An analysis on the inserts for piezoelectric bone surgery: the effect of cutting and sterilization processes

Piezoelectric bone surgery, also known as piezosurgery, is a technique which has been developed to overcome problems related to conventional surgery through rotating tools such as reamers and drills. Piezosurgery provides a cutting capability of mineralized tissues, however preventing soft tissue damage. Furthermore, it seems that piezosurgery also favors wound healing. Such technique is based on cutting tools (i.e., inserts) vibrating at ultrasonic frequencies. The tip of these inserts is generally covered by a diamond or titanium nitride deposition to enhance the tip hardness, thus improving cutting capability and avoiding instability due to wear. It is well known that efficiency of conventional rotating reamers and drills for bone surgery depends on wear. Anyway, little is known about the coating stability of piezoelectric inserts. Accordingly, the aim of the current work was to analyze the effect of cutting and sterilization processes on the properties of inserts for piezoelectric bone surgery. In particular, the degradation of titanium nitride coating as consequence of a repetitive and controlled 5-cycle cutting/sterilization was studied. SEM and AFM were used to analyze the morphology of the worn coating, while EDS analysis was performed to assess the chemical composition and the element distribution. Results suggested that the stability of titanium nitride coating depends on the quality of the insert. Basically, a poor quality coating negatively affects the cutting process also producing a marked wear of titanium nitride deposition. Bulk alloy was exposed, mainly consisting of iron, as well as alloying elements and impurities (i.e., manganese and sulfur) which may be dangerous for the health of the patient.