Comparison of zirconia ceramic and stainless steel tools in dental implantology

Abstract

The aim is to study the influence of the cutting conditions in the lives of drills used in dental implantology, when bovine tibia is used as work material. The input variables were the cutting tool materials (tetragonal zirconia polycristals ceramic and martensitic stainless steel) both uncoated, the feed velocity (24 and 45 mm/min) and the spindle speed (1,000 and 2,500 rpm). The output variables monitored were the tool life, the temperature next to the hole wall and the thrust force. The tests were carried out in a CNC Machine Center (15 kW of power) varying the cutting parameters following a 23 factorial design. The tool lives were expressed by the number of drilled holes, considering the temperature close to the hole wall of 47 °C as the end of tool life criterion. The temperatures were monitored using three type T thermocouples inserted into the workpiece samples and positioned along the depth of the holes. The thrust force was measured with a Kistler rotating dynamometer. A mixture of 20 % of ethylene glycol and water was applied as coolant (irrigation) with a flow rate of 160 ml/min, simulating a saline solution. The results showed that the martensitic stainless steel outperformed the ceramic drills. The lowest temperatures and a conformity state at the clinic standard for thrust force values were obtained with the highest cutting parameters (45 mm/min and 2,500 rpm). It was observed that the higher feed velocity provided mainly a drop in temperature, while the higher spindle speed decreased the thrust force.