Profile characteristics of cut tooth surfaces developed by rotating instruments.

THE irregularity of the cut tooth surfaces resulting from the shaping of cavities would appear to have a twofold significance. First, these irregularies should have some effect on the adaptation of the specified filling material to the cavity walls, and second, they may tend to undermine or weaken groups of enamel rods at the eavo-surface margins, thus resulting in a failure of the tooth structure surrounding the restoration rather than a failure of the restoration itself. In order to determine the significance that these irregularities may have in either case, it is desirable to know their magnitude as produced by various instruments. Appraisals of such surface roughness have been made previously by Street,6 and Peyton and Mortell.5 These methods of evaluation have been somewhat qualitative since they rely on observation at right angles to a cut surface which has been previously treated to make the crests of the irregularities more distinguishable. The eye is, however, more sensitive to the spacing of the irregularities rather than their height.2 Lammie4 used a stylus-type surface analyzer which gives an average height rating for a given surface. Such recordings do not provide a profile of widely spaced irregularities. Therefore, the Proficorder, an instrument of different design, has been employed in this study.