New "maintenance free" replacement turbines or bearings eliminate lubrication by clinicians, which minimizes release of unwanted excess lubricant inside & outside the oral cavity. Objective: This study evaluates in-vitro performance of the new handpiece (HP) parts vs. conventional, factory-installed parts. Methods: 430SWL (Star) & XGT (Midwest) HP's were tested with (A) unused, factory-installed turbines & bearings; (B) "maintenance free" turbines; & (C) "maintenance free" bearings installed on conventional turbines. HP's were assigned by serial number to either steam (StatIM) or chemical vapor (Harvey Chemiclave 5500) sterilizers. A total of 12 HP's were tested until failure, using the following steps, which together comprised one cycle: (1) cut bovine tooth w/ coarse diamond for 60 seconds, (2) disinfect & clean HP exterior, (3) lubricate & purge (A only), (4) bag & sterilize. HP failure was defined as: (1) inability to rotate bur, (2) stalls easily, (3) inability to retain or release bur, or (4) separation at solder joint. Failure data were analyzed using GLM & Hochberg's multiple comparison procedure (alpha=0.05). Results: Below are average cycles to failure of HP's. Bars show statistical differences. The (**) below denotes 1 HP in the set is still functioning. This fact was taken into account in statistical model.

The data show no statistical differences in durability of the "maintenance free" turbines & bearings & factory-delivered turbines for the 430SWL HP's in the 2 types of sterilizers. XGT HP's, with factory delivered turbines & bearings, performed statistically better than the "maintenance free" parts in both types of sterilizers. Conclusion: Durability of the "maintenance free" turbines & bearings was HP dependent.

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