In which cases should the porcelain inlay-onlay fillings be preferred?

Porcelain inlay-onlay filling is used as an alternative to porcelain crowns to protect the dental integrity, especially for teeth, those underwent canal root treatment, lost their fluid and their fragility is increased. Another area of use is being an alternative to composite fillings in teeth with excessive material loss, both to provide an aesthetic look and to provide dental contact concordance.  Moreover, they are also used in increasing of vertical size of excessively eroded teeth.