Resin Retained Fixed Partial Dentures

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Resin retainedResin retained
fixed partialfixed partial
denturesdentures
INDIAN DENTAL ACADEMY
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 INTRODUCTION
Conservation of the tooth structure has been one
of the main goals of restorative dentistry.
Conventional procedures for the preparation of
abutment teeth often involve major removal of
tooth structure. If coverage is necessary for
cosmetic purposes or because of caries or pre-
existing restorations, this removal of structure is
acceptable.

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However, when the abutment is sound,
conventional full coverage procedures seem
quite radical. More conservative procedures,
such as partial veneer crowns or pin-retained
restorations, present limitations in esthetics and
retention. Many patients object to these
drawbacks and consequently choose removable
partial dentures which may not be used. Recent
innovations in the acid-etch technique have led
to new alternatives to traditional treatment for
esthetic and restorative procedures.

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 DEFINITION
According to the glossary of prosthodontic terms
Resin bonded prosthesis: A prosthesis that is
luted to tooth structures primarily enamel which
has been etched to provide mechanical retention
for the resin cement.
Early design incorporated perforation on the
lingual plate (Rochette bridge) through which the
resin bonded material passed to achieve a
mechanical lock; subsequently use of acid
etching of the metal plate (Maryland bridge)
eliminated the need for perforations.

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History
Date Contribution Personel
1955 Bonding to enamel Buonocore
1962 Development of composite resin Bowen
1973 First bonded cast alloy framework Rochette
perforated retainer for periodontal
splinting
1976 Electrolytically etched dental alloy Dunneries Bick
1977 Improved splint For missing anterior Howe Danley
teeth
1981 Developing of etched metal bridge Gerald McLaughlin

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 ADVANTAGES
1.Non invasive to dentin with lingual and proximal tooth
preparation including occlusal rest.
2. Conservative with undeniable patient appeal. The
preparations are supragingival so more tooth structure is
preserved.
3. Tissue tolerant because of supragingival margins without
gingival irritation.
4. Esthetically more appealing since only lingual surface of
anterior teeth are covered
5. Unaltered casts without removable dies.

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6. No anaesthesia hence less trauma to patient.
7. Reduced cost with less chair side time.
8. Excellent marginal seal especially with well fitting
casting.
9. Simplified impression procedures
10. Reversibility of procedures.
11. Rebonding possible.

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 DISADVANTAGES
1. Demanding technique and tooth modification is
necessary
2. Heavy dependence on laboratory for competent
treatment of cast metals.
3. Very thin or translucent anterior teeth are limiting factor
because of esthetics.
4. Usually restricted to single tooth replacement
5. No space and alignment correction

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6. Difficult temporization.
7. Uncertain longevity
8. Plaque accumulation may occur because design is
outside the dimension of the natural tooth and bully
contours are intolerable.
9. Patient selection is limited.
10. Caries may occur below the restoration
11. Gingival tissue irritation from application of acid
solutions.

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INDICATIONS
1. Retainers of FPD for abutment with sufficient
enamel to etch for retention.
2. Splinting of periodontally compromised teeth
3. Stabilizing dentition after orthodontic treatment or
movement.
4. Medically compromised and adolescent patients.
5. Replacement of congenitally missing tooth or teeth
lst by traumatic injuries especially in young
patients.
6. Bonded attachments for RPD
7. Adjusting occlusion.

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 CONTRAINDICATIONS
1. Patients with acknowledged sensitivity to base
metal alloy.
2. When facial esthetics of abutment require
improvement eg: stained, malformed or malposed
teeth.
3. Insufficient occlusal clearance to provide 2-3 mm
vertical retention. eg: abraded teeth
4. Inadequate enamel surface to bond eg. caries
existing restoration.
5. Incisors with extremely thin facilingual dimension
6. Long span involving 3 or more abutments.
7. Exceptionally demanding esthetics for adults.www.indiandentalacademy.com

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TYPES OF RESIN BONDED FIXED
PARTIAL DENTURE DESIGNS
1) Rochette
2) Maryland
3) Sockwell
4) Virginia
5) Fung

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Rochette type
Introduced by Alain Rochette in 1973. This type
uses small perforations in the retainer sections for
retention and is best suited for anterior bridges.
Care must be exercised in placing the
perforations to prevent weakening the framework.
Perforations that are too large or too closely
spaced will invite failure of the metal retainer by
fracture.
The perforations should be approximately 1 mm
apart and have a maximum diameter of 1.5mm.

