resin cast prepared and examined in a SEM. The replicas reproduced the dentine surface accurately when there was no outward flow through dentine. With a pressure of + 30 mmHg in the pulp cavity, but not at the lower pressures, droplets were present on unetched dentine after 30s. Droplets accumulated less rapidly on etched dentine, indicating that it may act as a sponge.
Subject(s)
Dentin/metabolism , Dentinal Fluid/metabolism , Acid Etching, Dental , Dental Impression Technique , Dentin/ultrastructure , Humans , In Vitro Techniques , Microscopy, Electron, ScanningABSTRACT
Remineralized surfaces of human tooth enamel were dissolved at constant rates in 10 mM acetic acid at pH 4.0, and in 10 mM EDTA at pH 7.4 in a system that prevented redistribution of dissolved F-. Surfaces remineralized 25 hours in 0.4 mM NaF (8 ppm F-) dissolved slower in acid or in EDTA than those remineralized in the absence of F-. The F- in three-hour remineralized surfaces had no effect on rates of mineral dissolution. Resistance to EDTA, as well as acid of 25-hour remineralized surfaces, indicates the occurrence of a maturation process, which may involve F- exchange for OH- ions in newly formed crystals. The results indicated that F- may slow caries by its action on remineralization if given sufficient time for this maturation.
Subject(s)
Dental Enamel Solubility/drug effects , Dental Enamel/drug effects , Fluorides/pharmacology , Sodium Fluoride/pharmacology , Tooth Calcification/drug effects , Acetates/pharmacology , Dental Enamel/ultrastructure , Edetic Acid/pharmacology , Humans , Time FactorsABSTRACT
Labial surfaces of bovine incisor enamel, after weak acid demineralization, were exposed for 24 h in solutions that contained trace levels of calcium as 45Ca, 0.4 mM NaF, and 1.0 mM MgCl2 at pH 7.0. The solutions approached saturation with apatites in the absence of NaF, and saturation with fluorapatites in the presence of NaF. NaF greatly increased the exchange of 45Ca. MgCl2 decreased 45Ca exchange, but had no effect on F- exchange in the surface minerals. MgCl2 decreased, while NaF increased the acid resistance of the exchanged surface minerals on later exposure to 10 mM acetic acid at pH 4.5. These results indicated that magnesium in oral fluids and tooth minerals may promote caries.
Subject(s)
Acetates/pharmacology , Dental Enamel/drug effects , Fluorides/pharmacology , Magnesium/pharmacology , Animals , Calcium/metabolism , Cattle , Dental Enamel/metabolism , Fluorides/metabolism , Hydrogen-Ion Concentration , Ion Exchange , Phosphates/metabolismABSTRACT
Enamel surfaces were demineralized in acetic acid and remineralized in solutions that contained 1.5 mM calcium, 1.0 mM phosphate, and 0.0, 5, 15, and 25 mM NaHCO3, and 0.00 or 5.0 mM Naf at pH 7.0. NaF in CO2-free solutions increased the rates of calcium and phosphate uptake during remineralization. Bicarbonate in NaF-free solutions caused small increases of calcium and phosphate uptake. Bicarbonate with NaF in solutions synergistically increased calcium uptake, but did not affect phosphate uptake. Bicarbonate reduced fluoride uptake by about 50% during remineralization, and increased the Ca/P ratios of deposited minerals from about 1 (dicalcium phosphate) to approach and exceed the ratios of apatites.
Subject(s)
Bicarbonates/pharmacology , Dental Enamel/metabolism , Tooth Calcification/drug effects , Animals , Calcium/metabolism , Cattle , Fluorides/metabolism , Phosphates/metabolismABSTRACT
Analyses were made of samples of surface enamel collected before and after acid demineralization and after subsequent remineralization in solutions containing calcium and phosphate and various levels of bicarbonate and fluoride ions. Demineralization caused a preferential loss of carbonates. Remineralization was increased by both fluoride and bicarbonate ions. With no bicarbonate in the calcifying solution, 0.25 to 4.0 mM NaF increased mineral formation and thereby caused a relative reduction of its carbonate content. With 0.5 mM NaF (10 ppm F-) and 5, 15, and 25 mM HCO-3 in remineralizing solutions more carbonate was deposited than in the absence of NaF. Five and 15 mM HCO-3 increased, but 25 mM HCO-3 decreased, deposit of fluoride in enamel.
Subject(s)
Carbonates/analysis , Dental Enamel/analysis , Fluorides/analysis , Acetates/pharmacology , Animals , Bicarbonates/pharmacology , Cattle , Fluorides/pharmacology , Tooth Calcification/drug effectsSubject(s)
Calcium/metabolism , Dental Enamel/metabolism , Fluorides/pharmacology , Animals , Cattle , Dental Enamel/drug effects , Humans , IonsABSTRACT
The acid resistance of powdered human dentin increased linearly after pretreatments in 2.5, 25, 250, and 1,000 mM NaF in water. The acid resistance was not directly correlated to the F content of the dentin. The results indicated F uptake by the dentin to be a result of chemical reaction and of absorption.
