RETAINERS IN FIXED PARTIAL DENTURES
Submitted by-Apoorva sharmaintern
RETAINERS- The part of a fixed partial denture which unites the abutment to the remainder of the restoration.
Retainers with pontics
Abutment
Bridge
IDEAL RETAINER
Should cause least amount of destruction to the abutment
least destroys the outline form of the tooth
Marginal line should be Finished with great accuracy
Rigidity – withstand the 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
TYPE OF RETAINERS-1. based on the tooth coverage- full veneer crown partial veneer crown conservative retainers telescopic retainers2. Based on material being used- all metal retainers metal ceramic retainers all ceramic retainers all acrylic retainers
FULL VENEER CROWN- These retainers cover all the five
surfaces of the abutment Most retentive Ideal retainers Design can resist masticatory forces in
all direction
Disadvantages- Extensive tooth preparation
Gingival decay is prevalent
Reduced strength
PARTIAL VENEER CROWN- Preferred over full veneer crown Require less tooth reduction Guides for coronal contours Embrasure forms are pre-established
ADVANTAGES – - conservative tooth preparation - improved periodontal health as limited
contact between margin of restoration and gingiva
- marginal fit can be easily veryfied - unveneered portion of tooth can be
used for electric pulp testing DISADVANTAGES – - lacks retention - some display of metal
TYPES OF PARTIAL VENEER RETAINERS
1.Proximal boxes
2.Seven eight crowns
3.Reverse three quarter crown
4.Proximal half crown
1 Posterior three quarter crowns
2 anterior three quarter crown
3 pin modified three quarter crown
CONSERVATIVE RETAINERS- Require minimal tooth reduction Acid etching These dentures do not accept heavy
loads 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
Advantages- - non invasive to dentine - conservative preparation - reduced cost and chair side time - decreased tissue irritation –
supragingival margins Disadvantages- - plaque accumulation - bulky contours may be intolerable to
some patients - not ideal for replacing more than
one tooth
TYPES- Rochette bridge Maryland bridge Castmesh fixed partial denture
Virginia bridge.
ROCHETTE BRIDGE - Wing like retainer - Funnel shaped perforations MARYLAND BRIDGES - Mechanical retention - microporosities present on the tissue surface
of the retainer created by etching CASTMESH FPD - nylon mesh is placed on the tissue surface of
the retainer wax pattern to create the microporosities
- doesn’t require acid etching VIRGINIA BRIDGE - utilizes lost salt technique to create voids in
the cast metal retainer - this provides mechanical retention
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 Primary coping Secondary coping
Primary coping- functions to modify the morphology
of the tooth 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
ALL METAL RETAINERS-
Either can be partial or full veneer crowns
Strong enough even in thin sections
Advantages – - strength - high retentive qualities Disadvantages- - large amount of tooth reduction - adverse effects on tissues - vitality test not readily feasible - anesthetic – display of metal
PREPARATION- reduction- - non centric cusp – 1mm - centric cusp – 1.5mm margin- - chamfer – allows 0.5mm thickness
METAL CERAMIC RETAINERS-
They require more tooth reduction Can be fabricated over full veneer
crown or partial veneer crown
Advantages – - superior esthetics as compared
to complete cast crowns Disadvantages- - removal of substantial tooth
structure - subject to fracture - shade selection is difficult
PREPARATION- Incisal reduction – - 2mm Occlusal reduction – - 1.5 – 2mm - 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.
ALL CERAMIC RETAINERS- May be fabricated as full or partial
veneer crown Require maximum tooth reduction Porcelain requires sufficient bulk for
adequate strength
Advantages- - esthetically unsurpassed - good tissue response even with
subgingival margins Disadvantages- - reduced strength - least conservative - brittle –tend to fracture
PREPARATION- Incisal reduction- - 1.5 – 2mm clearance -this enables cosmetically pleasing
restoration -provides adequate strength Facial reduction- -1mm clearance Lingual reduction- -1mm clearance Margin- -shoulder preparation – 90 degree angle
ALL ACRYLIC RETAINERS-
Used for long term temporary fixed partial dentures
Not indicated for permanent restorations
OCCLUSAL ELEMENTS- Proper occlusal anatomy Definite cusp, ridges, grooves. The lingual surfaces of anterior teeth
have a definite concave surface. Incisal edge of anterior teeth are
rounded
DISTRIBUTION OF OCCLUSAL LOADS- Stress of occlusion in unworn teeth fall
very near the long axis. On worn teeth stress are spread over
wide and more dangerous area.
Unworn teeth Worn teeth
Forces directed along the long axis of the tooth.
Oblique forces.Causes destruction of the periodontium
CRITERIA OF SELECTING TYPE OF RETAINER- Abutment teeth are aligned parallel to
one another – full veneer crown can be given
Partial veneer crown are preferred for non carious abutments or abutments with large restorations but intact facial or buccal surfaces.
Endodontically treated tooth may have to be restored with core post before designing the retainer
APPEARANCE- Full veneer crown show superior
esthetics to partial veneer crown Anterior restoration – all ceramics Best to retain facial or buccal
surfaces of natural teeth as they provide best esthetics
In case with inadequate pontic space full coverage restoration can be designed for better appearance
Thank you