HANDPIECE DEGRADATION ASSOCIATED WITH PERFORMANCE TESTING OF DIAMOND ROTARY CUTTING INSTRUMENTS

Reliable standardized testing of dental rotary cutting instruments rem ains a problem because of the many significant parameters that require identifying and quantifying. In a previous study, handpiece wear or d egradation was identified as a potentially significant confounding var iable leading to the suggestion that the use of industrial hand-pieces might be necessary. Therefore, the objective of this investigation wa s to measure and compare industrial and dental air rotor degradation d uring a simulated diamond rotary cutting instrument test. Two dental a nd two industrial products were tested in a random sequence using thre e replicate samples of each air rotor. The simulated test consisted of 10 diamond instruments each making 90 passes through a float glass su bstrate. The testing apparatus comprised a computer-interfaced device that controlled the contact force between the cutting diamond and the substrate. Air rotor performance was based on the time required to cut a standardized path through the substrate. The performance change tha t occurred from diamond instrument to instrument during the simulated test was attributed to air rotor degradation. Multiple regression anal yses showed significant differences between replicate samples of the s ame type and between regression intercepts for different air rotor typ es. Surprisingly, four air rotors exhibited improving performance duri ng the simulated test. Changing air rotor performance must be consider ed to achieve reliability for the testing of diamond rotary cutting in struments.