3. ● As the name implies, these are fixed partial dentures,
which are cemented onto the abutments using special
resins.
● Composite resin bonded/retained fixed partial dentures
were developed from noninvasive, micro-retentive
techniques used in restorative dentistry."
10. ● one or more pontics supported by thin metal retainers
placed only on the lingual and/or proximal surface of
the abutments.
● Retention in these prostheses relies on the adhesive
bonding between etched enamel and the metal casting
(retainer).
11. ● They are held in place by resin, which locks
mechanically into:
a. The microscopic undercuts present on etched
enamel
b. Undercuts present in the casting.
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12. Indications
● Retainers of fixed partial dentures for abutments with
sufficient enamel to etch for retention.
● Splinting of periodontally compromised teeth.
● Stabilizing dentitions after orthodontics (permanent
● retainers).
● Medically compromised, indiligent and adolescent pati-
ents who cannot cooperate with long sessions of
therapy.
13. Contraindications
● Patients with an acknowledged sensitivity to base metal
alloys (NI),
● When the labial aesthetics of abutments require
improvenment.
● Insufficient occlusal clearance to provide 2 to 3 mm
● vertical frictional retention in the axial walls. E.g.
abraded teeth
14. ● Deep vertical overbite.
● Inadequate enamel surfaces to bond. E.g.
extensive caries, existing restorations.
● Incisors with extremely thin faciolingual
dimensions.
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15. Advantages
● Noninvasive to dentin with lingual and proximal tooth
preparation including occlusal rests.
● Decreased pulpal Irritation
● Conservative with undeniable patient appeal/comfort.
● Decreased tissue irritation due to the placement of
supragingival margins"
● Does not require cast alterations or removable die
preparation.
● Reduced cost with less chair time.
16. Disadvantages
● Criteria for choosing the patient are not discrete.
● Demanding technique and tooth preparation- Even
minor laboratory errors cannot be corrected easily.
● Plaque accumulation may occur because design is
outside the dimensions of the natural tooth.
● Bulky contours may be intolerable in some patients.
Patient expectations of esthetics are high but routine
results are not outstanding
● Not ideal for replacing more than one tooth.
● Graying of the incisal surfaces especially in labio
lingually thin teeth,
17. Types of Resin-bonded Fixed Partial
Dentures
Based on the technique used to finish the tissue surfaca
resin-bonded fixed partial denture can be classified as:
● Rochette bridge
● Maryland bridge
● Cast mesh fixed partial dentures
● Virginia bridge
18. Rochette Bridge
● Rochette was the first to design a resin-bonded
prosthesis (1973)
● He used wing like retainers with funnel shaped
perforations with the base towards the tooth surface
19. ● He also used silane-coupling agents for
additional retention.
● This was one of the most widely accepted
designs
● Etched retainers coated with pyrolyzed silane
showed up to 47% superior retention.
19
20. ● The major disadvantage of Rochette Bridge is that the
resin exposed through the metal perforations is subjected
to external stress, abrasion and marginal leakage.
20
21. Maryland Bridges
● Many scientists developed different designs to overcome
the shortcomings of Rochette bridges;
● Dunn and Reisbick used electrochemical pit corrosion to
study ceramic bonding to base metals
● Tanaka et al. studied the retention of acrylic resin on
metal copings.
23. ● Finally, Livaditis and Thompson from University of
Maryland School of dentistry used Dunn's study and
developed Maryland bridges
24. ● Here mechanical retention was developed by the micro
porosities present on the tissue surface of the retainer.
● Micro-porosities are created by etching the tissue
surface of the retainer
25. ● Etching Technique
● The suggested etching techniques that can be employed
while fabricating Maryland bridges can be broadly
divided into:
1.ELECTROCHEMICAL ETCHING.
2.NONELECTROCHEMICAL ETCHING.
26. Electrochemical etching:
● Here etching is done using a chemical electrolyte in the
presence of an electrical gradient.
● Before etching, the retainer is coated using paraffin wax.
● The Wax should cover the entire retainer except for the
area to be etched.
27. ● For non-Beryllium Nickel Chromium alloys: Etching is
done in two stages.
In the first stage, the retainer is immersed in 3.5% nitric acid
unders a current of 250 mA for 5 minutes.
Next the retainer is cleaned by immersing it in 18% HCl in an
ultrasonic cleaner for 10 minutes
28. ● For Beryllium containing Nickel Chromium alloys: It is
also a two-step technique.
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30. Disadvantages is electrochemical etching:
● Expensive.
● Very sensitive technique.
● Tedious procedure, difficult to Control the area to be
etched
31. Non-electrochemical Etching:
● Commonly used nonelectro chemical etching techniques
include:
● Livaditis proposed a technique wherein Nickel-Chromium
Beryllium alloys were successfully etched In an etching
solution placed in a water bath for one hour at 70 Degree
Celsius
32. Advantages of nonelectrochemical
etching
● Does not require special equipments.
● Etching is comparable to more expensive techniques.
● The prosthesis can be fabricated and bonded in two
stages.
33. Cast Mesh Fixed Partial Denture
● Here a nylon mesh
is placed on the
tissue surface of
the retainer wax
pattern.
