Which of the following is considered a non-critical instrument?

The X-ray unit position indicator device is classified as a non-critical instrument because it does not come into direct contact with mucous membranes or breaches the body's protective barriers. Non-critical instruments are those that typically only come in contact with intact skin. The position indicator device is used to direct the X-ray beam but does not touch the patient's tissues, which means it requires less stringent infection control procedures compared to semi-critical or critical instruments.

In contrast, instruments such as scalpels and dental drills are considered critical because they can penetrate tissues and potentially transmit infections if they are contaminated. A probe, while it does touch tissues, is categorized as semi-critical as it contacts mucous membranes, necessitating high-level disinfection. Understanding these categories is crucial for implementing appropriate infection control measures in a dental setting.