This diagnosis can be determined with an exam and radiographs. If the teeth are healthy, the restorations are acceptable, and the esthetics are fine, there is no reason for further treatment at this time. If the restorations do need to be replaced, your son may have several options. I am guessing that your son currently has composite resin fillings, which are a plastic tooth-colored filling material. It may be possible to replace his composites with improved composite material.
New materials are more esthetic and seem to wear better.
However, composites are still not as strong as the original tooth structure. Other options include some type of porcelain restoration, such as porcelain veneers, porcelain jacket crowns, or porcelain fused to metal crowns. While porcelain restorations are generally more expensive than composite resin restorations, they maintain their color well, do not stain, and usually last longer. If the current restorations match the shade of the tooth well, it can be quite challenging to determine the difference between the filling and the natural tooth structure. A good technique for determining the difference is to run the dental explorer along the surface in question.