Principles and practice of operative dentistry . Section of root, parallel to dentinal canals. (After Stowell.) It is further observed that Hke the canaHculi of bone the dentinal tubuligive off numerous branches in their course which unite with neighboringtubuli and with each other (Fig. 157). As the tubuli approach the surfacethe division is more rapid, and the size of the branches is cor- ^ ^^^ -^^^• respondingly decreased. At theexternal surface of the dentinmany of the tubules unite byanastomosis (Fig. 158), othersterminate in the granular layerof Purkinje and Tomes, whilea third set penet
Principles and practice of operative dentistry . Section of root, parallel to dentinal canals. (After Stowell.) It is further observed that Hke the canaHculi of bone the dentinal tubuligive off numerous branches in their course which unite with neighboringtubuli and with each other (Fig. 157). As the tubuli approach the surfacethe division is more rapid, and the size of the branches is cor- ^ ^^^ -^^^• respondingly decreased. At theexternal surface of the dentinmany of the tubules unite byanastomosis (Fig. 158), othersterminate in the granular layerof Purkinje and Tomes, whilea third set penetrates the ce-mentum and may unite with itslacunae through their canaliculi; or enter the enamel by means of theopen spaces, or interstices between the enamel-rods, already referred to asexisting in that portion of the enamel next to the dentin (Fig. 159). Thissystem of canals terminates, or rather has its beginning, in free openingsupon the internal surface of the 1, tubuli of dentin ; 2, enamel. 48 OPERATIVE DENTISTRY. Fig. 160, whicli is highly magnified, shows the dentinal fibrillee crossingfrom the dentin to the enamel and apparently passing between the enamelrods. The Dentinal Sheaths.—The dentinal sheaths, or walls of the tubuli,as they are termed, are composed of a singularly indestructible substance,which is peculiarly resistant to the action of acids, boiling in caustic alka-lies, or to putrefaction ; caries does not destroy them, and they can also bedemonstrated in fossil teeth; this substance is in all probability calco-globulin. [Neumann and Henle are of the opinion that the dentinal sheaths arecalcified. The existence of the dentinal sheaths can be demonstrated bydecalifying the dentin with strong acids. This process requires severaldays for its accomjilishment. The residue is found to be composed of atangled mass of a fibrous-appearing material (Fig. 161) which upon care-ful examination is found to be composed of the dentinal sh
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectdentist, bookyear1920
