[Importance of the palatal seal for complete denture's retention]

By preserving the anatomic integrity of the stomatognathic system, a prosthesis allows its physiologic activities to proceed normally. A function imprint provides a picture of the prosthesis support and relationship between mobile tissues and prosthesis rims. A high-quality function imprint required, but current literature offers different opinions and views concerning the choice and method of taking a function imprint. Several procedures covering all methodologic differences can still be singled out: taking a function imprint without pressure, taking a function imprint with pressure, taking a function imprint with the mouth open, taking a function imprint with the mouth closed. The regions with a thin and less keratinized mucosa over the bone but without a submucosal interlayer must be relieved or imprinted without pressure. Forward inclination of the head and the position of the tongue make the soft palate to acquire a functional position on taking the imprint, thus allowing the posterior pharyngeal rim of the upper prosthesis to be determined. The greater the valve effect and the lesser the space between the prosthesis base and support, the higher the negative pressure upon the support. Imbibition is achieved by the prosthesis rims lying in the initial part of mobile mucosa, and the pharyngeal rim on the border between the hard and soft palate, in the region of the "ah" line. Retention of the prosthesis is mostly secured by its posterior, dorsal patal or pharyngeal rim. When pointing to its importance in retention, it applies to the rim margins, its relation to the support and its role in the valve closure of the upper total prosthesis.