Intracoronal retainer placed in the abutment teeth has the following disadvantage
Internal or precision attachments
Advantages:

Improved aesthetics, by elimination of a visible retentive component and vertical support.

Disadvantages:

Difficulty in repair and replacing.
Greater cost to the patient.
Inability to use in teeth having short clinical crowns and tissue-supported distal extension denture bases.
It is unaesthetic
They cannot provide support and stability
Difficult laboratory procedure
Difficult to repair and replace