R ESTORATIVE D ENTISTRY AND P RIMARY DENTAL CARE
Resin-retained Bridges Re-visited
Part 1. History and Indications
Geoffrey St George, Ken Hemmings and Kalpesh Patel
Resin-retained bridges have been used
clinically since the 1970s, and offer a
more conse rvati ve approach to the
restoration of edentulous spaces than
conventional bridgework. They are
easy to place, cheap to fabricate and
have been shown to be cost effective.
D espite this, they are not f requentl y
used in genera l dental pra ctice a nd
they have an undeserved reputati on
for failure.
Since their initial introduction, they
have undergone a number of changes
to their method of retention, and the
materials used in their constructi on.
This has resulted in a predictable, aes-
thetic restora tion which, barring the
use of implants, is often the treatment
of choice whe re teeth adjacent to an
edentulous space are minimally or not
restored.
This first article details the history,
advantages, indications, and designs of
resin-retained bridges.
KEY WORDS: D ENTURE, PARTIAL, FIXED, RESIN - BONDED; D ENTAL BONDING; RESIN C EMENTS; TOOTH PREPARATION, PROSTHODONTIC
History
Resi n-retained bridges have been
used clinically for nearly 25 years,
and today are considered to be
capable of producing long lasting,
aesthe tic results (Figure 1). Their
Figu re 1
A resin- retain ed bridg e replacin g
2 2, which has remained in place fo r seven
years without de-cementing.
success is partly due to the development of better retention methods, appropriate choice of metals
for casting and adhesive cements.
G St George BDS, MSc, FDS, DGDP(UK).
Specialist Registrar in Restorative Dentistry.*
K Hemmings BDS, MSc, MRD, FDS.
Consultant in Restorative Dentistry.*
K Patel BDS, MSc, FDS(Rest Dent).
Consultant in Restorative Dentistry.*
*Eastman Dental Hospital, London, UK.
Retention
In 1955, Buonocore 1 introduced the
concept of adhesion in dentistry
when he etched enamel with 85%
phosphoric acid and attached acrylic
resin. This technique has been developed allowing restorative materials
to be attached to teeth with little
or no tooth preparation. The development of a composite resin conta inin g b is G MA (b isp h en ol- Aglycidyl methacrylate) by Bowen, 2
produced a filling material which
could be bonded predictably to
enam el without the problems
associated with acrylic.
With these advan ces in dental
technology came a number of techniques to restore edentulous spaces:
• Bonding of extracted natural teeth
crowns to adjacent teeth using
composite resin. 3
• Attaching acrylic resin dentu re
teeth with composite 4 to adjacent
teeth.
• Attaching composite pontics to
adjacent teeth. 5
Although some of these techniques
were moderately successfu l, a common clinical finding was fracture of
composite connectors.
In 1973, Rochette 6 used a perforated type IV gold casting to splint
© P RIMARY D ENTAL CARE 2002;9(3):87-91
periodontally involved teeth together
using self-cured acrylic resin . The
applic ation of this appliance to
replace missing teeth was quickly
s een , 7 sp aw n in g t he first resin retained bridge, the Rochette bridge
(Figure 2 ). The main disadvantages
Figure 2 Rochette bridge.
of this type of bridge were the
limited retention provided by the
composite retained metal, the thickening of the metal retainers required
to compensate for the weakening
effect of the perforations, and the
wear of the resin cement. 8
Other forms of retention have
included:
Macro-mechanical retention.
• Mesh retention. 9 This technique
used a mesh within a solid ret aine r. The reten tive area was
less than the fit surface area,
because the mesh was sealed at
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R ESIN- RETAINED B RIDGES R E - VISITED . PART 1
the margins. Poor castings were
an oxide coating and was used
b io c om pa t ib le , wh ere as b as e
common with this technique.
with a chemically active resin. 16
allo ys suc h as nic kel-chrom e
may cause hypersensi tivity reac• Acrylic beads. 10 Acrylic beads
(0.2-0.3 mm) were placed on the
tions, 20 Beryllium was originally
Chemical bonding
17
fit surface of the retainer wings,
added to nickel-chrome as it pro• Tin coating. The fit surfaces were
which were then duplicated in
tin co ated elect ro chem ic ally.
