“Why did the Oreo go to the dentist?”/“Because it lost its filling.”

The Oreo creme-filled cookie was first sold by the National Biscuit Company of New York City in 1912. A popular Oreo joke is:
 
Q: Why did the Oreo go to the dentist?
A: Because it lost its filling.
   
“Joke of the day: Why did the Oreo go to the dentist? because he lost his filling” was cited in Twitter on June 16, 2009. However, the joke didn’t become popular until late 2012.
 
“Why did the pie go to the dentist?”/“To get a filling.” is a similar joke.
     
 
Wikipedia: Oreo
Oreo /ˈɔrioʊ/ is a sandwich cookie consisting of two chocolate wafers with a sweet creme filling in between, and (as of 1974) are marketed as “Chocolate Sandwich Cookies” on the package they are held in. The version currently sold in the United States is made by the Nabisco division of Mondelēz International. Oreo has become the best-selling cookie in the United States since its introduction in 1912.
 
Twitter
Prongo kids games
‏@Prongo
Joke of the day: Why did the Oreo go to the dentist? because he lost his filling Submitted by: tor
12:45 PM - 16 Jun 2009
 
Twitter
Daily Groaner
‏@DailyGroaner
Q: Why did the Oreo go to the dentist? A: Because he lost his filling. #jokes #humor #funny
1:46 PM - 12 Jul 2012
 
Twitter
Emily Whitney
‏@emswhitney
Why did the Oreo go to the dentist? It lost it’s filling. #classicjokemonday
2:57 PM - 31 Dec 2012
 
Google Books
More One Liners, Jokes and Gags
By Grant Tucker
London: The Robson Press
2013
Pg. ?:
Why did the Oreo go to the dentist? To get his filling.
 
15 August 2013, The Carillon (Steinbach, Manitoba), “Middlebro” by Jodi Overton, pg. 10C, col. 6:
Here is the answer to the question last week: Why did the Oreo go to the dentist? The answer: He lost his filling. Cute, eh?
 
Google Books
Very Funny Jokes For Kids Again
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
Why did the oreo go to the dentist?
To get his filling!
     
Google Books
Lots of Jokes for Kids
By Zondervan
Grand Rapids, MI: Zonderkidz
2015
Pg. ?:
Why did the Oreo go to the dentist?
Because he lost his filling.
 
KEY103
10 of the corniest food jokes
Posted on Tuesday 8 September 2015
(...)
10. Why did the Oreo go to the dentist?
It lost its filling.