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Each hole is countersunk so
that the widest diameter is
toward the outside of the
retainer.
When the bridge is bonded with
a luting resin, it is mechanically
locked in place by microscopic
undercuts in the etched enamel
and the countersunk holes in
the retainer.

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Advantages of this design are follows:
1) It is easy to see the retentive perforations in the
metal.
2) If the bridge must be replaced, the composite
resin can be cut away in the
perforations to aid in the removal process.
3) No metal etching is required.

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Disadvantages are as follows:
1) The perforations would weaken the retainers if
improperly sized of spaced.
2) The exposed resin is subjected to wear.
3) It is not possible to place perforations in
proximal surface or in the rest.

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Maryland type
Lividatis and Thompson of the University of
Maryland used a 3.5% solution of nitric acid with
a current of 250 mA/cm2 for 5 min,followed by
immersion in an 18% hydrochloric acid solution
in an ultrosonic cleaner for 10 min to etch the
internal surfaces of solid base metal retainers.
This technique was specific to non beryllium
nickel chrome alloy.
Thompson et al reported that 10% sulphuric acid
at 300 mA/cm2, followed by same cleaning
methods, would produce similar results in
beryllium containing nickel chrome alloy.

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McLaughlin proposed a faster technique by
immersing in a beaker of a combined solution of
sulphuric and hydrochloric acids placed in a
ultrasonic cleaner for 99 seconds while electrical
current is passed through the solution.
Lividatis reported acceptable results with a non
electrolyte technique by placing the restoration
in an etching solution in a water bath at 70ºC

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Advantages
 It is reported to have improved bond strength.
 Instead of perforations, the tooth side of the
framework is electrolytically etched, which
produces microscopic undercuts.
 The bridge is attached with a resin luting agent
that locks into microscopic undercuts of both the
etched retainer and the etched enamel.
 It can be used for both anterior and posterior
bridges

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Disadvantages
 Although this design has been reported to be stronger, it is
more technique sensitive because the retainers may not be
properly etched or may be contaminated before
cementation.
 Because the retentive features are not seen with the
unaided eye the etched surface must be examined with a
microscope to verify proper etching.

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Sockwell Type
 It incorporates both perforations and etching of
metal.
 The perforated type can be etched on the tooth
side of metal retainer to provide microscope
undercuts for added retention. This is especially
important in areas where perforations cannot be
placed.
 The etched metal type can be improved by
adding perforations to provide both types of
retention.

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Virginia Type
 Moon and Hudgins et al produced particle
roughened retainers by incorporating salt
crystals into the retainer patterns to produce
roughness on the inner surfaces.
 This method is also known as lost salt technique
 The framework is outlined on the die with a wax
pencil and the area to be bonded is coated first
with model spray and then with lubricant.
 Sieved cubic salt crystal (NaCl), ranging in size
from 149 to 250ųm are sprinkled over the
outlined area.

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 The retainer patterns are fabricated from resin
leaving 0.5 to 1.0mm wide crystal free margin
from the outlined area.
 when the resin has polymerized, the patterns are
removed from the cast, cleaned with a solvent
and then placed in water in an ultrasonic cleaner
to dissolve the salt crystals.
 This leaves cubic voids in the surface that are
reproduced in the cast retainer producing
retention for the fixed partial dentures
 Subsequent investigation showed that retainer
fabricated by this technique could be 30% to
150% more retentive than retainers prepared by
the electrochemical technique, depending on the
resin used. www.indiandentalacademy.com

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Fung Bridge
 Introduced by Fung 1998.
 It consists of prefabricated pontic with channel
inside it.
 The channel permits the placement of bridge
post.
Advantages:
 Minimum tooth reduction.
 Reduced appointments and less chair time.
 Esthetically pleasant.
 No expensive equipment

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Disadvantages
 Longevity is questionable.
 Requires occlusal adjustments.
Indication:
Single tooth replacement.
Contra indication:
Teeth with large pulp chambers.

