For a small gap between two teeth that are otherwise in alignment there are a few choices of treatment.  The first would be closing the space with composite, or white filling material.  Composite fillings do stain and darken as they age, so this would have to be replaced every 3 to 5 years.  The more permanent treatment would be porcelain veneers, which cover the entire front of the tooth and are made of a material that will not stain or darken.