A text-book of dental histology and embryology, including laboratory directions . al papillae becomes, the more imperfect dentine itforms, until finally it simply throws down granular calcifiedmaterial. The formation of dentine begins at the dento-enameljunction, at a number of points in each tooth, and progressesfrom without inward (strange to say, exactly the oppositestatement has been made several times in papers by veryprominent men). This matter will be taken up more indetail in Chapters on Dental Embryology and is enough to say here that in studying all sections ofdentine, w
A text-book of dental histology and embryology, including laboratory directions . al papillae becomes, the more imperfect dentine itforms, until finally it simply throws down granular calcifiedmaterial. The formation of dentine begins at the dento-enameljunction, at a number of points in each tooth, and progressesfrom without inward (strange to say, exactly the oppositestatement has been made several times in papers by veryprominent men). This matter will be taken up more indetail in Chapters on Dental Embryology and is enough to say here that in studying all sections ofdentine, whether cut longitudinally or transversely, theformation of dentine began at the dento-enamel junctionand the dentocemental junction, and progressed towardthe pulp chamber. SECONDARY DENTINE 185 From the study of longitudinal and transverse sectionsit is apparent that a certain typical amount of dentine isformed before the tooth is erupted and while it is cominginto full occlusion. This is primary dentine. In it thetubules are very regular in size and arrangement. From Fig. 144. Secondary dentine: A, margin of primary dentine, showing a few of the tubulescontinuing into secondary dentine; P, pulp chamber. (About 80X) this time on the formation of dentine is intermittent, andapparently is the response to some outside condition. Theseconditions may arise in the tooth in which the formationoccurs, or the irritation of one tooth may cause tissue forma-tion in all or part of the others. It has not been determined 186 THE DENTINE whether such reflex trophic stimuli are confined to the samelateral half or the same nerve distribution. Apparently theformation of dentine proceeds again, after a pause, in allteeth. It will seem, therefore, that the mere exposure ofthe entire crown to conditions of thermo-change producessufficient stimulus to the pulp tissue to cause a renewal ofdentine formation. After the first period of rest the dentine Fig. 145
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
