Retainer in FPD

Retainers in FPD
Restraining what is left
By: Ghida Lawand
Hind Tabbal

What is a Retainer?
It’s that component of an FPD which takes
support from the abutment tooth and provides
retention to the prosthesis.

Ideal Requirements:
1) Should cause least amount of
destruction to the abutment
2) Least destroys the outline form of
the tooth
3) Marginal line should be finished
with great accuracy
4) Rigidity  withstand requisite load

 Functional adaptation and protect the tooth
against its fracture
 Least destroys the cervical marginal ridge
 Positioned margins at less susceptible to caries
or recurrence of caries
 Preparation should be made without trauma to
the pulp or surrounding tissue
 Accurate complement to the lost tooth
structure
 Cleansable
 Esthetic

Retainers
Extracoronal
Complete
Crowns
-All Metal
-All Ceramic
-Metal Ceramic
Partial Veneer
Crowns
-3/4th crown
-Mesial half Crown
-7/8th crown
Intracoronal
-Inlay
-onlay
Radicular
-Cast Post
-Prefabricated post

Criteria of selecting type of retainer
Full Veneer crown
Partial Veneer crown
All Ceramic
Abutment teeth are aligned
parallel to one another
Non carious abutments
/abutments with large
restorations but intact buccal
and lingual surfaces

Classification of retainers
Based on the
tooth coverage
Based on the
location
Based on mode
of retention
Based on
material being
used

Based on the tooth coverage
Partial coverage
retainer
Full coverage
retainer
Conservative
retainer
Telescopic retainer

A- Full coverage
retainer
These retainers cover all the five surfaces of the abutment
tooth.

Advantages
 Contact area can be properly developed
 Embrasure area can be enhanced
 Buccal contours can be correctly developed
 Facilitate occlusal plane modifications
 Indicated for endodontically treated abutments
 Ideal for restoring edentulous area in patients with
craniofacial anomalies

Disadvantages
Extensive tooth preparation
Poor supportive tissue response
(subgingival finish line)
Gingival decay is prevalent
Poor esthetics (metal crowns), restricted to
posterior teeth

Indications
1. Short clinical crown
2. For a patient with a history of active caries and
poor hygiene
3. In both vital and pulpless teeth

4. Metal ceramic crowns and all ceramic crowns are used in
situations that require good cosmetic results with maximum
resistance and retention requirements.

It is an artificial metallic restoration used to cover the all surfaces of the clinical crown.
It is made only from metal, e.g. gold.
Can be either partial or full veneer crown.
Require minimal tooth reduction.
Strong even in thin sections.
Preperation:
Occlusal reduction:
 non centric cusp – 1mm
 centric cusp – 1.5mm
Margin:
chamfer – allows 0.5mm thickness
1. Full metal crown:

1.As single crown or as a bridge.
2.Only for posterior teeth.
3.In patients with high caries index.
4.For an endodontically treated tooth/or teeth.
5.For malalignment tooth/or teeth.
6.For teeth with a short occluso-gingival height.
7.For a badly broken clinical crown.
8. In a long span bridge.
Indications

1. In case of anterior teeth, for esthetic reasons.
2. In a situation where anther conservative preparation can be
used.
3. When less than maximum resistance and retention is needed.
4. When caries extend gingivally, as that the finish line cannot
be made.
5. In case of uncontrolled caries.
Contraindications

ADVANTAGES DISADVANTAGES
1. Great resistance form.
2. Great retention.
3. High strength.
4. Good protection for a tooth to
be restored.
5. Can modify occlusion in case of
overeruption.
6. Can modify tooth contour in
case of open contact or in buccal
or lingual contour in a tooth used
as a retainer for FPD.
7. Ideal restorations for teeth with
developmental defects.
1. Bad esthetics (especially for
anterior teeth).
2. Pulp vitality can-not be
detected.
3. Incipient caries can-not be
detected.
4. Extensive amount of tooth
reduction

Tare full cast crowns having porcelain or acrylic facing on facial or
lingual surface. They require more tooth reduction
• Can be fabricated over full veneer crown or partial veneer crown
• Indicated on teeth that require complete coverage & esthetic demand
• Can accommodate cast or soldered connectors
• Can afford high force—metal
Preparation:
Incisal reduction
- 2mm Occlusal reduction
- 1.5mm – for metal coverage
- 2mm – for metal with ceramic veneer
Margins
- facial surface- shoulder
- lingual surface- chamfer
- Shoulder must extend at least 1mm lingual
to proximal contact area.
2. Metal ceramic crown:

 Have the strength of cast metal crowns
with the esthetic of the all ceramic
crowns
 Have good retention.
 Permit easy correction of the axial
walls.
X Their preparation requires more tooth
reduction to provide sufficient space
for the restorative materials.
X Their facial margins for anterior teeth,
is often placed sub-gingivally which
increase the risk for periodontal
disease.
X The laboratory casts are expensive.
X A frequent problem is the difficulty of
accurate shade selection.

