A text-book of dental histology and embryology, including laboratory directions . The relation of the edge of a sharp and a dull chisel. 7S RELA TION OF STRUCTURE TO CUTTING OF ENAMEL placed on the surface of the enamel it will rest across theends of many rods, and force applied will only crumble them,but will not split the tissue. The edge must be keen (), so as to engage between the rods and so startthe cleavage. Cutting instruments as furnished by dentalsupply houses are not tempered hard enough to hold anedge. There is no fault to be found with the supply housesfor this, for they mak
A text-book of dental histology and embryology, including laboratory directions . The relation of the edge of a sharp and a dull chisel. 7S RELA TION OF STRUCTURE TO CUTTING OF ENAMEL placed on the surface of the enamel it will rest across theends of many rods, and force applied will only crumble them,but will not split the tissue. The edge must be keen (), so as to engage between the rods and so startthe cleavage. Cutting instruments as furnished by dentalsupply houses are not tempered hard enough to hold anedge. There is no fault to be found with the supply housesfor this, for they make them as the dentist wants them, andany dealer will furnish hard-tempered instruments if theyare ordered. To use hand instruments successfully in cuttingenamel, the stock instruments must either be retempered orthey must be ordered hard tempered. The cutting edge of Fig. 40 Fig. 41 Fig. 42. The use of the chisel in cleaving enamel. Opening an occlusal cavity. (Black.) the blade of an enamel instrument should be straw-coloredwhen tempered. The chisel and hatchets are the instrumentsfor removing enamel. The burr is the instrument forremoving hard dentine. When the burr is used on enamelit should be remembered that it is used as a revolvingchisel. It is by the thoughtful use of hand instrumentsthat knowledge of enamel rod direction is gained, andonly by the use of them can the enamel walls be pre-pared in terms of their structural elements. In cleavingundermined enamel the edge may be used either with apulling or a pushing motion. For instance, in opening upa cavity in the occlusal surface of a bicuspid, the buccal SHARP INSTRUMENTS 79 portion of undermined enamel is split off by placing theinstrument as shown in Figs. 40 and 41. The bevel of the bladeis held toward the cavity and the shaft of the instrument ata slight angle to the rod direction, and the force is appliedin
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
