Why do you still have the effect of the novocaine from being at the dentist twenty four hours later hours later?

It is possible that the type of local anesthetic the dentist used was particularly potent on you, although 24 hours is unusual. It is also possible the procedure the dentist performed may have bruised a nerve and that is why you are still numb. This is called a transient or temporary parasthesia. In severe cases, parasthesia can persist for months. Regardless of the cause, it is important that you let your dentist know you are experiencing this lingering numbness.