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Step by step procedure.
 Try in of Fung bridge pontic.
 Preparation of locking slots on proximal aspect
of abutment tooth on edentulous side.
 Try in of bridge post and adjustment of bridge
post.
 Cementation with resin cement.
 Occlusal adjustments

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CLINICAL CONSIDERATIONS
There are three cardinal requirements for
construction of DBR
1) The framework must be strong enough to with
stand forces that will be applied to it.
2) The teeth themselves must be strong enough to
withstand pressures that will be applied to them
when the retainer is in place.
3) The secret of successful design in DBR in
making each tooth retentive. No tooth should be
able to break free of the retainer after cementation.

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 FACTORS IN RETENTION OF DBR
The total retention of any case depends on the following
The total surface area bonded, the quality of the bond, the
strength of the materials and the direction and magnitude
of the dislocating forces
Surface area
In etched metal framework the total retention of the case in
directly proportional to the total surface area that is
bonded. Maximum consideration in designing a
framework is to cover with etched metal, maximum area
of enamel that in consistent with good esthetics,
The alloy used is not flexible hence the framework cannot
extend into undercuts. Hence slight preparation of
abutment teeth is mandatory

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Resistance to torquing
The most important consideration in designing the
shape of metal framework is that it should be able to
resist all the occlusal and torquing forces. Resin cement
is exceptionally strong except for cleavage and peel. Due
to the rigidity of the metal, peeling is not generally
involved with the etched metal restorations. Cleavage is
however, a problem with resin cement that applies here.
The greatest weakness of the etched metal technique is
found when the cement must withstand cleavage forces.
If the case is designed so that it is not the cement but the
metal framework that withstand the cleavage forces, the
cement can easily provide retention against all remaining
forces.

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There are many directions from which forces can be
exerted on a tooth bound to an etch metal splint but the
major forces are in only' three directions or a
combination gingival, lingual and facial. If force in
applied only to the etched retainer and not the other
teeth in the splint, the splint will tend to remain stationary
while tooth attempts to move.
If force is applied gingivally, resistance to
displacement will be provided by the periodontium. Other
forces from this direction will be shear tensile stress.
Composite bond is extremely resistant to such stress
and is easily able to resist these forces. If the force is
lingual, the compressive strength of the composite bond
as well as resistance of the other teeth in the splint come
into play and resist forces in the lingual direction.

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If the stress is towards the facial direction it cannot
be easily resisted, the force exerted on the bond
between splint and tooth is in a cleavage direction. This
is because the tooth does not move linearly but rotates
around a point in the root. The application of force is at
the incisal edge of the tooth, the resistance to movement
is at the incisal edge of the framework and fulcrum is at
the axis of rotation of the tooth. The result is that the
increased length of the lever arm from the dislodging
force to the fulcrum creates a mechanical disadvantage
for retention.
Even for teeth that are slightly periodontally involved
the design of the metal framework is extremely important
in providing positive resistance against torqueing of the
teeth away from the splint in the facial direction.

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Buccal wraps: Perhaps the easiest way to create
positive resistance to torque is to provide the
restoration with a single path of insertion that is
approximately parallel to the long axis of the
teeth. This resistance is generally provided for by
the inclusion of buccal wraps. The buccal wrap is
simply an extension of metal around the buccal
surface of the tooth so that it resists any
movement of the tooth in buccal direction.
Retentive slots: It is necessary to provide positive
resistance to torquing by creating a single path of
insertion for the splint. This is usually
accomplished by placing small vertical slots in the
interproximal surfaces of the teeth to be splinted.

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Occlusal rests: The greatest forces on the
teeth in normal occlusion are occlusal
forces. The forces on a pontic in a vertical
direction can be considerable and as the
surface area of the pontics increase, the
total amount of force that must be resisted
by framework increases rapidly. The
inclusion of a positive occlusal rest of some
sort, which allows the metal framework to
resist these forces, eases the stresses on
the cement bond.

