Abstract
As part of the experiments on enamel destruction planned by our study group, microscopical observation was made on the changes of the destructive process in enamel by EDTA in the acidic range, employing the sandwich method devised by Ishii and Yoshida, as outlined below. Sections approximately 30μ thick of undecalcified teeth were cemented between the slide and cover glass using polyvinylmethylether as the adhesive, with exposure of the surface area of enamel alone. The decalcifying solution was then allowed to act on the enamel surface to study the main changes continuously under the microscope. As the decalcifying solution, 0.01 M EDTA 2 Na solution (pH 4.8) was used with a flow rate of about 1 mm/5 min. The process of change occurred was studied under the phase contrast microscope and recorded by 16 m/m automatic microspeed photographic apparatus. In order to compare the pattern of destruction in the inner enamel layer with that in decalcification with organic acid, 0.1 N acetic acid buffer solution, pH 5.0 was used for decalcification by the same method described above.
In both experiments, microradiograms of decalcified specimens were obtained by the contact method.
The following results were obtained.
1) As to the attack entry on the enamel surface, micro-channels of 1-2 pm in diameter, ends of striae of Retzius and some small defects can be cited. These are identical with those already reported in the study on acid decalcification.
2) The spread of destruction was considerably more rapid than that in acid decalcification.
3) The degree of destruction was also much more pronounced than in acid decalcification. Due to this reaction, the prismless layer and striae of Retzius have almost no influence the pattern of destruction. Considerable injury appears to be inflicted on the mechanism of recalcification of enamel.