● The nylon mesh is
placed on the cast
before fabricating
the wax pattern.
● These retainers do
not require acid
etching
34. Drawbacks of this design include:
● The nylon mesh may not adapt well to the cast during
pattern fabrication
● The wax may flow in between the mesh locking all the
undercuts.
35. Virginia Bridges
● These are resin bonded fixed partial dentures which use
particle roughened retainers.
● 1hey were proposed by Moon and Hudgins.
36. ● The retainer wax patterns are fabricated using resin.
● 150-250 um salt crystals are sprinkled on the cast prior
to resin fabrication.
● The salt crystals get incorporated onto the tissue
surface of the resin patten. The salt crystals are
dissolved and the resin pattern is invested and cast.
37. ● Dissolved crystals will produce voids in the
resin pattern ('Lost salt technique").
● These voids will also be reproduced in the cast
metal retainer and they help in mechanical
retention
39. ● No surface treatment of the retainer is necessary.
● Air abrasion with aluminum oxide is sufficient.
● Tanaka et al. proposed few techniques to improve the
bonding of these dentures:He suggested the immersion
of the retainer in sulfuric acid for proper oxide layer
formation.
40. ● For noble metal alloys, he suggested inducing
a heat accumulated copper oxide deposition.
This gives the necessary oxide layer.
● He also proved that air abrasion with
aluminum oxide aids to improve retention.
41. Advantages
● Even noble metal alloys can be used.
● Surface treatment of the retainer is not
necessary.
42. Steps in the Fabrication of a
Resin-bonded Fixed Partial Denture
The steps in the fabrication of a resin-bonded fixed partial
denture can be grouped into three major categories.
..predominantly in relation to Maryland bridges.
● Preparation of abutment teeth.
● Fabricating the provisional restoration.
43. Preparation of Abutment Teeth
common principle are followed during tooth preparation.
● Single path of insertion.
● Proximal undercuts must be removed.
● Rest seats should provide good resistance form
● (posterior teeth only)
● The prepared area should have definite and distinct
margins.
44. Principles of Tooth Preparation
● The margins of the prepared area should be at least
1mm away from the incisal/occlusal edge, and 1 mm
away from the gingival margin
● Definitive lingual ledges should be formed during tooth
preparation.
● This will help to provide resistance form for the retainer,
and assist in positive (proper) seating during
cementation.
45. ● Sometimes, the preparation can be extended more than
180° of the tooth circumference in order to enhance
retention
● Marginal fit is important for resin-retained restoration
just as for conventional fixed partial denture.
46. Fabricating the Provisional Restoration
● An accurate impression should be made of the prepared
tooth.
● It is vital for the impression to reproduce the small
preparation done on the tooth.
47. ● After impression making, a provisional restoration made
of auto-polymerizing acrylic resin should be fabricated
and inserted.
Preparing a provisional restoration for such cases poses
certain challenges, namely:
● -It is difficult to achieve good retention with minimal
tooth preparation.
48. ● Sometimes, a removable appliance may be sufficient, but
the provisional restoration should stabilize the
abutments.
● Significant and rapid tilting or supra eruption of the
abutment teeth can occur, particularly in younger
patients.
50. Design of a Resin Bonded Prosthesis
● The design of the prosthesis varies for anterior and
posterior teeth replacements.
● Hence, we shall discuss about the design of anterior and
posterior replacement separately.
51. Design of Anterior Resin
● For an anterior prosthesis, enamel preparation should
extend over the largest possible area, without
compromising aesthetics.
● If a single anterior tooth is to be replaced, the retainers
(wings) should extend over at least one tooth on either
side of the edentulous space.
● If two teeth are being replaced, the retention wing
should extend over two teeth on either side (double
abutments).
52. ● Design considerations for an anterior resin
bonded fixed partial denture: The following
design concepts should be considered while
designing an anterior resin bonded fixed
partial denture.
53. ● Sufficient lingual clearance about 0.6-0.8 mm (1.0 mm is
optimal), should be provided for occlusion.475
● A cingulum rest seat should be prepared. This acts like a
vertical stop against occlusal forces
A single path of insertion should be created (usually in
the incisogingival direction along the proximal surface
54. ● There should be an identifiable supragingival finish lin e
about 1 mm above the crest of tissue
● An additional 0.2 mm relief should be provided to
accommodate protrusive movements of the mandible
55. ● Two plane proximal facial extensions without metal
display
● may be provided for additional retention
56. Principles of Posterior Tooth Preparation
● Posterior tooth preparation consists of preparing three
major components namely:
● The occlusal rest (for resistance to gingival
displacement)
● Lingual segment of the proximal reduction done using a
flat end tapered diamond.
● The retentive surface (for resistance to occlusal dis-
placement)
● The proximal wrap (for resistance to torquing forces).
57. ● Occlusal Rest Seat
● It should be spoon-shaped and placed on the proximal
marginal of the abutment adjacent to the edentulous
area
● Any design modification, which is incorporated into the
prosthesis, should be harmonious with the
predetermined path of insertion.
