. Comparative dental anatomy. Teeth; Dentistry. 72 COMPARATIVE DENTAL ANATOMY This triangular arrangement of the cusps forms the trigon of the upper molars. In the lower molar, the primitive cusp is called the protoconid and moves to the buccal side and becomes the mesio-buccal cusp. The paraconid becomes the mesio-lingual cusp and the metaconid becomes the disto-lingual cusp, thereby forming the trigonid of the lower molar. Thus the tri-. Fig. 20.—Diagram showing the occlusion of the talonid of the lower molar in the trigon of the upper. 1. Protoconid (Mesio-buccal cusp). a. Protocone (Lingua
. Comparative dental anatomy. Teeth; Dentistry. 72 COMPARATIVE DENTAL ANATOMY This triangular arrangement of the cusps forms the trigon of the upper molars. In the lower molar, the primitive cusp is called the protoconid and moves to the buccal side and becomes the mesio-buccal cusp. The paraconid becomes the mesio-lingual cusp and the metaconid becomes the disto-lingual cusp, thereby forming the trigonid of the lower molar. Thus the tri-. Fig. 20.—Diagram showing the occlusion of the talonid of the lower molar in the trigon of the upper. 1. Protoconid (Mesio-buccal cusp). a. Protocone (Lingual cusp). 2. Paraconid (Mesio-lingual cusp). b. Paracone (Mesio-buccal cusp). 3. Metaconid (Disto-lingual cusp). c. Metacone (Disto-buccal cusp). 4. Hypoconid (Disto-buccal cusp). angles of the upper and lower molars alternate (Fig. 19),—the apex of the upper one being di- rected lingually and the lower one buccally,—so they pass in a shear-like motion. The next step is the addition to the trigonid (of the lower molar), on the disto-buccal surface, of a heel or talonid, which may support one, two or three cusps. The buccal is called the hypoconid, the disto-buccal the hypoconulid, and the disto-lingual. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thompson, Alton Howard, 1849-1914; Dewey, Martin, 1881-. St. Louis, C. V. Mosby
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