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Thickness of the metal
0.3 mm is the ideal thickness required of the metal where it
is covered with porcelain. Within pontic and connecting
areas minimum thickness should be lmm. Without this the
entire framework could bend or fracture in function.
Making clearance for the metal
Clearance should be made in areas of occlusal contact or in
areas where thickness is required for strength Clearance
can be obtained from opposing arch or both the following
factors should be considered in deciding where tooth
reduction should be made
a) Wear patters of the teeth involved
b) Type of restorations already present in involved teeth

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In fabrication of resin retained fixed partial dentures, all three
phases are necessary for predictable success:
1) Preparation of abutment teeth.
2) Design of restoration
3) Bonding of restoration.
 Whether anterior or posterior teeth are prepared common
principles dictate tooth preparation design.

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 A distinct path of insertion must be established, proximal
undercuts must be removed, rest seats to provide
resistance form and a definite and distinct margin must
be prepared.
 The amount of reduction is less because the enamel
must not be penetrated. If necessary, the opposing teeth
can be recontoured to increase interocclusal clearance.
It is essential that there should be sufficient enamel area
for successful bonding and that the metal retainers
encompass enough tooth structure to resist lateral
displacement.

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Bur selection
 Gingival margins and circumferential preparation
are easily accomplished with a chamfer or round
tipped diamond.
 Occlusal and incisal rest seats can be prepared
with a diamond or carbide inverted cone burs.
 Additional retentive features such as slots,
grooves or pinholes can be made with a tapered
fissure carbide bur.

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Step-by-step procedure
 Leave the margins about Imm for the incisal or occlusal
edge and Imm supragingival if possible. Definite lingual
ledges will provide resistance form for the retainers and
assist in positive seating during cementation. Wherever
possible to enhance resistance more than half the
circumference of the tooth should be prepared.
 Make an accurate impression Marginal fit is critical for
a resin retained restoration as for a conventional fixed
partial denture
 Fabricate a provisional restoration with autopolymerizing
acrylic resin.

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Anterior tooth preparation and frame
work design
 In designing an anterior prosthesis the largest possible
surface area of enamel should be used that will not result in
compromise of the esthetics of the abutment teeth.
 The retentive retainers (wings) should extend on one tooth
mesially and distally if a single tooth is replaced.
 If a combination of tooth replacement and splinting is used
the framework may cover more number of teeth.
 The gingival margin should be designed so that a slight
supragingival chamfer exists.

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 Any undercut enamel is removed at this time.
 The chamfer finish line may also extend incisally through
the distal marginal ridge area.
 The finish line on the proximal surface adjacent to the
edentulous space should be placed as far facially as is
practical. Abutments should have parallel proximal
surfaces.
 An optional slot, O.5mm in depth, prepared with a
tapered carbide bur, may be placed slightly lingual to the
labial termination of the proximal reduction.

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 The occlusion is assessed to ensure at least O.5mm of
interocclusal clearance for the metal retainers in the
intercuspal position and throughout the lateral and
protrusive excursive pathways. If inadequate clearance
exists, selective enameloplasty is performed.
 Occasionally additional clearance can be obtained through
reduction of opposing teeth. In presence of wear or
attrition on incisal edges, however, this is not advised.

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 A distinct rest seat is then placed in the cingulum area of
abutment tooth. This may consist of ledges similar to
those incorporated in a pin ledge preparation or it can be
a notch or flat plane perpendicular to the long axis of the
tooth. The objective is to provide resistance to gingival
displacement and to add rigidity to the casting. Rest
seats are prepared with an inverted cone bur. to facilitate
internal refinement.
 The framework is extended labially past the proximal
contact point to prevent torquing forces from dislodging
the prosthesis to the lingual.

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 To optimize esthetics the proximal wrap in the anterior
region may be achieved in part through using the metal
ceramic pontic.
 Preparation of mandibular anterior teeth is similar to that
for the maxillary incisors. Lingual enamel thickness is 11
to 50 percent less than for maxillary teeth and
consequently tooth preparation must be more
conservative. Combinations of periodontal splinting and
tooth replacement is commonly used in the mandibular
anterior region.

