Prosthodontics

1. RELIEF and POSTERIOR PALATALSEAL
(POST DAM)
Assistant professor: Sadeq Al-tayar
BDS, MSc, DDS (PHD) - Egypt
Department of Prosthodontics
Ibb University
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2. Releif = pressure
 RELIEF:
 Relief Areas:
Are that portion of dental prosthesis that is reduced to eliminate
excessive pressure. As the muco-periosteum covering the jaw
bones is not uniform in thickness, softness, resiliency and
sensitivity, so denture relieves are made to reduce pressure on the
sensitive areas.
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3.  Areas To Be Relieved:
1- Hard bony areas 2- Sensitive areas
1-Hard bony areas:-
 Relieved In The Maxilla
• The median palatine raphe.
• Torus Palatinus if
present.
• Sharp Thin bonyedges.
 Relieved In The
Mandible
• Thin, wiry, knife-edgedridges.
• Sharp thin bony edges.
• Torus mandibularis.
• prominent genial tubercle.
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4. Thin bony edges
Torus palatines
Thin wiryridge Torus Mandibularis
Superficial mental foramen
sharp mylohyoid ridge
prominent genial tubercle
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5. .
2- Sensitive Areas:
 Mental foramenarea.
 Thin mucosa directly covers
sharp mylohyoid ridge.
 Thin wiry ridges,which are most
common in lower ridges.
 This type of relief is performed for patient comfort.
 RelievedInTheMaxilla
• Incisive papilla in the anterior
part of the hard palate.
• Prominent tuberosities.
• Prominent rugae.
 RelievedIn TheMandible
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6. Prominent Rugae
Thin mucosa directly covers sharpmylohyoid ridge
Prominent tuberosities or bony
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7. Relief
Direct Automatic
• Scrape the final
impression
• Build on the
master cast
 METHODS OF RELIEF:
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8.  Automatic Relief:
This type of relief can be obtained by
the use of a viscous impression
material in a closely fitted special tray.
 Direct Relief:
• This type of relief can be obtained
either by:
A- Scraping the final impression
according to the required
depth and width of the relief.
B- build up on the cast.
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9.  B- Relief done on the cast:- (most common)
the relief done befor construction of denture base.
• One or more layer of tin foil of the desired shape and thickness is
furnished over the cast by a blunt instrument and fixed in position by
cement.
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10.  Depth ofrelief:
• The depth of relief depends mostly upon resistance or
yield of the area to be relieved as compared with that of the
surrounding areas. (I.e with the level of adjacent area)
 Shape of relief area
• The outline of the relief
is determined by the
extent of the hard or
sensitive areas.
• Shape of relief area
differs from case to
other.
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11.  Functions of Relief:
A- Relief areas improve stability of dentures and prevent it
from rocking.
B- Compensate for tissue displacement over the ridges during
settling of dentures and some ridge resorption.
C- Compensate for some technical discrepancies.
D- Relief of sensitive areas gives comfort to the patient.
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12. • The soft tissue area at or beyond the junction of the hard and soft
palates on which pressure within the physiologic limits can be
applied by RDP (Removable dental prosthesis) to aid in retention of
thedenture.
• Areaofresilientsofttissuebetweenhard&softplateonwhichpressure
withinphysiologiclimitsoftissuecanbe appliedbytheposteriorborder of
thedenturetoaidindentureretention.
• Thesealattheposteriorborderofamaxillaryremovabledentalprosthesis.
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13.  Functions of posterior palatal seal
• Retention of maxillary denture: Maintain contact with the anterior portion
of the soft palate (the tissue undergo shallow displacement) during functional movement
(mastication, deglutination & phonation).
• Eliminate the gagging reflex.
• Prevent food accumulation under the denture.
• Compensate for polymerization shrinkage away from
palate.
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14.  Anatomic and Physiologic Considerations
A- The posterior palatal border of the upper denture:
should extend from one hamular notch to the other, following the contour of
the hard palate just anterior to the vibrating line.
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15. Vibrating Zone Post Palatal SealArea
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16.  Isanimaginaryline acrossthe posterior part of the palate makingthe division between
the movable& immovable tissue ofthe soft palate.
 It canbe identifiedwhen the movable tissue are moving. (duringfunction).
1. Anterior vibrating line.
2. posterior vibrating line.
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 Types of vibrating line:-
B- VIBRATING LINE
Anterior Posterior

17.  It is an imaginary line lying at the junction between the immovable tissues
over the hard palate & the slightly movable tissue of the soft palate.
 Instructing the patient to say “AH” with short vigorous bursts.
 The anterior vibrating line is not a straight line, due to the projection of
posterior nasal spine.
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1- Anterior vibrating line.

