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Results for “Dentin Permeability”

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At least 631 records · Page 35Linked to original sources
PubMed1985

The movement of radioactive molecules across dentine in vivo in the dog.

Using a technique for measuring the movement of circulating molecules across the odontoblast-dentinal complex, the movement of water and alpha-aminoisobutyric acid through dentine and into a flow cell prepared on the tooth is described. The movement of water depended on dentine thickness, and varied from 0.40 microliter/min per cm2 in a flow cell overlying an average thickness of 0.74 mm of dentine, to 1.23 microliter/min per cm2 in a flow cell with a dentinal floor of 0.40 mm average thickness. The data suggest that alpha-aminoisobutyric-acid concentrations were lower in dentinal fluid than in blood plasma.

Aminoisobutyric Acids↗
PubMed1988

A theoretical model for the hydraulic conductance of human dentine.

A theoretical model was devised that describes the dependence of the hydraulic conductance of dentine disks on the decrease in dentine tubule radius and dentine tubule density (number per area of cross-section) in the pulp-enamel direction. A parameter that describes the decrease in tubule radius was calculated from experimental results from the literature.

Chemical Phenomena↗
PubMed1991

Temperature dependence of water transport into the mineralized matrix of freeze-dried human dentine.

Ten dentine sections cut perpendicular to the dentinal tubules from human mature non-carious third molars, were freeze-dried and then rehydrated by immersion in water at four temperatures, 10, 25, 40 and 70 degrees C. The uptake of water by the sections was assessed as a function of rehydration time. The data were analysed using a theoretical model in which the uptake is ascribed to two processes. The first is capillary suction of water into the dentinal tubules, the second is the diffusion of water from the two faces of the section into the mineralized matrix. By fitting theory to experiment the diffusion coefficient of water in intertubular dentine at the different temperatures was found. Using the Arrhenius relation the activation energy of diffusion of water in intertubular dentine was calculated as Ea = 29.5 +/- 2.2 kJ/mol, which is of the order of the strength of a hydrogen bond. Transport of water in the mineralized matrix during rehydration is thus most likely a hopping of water molecules along the surfaces of the collagen and/or mineral, each jump involving the breaking of one hydrogen bond.

Dentin↗
PubMed1992

The effect of dietary factors on intradentinal dye penetration in the rat.

Fluorescent dye injected systemically into rats penetrated the dentinal tubules of molar teeth in a dynamic fashion. The presence of dye was established using histological and fluorescence microscopy techniques. The rate of intradentinal dye penetration was dependent on dietary factors: it was high in rats chronically fed Purina rat chow and low in rats fed a cariogenic, high-sucrose diet. In addition, parotidectomized rats showed low levels of intradentinal dye penetration, even though they were maintained on Purina chow. One and 2 ml of plasma from Purina-fed rats were effective in stimulating the dye penetration in intact and parotidectomized rats, whereas 2 and 4 ml of plasma from rats fed a high-sucrose diet were ineffective when infused in either intact or parotidectomized animals. The results suggest that rats fed Purina chow have a significantly higher titre of a circulating, dye penetration stimulating factor than animals fed a high sucrose diet. This circulating factor could be the equivalent of the parotid hormone isolated from porcine tissue. It is suggested that dietary factors may affect secretion of a parotid hormone and thereby regulate the rate of dentinal fluid movement. There is therefore the prospect of a functional relationship between diet, the regulation of dentinal fluid flow by an endocrine system and dental health.

Acriflavine↗
PubMed1992

Fluid flow through cat dentine in vivo.