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Posterior tooth preparation and
framework design
 The basic framework for the posterior resin retained fixed
partial denture consists of three major components. The
occlusal rest (for resistance to gingival displacement) the
retentive surface (for resistance to occlusal displacement)
and the proximal wrap (for resistance to torquing forces).
 A spoon shaped occlusal rest seat is placed in the proximal
marginal ridge area of the abutments adjacent to the
edentulous space. An additional rest seat may be placed on
the opposite side of the tooth.

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 To resist occlusal displacement, the restoration is designed
to maximize the bonding area without unnecessarily
compromising periodontal health or esthetics.
 Proximal and lingual walls are reduced to lower their height
of contour to approximately Imm. The proximal wall are
prepared so that parallelism results without undercuts.
 The bonding area can be increased through extension onto
the occlusal surface provided it does not interfere with the
occlusion. Generally a knife-edge type of margin is
recommended.

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 Resistance to lingual displacement is more easily
managed in the posterior region of the mouth. A single
path of insertion should exist.
 The alloy framework should be designed to engage at
least 180 degrees of tooth structure when viewed from
the occlusal. This proximal wrap allows the restoration to
resist lateral loading by engaging the underlying tooth
structure. It should not be possible to remove a properly
designed resin bonded F.P.D. in any direction but
parallel to its path of insertion.

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 In general, the preparation differs between maxillary and
mandibular molar teeth on the lingual surface only. The
lingual wall of mandibular tooth may be prepared in a
single plane and the palatal surface of maxillary molars
dictates a two plane reduction due to taper of these
centric cusps in the occlusal two thirds and occlusal
function.
Occasionally, combination prosthesis can be used.
This type of prosthesis includes a resin-bonded retainer
on one of the abutment teeth and a conventional cast
restoration on the other.

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Resin to metal bonding
In the original design Rochette made six perforations
with a waxing instrument, thus providing mechanical
undercuts for the resin cements.
 A perforated design has a disadvantage of exposing the
resin to oral fluids, which may lead to problems of
abrasion of the resin or micro leakage at the resin metal
interface.
 A non perforated design avoids this potential problem
and can be highly polished, resulting in improved oral
hygiene.
 Presently non perforated retainers are recommended.

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Metal resin bonding can be classified as either
i] Mechanical or ii] Chemical
Primarily mechanical bonding is subdivided into:
1) Micro mechanical retention - which uses etching to
create microscopic porosities and
2) Macro mechanical retention - which relies on visible
undercuts usually with a mesh or pitted metal.
Chemical bonding generally employs tin plating of metal
framework and specific resin adhesives for metal and
enamel.

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Electrolytic etching:
In this procedure microscopic porosity is created in the fitting
surface of a nickel chromium framework by electrolysis. The
fabrication technique was developed at the University of
Maryland of School Dentistry, and, hence the prosthesis
sometimes referred as the "Maryland Bridge".
Procedure
 Clean the fitting surface of metal restoration with an air
abrasion unit with aluminium oxide.
 Cover the polished surfaces with wax and attach the
prosthesis to an electrolytic etching unit following the
manufacturers instructions.

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 A typical etching cycle will be 3 minutes in 10% H2SO4
with a current of 300 milliamp per square centimeter of
casting surface.
 Clean the etched surface ultrasonically in 18% HCI, then
wash and air-dry it.
 The etched surface must not be handled after this stage.
Chemical etching
A gel consisting of nitric and hydrochloric acid is applied
to the internal surface of the metal framework for
approximately 25 minutes.
As electrolytic etching is extremely sensitive, many
authors believe that chemical etching provides more
reliable results due to procedural simplicity.

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Macroscopic retention
In non-perforated retainer, porosity is cast in the pattern
itself rather than subsequently obtained by etching.
This is done in variety of ways:
 One techniques uses a special pattern to form a
meshwork on the fitting surface and the external lingual
surface is waxed to give a smooth finish that can be
highly polished.
 An alternative technique uses water soluble salt crystals
sprinkled onto the die and incorporated into the wax
pattern. The crystals are dissolved away before
investing.