18. It is an imaginary separates the movable and the immovable portions
of the soft palate.
It represents demarcation between the part of soft palate that has
limited or shallow movement during function (quivers) & the
remainder of the soft palate that is displaced during functional
movement.
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2- Posterior vibrating line.

19.  Posterior Palatal Seal Classification
 According to the curvature of the soft palate, the
palate is classified into three classes:-
• Class I: The soft palate has a gentle curvature and this allows a broad palatal
seal area.
• Class II: The soft palate has a medium degree of curvature and this allows a
medium
width posterior palatal seal.
• Class III: The soft palate shows abrupt curvature and this allows a
narrow posterior palatal seal.
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20. Three classes:
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21.  Width and Depth of posterior
palatal seal (post dam area)
• The post dam should be about 4-6mm wide in its widestpart.
 The depth or thickness of the post dam should vary in different
individuals, according to compressibility and softness of the
tissue.
• Its depth vary between (0.5 – 1,5mm) in different parts of the same mouth.
 The average depth is 1mm.
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22. Methods To
Create Post
Dam
1-Scraping
method
2- Functional
post-damming
method
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23. 1- Scraping method
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A- Scraping of the master cast:
 A line is drawn across the posterior border of the cast
passing
behind the fovea palatine and the two hamular notches.
 Another line is drawn anterior to the first line in the
shape of butterfly.
 A sharp knife or carver is used to carve the posterior border
of the cast starting from the hamular notch towards the
midline deeper laterally and shallow at the midline.
 The cast is scraped to the butterfly outline tapers to zero
towards
the anterior border.

24. Scraping of the master cast is finished
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25. B- Arbitrary method:
 The posterior portion of the denture is determined in the
mouth, and its location is transferred onto the cast.
 Its subdivided in to:
1 Conventional method using custom tray.
2 Post damming during try-in stage using the trial denture base.
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26. o The posterior vibrating line is marked with an indelible pencil, from the
hamular notch & extended 3-4 mm anterio- laterally thetuberosity.
o The custom tray inserted into the mouth & seated firmly.
Upon removal from the mouth, the indelible lines will be transferred to the tray.
o The excess part of tray is reduced to thisline.
o The tray is return to master cast tocomplete
the transfer of the complete posteriorborder.
1- Conventional method using custom tray:
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o The cast then scraped according the transferred lines from the custom tray.

27. o The trial denture base is inserted so the indelible pencil
line marked on vibrating line of the soft palate that will
be transferred from the soft palate to the trial denture
base.
o The excess denture base is reduced to thisline.
o The trial denture base is placed on the cast and a knife or
pencil is used to mark a line following the posterior limits
of the base plate.
2- Post damming during try-in stage:
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28.  This method is based on displacement of
posterior palatal seal by impression
material at the time of final impression
making.
 Fluid wax or compound technique:
 Steps:-
 After the final impression is made using
ZOE/impression plaster, a melted wax or compound
(3mm in width) is added at the posterior border of the
impression from one hamular notch to the other.
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 The impression is placed in its position while the wax is still soft. Meanwhile ask the
patient to raise the soft plate by breathing deeply from the nose. The posterior limit of
the post-dam should have contact with the soft plate at function and atrest.

30. 3
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 Post damming the lower denture:
 The retromolar pad is compressible and accordingly the lower denture can
be post dammed at its distal end.
 This could be done at the impression stage.
 Adding a post dam to an existing denture:
Some times a completed denture may be deficient in the posterior palatal seal
area. The deficiency may be in depth or in width or in both.
The correction of the posterior seal area is essential to improve denture retention.
 This can be done by three methods:
a. Self cured resin can be used for intraoral correction of the posterior palatal seal.
b.Impression material (compound impression or wax) and then duplicated in self cure
acrylic resin.
c.Scraping a cast poured on the denture as before, The cast is coated with separating
medium and self-cure repair material is added to the denture then seated firmly on the cast.
Then trimming and finishing.

31. Thankyou
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