All NCCLs were characterized preoperatively relative to height of the lesion, width, depth, percent of margin in enamel, internal angle of the lesion, and degree of sclerosis as measured by the UNC Sclerosis Scale (Appendix 1). The shape of the lesions was documented as "saucer-shaped" or "notch-shaped." Evidence of stressful occlusion (wear facets, fremitus) also was noted. These clinical co-variables can retrospectively be analyzed if any retention failures occur to assess potential cause and effect relationships.