By a roentgen-ray densitometric method, it was found that (a) certain areas of dentin, between carious cavity and pulp chamber, gave increases in roentgen-ray absorption of 10 to 25 percent compared with normal dentin; (b) transparent and opaque specimens of dentin absorbed the same amount of roentgen-radiation, which is from 2 to 3 percent higher than that by unmodified dentin; (c) certain areas of dentin affected by caries gave increases in roentgen-ray absorption of 5 to 40 percent, when compared with normal dentin of the same tooth-section—but marked increases in roentgen-ray absorption (10 to 40 percent), by dentin affected by caries, are exceptions; (d) roentgen-ray absorption, per unit of thickness of dentin (160 specimens), was 0.94 mm. Al for dentin from 89 sound teeth, and 0.94 mm. Al for dentin from 71 carious teeth.
References: Den. Cosmos, 1933, 1935, 1936; Amer. J. Roentg. Rad. Therap., 1934; J. Am. Den. Assoc., 1935.
VAN KIRK, LAWRENCE E.: Dental School, University of Pittsburgh, Pittsburgh, Pa. (May 24, 1939).
In a study of ground sections of 1000 human teeth, the author found peculiar, apparently defective, areas of enamel in practically every section. ” Granular rods ” occurred near the dento-enamel junction where enamel calcification was begun. Beust believed they were cross-sections of tracts that connected enamel with vital elements of dentin. Their universal occurrence cannot be overlooked in a study of histologic structures that might be related to extension of caries at the dento-enamel junction.
References: J. Am. Den. Assoc., 1928, 1929.