Recently a new ultrasonic system was introduced using a different type of energy transmission in order to offer a less abrasive and less painful therapy. The aim of the present study was to investigate the effects of this system in combination with the straight metal probe compared to conventional ultrasonic and hand instrumentation. 50 extracted decapitated teeth were randomly assigned to 5 groups (n=10). Group 1 was treated with a Gracey curette No. 5 for 3 minutes, group 2 and 3 with the Siroson® S ultrasonic tip for 3 minutes/6 minutes, group 4 and 5 with the Vector®-system for 3 minutes/6 minutes. The Vector®-system was used in accordance with the manufacturer's manual. The samples were fixed in an artificial periodontal socket to simulate a periodontal lesion. Before and after treatment the root surfaces were documented by micrographs. For histological examination the undecalcified samples were cut lengthwise into sections of 20-30 µm thickness. In addition, the treated surface was investigated with SEM using a replica technique. The effects on the root surface were documented by scoring the presence of debris. Descriptive analysis was proved by the Kruskal-Wallis test and Wilcoxon signed rank test. Micrographic analysis showed a most complete calculus removal after hand instrumentation. The conventional ultrasonic system was more effective than the Vector® treatment. SEM evaluation of the hand instrumentation presented a characteristic surface. The conventional ultrasonic system left an irregular surface with smooth areas as well as small defects. The Vector®-system revealed a similar texture as the conventional system. The results were supported by the histological examination. In conclusion the treatment of the root surface with the new ultrasonic device in combination with the straight metal probe resulted in a less effective removal of calculus and more tooth substance preserving procedure. Schlagwörter: ultrasonic instruments, curettes, debridement, root planing, SEM