A text-book of dental histology and embryology, including laboratory directions . nthat the general arrangement of enamel rods, in the archi-tecture of the tooth crown is such as to give the greateststrength to the perfect tissue, and to furnish the greatest resist-ance to abrasion in the use of the teeth for mastication. In abuccolingual section through a bicuspid (Fig. 29), beginningat the gingival line, the enamel is normally slightly overlappedby the cementum, and in the gingival third the rods areinclined more or less apically from the horizontal degree of inclination varies con
A text-book of dental histology and embryology, including laboratory directions . nthat the general arrangement of enamel rods, in the archi-tecture of the tooth crown is such as to give the greateststrength to the perfect tissue, and to furnish the greatest resist-ance to abrasion in the use of the teeth for mastication. In abuccolingual section through a bicuspid (Fig. 29), beginningat the gingival line, the enamel is normally slightly overlappedby the cementum, and in the gingival third the rods areinclined more or less apically from the horizontal degree of inclination varies considerably. It may beas much as 12 centigrades, but is usually not more than general, the more convex the surface the greater will THE GENERAL DIRECTION OF ENAMEL RODS 67 be the inclination. At some point between the junction ofthe gingival and middle thirds and the middle of the middlethird of the surface they are in the horizontal plane and atright angles to the axis of the tooth, and at this point theyare usually very nearly perpendicular to the surface. Passing Fig. 29. Diagram of enamel rod directions, from a photograph of a buccolingual section ofan upper bicuspid. occlusally from this point, they incline more and moreocclusally until in the occlusal third they reach an inclina-tion of 18 to 20 centigrades occlusally from the horizontal. The rods which form the tip of the buccal cusps do notreach the tip of the dentine cusp, but the buccal slope of 68 DIRECTION OF ENAMEL RODS IN TOOTH CROWN the dentine. This becomes important, as will be seen the tip of the dentine cusp the rods are in the axialplane, but in this position they are usually very muchtwisted. Passing down the lingual slope, they become moreand more inclined lingually from the mesiodistal axial plane, Fig. 30
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
