Evaluation of temperature changes of zirconia frameworks while grinding with different techniques

Full ceramic materials have been an alternative to metal-ceramic restorations with their chemical stability, biocompatibility and aesthetic properties close to the natural tooth structure. Zirconia has increased the reliability of all ceramic systems with properties as; high mechanical performance, durability, tensile strength, chemical and dimensional stability. The mechanical properties of zirconia can be changed by these routine laboratory and clinical procedures as a result. Grinding procedure may cause heating and stress on the surface of the material resulting phase transformation of zirconia. In our study; temperature changes of zirconia frameworks while grinding with different techniques are evaluated. Sixty zirconia framework samples were fabricated and divided as each group has ten specimens. Two different grinding technique (high speed hand piece, micromotor) selected and divided in six groups ( fine grained diamond bur with and without water cooling, coarse grained diamond bur with and withoud water cooling, micromotor with and without water cooling). A mechanism is prepared for standardization and fixation of bur-material relation while grinding. High speed hand piece, micromotor and the material are fixed on mechanism and only back and forth movement was allowed for grinding. Each zirconia framework has grounded until 1mm3 material disappeard. Data tables and graphics are obtained and statistically analyzed. Mean maximum temperature values of two grinding techniques are compared. Mean maximum temperature of grinding with micromotor under water cooling (23,55±1,80c) was higher than grindings with high speed hand piece under water cooling (22,65±0,76c and 22,59±0,61c)