A text-book of dental histology and embryology, including laboratory directions . Enamel ground at right angles to the rods. Not treated with acid. (About 500 X) by the acid, and the section should be mounted etched sideup. If etched upon both surfaces, the grooves in the lowersurface cannot be in focus at the same time as those of theupper surface and will blur the definition. The difference in the solubility of the rods and cementingsubstance is beautifully illustrated in the effect of caries4 50 THE STRUCTURAL ELEMENTS OF THE ENAMEL on the structure of the enamel (see illustrations in Chapt
A text-book of dental histology and embryology, including laboratory directions . Enamel ground at right angles to the rods. Not treated with acid. (About 500 X) by the acid, and the section should be mounted etched sideup. If etched upon both surfaces, the grooves in the lowersurface cannot be in focus at the same time as those of theupper surface and will blur the definition. The difference in the solubility of the rods and cementingsubstance is beautifully illustrated in the effect of caries4 50 THE STRUCTURAL ELEMENTS OF THE ENAMEL on the structure of the enamel (see illustrations in ChapterXII), and caries of the enamel cannot be understood unlessthese fundamental facts are remembered. The question, What causes the difference in solubility between the enamelrods and the cementing substance? cannot be satisfactorilyanswered .at the present time. While both the rods and the Fig. 16. The same section as Fig. 15 after treatment with acid. (About 500 X) cementing substance are normally composed entirely ofinorganic salts, there may be different salts in the two sub-stances, or the salts may be in different physical is great need for careful work in this field. Recentwork has strongly emphasized the distinctness of the twostructural elements of the enamel. DIFFERENCE IN REFRACTING INDEX 51 First, the study of the beginnings of caries of the enamel,and the effect of caries upon the structure of the enamel,brought out the difference in solubility in acids and showedthe extent of tissue injury before a cavity is formed. Later,the study of atrophy developed the fact that certain patho-logic or abnormal conditions may hinder or entirely pre-vent the formation of the rods while the cementing sub-stance is formed, and still more recently the investigation ofdystrophies of the enamel occurring in certain prescribedlocalities, showed perfect rod formation and
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