duced a superior patter n when
the casting to produce mechNoble metals were mainly used
etching was employed. However
anical retention.
rather than non-precious alloys.
it is no longer used due to its
11
Little data was available to show
known carcinogenic potential, 21
• Virginia salt tec hniqu e. S alt
crys tals (0.15 -0. 25 m m) were
success rates, and the technique
and the availability of alternaincorporated into wax and rewh en ap plied to sa n db las te d
tives to etching.
moved in solution leaving cubic
nickel-chrome failed to improve
• Good bonding to porcelain and
retentive pits. This was a time
bond strengths when compared to
res in . G o ld allo ys h ave b een
saving method compared to the
sandblasting alone.18
shown to bond to porcelain well,
tech nique of etc hing. Th e
but the greater thickevaluation of the retent ive
ness of oxides present
su rfa ce w as e asier an d a
following the heating of
greater choice of non-etchbase meta l alloys can
able metals could be used. A
be more prone to fail
commercial product, Crystal
cohesive ly, r e s u l t i n g
B on d, w hich was a c om in p o rce lain fracture.
bination of salt and acrylic
• Aesthetics. Base metal
beads used to produce pits
alloys may cause greyand retentive beads on the
in g o f an terio r t eeth
fit surface of retainers, was
d u e t o m e t a l s h in e produced.
through, although this
All the above techniques reh as been redu ced to
quired thickening of the retains om e de gree b y th e
ers to incorporate the retentive
use of opaque cements.
Figure 3 Electron micrograph of sandblasted retainer surface.
system used, and were poorly
• Low cost. Base metal
retained at their margins due to
alloys are cheaper than
19 Silic a was
the retentive feature stopping short
S
i
l
a
n
e
c
o
a
t
i
n
g
.
noble
metal
alloys, hence their
•
of the retainer edges.
attached to metal surfaces by
widespread use.
vaporising silane in a propane/
The original Rochette bridge was
air flame, followed by a further
constructed from type IV gold, but
Micro-mechanical retentio n
coating of silane when the metal
t h e m a j o ri t y o f r e s i n - r e t a i n e d
• Etching. This has been carried out
by electrochemical 12 and chemihad cooled. Although promising,
bridges made today use a berylcal methods. 13 The electrochemilittle clinical data is available.
lium-free nickel-chrome alloy as a
cal etching technique, developed
superior material for frameworks.
at the University of Maryland,
Metals
gave rise to the name ‘Maryland
Metals used in the construction of
Cements
Bridge’. The tiny etching pattern
resin-retained bridges should posResin cements have been used for
produced was verified by examisess the following qualities:
the cementation of resin-retained
nation under a m icroscope to
bridges to etc hed en am el sinc e
• Rigidity. Base metal alloys have
ensure it was adequate. Bond
higher rigidity and hardness than
Rochette cemented his periodontal
strengths were good, but difficulnoble metal alloys. This makes
splint using Sevriton (self-cured
ties in calculating times for electhem ideally suited to being used
acrylic resin).
trochemical etching, the hazards
in thin section resulting in less
Acrylic resin had the following
of chemical etching, and producbulky retainers. Possible disadproblems:
ing uniform etch patterns, 14 led to
vantages include greater wear of
• L ow c om p ress ive a n d t en sile
the use of other methods.
opposing natural teeth, difficulty
strength.
in adjusting the finished metal,
• Sandblasting. This technique used
• High solubility.
50 µ alumina to produce a roughand the inability to burnish mar• Polymerisation shrinkage.
ened oxide layer over the surface
gins to optimise retainer fit.
• Thermal expansion.
( Fi g u r e 3) . S a nd b las te d ba se
Accurate
when
cast.
Noble
metal
These problems were largely over•
metals have been shown to give
alloys melt at lower temperatures
come by the introduction of bis
higher bond strengths than etchthan base metal alloys and thereGMA type composite resins, used
ing or using salt particles, 15 espefore shrink less on cooling.
to cement the original Rochette
cially when the metal used had
• Biocompatible. Gold alloys are bridges.