3. Non- metal crown (ALL Ceramic)
It is also called the jacket crown is an artificial non-metallic
restoration made of porcelain.
It is used to cover the all surfaces of the clinical crown. May be
fabricated as full or partial coverage crown.
Primary purpose: to achieve best possible esthetic results.
Risk of reduced restoration longevity—potential for fracture
Preparation:
Incisal reduction: 2mm clearance ( this enables cosmetically
pleasing restoration & provides adequate strength )
Facial reduction: 1mm clearance
Lingual reduction: 1mm clearance
Margin: shoulder preparation – 90 degree angle
3. Non- metal crown (ALL Ceramic)
It is also called the jacket crown is an artificial non-metallic
restoration made of porcelain.
It is used to cover the all surfaces of the clinical crown. May be
fabricated as full or partial coverage crown.
Primary purpose: to achieve best possible esthetic results.
Risk of reduced restoration longevity—potential for fracture
Preparation:
Incisal reduction: 2mm clearance ( this enables cosmetically
pleasing restoration & provides adequate strength )
Facial reduction: 1mm clearance
Lingual reduction: 1mm clearance
Margin: shoulder preparation – 90 degree angle

INDICATIONS CONTRAINDICATIONS
1. For anterior teeth (especially
incisors).
2. For severely discolored anterior
teeth.
3. over an existing post and core
substructure.
1. In Posterior teeth.
2. In case of tooth with short clinical
crown
3. In case of edge to edge or overbite
4. As a retainer for FPD.

1. Have the best cosmetic effect of
dental restorations.
2. Are very strong.
3. Are the best to use on the
incisors.
1. Have high risk of fracture
because they’re brittle.

All acrylic retainers
Used as temporary fixed partial dentures Not
indicated for permanent restorations

Advantages
Conservative tooth preparation
Guides for coronal contours
Embrasure forms are pre-established
Improved periodontal health as limited contact between margin
of restoration and gingiva.
Marginal fit and Complete seating of casting can be easily
verified before and during cementation
Margin accessibility for finishing and cleaning
Uncovered portion of tooth can be used for electric pulp testing
Acceptable esthetics.

Disadvantages
 Are not as retentive as complete coverage
retainers.
 There is a limited display of metal.
 Tooth preparation is difficult because only
limited adjustments can be made in the path
of placement.

Indications
• Intact or minimal restored teeth
• Normal anatomic clinical crown
• Teeth with adequate labiolingual thickness

Contraindications
1. Teeth with short clinical crowns
2. Thin teeth bucco-lingually
3. Teeth that are proximally bulbous
4. Poorly aligned tooth
5. Bad oral hygiene and high caries index
6. Retainers for long span bridges
7. Endodontically treated teeth
8. Malformed teeth

Types of partial coverage retainers
1
Posterior three quarter
crowns
2
Anterior three quarter
crown
3
Pin modified three
quarter crown

II. Partial coverage
1. ¾ crown:
Indications Contraindications
1. Carious or damaged tooth with
intact facial surface
2. As bridge retainer in short span
bridge
3. Long clinical crown
4. Splinting
1. Short clinical crown
2. Damaged facial surface of teeth
3. Long span bridge
4. Anterior teeth with thin labio-
lingual dimension
5. Malformed tooth
Ex: Pig shaped tooth, tilted tooth,
etc

Advantages Disadvantages
1. More conservative than full metal
crown
2. More esthetics as facial surface
remains intact
3. Pulp vitality test can b done as one
surface is un covered
4. Less gingival irritation
1. Less retentive than full coverage
2. Needs skill from operator
3. Metal display may occurs

2. ½ crown:
• It is a partial coverage restoration that restores the
occlusal surface (or incisal edge), the mesial surface
and a portion of the facial or lingual surfaces.
• This type is indicated for mesially tilted tooth.
3. Pin ledge:
• It is a technique that employs parallel long pins
prepared in the lingual or palatal surface of the clinical
crown, in order to increase retention of the restoration.
• These restorations used the both grooves and pins to
improve retention.

