How many dentists does it take to change a light bulb?

Three.

One to administer the anaesthetic.
One to extract the light bulb.
One to offer the socket some bad tasting pink mouthwash.

Why the mouthwash ? Did not you suffer enough already?

Be happy that you live in the 21st century! The Romans used human urine for mouthwash. The ammonia in the urine made it work. It also tasted horrible, so after some time, honey was added to the drink and during the early 19th century, eucalyptus leaves. Still later, alcohol (mmmm) was used.

Don't worry... Ammonia still is an active ingredient in some mouthwashes, but it comes from the laboratory and not from human urine.