In this study, contact angle measurements on enamel from four patients were carried out in vitro. The experiments were done with and without the acquired pellicle. The results show that if contact angle A, contact angle b, and contact angle C are the contact angles of enamel with pellicle, enamel 3-7 micrometers under the anatomical surface, and enamel 100-200 micrometers under the surface, then contact angle A greater than contact angle B greater than contact angle C, respectively. The biological variation in one patient is comparable to the biological spreading among patients; the biological variations are several times greater than are the experimental errors. Storage experiments indicate that enamel surfaces change strongly after extraction if stored in water; main changes occurred within one one wk.

Chemical Phenomena↗

PubMed1982

[In-vivo abrasion of composite fillings: a quantitative study].

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Acrylic Resins↗

PubMed1982

Fluoride deposited by topical applications with stannous fluoride in human enamel.

The aim of this study was to quantify the fluoridating effect of a 4% aqueous solution of SnF2 applied for 5 min. and 30 min. resp., and to measure the amounts of KOH soluble fluoride and acquired fluoride separately (APF gel data being included for comparison). Blocks of intact enamel were treated with the topical agents and subsequently exposed to 1 M KOH solutions for 24 h. No significant amount of fluoride was dissolved from control specimens by this treatment. Subsequently, the acquired F in the enamel was determined by the acid etch technique. The amount of fluoride in the KOH solutions after 5 and 30 min. SnF2 application are comparable : 6.2 and 7.4 micrograms . cm(-2) resp. A single topical treatment of SnF2 of 5 and 30 min. did not produce a significant enrichment of fluoride in the enamel. The considerable accumulation of fluoride reaction products on the outer enamel surface was only 1/3 of the amount deposited by APF gels.

Acidulated Phosphate Fluoride↗

PubMed1982

Determination and calibration of crystal lattice images of biological apatites.

Lattice imaging provides detailed information on the mineral phase of calcified tissues. The lattice space distances dhk1 depend directly on the accuracy of the magnification. Using synthetic apatite, K2PtCl6, graphitized C and crocidolite as calibration material the lattice parameters of human enamel have been determined. The relative errors in the mineral dhk1 values using crocidolite, K2PtCl6 and C are 0.6, 1.0 and 3.9 % resp. If hydroxyapatite is employed on the same grid as the enamel specimen, the d-values obtained are very close to the X-ray diffraction data; a reproducibility of 0.8% in a and c lattice parameter determination can be obtained on selected crystallites.

Crystallography↗

PubMed1982

Birefringence and mineral content of the first stage of artificial carious lesion formation (a combined polarizing microscopic, microradiographic and scanning electron microscopic investigation).

Artificial carious lesions were made using acetic buffer solutions of pH 6.0 containing calcium and phosphate. The solutions were highly undersaturated with respect to hydroxyapatite. Out of 72 lesions 51 showed subsurface demineralization, whereas in 21 only a superficial demineralization occurred. These superficial lesions were examined using polarized light microscopy, microradiography and scanning electron microscopy. This superficial breakdown of enamel material, considered as the initial demineralization of the enamel, appeared to occur at the prism junctions. This was indicated by the polarizing microscope technique and was made clearly visible using scanning electron microscopy. Quantitative polarizing microscopy and microradiography revealed results which correlated very well. From this it is probable that the initial superficial demineralization of the enamel is--under the described conditions--a simple dissolution reaction.

Birefringence↗

PubMed1982