Back suction prevention type dental drill handset

The back suction preventing hand dental drill consists of outer casing, back bearing, turbine rotor, front bearing, bit and front casing. High pressure air may be introduced via the high pressure air outlet in the handle, the air inlet in the outer casing and the ring space between the bearing and the outer casing to the air turbine to rotate the bit. The air after passing through the air turbine is made to flow back through the ring space between the back bearing and the outer casing, the air outlet and the air returning channel inside the handle. The present invention can prevent the back suction of liquid and air in the tip of the bit, raise the aerodynamic efficiency and shaft output power and lower noise.