Plant-eating dinosaur tooth

Continuing the discussion on teeth, one of the things I find interesting is that dinosaur teeth are very simple, unlike mammal teeth that are very complex.  I think most paleontologists would agree that the reason for this is that mammals generally only replace their teeth once during their lives whereas dinosaurs and other reptiles replace their teeth throughout their lives.  T.rex apparently replaced each of its teeth every year or so.  For this reason dinosaur teeth didn't have to be completely covered with enamel or have complex shapes.  They could be rather simple because they would be replaced before they were completely worn out.  So, almost all meat-eater teeth are identical to one another except for having variations in the number and size of serrations (ridges along edge).  Except for the different number of serrations, it’s hard to tell an Allosaurus tooth from the tooth of a young T.rex.  

Interestingly, the teeth of most of the plant-eaters are also very similar to one another.  The cheek teeth of the quadrupedal (walked on four feet) Stegosaurus look almost identical to the cheek teeth of bipedal (walked on two feet) Thescelosaurus.  Duck-bill dinosaur teeth all look similar to one another, and horned dinosaur teeth look similar to one another.  In other words there are basically only a few different kinds of plant-eating dinosaur teeth, even though the dinosaurs looked as if they probably ate a wide variety of plants.