Torque, power and efficiency characterization of dental air turbine handpieces

Objectives: In a previous paper the flow and free running speed characteristics of dental air turbine handpieces were discussed. The present work was to continue the analysis and characterization of these handpieces by addressing the issues of torque, power generation, efficiency and the specification of figures of merit to aid comparative testing and selection. Methods: Using the principle of the rope brake, torque was determined from stall to free running at a variety of supply pressures for fourteen models of handpiece. Using previous results for air flow rate and free running speed, power and efficiency were calculated. Results: Stall torque was demonstrated to depend on rotor position. Dynamic torque was found to closely approach the expected linear relationship over the range from stall to free running. Several figures of merit (performance indices) were identified which might be used for routine rating and specification of handpieces. Conclusions: Standardized testing can now be performed and effective figures of merit derived to characterize the behaviour of dental air turbine handpieces.