The estimated incidence of suffering from a true allergic reaction to local anesthetic in the dental surgery is 1 in 22 million*.
In comparative terms, you have a better chance of being canonized (1 in 20 million),^
or of dying in a Grand Canyon flash flood (1 in 14,270,000)…
Sambrook PJ, Smith W, Elijah J, Goss AN.
Aust Dent J. 2011 Jun;56(2):148-53
^20 things more likely to happen than winning the Mega Millions lottery
By Chris Higbee, Deseret News