First, go to Setup>Medical Setup>Dental Questionnaire.
Next click the Add New button
Enter text and select how you'd like the patient to answer, checkbox, textbox, date, memo, yes/no, or picklist and then save.
You can choose to move the question up or down by dragging and dropping the question
Lastly, you'll need to click the save button. When you go to the patient chart to add a new update you will see the question there. This does not affect any previously entered records, only new records going forward.