Final answer:
The nurse should reorient the patient to place and time.
Step-by-step explanation:
When a patient with dementia becomes disoriented, the nurse should best respond by reorienting the patient to place and time. This means reminding the patient of their current location and the current year. For example, the nurse might say, 'You are in the hospital and today is [current year].' This approach can help the patient gain a better understanding of their surroundings and reduce confusion.