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 An advantage of both these techniques is that any alloy
can be selected, whereas with electrolytic or chemical
etching the alloy usually must be nickel chromium.
 Additionally, try-in and bonding of the prosthesis can be
accomplished at the same appointment. These surfaces
are not likely to be damaged during handling as are the
very fragile etched metal surfaces.
 Disadvantages of the technique include difficulty on
adapting the mesh to create a closely fitting metal
framework and a potentially thicker metal framework
than can be obtained with a etched metal retainer

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 Also, the rate of microleakage along the cast mesh
composite resin interface is significantly greater than
along an etched metal resin interface.
Procedure:
I) Outline the mesh framework, trim it to the preparation
margins and adapt it to the master cast.
2) Develop the lingual contours, wax the pontic and
cutback and sprue the finished pattern as usual.

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3) Soak the cast in cold water to help release the pattern
and invest it normally.
4) Cast the framework and prepare the veneering surface
in the conventional way.
5) Buildup porcelain, polish the casting and clean the
fitting surface with an air abrasion unit.
6) The restoration is ready for try-in prior to bonding

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Tin plating
Tin plating is a recently introduced procedure
that can improve the strength of adhesive
cement to most metals. Precious alloys can be
plated with tin and used as frameworks for resin
retained fixed partial dentures. Tin forms organic
complexes with several specific adhesive resin
cements that result in significantly greater bond
strength.

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Bonding Agents
Composite resins play an important role in the bonding
of the metal framework to etch enamel. They conatin
I) Filled BisGMA composite resin (Bisphenol A glycidil
methacrylate).
2) TEGDMA (Triethylene glycel dimethacrylate).
3) 4META (4 methacrylyloxethyl trimellifate anhydrite).
4) UDEMA (Urethane dimethacrylate).

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Filled BisGMA composite resin: A
phosphate ester added to the monomer allows chemical
bonding to both the metal and the etched tooth enamel.
The powder contains approximately 75% quartz filler and
is almost insoluble in oral fluids. The material shows
excellent bond strength to non- noble metals and tin-
plated noble metals. It will not set in presence of oxygen.
To ensure a complete cure the manufacturers provides a
polyethylene glycol gel, which should be placed over
margins of restoration. This creates oxygen barrier and
can be washed away after the material has set.

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Cementation procedure:
1) Clean the teeth with pumice and water isolate them
with the rubber dam and chemically prepare them.
Currently 37% phosphoric acid is used to etch the
enamel and is applied for 30 to 60 seconds.
2) Place the cement on internal surface of the prosthesis
and completly seat the restoration.
3) Firm pressure should be exerted on the restoration
while excess uncured resin is removed prior to the
material completely setting.
4) The restoration should be held in place until resin has
polymerized.

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REVIEW OF LITERATURE
J. Ben Stolpa (1975) described an adhesive
technique for fixed partial dentures by using
aluminium foil and acrylic resin teeth stabilized
by adapting foil reinforced with acrylic resin to
form a matrix. He made Class III cavity
preparation on proximal mesial surfaces of
acrylic resin teeth and on proximal surfaces of
abutment teeth. A fresh mix of composite resin
was applied to the abutment teeth and Class III
cavity preparation of the pontic.

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Donald F. Howe and Gerald E. Denehy
(1977) described a technique which permits the
fabrication and attachment of an anterior fixed
partial denture without tooth preparation. The
fixed partial denture is attached to the lingual
surfaces of the abutment teeth utilizing a
composite resin and after acid etching enamel.
Since the frame had to be thick enough to
prevent flexibility that may adversely affect the
porcelain pontic, a potential for occlusal
interference exists.

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Dan Nathanson and Kambiz Moin (1980)
described a technique for replacement of single
anterior tooth. An artificial composite resin tooth
reinforced with orthodontic perforated metal
pads was used as a pontic and was bonded
directly to proximal and lingual surfaces of
adjacent teeth using composite resin after acid
etching.

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G.J. Livaditis and V. Thompson (1982)
described a technique for a retentive mechanism
that etches the inner side of the cast fixed partial
denture framework. They etched ceramo-metal
restoration with 0.5% nitric acid and it was then
bonded to the enamel surface utilizing the
technique for acid etching enamel. They
suggested that improved resin bonded retainers
provide innovative conservative and viable
alternatives to traditional fixed prosthodontics.

