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Results for “Tooth Permeability”

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At least 19 recordsLinked to original sources
PubMed1982

Effect of initial demineralization on the permeability of human tooth enamel to iodide.

Blocks of intact human enamel were exposed for four successive periods of 5 min to 2 ml of 10(-2) M K-acetate at pH 4.0, 4.5 and 5.0. The permeability to iodide (Ip) and the amount of Ca dissolved were determined after each exposure. The Ip values varied considerably, but for each block there was a consistent increase in Ip with increase in acid exposures, and the Ca-Ip relationship was linear at all pH levels. The slope and intercept of the regression lines varied widely, but the correlation coefficients showed close fit of the data. The mean Ip values after the same period of exposure at pH 4.0 and 4.5 were statistically different from those obtained at pH 5.0, but the differences between the pH 4.0 and 4.5 values were not. This discrepancy is attributed to dissolution of surface enamel by the pH 4.0 buffer. Because loss of surface enamel is minimized by partial saturation of the buffer with Ca and phosphate, and oral fluids contain high concentrations of these ionic species, the iodide method should give valid measurements of the demineralization produced intarorally by acid and cariogenic foods.

Acetates↗
PubMed1992

Some notes on the diffusion of acidic and alkaline agents into natural human caries lesions in vitro.

The aim was to obtain information on the penetration of ions, in particular H+ and OH-, into a wide variety of natural caries lesions in human teeth. Thirty-seven permanent teeth were slit in half and soaked in a 1% neutral (blue) litmus solution for at least a week. The cut face of the tooth was painted with a transparent, colourless nail varnish before the tooth was immersed in either of 0.1 M hydrochloric acid or 0.1 M phosphoric acid. In a reverse experiment the samples were soaked in acid (red) litmus solution and then immersed in 0.1 M sodium hydroxide after varnishing the cut face. All solutions were saturated with enamel apatite to avoid the possibility that the solutions might etch their way into the enamel. The colour change was recorded photographically. Several days of external acid/alkali exposure were required to change the litmus colour in the body of most of the lesions, suggesting that diffusion of acidic and alkaline species through the natural surface into the body was slow. The presence of a well-mineralized surface layer covering the lesion postponed the colour change. In contrast, the colour change of two root surface lesions was rapid, occurring within an hour. Thus, because the lesion body is relatively isolated and because lesion fluid is in intimate contact with the enamel apatite, we conclude that lesion fluid is close to saturation with respect to this mineral. Further, a pH change of lesion fluid in vivo paralleling that in plaque after a sucrose intake is unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Caries↗
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

Effect of cervical coating of ethyl cellulose polymer and metacrylic acid copolymer on the radicular penetration of hydrogen peroxide during bleaching.

Extraradicular leakage of oxidizing agents during bleaching is an undesirable event and thus need to be prevented. The effect of external cervical coating of ethyl cellulose (EC) and metacrylic acid copolymer (MAC) on the radicular penetration of hydrogen peroxide during intracoronal bleaching was examined. Single rooted human premolars extracted for orthodontic reasons were used. The cementum covering the cemento-enamel junction was mechanically removed and the teeth treated endodontically and bleached with 30% hydrogen peroxide. Radicular hydrogen peroxide penetration was measured before coating the teeth and after applications of 1-3 layers of EC or 3 layers of MAC external cervical coatings. It was found that the radicular penetration of 30% hydrogen peroxide was related to the number of layers of cervical EC coatings. Application of one layer of EC did not reduce the hydrogen peroxide penetration. Two and three layers of EC reduced the hydrogen peroxide penetration by 38% and 85% respectively. Three layers of MAC reduced the radicular hydrogen peroxide penetration in 83%. Statistically, a highly significant difference was found between the teeth coated with three layers of either EC or MAC and the noncoated teeth (p < 0.001). It was concluded that application of ethyl cellulose or metacrylic acid copolymer to exposed cervical root surfaces may effectively prevent extraradicular leakage of bleaching agents.

Cellulose↗