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PRIMARY D ENTAL CARE JULY 2002
G S T G EORGE
With new methods of increasing
retention of frameworks came better composite resins with smaller
filler particles, and better flow properties. The first true breakthrough
was the developmen t of the adhesive 4-META (4-methacryloxyethyl
trimellitate anhydride), which was
incorporated into the dental cement
Super Bond C & B. Although initially successful, it was found that
the high bond strengths obtained
decreased over time when im merse d in water and following
thermal cycling. 22
The development of Panavia-Ex,
which contained phosphate monomers, led to predictable bonding,
which overcame the problems of
Super Bond C & B. Adhesion occ u r re d b e t w ee n t h e p h o s p h a t e
group in the monomer and the
oxide coating of the nickel-chrome,
and also via mechanical bonding. 23
A st u d y 2 4 c a rried o u t wit h t h is
cement showed that it may be possible to bond strongly to nickel
chromium with little or no preparation of metal surfaces. This led to
the introduction of sandblasting in
combination with adhesive resin
cements to retain bridges. This has
since been validated in other studies, 15,16 and has brought reliable
bonding to resin-bonded bridges.
Panavia-Ex has since been superseded by Panavia 21 which is supplied as a two-paste system, unlike
Panavia-Ex, which was a powder
and liquid. It contains 10-methacryloyloxydecyl di-hydrogen phosphate which produces a strong bond
to metal. Both types of Panavia are
chemical-cured materials.
• Reversible. Providing there is little
o r n o t o o th pre pa ra t io n, th e
bridges can be removed with minimal damage to the abutments.
This feature is helpful when this
type of bridge is used as an interim restoration in the young, eg
prior to implant therapy.
• Cheap and quick. Laboratory bills
are reduced, as well as chair-time.
• Easy to do. Impres sions, a jaw
registration, and a shade are often
all that is needed.
• Patient preference, due to reduced chair-time, cost, and lack of
tooth preparation.
• Cost-effective. A recent study has
shown the median survival of
resin-retained bridges to be seven
years and ten months.25 Creugers
and Kayser (1992) 26 considered
resin-retained bridges to be costeffective if their median survival
was greater than 6.5 years.
Advantages and
Disadvantages of
Resin-retained
Bridges
Figure 4
Advantages
• Conservative. Retention does not
rely on conventional retentive
features, so little if any tooth
preparation is necessar y. When
p reparation is required, this
should be restricted to enamel.
Potential disadvantages
• More frequen t de-bon d when
compared to conventional
bridges.
• Resin-retained bridges have an
undeserved reputation for failure,
partly brought about by poor
bridge desi gn and cementati on
t ec h n iqu e . If d e -c em en t at io n
occurs, it is often easy to re-
•
•
•
•
•
•
Carious destruction under a de-
cemented bridge.
cement the same bridge. When
multiple retainers are used, one
retainer may de-bond leaving the
bridge in situ. Plaque may trap
underneath this de-bonded retainer, which can result in carious destruction if undetected
(Figure 4). This problem is not
unique to resin-retained bridges.
• Te chnique sensitive. Res in-retained bridges require careful
design and adequate isolation for
ET AL
cemen tation using rubber dam
application.
Aesthetics. Problems can occur
w ith inc isa l s h in e- th ro u gh o f
metal if an opaque cement is not
used. An opaque cement lute may
also be more visible. Retainers, if
extending onto occlusal or incisal
s urfa ces m ay a lso b e visib le.
These can be masked by abrading
the retainer surfaces with glass
beads. The matt finish produced
and lack of reflection makes the
metal surfaces disappear into the
darkness of the mouth.
Redistribution of spa ce. When
diastemas are present, or pontic
space is too large or small, it is
often difficult to distribute the
space between pontic and abutment teeth. Cantilever or spring
cantilever designs may be considered in these cases.
Limited tooth replacement. Small
spans tend to be more successful
than larger ones.
