Prof.

Eman Husseiny
dr. Eman Husseiny mohammed
Associate professor at prosthodontic department
Faculty of oral and dental medicine
zagazig University
2023-2024
 Clinical Removable
Prosthodontics (2)

@Sinaiunieg info@su.edu.eg www.su.edu.eg

 Steps of partial denture construction
Clinical procedures Laboratory procedures
History, Examination and diagnosis.
Diagnostic (primary) impression
 Diagnostic (study) cast.
 Surveying the study cast
 Construction of a special tray
Mouth preparation.
Final impression making.
 Make master cast. Surveying the master, Waxing-up the
framework.
 Investing the refractory cast. Casting the framework
 Finishing and polishing of the framework
Fitting the framework to the patient’s mouth.
Recording jaw relationships.
 Mounting the master casts on an articulator.
 Setting up of artificial teeth.
Esthetic try-in.
 PROCESSING
RPD insertion and follow-up.
 MOUTH
PREPARATION

@Sinaiunieg info@su.edu.eg www.su.edu.eg

 MOUTH PREPARATION
• Oral surgical procedures
• Periodontal therapy
• Operative and endodontic treatments
• Correction of occlusion
• Fixed prosthesis
• Orthodontic treatment
• Abutment teeth preparation
 Oral surgical procedures
• Extraction
o Non restorable teeth.
o Remaining roots
o Impacted or unerupted teeth.
• Palatal or mandibular tori.
• Frenum and muscle attachments
• Preprosthetic surgical such as
o Ridge augmentation
o Vestibular extensions.
Remaining roots
Non restorable teeth
Impacted second premolar and tilted
first premolar require extraction
 Rule 1
Applegate’s rules
• Classification should follow rather than precede extraction that might alter the
original classification.
Tori
Tori
ANTEROPOSTERIOR PALATAL BAR
ANTEROPOSTERIOR PALATAL STRAP
(CLOSED HORSESHOE)
HORSESHOE OR U-SHAPED
CONNECTOR
Frenum and muscle attachments
 Periodontal therapy
• Scaling and root planning.
• Elimination of local irritating factors. such as
overhanging amalgum and open contact.
• Pocket curettage, gingivectomy and flap operations.
• Correction of traumatic occlusion.
• Splinting of abutment teeth. by a fixed restorations or by
the partial denture (e.g. continuous clasp and swing-lock
partial denture).
Plaque and calculus
Gingival inflammation
Gingival inflammation
Operative and endodontics treatments
 Correction of the occlusal plane

1) Reduction of cusp heights.

2) Cast onlay.

3) Full crowns.

4) Endodontic therapy and crown.

5) Extraction of severely malposed tooth.

 Common occlusal disharmonies
Tilting and super eruption of second and third molars:
If the molars are not severely tilted,
Selective grinding
Reduction of cusp heights.
Metal template
 When more than a moderate amount of tooth
reduction is found necessary

• Fixed bridge
• RPD. with Onlays
• Orthodontic repositioning of the tilted molars.
Fixed bridge
Crown
 RPD. with Onlays

In severly tilted abutments , the extended occlusal rest may take form
of an onlay to restore occlusal plane
contoured restoration on tipped molar to avoid inclined plane effect.
(A) Buccal view. B) Mesial view. C On-lays on multiple abutments and
joined together during casting to help m splinting periodontally weak teeth.
Orthodontic repositioning of the tilted molars.
Mesial tilting of lower third molar corrected by
orthodontic treatment
If the molars are severely tilted and
modification is not possible
Root canal treatment and over denture
 If the molars are severely tilted forward and
supererupted, and modification is not possible

Extraction is necessary.
 Fixed restoration
• Restore coronal contours
• Improve occlusal plane
• provide ideal rest form
• Splint the abutments (pier abutments)
• Path of insertion
Reestablishment of Arch Continuity
Pier abutment
VII.Abutment teeth
preparation
 Abutment teeth preparation
1. Reshaping the abutment teeth
a) Guiding planes preparation
b) Changing height of contour
c) Creation of retentive undercuts
2. Crowns
3. Rest seats preparation
a) Occlusal rest seat preparation
b) Lingual or cingulum rests
c) Incisal rest seat preparation
 Guiding planes preparation
Reciprocation
 Guiding planes on the proximal walls
 Stability
 Esthetics:
 Increase retention by frictional resistance.
Bracing and stability
• Guide planes
Esthetics
dr.Eman Husseiny Mohamed
 When a maxillary cast,
containing an anterior edentulous
area, is surveyed with the occlusal
plane horizontal it will often be
found that there are undercuts on
the mesial aspects of the
abutment teeth.

Fig. 19 Appearance

dr.Eman Husseiny Mohamed

 The mesial gap can be
avoided by giving the cast a
posterior (heels down) tilt so
that the analyzing rod is
parallel with the mesiolabial
surface of the abutment
tooth.
Fig. 20 Appearance

dr.Eman Husseiny Mohamed

 With this posterior path of
insertion the saddle can be
made to contact the abutment
tooth over the whole of the
mesiolabial surface and a
much better appearance
results.

