I worked for years, off and on, for my dad, a dentist, and we NEVER gave patients anything to swallow. That's ridiculous.
I worked for a dentist that used to use a lot of NO2 on patients, especially late in the day. He had certain patients that he always scheduled late and would send everyone in the office home, while he worked on him. The office manager used to tell everyone never to let him work on a patient alone with the door shut, because she didn't trust him. He proved he wasn't trustworthy with one of the employees, one day.