How long will novocain (procaine) last when you get injected with it at the dentist?

Anesthetics: It depends on the type he used and if it has a long lasting Epinephrine . It can range from less than one hour to eight hours depending on the type

3 to 5 hours: No one really uses novocaine anymore. Local anesthetics most often used in the dental office are Lidocaine (aka xylocaine) and septocaine (aka articaine) which are safer and cause less allergies. Local anesthetics last 3 to 5 hours.