. Descriptive anatomy of the human teeth . ncave. The crown is also slightly bent in the mesio-distaidirection, so that the labial surface is convex and the lingualconcave in this direction. Therefore, there is a general con-vexity of the labial, and a general concavity of the lingual sur-face. 17. The labial surface of the crown of the upper centralincisor (Fig. i), in its general form, is an imperfect square,with its gingival side rounded. The mesial margin is a littlelonger than the distal, so that the cutting edge slopes awaytoward the disto-incisal angle (Fig. i, h). Both the angles,forme
. Descriptive anatomy of the human teeth . ncave. The crown is also slightly bent in the mesio-distaidirection, so that the labial surface is convex and the lingualconcave in this direction. Therefore, there is a general con-vexity of the labial, and a general concavity of the lingual sur-face. 17. The labial surface of the crown of the upper centralincisor (Fig. i), in its general form, is an imperfect square,with its gingival side rounded. The mesial margin is a littlelonger than the distal, so that the cutting edge slopes awaytoward the disto-incisal angle (Fig. i, h). Both the angles,formed by the proximate surfaces and cutting edge, are slightlyrounded, the disto-incisal more than the mesio-incisal, afterwhich the proximate surfaces converge toward the long axis ofthe tooth, making the crown a little narrower at the neck thanat the cutting edge. 18. The lingual surface of the crown (Fig. 2) is con-cave in all directions, forming a fossa, bounded by the cuttingedge (a), the mesial and distal marginal ridges (n, m), and the. Fie. 4. Fig. 5. Fig. I* (Par. 17).—Right Upper Central Incisor, Labial Surface, a, Cut-ting edge; b, mesial surface; c, distal surface; d, labial surface; e, e, labial grooves;g, mesio-incisal angle; /;, disto-incisal angle; i, body of root; k, apex of root. Fig. 2* (Par. 18).—Right Upper Central Incisor, Lingual Surface, a. Cut-ting edge; b, mesial surface; c, distal surface; d, linguo-gingival ridge, or cingu-lum; /, gingival line; g, mesio-incisal angle; /;, disto-incisal angle; i, body of root;k, apex of root; m, distal marginal ridge; n, mesial marginal ridge. Fig. 3* (Par. 18).—Left Upper Central Incisor, Lingual Surface, showinglingual pit. The cutting edge, a, is considerably worn. The mesial and distal mar-ginal ridges, b, c, are prominent; d, linguo-gingival ridge; f, gingival line; ff,mesio-incisal angle; /;, disto-incisal angle; j, body of root; k, apex of root; m,lingual pit. Fig. 4* (Par. 19).—Right Upper Central Incisor
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