After a root canal, a tooth may be structurally compromised or may be subjected to chewing pressures or forces that require better protection. A crown may be suggested to help strengthen a large filling or help protect an area that is compromised. If this is the case, the recommendation of a crown should be done sooner than later.  A crown or a cap is suggested simply because it allows the visible part of a tooth to be strengthened and covered by a more robust shell than it has at present.