Multiple use of dental drills is known to raise drilling temperatures. Therefore, to minimize surgical trauma, well sharpened drills are recommended. In order to evaluate surgical trauma due to multiple use, 20 Timedur cannon drills (ZL-Duraplant-Implant-System) were used 51 times in an in vitro experimental setting using pigs' mandibles. Preparations of implant sites were performed with cannon drills at a maximum rotational speed of 1200 r.p.m. with low pressure and water irrigation. Drills were divided randomly into 3 groups and were treated differently after each preparation: 10 cannon drills were cleaned only with distilled water (group 1), 5 cannon drills were disinfected with Secudrill and autoclaved (group 2) and 5 cannon drills were cleaned with Instrument Detergent MIS 027 and autoclaved (group 3). Temperature measurements were performed with a NiCrNi thermocouple placed 0.5 mm from the drilling site. The width of the cutting edge of the cannon drills was repeatedly examined by scanning electron microscope (SEM). Results revealed that temperatures measured at all times were below the bone injuring level. Drills reused more than 40 times stood out with an increased number of higher temperatures. Only autoclaved drills showed an increased width of the cutting edges. From the present investigation it can be concluded that cannon drills of the ZL-Duraplant System should not be re-used more than 40 times.