A text-book of dental histology and embryology, including laboratory directions . l it is alwaysnecessary that there be a break or opening in the a small portion can be split off at a time. The edgeof the chisel should be placed on the enamel a quarter orhalf a millimeter from the opening, rarely more, and sopiece after piece is split into the cavity. Fig. 34 shows asection of enamel. The edge of the chisel is placed at 1, withthe shaft in the relation to enamel rod direction indicated;a tap of a steel mallet will split off a piece, and the chisel ismoved back to position 2 and a s
A text-book of dental histology and embryology, including laboratory directions . l it is alwaysnecessary that there be a break or opening in the a small portion can be split off at a time. The edgeof the chisel should be placed on the enamel a quarter orhalf a millimeter from the opening, rarely more, and sopiece after piece is split into the cavity. Fig. 34 shows asection of enamel. The edge of the chisel is placed at 1, withthe shaft in the relation to enamel rod direction indicated;a tap of a steel mallet will split off a piece, and the chisel ismoved back to position 2 and a second piece is split enamel will split easily in this way. As soon asa point is reached where the enamel rests on sound dentine,it is recognized by the resistance. Straight enamel can besplit off from sound dentine without difficulty if attackedin the proper way, but if the inner portion is gnarled and 74 RELATION OF STRUCTURE TO CUTTING OF ENAMEL twisted, it can only be cleaved by removing the dentinefrom under it. Such enamel, if resting on dentine, will split. as far as the rods are straight; but where they begin to twistthey will break off, leaving a portion which is very difficultto remove by attacking it from the surface. If the dentine CLEAVING OR CHOPPING ENAMEL 75 is removed from under gnarled enamel, it will crack throughin an irregular way, following the general direction of therods. In preparing teeth for crowns it is often necessary toremove a large amount of enamel. This is always moreefficiently accomplished by the intelligent use of sharpinstruments than by force. The enamel on axial surfaces,especially in the gingival half of the crown, is usuallystraight, and if a cleavage line can once be established,the enamel can be more easily and rapidly removed bysplitting it off piece after piece than in any other doing this a straight or contra-angled chisel is often themost efficient instrument, and it must be remembered thatthe root trimmers are
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
