Final answer:
The ethical principle violated when a dentist practices while impaired is the principle of nonmaleficence, as it requires acting in ways that avoid causing harm.
Step-by-step explanation:
The ethical principle violated when a dentist practices while impaired is the principle of nonmaleficence, which dictates that healthcare providers should act in ways that do not cause harm to others. In the context of clinical settings, this means that a dentist must ensure his or her personal capacities do not risk causing harm to patients, whether it be through impaired judgement, reduced motor skills, or any other impairment. Therefore, practicing dentistry while impaired directly contradicts this ethical principle.