4. ¾ reversed crown:
• It is a partial coverage restoration that restores the occlusal
surface (or incisal edge), and three axial surface of the clinical
crown (the lingual surface is not included).
• This type is indicated for lower posterior teeth. And it is
useful for server lingual indications.
5. 7/8 crown:
• It is a partial coverage restoration that restores all surfaces of
the crown except the mesio-buccal cusp.
• This type is only used for the upper 1st molar.

6. Modified type:
Indications Contraindications
1. For both anterior and posterior
teeth.
2. When the coronal portion is intact.
3. When there is a good crown length.
4. as a retainer for FPD (short
edentulous span).
5. When there is a minimum occlusal
stress.
1. When maximum retention is
required.
2. in case of a thin or short clinical
crown.
3. for patient with high caries index.
4. When there is active periodontal
disease.
5. In case of mal formed tooth, e.g.
Bellshaped canine.

Advantages Disadvantages
1. Preservation of tooth structure.
2. More esthetic than full coverage
restorations.
3. The finish line is easy to place.
4. Less periodontal irritation due to
the less contact with the tissues.
5. Pulp damaged is reduced.
1. Less retentive than the full
coverage.
2. Difficultly of placing the grooves
and pins properly.
3. In some restorations, the metal is
displayed and this is not acceptable
by the patient.

Complete or Partial coverage?
(Periodontal point of view)
• The complete retainers accumulate more plaque,
which leads to gingivitis and increases pocket depth
than abutment with partial retainers.
• The difference may not be evident if the patient
practices meticulous oral hygiene.

• Complete retainers are performable in patients with
long span FPDs or splints with few abutment teeth.
• Partial veneer retainers have less resistance to
deformation than complete retainers.

C- Conservative retainers
• Require minimal tooth reduction
• Do not accept heavy loads, therefore indicated for
anterior teeth.
• Have a small metallic extension which are designed
to be luted directly onto the lingual surface of the
abutment tooth using resin cement.

Resin bonded FPD
Missing anterior teeth
Retainer with wings
Wings bonded to the
lingual surface of the
abutment teeth

Why resin-bonded FPD ?
• Conventional FPD’s requires abutment
preparation which leads to destruction of
adjacent teeth.
• Various solution tried for this problem but
not of much result oriented
1.Inlay retainer
2.Cantilever FPD
loss of PDL support of abutment teeth
3.Unilateral RPD
lack of retention stability and risk of
aspirated if dislodged

Classification of RBFPD
• Classified on the basis progression of
development:
–Rochettebridge
–Maryland bridge
–Cast Mesh
–Virginia bridges

Rochette bridge
 wing-like retainers,
 with funnel-shaped perforations through them to enhance
resin retention
 combined mechanical retention with a silanecoupling agent
to produce adhesion to the metal

Disadvantage
• Weakening of the metal retainer by the perforations
• Limited adhesion of the metal provided by the perforations
• Wear of composite resin
• Thick lingual retainers
• Plaque accumlation
• 50% fail in about 110 months

Maryland Bridge:
 Etched-metal prosthesis
 Done in either two step process or one step process –equally
retentive.
 Advantages over the caste perforated restorations:
 resin-to-etched metal bond can be substantially stronger than the resin-to-
etched enamel
 The retainers can be thinner and still resist flexing
 oral surface of the cast retainers is highly polished and resists plaque
accumulation

Two-step process
• Livaditisand Thompson
• Electrochemical pit corroding technique
• 1ststep
o 3.5 % Nitric acid at 250 mA/sq cm (current) for 5
min –non-beryllium-containing nickel-chromium
alloy
o 10% sulfuricacid at 300 mA/cm2 (current) for 5 min
-beryllium nickel-chromium alloy
• 2nd step :
18% HClfor 10 minutes in an ultrasonic cleaner bath

1-step
• McLaughlin
• Faster technique
• Combined solution of sulfuricand
hydrochloric acids placed in an
activated ultrasonic cleaner for 99
seconds passing electrical current.

