DEFINITION FACTORS AFFECTING RETENTION- Anatomical factors Physiological factors Physical factors Mechanical factors Muscular factors 1. Retention 2. Stability 3. Support 4. Preservation of residual structures 5. Aesthetics #CompleteDenture #DentureRetention #Prosthodontics #DentalEducation #RemovableDentures #DentalRetention #OralRehabilitation #DentalProsthesis #Dentistry #DentalScience

1. RETENTION IN
COMPLETE DENTURE
Prepared by:
Dr. KAVAN Y. DOSHI
MAXILLOFACIAL PROSTHODONTIST AND IMPLANTOLOGIST

2. OBJECTIVES OF IMPRESSION MAKING
1. Retention
2. Stability
3. Support
4. Preservation of residual structures
5. Aesthetics

3. CONTENTS
• DEFINITION
• FACTORS AFFECTING RETENTION-
1. Anatomical factors
2. Physiological factors
3. Physical factors
4. Mechanical factors
5. Muscular factors

4. DEFINITION
• RETENTION - According to
(GPT 9 ),
• That quality inherent in the
dental prosthesis acting to resist
the forces of dislodgment along
the path of placement.

6. FACTORS AFFECTING RETENTION
• The factors that affect the retention can be classified as are-
1. Anatomical factors
2. Physiological factors
3. Physical factors
4. Mechanical factors
5. Muscular factors

7. I. ANATOMICAL FACTORS
• The various anatomical factors that affect
the retention are-
1. Size of the denture bearing area.
• Retention with in size of
denture bearing area.
2.Quality of denture bearing area.
• the displaceable tissue will be the
retention.
Maxillary edentulous ridge – 24 cm 2
Mandibular edentulous ridge – 14 cm2

8. II. PHYSIOLOGICAL FACTORS
• SALIVA-
• The amount and consistency of saliva affects retention .
• Thin watery saliva affords best retention.
• saliva – that is thick and ropy accumulate between the
tissue surface of the denture and the palate leading to loss of
retention.
• saliva - affects retention and can also cause irritation and
soreness of the denture bearing tissues.

9. III. PHYSICAL FACTORS
• The various physical factors which affect retention are :-
1. Adhesion
2. Cohesion
3. Interfacial surface tension
4. Capillarity or capillary attraction
5. Atmospheric pressure and peripheral seal
6. Gravity

10. 1. ADHESION
• Adhesion is the physical
attraction force of
unlike molecules to one
another.

11. • Saliva is present in between the denture base and the
mucosa, and its contact with both these surfaces creates
adhesion.
• It is achieved by ionic forces between the salivary
glycoproteins and surface epithelium or acrylic resin.

12. It depends on:
• Close adaptation of denture
• Size of denture-bearing area
• Type of saliva
• Adhesion also takes place directly between the denture base and
mucosa in case of xerostomia (lack of saliva), but this leads to
ulcerations and abrasions in the mucosa.

13. 2.COHESION
• Cohesion is defined as the
physical attraction of like
molecules to one another.
• This occurs within the film
of saliva and aids in retention.

14. • Normal saliva is not very cohesive; hence, retention from
mucosa interface is more dependent on adhesion and surface
tension.
• As viscosity of saliva increases, greater is the cohesion
• Very thick, mucous saliva can physically push the
denture out, resulting in loss of retention.

15. 3. INTERFACIAL SURFACE TENSION
• Interfacial surface tension is
defined as the tension or
resistance to separation
possessed by a film of
liquid between two well
adapted parallel surfaces.

16. Stefan`s Law :
Stefan proposed formula to calculate Interfacial
surface tension.
F=3/2*3.14*kr4
/ H3
* V .
K= viscosity of liquid.
r = denture surface area.
H= width of space between denture base and mucosa.
V= velocity of the displacing force.

17. • These forces are found within the thin film of saliva that is
present between the denture base and tissues.
• It is dependent on the ability of the liquid to ‘wet’ the
surfaces. The ‘wettability’ of the fluid is inversely
proportional to the surface tension of the surfaces.

