My experience with MetLife thus far is they deny everything at least once. My wife had a root canal last year. No problem. They paid up.
They did give her a hard time over a periodontic cleaning. It took a phone call to get everyone on the same page. None of our dental specialists are in network. It's gotten to the point where if they are actually in network, I question their competence.
Karen Browne-Fleck at DALPA can help you. She prefers to be contacted by email. Her response will be very fast.