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At least 91 records · Page 5Linked to original sources
PubMed1977

Rate of permeation of isotopes through human dentin, in vitro.

A simple in vitro method has been described for quantitatively measuring the rate at which isotopically labeled substances permeate through dentin in occlusal cavity preparations. The presence or absence of pulp tissue had only a minor effect on the kinetics of permeation. As the dentin was made thinner there was a resulting increase in the rate of iodide permeation. The relative rates of permeation were 3H2O greater than 131I greater than 99mTc greater than 14C-urea, a sequence that follows the molecular dimensions of these substances.

Carbon Radioisotopes↗
PubMed1987

The effects of burnishing NaF/kaolin/glycerin paste on dentin permeability.

The effects on dentin permeability of burnishing NaF, kaolin, or glycerin, alone and in various combinations, were determined using an in vitro system. The results indicate that the important variable was not any of the constituents of the paste but the burnishing process itself. Burnishing dentin creates a partial smear layer on the dentin surface, thereby occluding the orifices of dentinal tubules sufficiently to reduce fluid movement across dentin 50 to 80%.

Acid Etching, Dental↗
PubMed1990

[Demineralization behavior, enamel permeability and the morphological characteristics in relationship to the stage of eruption of the permanent teeth].

The posteruptive maturation of enamel is an important factor in caries disposition. In an experimental study the demineralization of enamel as well as its permeability and its morphological features in dependence of eruption stage were examined on extracted premolars. Chemical analysis showed variations in the Ca/P molar ratio. It is possible, that the instability of Ca-ions in crystalline configuration decreased during the time of eruption. The permeability of enamel decreased between 5 and 11.8%. It appears to be useful to concentrate preventive measure on this phase of dentition development.

Bicuspid↗
PubMed1989

Systemic distribution of 14C-labeled formaldehyde applied in the root canal following pulpectomy.

The systemic distribution of 14C-labeled formaldehyde which had been placed in the root canals of the canines of cats following pulpectomies was studied using liquid scintillation counting and wholebody autoradiographic technique. Radioactive 14C which had been placed in the canals was found in the plasma 30 min after the root canal procedure. The recovery of systemic 14C radioactivity increased with time. In addition, it seemed that approximately 3% of the dose placed in the teeth was excreted in the urine within 36 h. Whole-body autoradiograms indicated extensive concentration of 14C radioactivity in tissues other than those analyzed with the liquid scintillation technique.

Animals↗
PubMed1988

Increased permeability of enamel to iodide ions following the ingestion of cookies varying in sucrose or fat content.

Experiments showed that the intraoral iodide permeability (Ip) method can be used in a reproducible and sensitive manner with solid foods. Ingestion of 5-gram portions of cookies made with defined concentrations of sucrose or fat led to an increased Ip (due to demineralization) of Streptococcus mutans-covered bovine enamel blocks in vivo. Demineralization increased with time to a maximum of 45 min, and the pH of the plaque dropped accordingly. Continued exposure in the mouth beyond 45 min led to an elevation of the pH and a decrease in delta Ip consistent with remineralization of the enamel. Control blocks worn without ingestion of cookies exhibited negative delta Ip values. Demineralization increased with increasing sucrose content of the cookies and reached a plateau when cookies containing 1.08 g sucrose per morsel were administered. Cookies prepared without added sucrose gave a high delta Ip. High fat content raised the delta Ip when sucrose was low. These findings are consistent with clinical and other observations, and emphasize the complex relation between foods and enamel demineralization.

Animals↗
PubMed1990

The effect of 25% tannic acid on prepared dentin: a scanning electron microscope-methylene blue dye study.

The effect on the permeability of prepared dentin treated with 25% tannic acid and 6% citric acid was compared with the untreated dentinal surface. Methylene blue was applied to the dentin surface after treatment to evaluate penetration into dentinal tubules. The tannic acid solution reduced or prevented dye penetration of the dentinal tubules. Citric acid treatment permitted severe penetration. The 25% tannic acid solution removed the smear layer while inhibiting penetration of the dye.

Acid Etching, Dental↗
PubMed1986

Diffusion of fluorides in human dental enamel in vitro.

The diffusion of fluoride (F) from sodium fluoride, sodium fluorosilicate, and sodium monoflurophosphate solutions (containing 0.1 per cent F in physiological saline) was studied using a two-chamber diffusion cell separated by enamel membrane. The diffusion coefficient, D in cm2s-1, of F was determined under steady-state conditions over 3 weeks. The D value of F for NaF was significantly higher than for Na2SiF6 and Na2PO3F (p less than 0.001; unpaired t-test). F for acidic Na2SiF6 diffused more rapidly than for Na2PO3F (p less than or equal to 0.001), presumably as HF molecule. Despite the F in the tested solutions being in different forms, i.e. simple ion in NaF or mainly complex ions as in Na2SiF6 and Na2PO3F, the diffusivity of the F in enamel for these compounds was of the same order of magnitude (D = 10(-9)cm2s-1). The findings support the concept that enamel can behave as an ion-selective membrane with certain molecular-sieve effects.

Dental Enamel↗
PubMed1988

[Changes induced by ouabain and colchicine in the transdentinal flow estimated in vivo by perfusion: the "push-pull" of the incisors of rats].

The active or passive mechanisms regulating the various movements of dentinal fluid have not yet been sufficiently studied. For this reason different "in vivo" factors that may modulate the kinetics of transdentinal flow were investigated. After systemic administration of a radiotracer in rats, the kinetics were examined with a push-pull perfusion device fixed to the incisor dentin. The drugs chosen, i.e. ouabain and colchicine, were for their respective effects on microtubules and on the ATPase-dependent Na+ K+ pump, since these two factors are involved in the transport process. Anesthetized animals were prepared to allow intravenous injection of iodine 125 (0,5 to 0,7 mCi), carotid sampling, and perfusion of upper incisors. Ouabain induced a very significant decrease in transdentinal flow, which was particularly evident in younger animals (2,81 x 10(-2) % vs 0,04 x 10(-2)%, p less than 0,05). However, colchicine produced two different kinds of results : at low doses (3,5 to 5 mg/100 g) the pulsatile pattern of the curves was partially inhibited, whereas, at higher doses (6 to 7 mg/100 g), the transdentinal flow of radioactivity increased. These results suggest that a combination of active and passive transport may be involved in the various movements of this fluid.

Animals↗