Saw an endotontist today about a molar that gives me grief on and off past 5 yrs. Stabbing pain every now and then. Recently (December) dentist mentioned I have an infection evident on my otherwise healthy gum. The endo has determined that when a crown was fitted 20+yrs ago only 3 root canals were cleared. Evidently they now know that molars have 4 roots canals and not 3. Excuse me if I am not using the terms correctly. It seems the uncleared 4th canal is infected and the surrounding bone is wasting. So I've booked in to have the root canal cleaned out. Treatment is around $2,900! It could be worse as he reckons he can do this without destroying the crown. Still a bit of a shock. MrsP says now I have to live long enough to get my money's worth.