Dental review; devoted to the advancement of dentistry. . dwill attain a better understanding of them from the micro-photo-graphic pictures presented. For these illustrations I am indebted toDr. F. B. Noyes, whose extensive work along these lines has wonfor him a most enviable position. You understand that by thecleavage of enamel is meant the characteristic of breaking up alongthe lines of the cement substance, parallel with the long axis of therods. The interprismatic substance being weaker than the rodsthemselves sustains the fracture. A cross section of the enamel *Read before the Minnesot
Dental review; devoted to the advancement of dentistry. . dwill attain a better understanding of them from the micro-photo-graphic pictures presented. For these illustrations I am indebted toDr. F. B. Noyes, whose extensive work along these lines has wonfor him a most enviable position. You understand that by thecleavage of enamel is meant the characteristic of breaking up alongthe lines of the cement substance, parallel with the long axis of therods. The interprismatic substance being weaker than the rodsthemselves sustains the fracture. A cross section of the enamel *Read before the Minnesota State Dental Society. 16 THE DENTAL REVIEW. (Fig. i) clearly shows the relative positions of rods and cementingsubstance. These are represented by the multi-lateral forms in situwith the cementing substance encasing them. These rods, sup-ported on their inner ends by the dentine, pass outward perpendic-ular to, or at acute angles to, the perpendicular to the surface ofthe tooth. (Fig. 2.) They vary slightly in diameter throughout their length, but are. practically the same at the dentinal ends as at the periphery. Theouter circumference of the enamel being greater than the innernecessitates a filling in at the surface with shorter conically shapedrods. A point of some clinical importance. The direction of the rods will be found to vary in the differentpartfl of tin- tooth. (Fig. 3.) In the middle third of the crown theirdirection is nearly perpendicular to the surface; but passing out- ORIGINAL COMMUNICA TIONS. 17 wardly they diverge in both directions from the middle of the is, in approaching the gingival the rods are directed apically(Fig. 4), and as they pass occlussally the angle of their directionwith the perpendicular becomes greater, until at the crest of thecusp they have assumed the direction of the long axis of the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectdentist, bookyear1901