Cast Mesh FPD
• Non etching method after casting
• Produce roughness before the alloy is
cast.
• Net-like nylon mesh –lingual surfaces
of the abutment teeth on the working
cast
• Covered by and incorporated into the
retainer wax pattern
• Mesh-like surface when the retainer
is cast
• Eliminates the need for etching

Advantage:
Use of noble-metal alloys
Disadvantage:
 stiff, making it somewhat difficult to adapt to detail of the
abutment tooth
 Wax runs too freely into mesh –blocks undercut compromising
retentivity

Virginia bridge
 Lost salt technique
 Particle roughened retainers by incorporating salt
crystals into the retainer patterns to produce
roughness on the inner surfaces

1. Sieved cubic salt crystals (NaCl) -
sprinkled over the outlined area sparing
0.5-1.0 mm wide crystal free margin
2. Retainer patterns were fabricated from
resin
3. Removed from the cast-resin was
polymerized
4. Cleaned with a solvent
5. Placed in water in an ultrasonic cleaner
to dissolve the salt crystals
6. Left cubic voids in the surface
Steps

 Non invasive to dentin with lingual
and proximal tooth preparation
including occlusal rest.
 Conservative preparation.
 Good esthetics.
 Tissue tolerant because of
Supragingival margin, and no
pulpal irritation.
 Reduced cost and less chair side
time
- Demanding technique and tooth
prep.
- plaque accumulation
- bulky contours may be intolerable
to some patients
- not ideal for replacing more than
one tooth
- Graying out of teeth that are thin
labiolingually.

INDICATIONS CONTRAINDICTIONS
• As retainers of FPD, on abutment with
sufficient enamel to etch.
• Splinting of periodontally compromised
teeth.
• Stabilizing dentition after orthodontic
treatment.
- In patients with sensitivity to base metal
alloys.
- When facial esthetic of abutment require
improvement.
- Inadequate enamel surface to bond eg;
caries, existing restoration.
- Incisor with extremely thin faciolingual
dimension.

D-Telescopic retainers
• These are used when path of insertion of the fixed
partial denture does not coincide with the long axis
of the abutment tooth.
• Indicated in tilted abutment.

• The design involves the fabrication of two copings
one over the other:
- Primary coping:
Functions to modify the morphology of the tooth and
helps to change the path of insertion.
- Secondary coping:
Designed to fit over the primary coping along the new
path of insertion.
• Thus accurate parallelism of the copings is necessary.

2. Based on location
• Extra-coronal (complete coverage or partial
coverage)
• Intra-coronal (Inlay / onlay)
• Intra-radicular (Post and core)

Intra-coronal Retainers
Intra-coronal retainers can either be
I. Inlay
II. Onlay

I. Inlay
• Inlay is defined as a restoration which has been
constructed out of the mouth from gold, porcelain or
other metal and then cemented into the prepared cavity
of the tooth.
• It is mostly used.
II. Onlay
• It is essentially an inlay that covers one or more cusp and
adjoining occlusal surface of the tooth.
• It is retained by mechanical or adhesive mean.

1. Onlay is used in large restorations
2. Endodontic ally treated teeth
3. Teeth at risk for fracture
4. Dental Rehabilitation with cast Metal Alloys
5. Diastema closure and occlusal plane
correction
6. Removable prosthodontic abutment
1. High caries rate
2. Young patients
3. Esthetics
4. Small restorations

1. Strength
2. Bio-compatibility
3. Low wear
4. Control of contours
1. Number of appointment
2. Higher chair time
3. Temporary Restoration
4. Cost
5. Technique sensitive
6. Splitting forces

Intra-radicular Retainers
• Radicular retained prosthesis consists of a post or dowel with an
attached core that obtains its retention and resistance to
displacement from the prepared root portion of an endodontically
treated teeth.
• While the root preparation retains the post, the core establishes
retention and resistance for a complete veneer crown that restores
the pulp less tooth to normal form and function.
• The post or dowel and core may be custom cast, where the
radicular retainer is fabricated to fit the root preparation or
prefabricated where the root preparation is designed to fit a stock
post and core is build up with silver amalgam or composite resin.

Post
1. Custom made
2. Prefabricated
Tapered smooth sided posts
Tapered serrated posts
Tapered threaded posts
Parallel threaded posts
Parallel serrated posts
Parallel smooth side posts

1. Detached dowel crown
(Davis):
All porcelain crown with a post that is
detached and can be placed on a
prepared root end by cementation of
both the post in the root and the
cementation of crown on the post.

