A text-book of dental histology and embryology, including laboratory directions . 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 CR
A text-book of dental histology and embryology, including laboratory directions . 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. A section showing the primary curvature of the dentinal tubules in the gingivalportion. (About 20 X) The dentinal tubules give off minute lateral branches,which extend from one tubule to another. These are veryminute, and in the crown portion of the dentine are not atall conspicuous, but in the region of the dento-enamel 174 THE DENTINE junction the tubules branch dichotomously, each fork havingabout the same diameter as the original tubule (Fig. 136.)These forkings of the tubules resemble the appearance ofthe delta of a river on the map. The branches anastomosewith each other very freely. This anastomosis of thetubules at the dento-enamel junction is very important indetermining the spreading of caries in this area. Itprobably also explains the sensitiveness of this area noticedin the preparation of cavities, which will be noted again inconsidering the sensitiveness of the dentine. Fig. 135 ^ ^ iB JMt t%. ^ jHr *^>V > | . --. • * ? ? AWl-U-M lllllllill • //? .
Size: 1298px × 1925px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
