DRILL FREE SCREWS - A NEW FORM OF OSTEOSYNTHESIS SCREW

Although the application of self-tapping and non self-tapping screws i s virtually universal in cranio-maxillofacial surgery, the inevitable, time consuming procedure of drilling a pilot hole has some potential disadvantages, such as damage to nerves, tooth roots or tooth germs, t hermal necrosis of the bone and drill bit breakage. Drill Free Screws (DFS) are a recently developed type of osteosynthesis screws, having a tip like a cork screw and specially formed cutting flutes which enabl e insertion of the screws without drilling. DFS 1.5 and 2 mm were inse rted into discs of wood, polyvinylchloride (PVC) and porcine mandibula r bone of varying thicknesses between 2 and 4 mm. The values of insert ion torque and maximum torque were recorded using an electric torque t ester. Thereafter, the screws were inserted with a fixed torque and un iaxial pull out tests were performed. In comparison with this, the sam e procedure was performed using 1.5 and 2 mm self-tapping titanium scr ews. Ten trials for each screw-material-combination were conducted to determine insertion torque, maximum torque and pull out analysis. The results showed that the holding power of DFS lay between 70 and 104% o f the holding power of self-tapping titanium screws; only in PVC was t he difference more than 15%.