Influence of Thread Design for Primary Stability

Immediate loading has become one of the most interesting topics in clinical research, since it can result in increased patient acceptance and reduce treatment time and management problems. Favourable results with different clinical procedures are shown in case presentations. All authors claim to gain a maximum of primary stability with the surgical and prosthetic procedures applied.The aim of this in vitro study was to evaluate the precision of osteotomies by using the same drills in various bone qualities and at different speeds. In addition, the insertion torque as a factor for primary stability was determined by various thread designs. Self tapping threads require sufficient space for the prepared bone. Consequently, the thread design determines the size of the final osteotomy. The precision of the implant sites varies according to bone quality and the drilling speed. While better results are achieved by preparing bone of density type I with 800 rpm, the best results were obtained by preparing bone of density type IV with a higher speed of 1500 rpm. In cortical bone type I, highest primary stability was achieved with a precut thread and a low thread height of 0.1 or 0.2 mm. In bone of type III or I, 0.3 mm to 0.5 mm self-tapping threads provided the best results. Due to the difficult evaluation of the exact bone quality between type II and type III, a combination of the two thread heights seems to be optimal to ensure sufficient primary stability. Keywords: immediate loading, implant design, thread design, insertion torque, self-tapping implant design, bone quality, primary stability