Just out of curiosity let me ask this:
Do any of your dogs have serrations on the back side of their top canine teeth? Could you state the breed or breeds that you have and if they do or don't? I'm really interested, but on a personal basis.
I ask because one of my coworkers bagged a coyote on a hunt this past weekend. In examining the photos I noticed the serrations on the back of the coyote's teeth. Xerxes has these same serrations. I would assume that a more domestic dog wouldn't have them but before I make that assumption, I'd like to find out from others. The ridge is used for slicing through tendon and muscle, primarily for eating but also for "hamstringing" prey.
So just rub your fingertip on the back edge of the canine teeth of your dogs, see if that ridge is there. Thanks!