Temporisation/trial prosthesis is
not usually possible. This prevents eva luation of aest hetics,
g u id a n c e , a n d s p e e c h . W h e n
bridges are temporarily cemented,
re-preparation of both tooth and
retainer fit surfaces is necessary.
Dramatic failure. A partial denture
can be made simultaneously to
restore function if there is dramatic failure of the resin-retained
bridge.
Poor remuneration. This treatment can be well rewarded in
the private sector, but remuneration is poor under the National
Health Servi ce. This, combined
with scepticism about success
from many practitioners, has led
to their limited use in general
dental practice.
Indications and
Contra-indications
Indications
• Un-restored/minimally restored
teeth. The highest bond strengths
a re o b t a i n e d w h e n m e t a l i s
bonde d to e nam el. M ini mal
exposure of dentine or the presence of fillings, are not absolute
contra-indications. Restor ations
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R ESIN- RETAINED B RIDGES R E - VISITED . PART 1
imise d by the use of opaque
cements.
• Excessive occlusal loading. Debonding may occur when occlusal contacts are prese nt on
the pontics in excursive movements.
• Difficulty in isolation for cementation to achieve a dry field.
Figure 5 (a) Poten tial abutments showing erosion . (b) Reduced bonding area on diminu-
Bridge Design
tive lateral incisors.
on a but men t teeth sh ould be
composite resin, and require replacement prior to taking the impressions for bridge construction.
• Sufficient, good quality enamel.
Toothwear (Figur e 5a), diminutive teeth (Figure 5b) and certain
abnormalities of enamel eg amelogenesis imperfecta, may reduce
the quantity/ quality of enamel
for bonding and therefore the
strength of the adhesive bond.
• Sufficient inter-occlusal space
for retainers exists. Lack of inter-occlusal space can be overcome by cementing restorations
‘high’ at an increased occlusal
vertical dimension, similar to the
appliance developed by Dahl. 27
Occlusal contacts between the
remaining teeth are usually rest o red in a few m o n t hs in a
young pati ent and sli ghtly
longer, 9-12 months, in an older
patient. Bridges cemented this
way spare enam el, have been
shown to be well tolerated, and
have good retention rates. 25 This
is the preferred method of the
authors, and is indicated in most
clinical situations apart from:
u Teeth with little periodontal
support or increased mobility.
Splaying of abutm ent teeth
may occur, rather than intrusion and compensatory
e ru p tio n o f t he re m a in in g
teeth. Rotation of abutments
m ay o ccu r when ca ntilever
bridges are cemented high on
these teeth.
u Patients with a large horizontal slide from their retruded
contact position, to their intercuspal position. Posterior repositioning of the mandible
may occur in these patients
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PRIMARY D ENTAL CARE JULY 2002
resulting in anterior guidance
being lost. Luckily, these cases
are rare in clinical practice.
u ‘Occ lu sally-aware’ patient s.
The harmony in some patients’
mouths can be upset by the
placement of high retainers.
Again, these patients are rare.
Patients should be warned that
chewing food may be difficult until tooth contacts are
restored.
• Where a resin-retained bridge is
an intermediate prosthesis (prior
to implants). This is very useful
during growth years when implants are contra-indicated.
• Patien t wishes. Som e patients
are reluctant to have minimally
restored teeth prepared.
Contra-indications
• H e a v il y re s t o r e d t e e t h . T h is
re d u c e s t h e a re a o f e n a m e l
bonding.
• Little enamel to bond to. Despite
the recent advances in dentine
bo nd in g, on e s till p re fers t o
bond mainly to enamel.
• Po or q ua lity en am el/f req uen t
de-bonds.
• Tr a n sl u c e n t i n c is a l ed g e s o f
ab u t m en t t e e t h . T h es e a llo w
shine-through of metal retainers
(Figur e 6). This may be min-
Figure 6 . ‘Shine-through’ of a metal retainer
through a lateral incisor.
There are three possible designs
based on retainer type and connectors:
Figure 7 A cantilever bridge.
Cantilever (Figure 7)
Using a single retainer eliminates
the problems of partial de-cement a tio n a s th e p a t ien t / de n t ist is
instantly aware of bond failure!
