I have searched the web and dictionaries and they are both used in dentistry ...toss a coin time I think .
Although Lidocaine gets 16,600 hits on Google but Dibucaine only 1,880 That's UK searches... .searching by the name + dentistry.
I've been retired a while now, so a bit out of touch, but in thirty-five years general dental practice I never heard of Dibucaine, but I used lidocaine every day; aka lignocaine, trade name Xylocaine.