Alex presented a couple of issues for me. I was taught that it is best to shoot high to low, to be a little bit higher than the subject. As more light comes from above than is reflected from below, there is usually better light in the eyes when shooting high to low. A second advantage is that when shooting high to low, the jaw partially blocks the neck, and our culture does not value the appearance of necks. I once photographed a lady who nearly refused, because her neck had wrinkles. She was 86! See here here.
(click to enlarge)
As I try to avoid cliché smiles, most of my images do not show a lot of teeth. But in Alex’s case, I had to make an exception :-).