An outward flow of fluid through exposed dentine was demonstrated in anaesthetized cats. The flow was measured by observing the movement of the fat droplets of dilute milk in a glass capillary (i.d. 30 microns) with a microscope. The capillary was sealed to the dentine with a plastic cap. The resting flow rate through dentine exposed by fracturing off the tip of a cat's canine ranged from 2.8 to 50.9 pl.s-1.mm-2 (mean 18.1, SD 15.9, n = 12). Raising the pressure at the dentine surface to about 15 cmH2O stopped the flow. Immediately after cutting the pulp at the root apex, in 11 of 12 preparations, the flow reversed. The average flow rate was then 3.8 pl.s-1.mm-2 inward (range 8.4 outward to 15.9 inward, SD 5.4, n = 12). The inward flow after pulp section suggests that an osmotic effect may contribute to the net pressure causing flow. The average hydraulic conductance of the exposed dentine was 1.6 x 10(-8) m.s-1.kPa-1 (range 0.5-2.9, SD 0.8) before pulp section. After pulp section, it increased to an average of 2.5 x 10(-8) m.s-1.kPa-1 (range 0.8-5.2, SD 1.3).

Absorption↗
PubMed1993

Stimulation of intradentinal dye penetration by feeding in the rat.

Dentinal fluid movement, as measured by intradentinal dye penetration (IDDP), may be under the control of an endocrine system that includes the parotid glands. It was earlier demonstrated that parotid hormone stimulates IDDP when infused into rats, and in the pig the onset of feeding signals the release into the circulation of immunoreactive parotid hormone (iPH), the titre of which remains elevated for more than 1 h after feeding. As, for technical reasons, it is impossible to measure iPH and IDDP activity in the same animal, the hypothesis that feeding causes IDDP stimulation in the rat was now tested. Feeding rats for 15 min stimulated IDDP to a level significantly higher than when fasting (0.418 +/- 0.040 versus 0.106 +/- 0.022, p < 0.001). Within the experimental conditions, IDDP stimulation lasted longer than 15 min. Sialoadenectomy before the feeding experiment did not change the feeding-stimulated IDDP response unless the parotid glands were removed. In parotidectomized and totally sialoadenectomized rats fed for 15 min, the level of IDDP was not different from that of sham-operated fasting animals. It is postulated that, in addition to the existence of possible local regulatory factors in the pulp, dentinal permeation may be under a physiological control mechanism involving a parotid endocrine function. It is also suggested that a hormonally controlled mechanism of dentinal fluid movement may play a systemic, protective role against the bacterial acidogenic challenge to teeth.

Acriflavine↗
PubMed1993

The effects of outward forced convective flow on inward diffusion in human dentine in vitro.

In vitro experiments were conducted to evaluate the influence of outward forced convective flow on the inward diffusion of radioactive iodide. When the smear layer was present, application of 15 cmH2O (1.47 kPa) outward-directed filtration pressure reduced the inward flux of iodide by about 10-20% depending upon the hydraulic conductance of each specimen. When the smear layer was removed by acid etching, the same 1.47 kPa pressure lowered the inward iodide flux by as much as 60%, depending on the hydraulic conductance. The results demonstrate the importance of the balance between inward diffusion and outward bulk-fluid movement on the rate of permeation of exogenous solutes.

Acid Etching, Dental↗
PubMed1995

Human dentine as a hydrogel.

The pores (tubules) of human dentine in 0.02-cm planoparallel sections of newly extracted permanent teeth were investigated. By the conventional scanning electron microscopy these pores appear empty, but by the newly developed scanning-probe microscopy the presence of a complex matrix could be established. By measuring the transport of neutral myoglobin by diffusion alone and diffusion+bulk flow, the area of dentine occupied by the matrix was calculated to be 1.9 +/- 0.9% and 2.3 +/- 0.5%, respectively. The hydraulic conductivity was surprisingly small, 1.35 +/- 0.55 x 10(-7) ml/(s.cm2 dentine) at a pressure difference of 0.1 kPa across a 1-cm thick section. This suggests a hydrogel with a relatively dense network, the width of meshes estimated at 2 x 30 nm. In line with this concept, enzymatic degradation of the organic matter increased the hydraulic conductivity 3000 times. By studying the transport of negatively charged myoglobin, the matrix was calculated to carry 18 mEq/l of positive charges. Due to the consequent attraction of small, negative ions and thence of water, the pressure within the matrix would be about 1.33 kPa, a force which will act to immobilize the water in the channels. The concept of a hydrogel in the dentine tubules was also supported by the finding that shielding the charges with bathing media of high ionic strength reduced the hydraulic conductivity.

