RETENTION AND STABILITY

WHAT IS RETENTION?• IT IS THE ABILITY OF THE DENTURE TO RESIST

VERTICAL TISSUE AWAY MOVEMENT.

WHAT IS STABILITY?• IT IS THE QUALITY OF THE DENTURE TO BE FIRM AND

STEADY, WHEN FUNCTIONAL FORCES ARE APPLIED.

(RESISTANCE TO HORIZONTAL AND ROTATIONAL FORCES).

FACTORS AFFECTING RETENTION.

PHYSICAL.

MECHANICAL.

ANATOMICAL.

RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

1- ADHESION

• PHYSICAL ATTRACTION BETWEEN UNLIKE MOLECULES.(DENTURE-SALIVA-MUCOSA)

2- COHESION

• PHYSICAL ATTRACTION BETWEEN SIMILAR MOLECULES.(SALIVARY MOLECULES)

3-INTERFACIAL SURFACE TENSION(CAPILLARY ATTRACTION).

• THE ATTRACTIVE FORCES BETWEEN SURFACE MOLECULES.

• IT IS THE RESISTANCE TO SEPARATION POSSESED BY A FILM OF LIQUID BETWEEN 2 WELL ADAPTED SURFACES.

4- ATMOSPHERIC PRESSURE

WHEN YOU SEAT THE DENTURE, AIR ESCAPES FROM UNDERNEATH THE FITTING SURFACE,

FORMING A PARTIAL VACCUUM BETWEEN THE MUCOSA AND THE DENTURE, RESULTING IN

TRAPPED REDUCED PRESSURE. ATMOSPHERIC PRESSURE IS LARGER, THUS SEATS THE DENTURE.

5- VISCOSITY.

• THE RESISTANCE OF PART OF THE FLUID TO MOVE OVER ANOTHER.

THE GREATER THE VICOSITY THE BETTER THE RETENTION.

6- GRAVITY.

• IS CONSIDERED RETENTIVE TO THE LOWER DENTURE, AND DISPLACING TO THE UPPER

DENTURE.

ALL THE FACTORS

WORKING TOGETHER.

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

1-SHAPE OF POLISHED SURFACE.

2-DENTURE FOUNDATION AREA

3-PRESENCE OF UNDERCUTS

4- DENTURE EXTENSION

5- INTIMATE CONTACT

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

1-RIDGE HEIGHT

2-SOFT PALATE ANATOMY

3- ARCH RELATIONSHIP

4- TONGUE SHAPE

5- VISCOSITY OF SALIVA

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

1- RIDGE AUGMENTATION

2- VESTIBULOPLASTY

DEEPENING OF THE

VESTIBULE TO GAIN

RIDGE HEIGHT.

3- DENTAL IMPLANTS

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

1- ADHESIVES

• CREAMS USED AS ADHESIVE IN THE FITTING SURFACE OF THE DENTURE.

2- MICRO SUCTION DISCS

3- DENTAL IMPLANTS

PHYSICAL.

MECHANICAL.

ANATOMICAL.RETENTIVE AIDS.

SURGICAL.

PSYCHOLOGICAL.

SOME PATIENTS HAVE THE

NEUROMUSCULAR AND PSYCOLOGICAL

ABILITY, TO COPE AND USE THE

DENTURE.

STABILITY

RETENTION.

BALANCED OCCLUSION.

HEIGHT OF OCCLUSAL PLANE.

POSITION OF POSTERIOR TEETH.

PROPER RELEIF.RIDGE FORM.PALATAL VAULT.WIDTH OF

OCCLUSAL SURFACE.SHAPE AND SIZE OF

THE TONGUE.SHAPE OF THE

POLISHED SURFACE.

RETENTION.

FOR A DENTURE TO BE STABLE IT SHOULD BE RETENTIVE FIRST.!!!!!!!

BALANCED OCCLUSION.

HEIGHT OF OCCLUSAL

PLANE.

WHICH IS MORE STABLE!!!!!!!!!!!

THE FURTHER AWAY THE OCCLUSAL PLANE , FROM THE RIDGE, THE LESS THE STABILITY.

POSITION OF POSTERIOR TEETH.

PLACING THE POSTERIOR TEETH SLIGHTLY LINGUAL TO THE CREST OF THE RIDGE, THE MORE STABLE. THE FORCES FALLING ON THE TEETH BECOMES MORE CENTRALISED.THIS IS KNOWN AS

“LEVER BALANCE”.

INCLINED PLANE ACTION

PROPER RELEIF.

FIRST ROCKING THEN

MIDLINE FRACTURE.

RIDGE FORM.

PALATAL VAULT.

V- SHAPED PALATE HELPS RESIST LATERAL LOADS.

WIDTH OF OCCLUSAL SURFACE.

THE OCCLUSAL WIDTH IS LESS

THAN THE NATURAL,

THUS DECREASING

THE AMOUNT OF LOAD

FALLING ON THE DENTURE.

SHAPE AND SIZE OF THE TONGUE.

LARGE AND MEDIUM SIZED TONGUES HELP STBILIZE THE LOWER

DENTURE.

SHAPE OF THE POLISHED SURFACE.

THE CHEEK AND THE TONGUE

SEAT THE DENTURES IN

PLACE.