This may be seen as a disadvantage
because of the dramatic failure. A
careful occlusal analysis is required
t o a vo i d h e a v y c o n t a c t o n t h e
p on t ic , es pe cia lly o n e xc urs iv e
movem ents, which could precipitate an early failure.
A c a n t il e v e r b r id g e is l e s s
expensive than a fixed-fixed resinreta in ed bridge, b ut lim ited to
replac ing one missin g tooth. A
diagnostic wax-up should reveal
any contacts in excursive movements, which may cause either
bond failure or tooth rotation. If
orthodontic stability of teeth adjacent to the space is required, this
design may be inappropriate.
Fixed-fixed (Figure 8)
With fixed-fixed bridges, one or
more retainers are placed on either
s id e o f t h e p o n t i c . D if f e re n t ia l
movement of abutments can result
in bond failure, but this can be
reduced by making sure opposing
teeth only contact retainer wings
and not tooth tissue in excursive
G S T G EORGE
References
1. Buonocore MG. A simple method of
increasing the adhesion of acrylic filling
materials to enamel surfaces. J Dent Res
1955;34:849-53.
Figure 8 Fixed-fixed bridges.
contacts, thereby biting the abutments out of the retainer. Double
abutments offer no advantages in
terms of retention as the weaker
abutment retainers are often put
under shear forces causing debonding. This can make maintenance difficult. Long sp ans , eg
replacing 21 12 using 3 3 as
te rm inal abutm ents, have been
sh o wn to be s u cc es sf ul. 25 Th is
design of bridge is indicated where
excursive movements on pontics
cannot be avoided, tooth stability
is required following orthodontic
movement, and lack of periodontal
support could produce abutment
movement.
Hybrid bridges (Figure 9)
This design has both resin-retained
and conventional retainers. They
are indicated where one of the
abutments is minimally restored,
and a resin-bonded retainer is used
ET AL
17. Van Der Veen JH, Krajenbrink T, Bronsdijk
AE, Van De Poel F. Resin bonding of tin
electro plate d prec ious metal fi xe d part ia l denture s: one year clinical results.
Quintessence Int 1986;17:299-301.
2. Bowen RL. Properties of a silica reinforced
polymer for dental restorations. J Am Dent
Ass 1963;66:57-64.
18. Asfour D, Wickens J. A comparison of two
methods for surface treatment of nickelchrome alloys [BSDR abstract 152]. J Dent
Res 1989;68:577.
3. Ibsen RL. Fixed prosthetics with a natural
crown pontic using an adhesive composite.
Case history. J South Calif Dent Assoc
1973;41:100-2.
19. Musil R, Tiller HJ. The Adhesion of Dental
R e si ns t o M e t a l S ur f a c e s . T he K ul z e r
Silicoater Technique. Wehreim: Kulzer & Co
GmbH, 1984.
4. Portnoy L. Constructing a composite pontic
in a single visit. Dent Surv 1973;49:20-3.
20. Moffa JP, Beck WD, Hoke AW. Allergic
response to nickel containing dental alloys
[AADR abstract 107]. J Dent Res 1977;56:B78.
5. Simonsen RJ. Clinical Applications of the
Acid Etch Technique. Chicago: Quintessence,
1978.
6. Rochette AL. Attachment of a splint to
enamel of lower anterior teeth. J Prosthet
Dent 1973;30:418-23.
7. Howe DF, Denehy GE. Anterior fixed partial
dentures utilising the acid-etch technique
and a cast metal framework. J Prosthet Dent
1977;37:28-31.
8. Swift EJ. New adhesive resins. A status
report. Am J Dent 1989;2:358-60.
9. Taleghani M, Leinfelder KF, Taleghani AM.
An alte rn at ive to cast etc hed ret ainers .
J Prosthet Dent 1987;58:424-8.
1 0. L a B a r r e E E , Wa rd H E . A n a l t e r n a t i v e
resin- bonded restoration. J Prosth Dent
1984;52:247-9.
