Is There a Way to Polish Old Crowns?

The shine on porcelain is quite difficult to remove. I would first want to determine why your porcelain is dull. I would need to evaluate the abrasiveness of your toothpaste, the hardness of your brush as well as the techniques of the hygienist. Many Hygienists improperly use a sandblasting prophy jet aiming it at the facial surfaces of the porcelain to remove light surface stain which normally is easily polished off. This can damage the porcelain creating a dull surface. Porcelain is just glass. Imagine sandblasting a clear windowpane. After sandblasting, it would then be frosted glass with a dull surface. Porcelain can be repolished in your mouth using micro fine polishing compounds, but it will never look as shiny as its original glaze. The ability to remove your existing work and send it to the lab to be reglazed is virtually impossible unless your work is temporarily cemented.

Porcelain crowns are polished back to their shiny appearance using prophy cups at your dental cleaning appointment.  There are also polishing tips that dentists can use in your mouth to smooth out any rough surfaces.  Best, Dr. Elizabeth Jahanian.

Porcelain crowns can be re-polished in the mouth, but since the original glaze was fired on in a high temperature oven, they never look quite the same unless the glaze is re-applied in an oven. The one exception I can think of would be a crown on a dental implant that was screw retained (not cemented). In this case the crown could be unscrewed from the implant, returned to the lab and re-glazed to the original shine.

Hello,
Yes the crowns can be polished in the mouth. There is a special polishing bur set that we can easily use while the crowns are cemented on your teeth.
Thank you,
Dr. Cristina Barba
 

Your crowns should ideally retain their finish (glaze). If for some reason they appear rough, it is fairly simple to re-polish them again with rubber wheels and porcelain polishing paste. The dental lab applies a glazing in a super heated ceramic oven. 

Normally crowns are quite durable and never need polishing, but if some accident, etc. caused some small scratches the surface can be polished to a high luster directly in the mouth.  There are special polishing systems for this purpose.