He is cooperative at the first visit but becomes progressively resistant during subsequent appointments, and basic behavior guidance no longer allows any treatment to be completed. Comprehensive restorative care is still required. What is the most appropriate approach?

Correct answer: A. General anesthesia in a hospital or surgical center setting

• A. Correct. When less restrictive techniques have been genuinely attempted and failed, and the patient has substantial treatment needs, general anesthesia allows all care to be completed safely in one session. It is the standard route for a patient with an intellectual disability whose cooperation cannot be obtained.
• B. Incorrect. Behavior guidance techniques have already been tried without success. Continuing them indefinitely delays necessary care and risks disease progression.
• C. Incorrect. Protective stabilization always requires informed consent from the parent or guardian, and it is not a substitute for definitive management when extensive treatment is needed.
• D. Incorrect. Nitrous oxide is a minimal sedation technique that still requires the patient to accept the nasal hood and follow instruction. In a child who has become actively resistant, it will not provide adequate conditions.

Note: Moderate sedation is a legitimate intermediate step and some keys favor it. General anesthesia is the stronger answer here because the stem specifies comprehensive treatment needs and failure of behavior guidance. Down syndrome adds specific GA considerations: screen for atlantoaxial instability, cardiac status, and a potentially difficult airway from midface hypoplasia and macroglossia.