Retention and stability Flashcards
what is retention ?
ability to resist vertical movement AWAY from tissue
what is stability ?
ability to be firm and resist horizontal and rotational forces
what is the main mode of retention of denture base?
mechanical retention
what is adhesion ?
physical attraction between unlike molecules
how is interfacial surface tension applied in denture fitting ?
-thin film of saliva between mucosa and denture(well adapted surfaces)
what is the significance of atmospheric pressure when fitting dentures?
- air escapes from underneath the denture when it is placed in the oral cavity , forming a partial vaccum between the mucosa and the denture base —> resulting in trapped reduced pressure . atmospheric pressure is larger than this pressure, thus seats the denture
as viscosity of saliva increase , denture base retention _____
increases
shape of polished surface should be :
concave (lower denture should be narrow at the premolar area to be away from the modiolus
how does the presence of an undercut affect the fitting of a denture?>
may make it difficult to insert and remove denture (may require flexible acrylic)
what is the neutral zone ?
space in oral cavity where force from the cheek and tongue are equal —> neutralized
what is support ?
ability to resist moving of denture towards the tissue (vertical plane)
which arch relationship is the worst for retention of denture?
class II (retrognathism) BECAUSE THA LOWER ARCH ALREADY FACES DIFFICULTIES WITH RETENTION DUE TO SMALL AREA , FLOODING OF SALIVA
how does tongue size affect the palatal seal ?
a moderate tongue permits an excellent seal
a small tongue compromises the seal
and a large tongue displaces the denture
what are the different palatal vault forms and what are their different advantages ?
U shaped: resists vertical and horizontal forces
-> both have the same support^
flat vault : resists vertical forces not lateral ones
V shaped: Resists lateral forces and not vertical ones (Best stability)
what are some surgical measures that can be taken to increase retention ?
-bone grafting to increase ridge size
-vestibuloplasty (deepening of vestibule to gain ridge height )
-implants of overdenture with attachments to denture
