Final answer:
The incorrect statement about mouth props is that they are placed close to the area being treated. Mouth props are used to keep the mouth open and relax jaw muscles, not necessarily placed near the specific area being worked on.
Step-by-step explanation:
The mouth prop is placed close to the area being treated. This is not typically the case as mouth props are usually placed between the molars to maintain an open mouth during a procedure, not necessarily near the area being treated, which could be anywhere in the mouth.
Mouth props, also known as bite blocks, are devices used during dental procedures to help patients keep their mouths open without straining the jaw muscles. These props serve multiple purposes, such as allowing the patient to relax and rest the jaw muscles (statement A), preventing the patient from unintentionally closing their mouth and potentially harming themselves or the dentist (statement B), and they are named correctly in statement D as a 'bite-block'. During procedures requiring general anesthesia, mentioned in the reference, the control of respiration along with muscle relaxation—including the jaw—is managed by an anesthesiologist. This further illustrates the importance of mouth props during surgical procedures.