An orthodontist is a dental specialist who focuses on the diagnosis, prevention, and treatment of dental and facial irregularities. The job for an orthodontist is to correct an OVERBITE, which is an excessive vertical overlap of the upper teeth over the lower teeth. An OVERBITE can be caused by genetics, thumb-sucking, or other habits that put pressure on the teeth. Orthodontists use braces, retainers, and other appliances to help correct an OVERBITE.