Formal:
* Il est beau et a de belles dents. (This is the most literal translation)
* Il est agréable à regarder et a un beau sourire. (This emphasizes his smile)
Informal:
* Il est mignon et a de jolies dents. (This is more casual)
* Il est beau gosse et a un sourire ravageur. (This is more flirtatious)
You can also combine different expressions depending on the context and your level of formality.