The Dental cosmos . on of enamel margins it is neces-sary that this fact be carefully considered in each case, and the decay THE MANAGEMENT OF ENAMEL MARGINS. 9 followed out until the enamel margin is found to rest on solid points relative to the caries to which the enamel should be cut inorder to do this are shown by the lines i, z, Fig. 7. Any less cutting-would leave the dentinal ends of the enamel-rods without in a given case it may be well to remove the carious por-tions and fill in the undercut, depending upon the strength of someportion of unsupported enamel,
The Dental cosmos . on of enamel margins it is neces-sary that this fact be carefully considered in each case, and the decay THE MANAGEMENT OF ENAMEL MARGINS. 9 followed out until the enamel margin is found to rest on solid points relative to the caries to which the enamel should be cut inorder to do this are shown by the lines i, z, Fig. 7. Any less cutting-would leave the dentinal ends of the enamel-rods without in a given case it may be well to remove the carious por-tions and fill in the undercut, depending upon the strength of someportion of unsupported enamel, must be determined by the circum-stances and special necessities. In certain cases the risks of breakagemay not outweigh other considerations ; but the enamel margin willnot have the same strength that it would have if it rested on the den-tine. Cleavage of the Enamel. The enamel has definite lines upon which it breaks, or splits, easierthan in other directions. These are called its lines of cleavage. These Fig. Broken section of enamel, showing the lines of cleavage to be parallel with the enamel-rods. lines are determined by its structure, and depend upon the fact thatthe enamel-rods separate from one another easier than they occurs, seemingly, because the cementing substance is weakerthan the rods. The cleavage of the enamel is therefore in the direc-tion of the length of the enamel-rods. Fig. 8 is an illustration of this,drawn from a fragment fortunately obtained by shattering a sectioncut parallel with the rods by a blow from a blunt instrument. Inorder to present the fragment entire it has been drawn with a low U) THE DENTAL COSMOS. power of the microscope, with which the rods appear as fine examination of the illustration will show how strong the tendencyis for the lines of fracture to follow the enamel-rods. In this littlefragment there are six lines of fracture running close together for aconsiderable distance, relatively to the size of the ena
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Keywords: ., bookauthor, bookcentury1800, bookdecade1890, booksubjectdentistry