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J. Robert Eshleman, Peter C. Moon, Robert F,
Barnes (1984) during a 32 month period bonded
39 anterior fixed partial dentures on 37 patients.
All used the perforated metal retainer design.
From their study they concluded that minimal
tooth preparation enhances the bond strength
and can provide occlusal clearances. The most
common clinical failure is the bond to the
enamel which suggested that retainer design
should cover the largest possible surface without
placing margins in inaccessible areas.

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Gerald Borrack (1984) suggested that the
vertical path of insertion be developed so that
the restoration will not be displaced during
function. The force is distributed through
wraparound design that includes substantial
enamel coverage. This provides the greatest
surface area for bonding and a vertical path of
insertion. He also suggested that the surface to
be etched should be cleaned with an air
abrasive with 50ųm particle size aluminium
oxide. After etching, the black alloy surface must
be cleaned by placing the casting in 18%
hydrochloric acid and in ultrasonic cleanser for
10 to 15 minutes.

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Jeffery L. Hudgins, Peter C. Moon and
Florian J. Knap (1985) placed 27 particle
roughened resin-bonded fixed partial dentures
during 6 month period. From their study they
concluded that particle roughened metal retainer
possesses sufficient mechanical bond strength
for resin-bonded system. The weak link in metal
to etched enamel resin bonded system was the
resin-etched enamel interface. They advised to
cover as much surface as possible when resin
bonded fixed partial dentures were used.

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Timothy Brady, Asterious Doukoudakis
and Stephen T. Rasmussen (1985)
compared the retention of the etched metal
retainers and perforated metal retainer. Metal
disks were bonded to prepared tooth specimens
and stored in saline solution for 20 days and
were measured for shear strength. The etched
disks were capable of withstanding more than
four times the breaking load of the perforated
disks. They concluded that etched retainers are
superior to the perforated retainers.

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Asterios Doukoudakis, Bernard Cohen
and Andreas Tsoutsos (1987) described a
method for etching metal alloys containing
beryllium silicon, boron and all nickel base alloys
in following ways:
1) Blast the metal surfaces to be etched with
aluminium oxide.
2) Apply a drop ofthe met-etch gel (containing
aqua regia solution) on metal surfaces and
spread with a plastic instrument.
3) Place the framework in warm oven at 150°F for
3 minutes.

80
4) Remove the framework from the oven and rinse
off the gel with tap water. The met-etch gel is
reapplied for 7 to 10 minutes or until the gel
becomes greenish in color for reverification that
the metal has been etched properly.
5) Rinse the gel with tap water. If the etched
surfaces has a dark oxide film, clean with an
18% solution of hydrochloric acid.
6) Then clean the restoration with distilled water in
an ultrasonic cleaner for 5 minutes.

81
The advantages of using this method of chemically
etching are:
1) This conservative procedure can be performed
in two clinical sessions.
2) The etching of the framework can be effectively
controlled by the dentist or laboratory technician,
and,
3) If the metal framework is dislodged it can be
cleaned, etched and reattached during the same
appointment.
The disadvantage of this method is that it
cannot etch gold alloys and those with high
palladium content.

82
G.F. Priest and B.A. Donatelli (1988)
evaluated 47 patients receiving 58 resin bonded
fixed partial dentures for 2 to 51 month periods
(perforated, electrolytically and chemical etched
retainers). During the evaluation period, 10
prosthesis became dislodged, six restorations
were successfully rebonded and four were
remade. Six anterior and four posterior
restorations were dislodged and one restoration
containing more than one pontic was dislodged.
They made the following conclusion.
 Based on retention rates demonstrated in their
study the resin-bonded fixed partial dentures are
indicated as definite prosthesis.

83
 Chemically etched prosthesis offer better
retention than electrolytically etched or
perforated prosthesis.
 Compromises to established design parameters
adversely affect retention, particularly when
bonded enamel is minimal or resistance form is
inadequate.
 Prosthesis location does not appear to affect
retention.
 Differences seem to exist in retentive strengths
of cementing agents.

