A restoration may be made in amalgam, composite, ceramic (porcelain), gold, or may be a temporary material. Each has their benefits and potential problems.
A tooth that is vital (nerve still alive) may experience some sensitivity especially to cold following a restoration. This is normal but should settle within 1-2 weeks. A tooth with early stages of inflammation may also settle with a restoration alone.
If root canal treatment is necessary, then a protective restoration is placed following this. This restoration, generally placed immediately, your dentist will need to carefully check this restoration over time. The general dentist over time will then decide if a crown or further protection of the tooth is required.