Portraits were the subject is not smiling and lit by moody lighting can definitley look mysterious and interesting. However, there are good reasons why your primary profile photo should show you smiling. Smiling sends the message that you are approachable and friendly - which is an absolutely essiential for dating profile photos. Futhermore, an open mouth smile with the teeth visible is even more inviting. It is a statistical fact that people who smile in online dating photos get a much higher hit rate than those that don't.
Many people are very self conscious about showing their teeth in photos due to their condition. Teeth whitening products can be used before the shoot. Another option is to use subtle digital retouching to whiten the teeth and to correct flaws in their appearance.
Our final piece of advise, is pracitise your smile in the mirror, until you are happy with it