84
John O. Burgess and James G. McCartney
(1989) compared the load required to dislodge
acid etched resin bonded castings from various
tooth preparations like casting with grooves, one
half groove, pins and the labial extensions. They
confirmed the effectiveness of tooth preparation
designs to increase the resistance to lingual
displacement of resin-bonded fixed partial
dentures. The most effective preparations involved
distinct proximal grooves or labial extension.
Preparations without facial wraparound, grooves or
a single pinhole were significantly less retentive.

85
Vincent D. Williams, Keith e. Thayer,
Gerald E. Denely, Daniel B. Poyer
(1989) evaluated ninety-nine anterior and
posterior cast metal resin-bonded prosthesis
from a 10-year period. The results of 10 years
retrospective study showed that:
 Caries rate on retainer teeth was minor.
 The periodontium did not show a greater
incidence of periodontal disease and few
prostheses needed to remade.

86
M.H. EI Sherif, A. EI Messery and M.N.
Haihoul (1991) evaluated the effects on
retention of three metal surface textures:
electrochemically etched, air abraded and
particle roughened and four resin luting
materials (Compsan, Conclude, Microfill pontic,
Panavia EX) by measuring the magnitude of the
force require for the removal of resin-bonded
fixed partial denture retainers. The result of
study indicate that a retainer surface prepared
by air abrading with 250ų aluminium oxide was
superior in retention than others and Panavia EX
material could successfully retain the resin-
bonded fixed partial dentures.

87
Gerald Borrack, Walter A. Bretz (1993) did
a prospective study to determine if resin bonded
prosthesis would prove to be a long term
alternative to traditional complete coverage and
partial coverage restorations.the success rate of
127 restorations has been 92.9 %, with a mean
longevity of 5 years and 8 months.

88
Spiridon Oumvertos, Matthias Kern,
Franco Ferraresso and Jőrg Rudolf
(2002) did a in vitro study to evaluate the
influence of framework design on the fracture
strength of all ceramic RBFPD. Single and two
retainer designs of all ceramic RBFPD’s
subjected to quasistatic loading exibhited similar
strengths. Under cyclic loading of 25 N, the
single retainer design withstood more cycles.

89
Thomas Kershbaum, Burkhard Haastert
and Carlo P. Marinello (1996) analyzed the
long term survival of 1637 three unit RBFPD’s.
Parameters such as debonding , rebonding and
renewal of the restoration were used. After
5years
 66.1% of the inserted remained in place.
 If additional rebonding was computed the
survival was 82%.
 Reconstruction after one or more dislodgements
raised success rate to 87.1%

90
Yoshiyuki Hogiwara, Hideo Matsumura,
Seigi Tanaka, and Julian B. Woelful
(2004) described the use of a modified metal
ceramic resin bonded fixed partial denture
(MMC RBFPD) as a conservative solution for
replacement an incisor . It’s characteristics are
 Minimal removal of tooth substance.
 narrow lingual wing type retainers designed to
fit into shallow crescent preparations across
lingual marginal ridges of enamel
 use of larger proximal porcelain bonded to
each abutment.

93
Summary & Conclusion
Resin bonded fixed partial dentures offer the following
significant advantages to the dentist and the patient in
properly selected clinical situations:
1) Tooth preparation is reduced to a minimum.
2) The procedure is reversible.
3) Soft tissue management is simplified.
4) There is less problem with color matching,
5) Reduced cost and simplicity give high
patient acceptability

94
There are two disadvantages
1) Bonding procedures are more difficult and time consuming
than conventional luting techniques.
2) Occlusal adjustment at the try-in of the restoration is more
difficult because of the lack of a retentive crown- tooth
relationship.

95
 One of the basic principles of tooth preparation for fixed
prosthodontics is conservation of tooth structure. This is
the primary advantage of resin retained fixed partial
dentures and a careful patient selection is an important
factor in predetermination of clinical success.
 All factors considered, it seems that the use of the cast
metal resin bonded fixed partial denture should be
encouraged where sound abutment teeth exist and only
one or two teeth are missing.

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