Abstract: A gas turbine operated handpiece instrument having a spin able front shaft mounted bur that is operated by pressurized gas or air. Two embodiments are disclosed. In one a flexible rubber like PVC one-way pinch valve is mounted on an exterior gas exhaust stack of the instrument's body housing. This embodiment allows for the internal lubrication of the turbine parts by compressing the valve sides towards each other and then spraying a lubricate into the housing through the opened valve. In another embodiment, a metallic one-way ball valve is mounted within an extension to the housing and this design is more suitable for dental bur offset instruments. In both designs, the turbine has impellers located within the hollow body of the instrument. The purpose of the one-way valves in both embodiments is to prevent contaminates from being sucked back into the housing as the gas turbine is being shut down during its complete operating range.