What I hated about Dogtooth was that their family was so disfunctional with no morality play in it. There was no greecian chorus (hah!) to comment on how sick the family was, their lives were just portrayed so matter of factly. If there is an overriding mood to the movie, it's matter of fact.
Then, at the end, when the dogteeth come out and you sense that the parents are going to get their comeuppance for their psycho ideas and ruining their kids, the movie ends.