Extraction was performed on 52 periodontally involved teeth. Of these, ten without any instrumentation served as controls, 19 were treated with hand instruments, and 23 with ultrasonics. The extent of cleaning and damage to teeth with the two treatment procedures employed were assessed by examining in the scanning electron microscope. Ultrasonics were superior in the treatment of incisor teeth but had no particular advantage over the hand instruments with respect to the treatment of molars. Also the microflora forming the bacterial plaque were visualized.