Scott, Mason's caninies were all mechanically filed flat as a pancake on the tips. Either that or he did a lot of straight pulling on sanpaper. Almost looks like he bit a spinning grinder wheel.
Rex:
Cals canine teeth look like that as well, although not to the extent that Masons' teeth are worn. Perfectly flat on the tips. I took a peek at his (masons) teeth there in the parking lot. I think that's a trait of dogs that have done a lot of retrieving. Rebas' teeth (Cals dam) were worn that way as well. Cal was whelped 8/1997 and Masons' teeth are worn more than Cals'. If you work with the dogs every day, once they get 10+ years old, 20-40 retrieves per day really start to add up. They are grabbing things on the run/swim/fly, and I think the canine teeth take the most abuse. Reba actually had the tip of one broke off, although not down to the root. It wore smooth in about 5 years.