It is quite common to be honest with you, I have seen quite a few.
Luckily all that I have seen havent needed removal but have needed rounding off to remove sharp points.
Main concern is to make sure he hasnt fractured the tooth further down the root end as well and also whether the pulp cavilty have been exposed leaving him more prone to infection/abcess in the future. TBH if the tooth isnt sore to palpate then it is best left in there without removal and canine have incredibly long roots that run up the bars and are hideoulsly difficult to remove and traumatic for the horse.
If the tooth and the bar area is very sore to squeeze then I advise that you get an x ray. Good luck!