Section 882.4310 - Powered simple cranial drills, burrs, trephines, and their accessories(a)Identification. Powered simple cranial drills, burrs, trephines, and their accessories are bone cutting and drilling instruments used on a patient's skull. The instruments are used with a power source but do not have a clutch mechanism to disengage the tip after penetrating the skull.(b)Classification. Class II (performance standards).