1. When impossible to restore crown by
other means so that vitality can be
maintained.
2. Mostly on anterior teeth, occasionally on
posterior teeth.
3. When there is normal occlusal relationship.
4. Sufficiently long and thick root structure.
5. Only when peri-apical and periodontal
conditions are favorable.
1. Heavy and close bite cases.
2. Poor oral hygiene.
3. Patients with para-functional habits.
4. Thin narrow roots.

1. Esthetics.
2. Adequetely strong.
3. Permits alignment with other teeth.
4. Good tissue adaptability.
5. Easily removed for treatment of required.
1. Tooth must be non vital.
2. Weakening of root face and canal by
enlarging.

2. Richmond crown:
A dowel retained crown made for an endodontically
treated tooth using porcelain facing.
3. Detached post crown with a cast base:
When the coronal portion of the remaining tooth is
missing to a point below gingiva and it is impossible
to adapt the crown and root face, a cast metal base is
interposed between the base of the crown and root
face.
This cast base is rigidly attached to the dowel.

1. Tooth broken or destroyed by caries to a
point sub-gingivally.
2. Mostly anterior teeth, occasionally
bicuspids.
3. In cases with heavy bite.
4. Sufficiently long or thick roots.
5. All periodontal factors favorable.
1. Poor oral hygiene.
2. Thin and narrow roots.
3. If possible to design other variety, such as
core and jacket restoration.

1. Quite strong and lasting.
2. Strengthens remaining tooth structures.
3. Esthetics.
1. Tooth must be non vital.
2. Difficult to construct in comparison to the
restoration without a cast base.

3. Based on mode of retention
• Encircling the tooth (Full coverage )
• Mainly by grooves (Partial coverage)
• Mainly by Dowel pins (Pin ledge)
• Post in root canal
• Conservative restorations (Resin bonded)

4. Based on material being used
• All metal retainers
• Non-metallic retainers (Ceramic / Acrylic)
• Combined retainers (Veneered / full veneered)
• Resin bonded bridge retainers

FACTORS AFFECTING SELECTION
OF RETAINERS
1-RETENTION
A- amount of remaining tooth structure influence retentive
properties of retainers
B- teeth with extensive defective restorations or fractures may
need intentional endodontic treatment and post & core.
C- crown lengthening when caries, restoration, or fracture are
present.
D- crown morphology and quantity of sound enamel & dentin.
Resin bonded bridge needs intact enamel to be etched for
microretention.

2-ESTHETICS :
A- Drifting of teeth into edentulous area may lead to
reduce pontic space.
This affects selection of retainer.
B- Diastema may lead to exccessive mesiodistal width.
C-long clinical crown due to recession or bone loss
may need full coveraage retainer & gingival porcelain
D- precision attachment to replace unesthetic clasp
arm.
E – Porcelain on occlusal surfaces of post teeth is not
recommended unless opposing occluding teeth are with
porcelain occlusal surfaces.

3- AGE OF PATIENT
Below 18—20 years
A- large pulp size & high pulp horns lead to pulp
exposure
B- If a crown is made when the gingival attachment
level is high (at young age), the margin of restoration
will become exposed with nomal gingival recession
leading to poor esthetics .

4- EXISTING CARIES
A- Simple proximal caries (partial coverage crowns)
B - MO or MOD caries ( inlay retained restoration or full
coverage crowns)
5- Amount & direction of stress Deep overbite:
complete coverage
6- Type of opposing restoration
RPD + complete dentures create less force than
natural dentition, so use either partial or complete
coverage.
7- Size & position of abutment

8- Condition of abutment
Crown, roots, bone level, gingiva, mobility, tilting , pulp
vitality, post & core all affect retainer selection.
9- Caries Index poor oral hygiene +high caries index
necessitate full coverage retainers
10- length of edentulous span Increased span length needs
retentive & strong retainers (complete coverage
restoration)
11- Patient musculature males have heavy muscules
(complete coverage restoration)

References:
• A.E. Kahn, Partial Versus Full Coverage. J. Prosthet.
Dent. 10:167-178, 1960.
• Johnstons, Modern Practice in Fixed Prosthodontics
4th edition 1986.
• T.Shillinburg.Fundamentals of Fixed
Prosthodontics, III edition
• •T.Shillinburg.Fundamentals of Fixed
Prosthodontics, IV edition
• •Rosenstiel, Land, Fujimoto. ContemperoryFixed
Prosthodontics, III edition

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