The 40 year old was on set filming an episode of her U.S. TV sitcom Up All Night when she felt a sharp pain in her mouth and ran to the bathroom - only to discover half her back molar had broken off, leaving the nerve exposed.
The actress contacted an after-hours dentist in her area, and the new mum is grateful she was able to get the problem taken care of quickly.
Appearing on America's The Tonight Show With Jay Leno the following day (03Oct12), she said, ""I had emergency dental work done last night after a 14-hour work day... My tooth broke. My molar, half of it just left. I'm sure I'll be seeing it again soon because I don't know what happened to the rest of it.
""I was sitting at work and I was like, 'My tongue feels really weird,' and I went back there and literally like a shard of tooth (was) stabbing me in the tongue. Then the nerve started to hurt so then we had to find someone... He (the dentist) was very nice, he did leave his dinner and come and do this for me in the middle of the night.""
Applegate insists she is already feeling much better: ""It's fine, I'm a little numb.""