The Dental cosmos . specimen is perhapsas perfect enamel as the other, though that of Fig. 2 is the are taken from well-formed teeth, free from irregularities ofstructure and presenting smooth surfaces. THE MANAGEMENT OF ENAMEL MARGINS. 5 Fig. 3. Fig. 3 is from a cross-section of the enamel-rods. In this specimenthe cementing substance has been partially dissolved out from betweenthe rods by weak hydrochloric acid,.in order to display them to betteradvantage. It will be seen that the ends ofthe rods do not present true hexagons. Whilethe hexagon is regarded as the typical form,it
The Dental cosmos . specimen is perhapsas perfect enamel as the other, though that of Fig. 2 is the are taken from well-formed teeth, free from irregularities ofstructure and presenting smooth surfaces. THE MANAGEMENT OF ENAMEL MARGINS. 5 Fig. 3. Fig. 3 is from a cross-section of the enamel-rods. In this specimenthe cementing substance has been partially dissolved out from betweenthe rods by weak hydrochloric acid,.in order to display them to betteradvantage. It will be seen that the ends ofthe rods do not present true hexagons. Whilethe hexagon is regarded as the typical form,it is not strictly adhered to, but rather therods seem to take such form as will best fillout the space between them when irregularlycrowded together. Often we will find anumber lying in a straight row, or it may beseveral rows superimposed upon one another,and these are usually hexagonal. More gen-erally they are irregular, and the forms areirregular. Indeed, the perfect hexagon is theexception rather than the Cross-section of the enamel-rods. Fig. 4. Action of Acids upon the Enamel. I have said that in the specimen from which Fig. 3 was made theenamel-rods were rendered more apparent by the partial solution of thecementing substance by an acid. This is an important fact, as it denotesa difference in the composition of the cementing substance and therods themselves. This difference in solubilityis such that by working slowly and carefullywe may take the rods apart by dissolving outall of the cementing substance. Fig. 4 is anillustration from rods separated in this way,using for the purpose a moderately thin cross-section. The cross-markings are renderedmore apparent at first, but are likely to becomeindefinite if the action of the acid is too longcontinued, and the entire rods will be dis-solved if the action of the acid is not our illustration the ends of the rods arereduced in size, or rounded by partial solution. This difference in the solubility of the enam
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