A text-book of dental histology and embryology, including laboratory directions . eeth of different animals, or in thehuman teeth at different ages. Direction of Tubules in Crown Portion. — In the crownportion and the gingival portion of the dentine the tubulespass from the pulp chamber to the dento-enamel junction,or the dentocemental junction, in sweeping curves, whichwere called by Tomes the primary curvatures. Thesehave been described as /- or ^-shaped (Fig. 133). Thetubule tends to enter the pulp chamber at right angles tothe surface, and to end at the dento-enamel junction at 1 Kolliker
A text-book of dental histology and embryology, including laboratory directions . eeth of different animals, or in thehuman teeth at different ages. Direction of Tubules in Crown Portion. — In the crownportion and the gingival portion of the dentine the tubulespass from the pulp chamber to the dento-enamel junction,or the dentocemental junction, in sweeping curves, whichwere called by Tomes the primary curvatures. Thesehave been described as /- or ^-shaped (Fig. 133). Thetubule tends to enter the pulp chamber at right angles tothe surface, and to end at the dento-enamel junction at 1 Kolliker gives 5 microns, also Schafer; Owen, microns. 172 THE DENTINE right angles to that surface. In the dentine forming theaxial walls of the pulp chamber the tubules make two bendsin passing from the pulp chamber to the surface of thedentine. In the first the convexity is directed apically, inthe second it is directed occlusally. The outer extremity ofthe tubule is, therefore, considerably farther to the occlusalthan the point at which it opens into the pulp chamber Fig. 133. A section showing the primary curvatures of the dentinal tubules in the crownportion. (About 20 X ) (Fig. 134). The outer part of this double curve is oftencomplex instead of simple (Fig. 135). The course of thedentinal tubules is not a direct one, but that of an openspiral. This may easily be demonstrated by changingthe focus up and down in examining sections cut at rightangles to the direction of the tubules. When examined inlongitudinal sections this spiral course gives to the tubule DIRECTION OF TUBULES IN CROWN PORTION 173 the appearance of having little wavy curves throughout itslength. These have often been called the secondary curva-tures. Each wave represents a turn in the spiral. As manyas two hundred have been counted in the length of a singletubule, or about one hundred in a millimeter of length. Fig. 134
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