Fig. 21 Appearance

dr.Eman Husseiny Mohamed

Increase retention by frictional resistance.
Preparation
Occlusogingivally
2-4 mm in length
Flat on the occlusal third
Buccolingually
3-4 mm in width
Curved in harmony with
tooth contour.
 Changing height of contour
• Retentive arm located no higher than the
junction of the gingival and middle
thirds.
• This position
– Enhances esthetic
– Provides mechanical advantage.
High survey line places clasp too high
and may cause occlusal interference
Lowering survey line by enameloplasty
 Creation of retentive undercuts

• Gentle depression not a pit or hole.

• Round ended tapered diamond stone.
• Slight concavity
• 0.01 inch deep,
• 4 mm in mesiodistal length and
• 2 mm in occlusogingival height
Crowns
 Crowns
When dose make crown for RPD
1. When correction of unaccepted tooth contour cannot be achieved
through enamel modification alone
2. To restore badly decayed crown
3. Reestablish occlusal plane
4. To create proper rest especially in anterior teeth
5. To create adequate retentive undercut for direct retainer and guide plane
when inadequate contour exists
 Crowns
• Wax knife is used to carve the guiding plane on the surveyor.
• Hand carved to place the height of contour. In the middle third of
the lingual surface reciprocal clasp arm. Buccal surface to receive
a retentive clasp arm.
• Undercut gauge.
Crowns
Crown for badly decayed second
premolar with rest seat prepared
Crowns for molars to reduce excessive buccal
undercut
Contouring the wax pattern
Guide plane by surveyor
The pattern is hand carved to place the height of contour to
receive a reciprocal clasp arm and a retentive clasp arm.
 Depression is added to the preparation to
accommodate the depth of the occlusal rest
Rest seats preparation
Importance of rest
seats preparation
 Direct the forces of mastication parallel to long axis of the
abutment.
Prevents the gingival displacement of a RPD.
Maintains the relationship between a clasp assembly and the tooth.
In certain applications a rest may act as an indirect retainer.
It may be used to close a small space between teeth, which restoring
continuity of the arch and preventing food impaction.
Direct the force vertically
Avoid occlusal interference
 Prevents the gingival
displacement of a RPD.
 Methods of preparing
abutment for posterior rest
Rest seats preparation
The tissue surface spoon shape.
Teeth marginal ridges should be reduced
 Occlusal rest seat preparation
Prepared in
– Sound enamel
– Crowns
– In existing crown.
– In new cast crown
– Inlay
• An amalgam restoration
 Preparation
• Follow proximal guiding plane preparation.
• Outline by No. 8 round bur.
• No. 6 round point form spoon shape
• Smooth with no 4 round steel bur
• A fluoride gel applied.
 A variety of burs may be used in the
preparation of rest seats.

• Round burs
• Tapered cylinders
When using a round bur, care must be taken to
ensure that mechanical undercuts are not created
Thickness of the rest is checked by interocclusal
wax record
  Occlusal rest seat preparation in existing crown is the same as in sound
enamel. To avoid perforation of the crown the rest seat can be made
wider to compensate the shallow preparation.
 In new cast crown, after tooth preparation for crown is complete, a
depression is added to the preparation to accommodate the depth of the
occlusal rest. Then the occlusal rest seat is prepared in the wax pattern

Depression is added to the preparation to

accommodate the depth of the occlusal rest
REST PREPERATION FOR EMBRASSURE CLASP

Left, Preparation of two rest seats for embrasure clasp. Middle; the preparation
should extend buccally and lingually. Right; a cylindrical diamond stone held
horizontal is used for this extension.
Lingual or cingulum rests
 Indications
• No posterior tooth
• On maxillary canine
• Multiple rests on incisors
 Design
1-The rest seat is half moon shaped when viewed from the lingual. The
broadest portion is in the middle of the lingual surface and becomes less
broad as it approaches the proximal surface

2- Rest is V shaped when viewed from the proximal, with rounded line
angles. The V shaped preparation direct the force into apical direction along
the long axis of he tooth.

3- Mesiodistal length of preparation should be a minimum of 2.5 mm,

labiolingual width about 2 mm, and incisal apical depth a minimum of 1.5
mm.
Design
 Preparation
To prepare a rest seat in enamel there should be:
a- Prominent cingulum.
b- Good oral hygiene.
c- Law caries index.
Incisal rest seat
 Indications
• On mandibular canine
• For indirect retention.
 Disadvantages
• Greater mechanical leverage than lingual rests
The display of metal
Design
Prepared on proximal line angle
(distal)
• From facial floor is concave and inclined towards the center of the tooth to direct the
forces along the long axis of the tooth.

The outline form of the rest seat is saddle shaped (Convex), with buccal and lingual
bevel, when viewed from the proximal.
 Preparation
• Cut by tapered cylindrical stone.
• Flaring the edges and beveling the buccal and lingual
walls with finishing bur.
• Smoothen by rubber points.
 THANK YOU

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