When there is not enough tooth left to fill due to damage from decay and/or trauma you are left with the choice of either extracting the tooth or crowning it. This involves shaving the tooth down and having a crown made in a dental laboratory which is them cemented onto the remains of the tooth to build it up to its proper size, shape and colour. Crowns are normally made from porcelain over a metal base. They last a long time, on average 15 to 20 years.