Adolescent↗
PubMed1993

A pilot study of exposure of the smear layer to tannic acid solutions.

This study examined the effects of tannic acid on smear layer removal. Class V cavities were prepared on the buccal surfaces of extracted human molars with a No. 1557 high-speed carbide bur under water cooling for cutting and a No. 701 low-speed steel bur for finishing. They were then washed with water followed by an application of 2%, 5%, 10%, 15%, 20%, or 25% tannic acid solution in water for 15, 30, or 60 seconds. The axial wall dentin surfaces were examined with scanning electron microscopy. This examination showed that an application of 2% tannic acid for 60 seconds or 5% tannic acid for 15, 30, or 60 seconds effectively removed the smear layer, leaving the dentinal tubules occluded. The dentinal surfaces treated with 40% phosphoric acid for 15 seconds showed many exposed dentinal tubules with flared orifices.

Acid Etching, Dental↗
PubMed1991

Diffusion of medicaments within root canal dentin. A scanning electron microscopic study.

Root canals of 21 maxillary human teeth were enlarged with reamers and flushed alternatively with sodium hypochlorite and hydrogen peroxide. After its mechanical preparation, root canals were dressed with camphorated paramonochloropherol and/or formocresol delivered by paper points. All three medicaments crystallize both on dentin walls and inside dentinal tubules. The clinical implications of these findings are discussed.

Adult↗
PubMed1993

In vitro study of the penetration of three bacterial strains into root dentine.

The purpose of this study was to assess in vitro migration of the following three bacterial species into dentinal tubules: Streptococcus sanguis, Actinomyces naeslundii and Prevotella intermedia. Twenty-seven bovine incisors were randomly divided into three groups. Only the root dentin was used for the experiment. Within each group, the nine incisors were sectioned into 36 dentin blocks that were incubated with one of the tested bacterial suspensions. Twelve samples were taken after 10, 20, and 28 days. Half the samples were observed with scanning electron microscopy and the others with light microscopy after standard histologic procedures, and the depth of bacterial penetration was measured. Analysis of the examinations showed that whatever the technique used, only one strain on this experimental model migrated into dentinal tubules. S. sanguis was observed at a depth of 792 microns, but no migration was observed for either A.naeslundii or P.intermedia. The differences in migration of the bacteria tested appear to be related to their morphologic factors and cellular arrangement.

Actinomyces↗
PubMed1989

Dentin perfusion effects on the shear bond strengths of bonding agents to dentin.

The effect of pulpal pressure on the shear bond strength of Scotchbond and Gluma was evaluated in the presence and absence of smear layers. There was no statistically significant difference in bond strength for either Scotchbond or Gluma on dentin with a smear layer in the presence or absence of 32 cm of hydrostatic pulpal pressure. When no pulpal pressure was present and the smear layer was removed, the bond strength of Scotchbond fell while that of Gluma nearly doubled. When 32 cm of pulp pressure was applied, the bond strength of Scotchbond/Silux fell 86% and that of Gluma fell 75% in 24 hours.

Dental Bonding↗
PubMed1992

Relationship between bond strength and microleakage measured in the same Class I restorations.

Microleakage measurements were made by use of a pressurized fluid method in Class I restorations prepared in extracted human teeth just prior to measuring the tensile bond strengths of the same restorations. The restorative materials included dentin bonding systems that are applied to smear layers as well as those which remove the smear layer. A light-cured glass-ionomer cement was also included. The results demonstrated that there was an inverse relationship between dentin bond strength and microleakage in some materials and that the bond strengths made to three-dimensional Class I cavities were much lower than those made to flat dentin surfaces. Measurement of microleakage by fluid filtration had no apparent effect on bond strength.

Adhesives↗