Sounds like manure to me, just pull the dumb tooth and get on with your life. I had a root canaled tooth pulled and didn't need to 'build up the area', it healed just like any other pulled tooth.

Bone grafts are usually done with your own bone, taken from other areas of your body. If you have a problem with a (dead) root canaled tooth how much worse will that be with cow bone in your jaw? Are they going to match the cow for compatibilty with you? If your body were to reject that I'd hate to hear about the damage to your face.

Personally I think most dentists have some very strange opinions, and I know from experience that they also lie a lot. They really are only drill and fill tradesmen, not doctors. If they were doctors they would all recognize the symptoms of the mercury poisoning they cause. I would never trust one in this area, they aren't educated enough.

Maybe they need experimental subjects. Sounds like an expensive experiment too, your expense.