Once the squirrel has reached the adult stage, their teeth do not regrow if lost. >Infant tree squirrels have three pairs of milk teeth that are replaced by adult teeth when the squirrel is four to five months old. **Once the adult teeth come in, they do not re-grow if lost or removed.** The baby’s lower incisors come in at between three and four weeks with the upper incisors following at five weeks. [Source][1] However their teeth do grow continuously throughout their lives. >Squirrel incisors continuously grow in a highly curved trajectory **throughout their lives, on average about 6 inches per year.** [Source][1] [1]: http://squirrelrefuge.org/teethissues.html