Mama Cakes, I answered a similiar question last month, concerning what illegal drugs do to a human body. Here is basically the same answer.
For about ten years, one of our vice squad officers began keeping a dated photo image of a very pretty 18 year old girl, addicted to meth. Just about each year, she was arrested for some crime, and again photographed. The lineup of her photographs were un believable. In ten years, she aged at least 30 years. She lost all of her teeth and her face went from thin and pretty to swollen and ugly. Mixing of various drugs will do this.
I wil say this, ill-fitting dentures can also cause this problem, according to my mothers dentist.
With Whitney Houstons money, I cannot believe she did not have the best dentist and dentures that money could buy.
If so, the only other assumption were the mix of drugs she was taking.