To prevent contact by a barrier even in the case that the bar blade part for cutting teeth of a dental hand piece head and an oral mucous membrane get closer to each other and to prevent a medical accident.

An adhesion part 1 to be adhered and fixed to the dental hand piece head 4 is provided and this barrier composed of a barrier plate part 2 extended and spread from the adhesion part 1 into the direction of a bar 5 for cutting the teeth mounted to the head 4 capable of separating the half side part of the outer periphery of the blade part 6 of the bar 5 from the outer side direction is stuck to the hand piece head 4. The barrier is partially or entirely provided with elasticity.