58. Design of a Posterior Resin-bonded
● Posterior resin-bonded fixed partial dentures should be
designed to withstand more occlusal forces. Here,
aesthetics is not a major concern
59. ● Retentive Surface
● Proximal and lingual axial walls should be reduced to
move their height of contour more cervically
● The height of contour should be about 1 mm above the
crest of the free gingiva.
● Knife-edge type of margin is recommended.
60. ● Proximal Wrap
● The alloy framework should be designed to engage
atleast 180 degrees of tooth structure when viewed from
the occlusal surface.
61. ● Bonding of Resin-bonded
● Fixed Partial Dentures
● As the name implies, an adhesive resin is used to cement
a metal retainer onto the abutment.
● The type of bonding that exists between the metal and
the resin can be either mechanical or chemical in nature.
62. ● In the original design, Rochette made six perforations on
the retainer using a warming instrument.
● This provides mechanical undercuts for the resin cement.
● The major disadvantage of the Rochette's perforated
design is that the resin is exposed to the oral fluids,
which may lead to abrasion of the resin or microleakage
at the resin-metal interface.
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63. ● Mechanical bonding of resin
● Retention obtained from mechanical bonding
can be either macroscopic or microscopic in
nature.
● Macroscopic retention is by mechanical
interlocking (Rochette's perforated design),
● Microscoplc retentlon is by electrolytie etching
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64. ● Microscopic retention or Electrolytic etching
● In this procedure, microscopic porosities are created on
the tissue surface of the nickel chromium framework by
differential electrolytic etching.
● The fabrication technique was developed at the
University of Maryland School of Dentistry and the
prosthesis is sometimes referred to as the 'Maryland
Bridge
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65. ● Procedure
● Wax pattern of the framework Is fabricated and cast
using nickel-chromium metal-ceramic alloy.
● Different alloys require different etching procedures.
● It is important to use an alloy that has been well tested.
● The pontic is fabricated using porcelain in the
conventional manner.
66
66. ● The pontic is glazed and stained after try-In.
● The tissue surface of the prosthesis should be sand
blasted using aluminum oxide.
67
67. ● The next step involves acid etching the tissue surface of
the retainers.
● Acid etching is done by immersing the metal retainer in
an acid.
● The areas that have to be protected are coated with
paraffin wax.
68
68. ● After blocking out the external surface of the retainer
with wax, the prosthesis should be attached to an
electrolytic etching unit
69
69. ● A typical cycle consists of 3 minute immersion in 109%
HSO, under a current of 300 nmilliamps per square (other
etching cycles were discussed before).
● Next the etched surface should be cleaned ultrasonically
in 189% HCl and then washed and air dried.
70
70. ● The etched surface must not be handled (touched) after
this stage
71
71. ● Macroscopic retention
● This can either be done by Rochette's method of per
foration or by fabricating the pattern with macroscoplc
surface porosities.
● We have already described Rochette's design previously.
● Hence in the following section, we will discuss only about
creating macroscopic porosities
72
72. ● Creating macroscopic porosities: This can be done by two
● methods discussed below. The advantage of both these
techniques is that any alloy can be selected.
● Altering the design of the wax pattern. A special wax
pattern witha plastic mesh on the tissue surface and a
polished external surface is fabricated and cast.
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73. ● The cast retainer will have a meshwork on the tissue
surface, which aids in mechanical interlocking of the
resin.
● Dentures fabricated using this technique are called cast
mesh fixed partial dentures
74
74. ● Incorporating water soluble salt crystals "Lost salt
technique
● Here water-soluble salt crystals are sprinkled onto the
die before fabricating the retainer pattern. Hence, the
crystals line the tissue surface of the wax pattern. The
retainer patterns are first fabricated using resin.
● The resin is polymerized and the salt crystals are
dissolved by washing and ultrasonic cleansing
75
75. ● The dissolved salts form voids on the tissue surface of
the resin pattern.
● The resin patterns with the voids are invested, burned
out and cast.
● The cast metal retainers will have the same voids, which
act as centers for mechanical retention.
● This technique is followed in Virginia bridges
76
76. ● Chemical bonding of resin
● Chemical bonding between the resin and the metal
retainer can be produced by chemical etching or tin-
plating or using
● chemical adhesives.
● Chemical etching
77
77. ● A gel consisting of Nitric and Hydrochloric acids applied
to the internal surface of the metal framework for
approxmately 25 minutes.
● As electrolytic etching s extremely technique sensitive,
chemical etching may be mnore relable as it is a single
procedure
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78. ● Tin-plating
● Tin has the ability to form organic complexes with
several specific adhesive resins resulting in significantly
greater bond strengths.
● Precious alloys can be plated with tin and used as
frameworks for resin retained fixed partial denture.
79
79. ● Bonding Agents (Cements)
● Composite resins play an important role in the bonding
of the metal framework to etched enamel.
● Other resin adhesives that are commonly used include, 4
META (4 methacryloxy ethyl trimellitic anhydride),MDP (O-
methacryloylo-xyde cyl dihydrogen phosphate).
80
80. ● These resins do not require acid etching as they bond
chemically with the retainer.
● An opaque composite resin can be incorporated into the
resin cement to minimize graying effect.
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