11. Hudgins JL, Moon PC, Knap FJ. Particle
r o ug h en e d r e s i n- b o nd e d r e t a i ne r s . J
Prosthet Dent 1985;53:471-6.
12. Livaditis G J, Thompson VP. Etched casti ngs: an improve d retentive mechanism
for resin-bonded retainers. J Prosthet Dent
1982;47:52-8.
13. Livaditis GJ. A chemical etching system for
c reati ng mic ro- mech anic al ret enti on in
resin bonded retainers . J Prosthet Dent
1986;56:181-8.
14. Lyttle HA, Louka AN, Young J. A study of
the consistency of etch patterns on samples
of various alloys as fabricated by commercial dental laboratories [abtract 11]. J Dent
Res 1986;65:532.
21. Moffa JP, Jenkins WA. Status report on
base-metal crown and bridge alloys. J Am
Dent Assoc 1974;89:652-5.
22. Thompson VP, Grolman KM, Liao R.
Bonding of adhesive resins to various nonprecious alloys [IADR abstract 1258]. J Dent
Res;64:314.
23. Yamashita A, Yamami T. Proceedings of the
International Symposium on Adhesive Prosthodontics. Nijmegen: Eurosound Drukkerij
B, 1986:61-76.
24. J e nki ns C BG , A bo ush Y EY. Th e bon d
strength of a new adhesive recommended
for resin-bonded bridges [BSDR abstract
18]. J Dent Res 1985;64:664.
25. Djemal S, Setchell D, King P, Wickens J.
Long-term survival characteristics of 832
resin-retained bridges and splints provided
in a pos t- gr adua te t ea c hing hos pit al
between 1978 and 1993. J Oral Rehabil
1999;26:302-20.
26. Creugers NH, Kayser AF. An analysis of multi ple failures of resin-bonded bridges. J
Dent 1992;20:348-51.
27. Dahl BL, Krogstad O, Karlsen K. An alternative treatment in cases with advanced localized attrition. J Oral Rehabil 1975;2:209-14.
Proprietary names
Sevriton: De Trey Division, Dentsply Ltd,
Weybridge, Surrey, UK.
Super Bond C & B: Ventura Oral Systems Ltd,
Halifax, Yorkshire, UK.
15. Harley KE, Ibbetson RJ. The adhesive
strengths of three resin cements used with
beryllium free nickel chrome alloy [BSDR
abstract 9]. J Dent Res 1987;66:835.
Panavia-Ex and Panavia 21: Kuraray Co Ltd,
1-12-39 Umeda Kita Ku, Osaka 530-8611, Japan.
16. Atta MO, Smith BGN, Brown D. Bond
strengths of three chemical adhesive cements
adhered to a nickel-chrom ium alloy for
direct bonded retainers . J Prosth et Dent
1990;63:137-43.
Correspondence: G St George, Conservation
Department, Eastman Dental Hospital,
256 Gray’s Inn Road, London WC1X 8LD.
E-mail: [email protected]
Figure 9 A hybrid bridge.
at this site to conserve tooth tissue.
Laboratory bills are increased and
care should be taken in the location
of the connectors to ensure that
drifting apart of the joint does not
occur. The male part of the joint is
often attached to the resin-bonded
retainer to simplify mainten ance
when de-bonds occur, as the resinretained part of the bridge invariably fails before the conventional
retainer. It also enables optimal
seating.
New CDO Appointed
The Department of Health announced the appointment of Professor Raman
Bedi to the post of Chief Dental Officer for Engla nd on 17th May 2002.
Professor Bedi is presently Head, Department of Transcultural Oral Health,
Eastman Dental Institute, Professor of Transcultural Oral Health, University
College London, Co-Director, WHO Collaborating Centre for Disability, Culture
and Oral Health. He qualified at the University of Bristol in 1976. He has held
academic posts at the Universities of Manchester, Hong Kong, Edinbur gh
and Birmingham. He is a specialist in both dental public health and paediatric
dentistry. The Faculty welcomes Professor Bedi’s appointment at a crucial time
for the profession. Professor Bedi has worked closely with the Faculty in the
past and we share his views on oral health equality issues.
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