A Quantitative Roentgeno-Densitometric Study of the Changes in Teeth Due to Attrition

Probably the first observations of change in dentine exposed by attrition of the occlusal surfaces of teeth were limited to its polished and often stained appearance. The exposed dentine not only was free from dental caries but actually seemed harder, clinically, to the point of the explorer than ordinary dentine, a fact which has been variously attributed (a) to a packing effect by the forces of mastication, (b) to a chemical change due to the action of the saliva or (c) to a physiological building up of a defense by the tooth. When a labio-lingual section is cut through the center of an abraded tooth, reflected light usually shows a symmetrical, white cone (1) with its base at the occlusal surface and its apex toward the pulp chamber. This cone-shaped changed area is opaque to transmitted light and has been called opaque sclerosed dentine (1). Between the apex of this cone and the existing pulp chamber, another cone is frequently discovered with its apex at the apex of the "attrition" cone and its base at the surface of the pulp chamber. This latter cone of secondary dentine which appears dark by reflected light but transparent by transmitted light is called "transparent" dentine. By the proper staining technic (1), (2) these cones may be demonstrated to be impermeable to stain whereas the remaining dentine, if free from other change (such as accompanies caries, age, etc.), may be heavily