18. Surface tension in maxillary denture Surface tension lost in mandibular denture
• Interfacial surface tension is also dependent on existence of a
liquid/air interface at the boundary of the liquid/solid contact.

19. 4.CAPILLARITY OR CAPILLARYATTRACTION
• That quality or state which
because of surface tension
causes elevation or depression
of surface of a liquid that is in
contact with solid walls of a
vessel.

20. • When adaptation of denture base to mucosa is close the space filled with
saliva acts like a capillary tube and helps retain the denture.
• This force like others is directly proportional to area of basal seat coverage.
• Factors that aid to improve capillary attraction are-
1. Closeness of adaptation of denture base to soft tissue.
2. Greater surface of the denture bearing area.
3. Thin film of saliva should be present.

21. 5.ATMOSPHERIC PRESSURE
• This can help resist dislodging forces if the dentures have an
effective border seal.
• Peripheral seal or border seal is defined as the contact of the
denture border with the underlying or adjacent tissues to
prevent the passage of air or other substances (GPT8).

23. • Retention due to atmospheric pressure is proportional to the
denture base area.
• Proper border moulding is essential for this retention mechanism to
function.

24. 6.GRAVITY
• When a person is in upright
posture gravity acts as a
retentive force for mandibular
denture and a displacive force
for maxillary denture.

25. IV . MECHANICAL FACTORS
1. Undercuts
• Moderate undercuts enhance retention because of
the resiliency of mucosa.
• Examples are unilateral tuberosity undercuts,
undercuts in maxillary premolar area,
distolingual areas and lingual to the midline of
mandible.

26. • Severe undercuts covered with thin mucosa compromise retention and need
to be surgically eliminated.
• Undercuts like those present in the retromolar areas and maxillary
anterior ridge allow insertion of denture with a rotational path with the
undercut area seated first.
• They provide good resistance to displacement in a vertical direction.

27. 2. Denture adhesives
• These commercially available products enhance retention by increasing
adhesive and cohesive properties and by eliminating voids between denture
base and basal seat tissues

28. • DENTURE ADHESIVE GEL-

29. 3. Suction chambers and discs
• These have been used to create a negative pressure in the palatal surface of the
maxillary denture, thereby enhancing retention.
• They are best avoided due to their potential to cause PAPILLARY
HYPERPLASIAS.

30. Suction disc Papillary hyperplasia

31. 4.Magnets
Intramucosal magnets aid in
increasing retention of highly
resorbed ridges.

32. V. MUSCULAR FACTORS
• The oral and facial musculature and tongue supply supplementary retentive forces.
• For this to be effective:
• Teeth must be positioned in the ‘neutral zone’ between the tongue and cheeks.
• Polished surfaces of the dentures should be properly contoured.
• Denture bases must be extended to cover maximum area.
• Occlusal plane must be at correct level.

33. • If the buccal flange of the maxillary denture slopes up and
out of the occlusal surface of the teeth and the buccal flange
of the mandibular denture slope down and out of the occlusal
plane , the contraction of the buccinator will tend to retain both
dentures on their basal seats.
• The lingual surface of the lingual flange should slope towards
the centre of mouth so the tongue can fit against them and
perfect the border seal on the lingual side of the denture.

34. • The base of the tongue serve as a emergency retentive force
for some patient.
• It rises up at the back and presses against the distal border of
the maxillary denture during incision of food by anterior
teeth.

35. QUESTION FROM UNIVERSITY POINT OF VIEW
1. Define impression. Mention objectives of impression making.
Explain retention in complete denture in detail. ( 7 marks )
2. Atmospheric pressure ( 5 marks )
3. Interfacial surface tension ( 5 marks )
4. Adhesion ( 1 mark )
5. Cohesion (1 mark )

36. TEXT BOOK YOU SHOULD REFER
•Boucher
•Nallaswamy 2nd
edition.

37. THANK YOU