W.: Form of Contact Surfaces and Their Relationship to Caries Susceptibility

It is apparent from the observations and statements of the majority of investi-gators that the typical tooth, upon eruption, is rounded or convex in form at the surface that makes proximal contact with adjoining or proximal teeth (1). It is assumed, therefore, that in newly erupted teeth the proximal surfaces have a marble like contact that is designated as the contact point. After eruption, wear starts immediately at the contact surface due to friction caused by the continued movement of the teeth in their sockets. Worn or flat planes are found. A microscopic study of the contact surfaces will demonstrate the concave surfaces and other varied forms caused by friction from the adjoin-ing tooth and thus will show that the contact surface of one tooth may be more resistant to wear than the contact surface of an adjoining tooth (figs. 1-4, p. 474). It is generally believed that caries usually starts below the contact point when no plane exists (2), but as soon as a plane or concave surface is formed frontal or undermining caries may be found on the altered surface. Beust concluded that interproximal caries (3) of enamel begins, in practically all cases, at the actua