connectors

1. Noreen Mohammed Naguib Mosaad
5212322
G.11
Connectors in fixed prosthodontics

2. To stress-break or notto stress-break, thatis the
question!!
Maxillary FPD
Anterior : fixed
Posterior : fixed-free
Mandibular FPD
Anterior : Fixed
Posterior : Fixed-free i.e. Fixed at the posterior
connector and stressbroken atthe anterior connector.
Now, it is becoming more common to stress break
ALL POSTERIOR BRIDGE
The occlusalforcesapplied to a fixed partialdenture (FPD) are
transmitted to the supporting structuresthroughthe pontic, the

3. connectors, and the retainers.
Variablesthat may influence the longevity of a bridge and its
abutmentsinclude the occlusion, span length, bone loss, and
the quality of periodontium.
The excessive flexing of the long-span FPD, which varieswith the
length of the span cubed, can lead to materialfailure of the prosthesis
or to an unfavorable tissue/bone response.
Biomechanicalfactorssuch as occlusaloverload, leverage,
torque, and flexing, induce abnormalstressconcentration in an
FPD.
This stress concentration isfound in the connectorsof the bridge
and in the cervical dentin area near the edentulousridge. This factor
playsan importantrole in the potentialfor failure, particularly in
long-span bridge.
Remember that connectorsare thatportion of the bridge thatunites the
retainersand the pontics. They are of two types, rigid connectorsand
non-rigid connectors(NRCs).
Rigid connector could be made by casting, soldering, and welding. The
cast connectorsshould be properly shaped in waxpatterns. The
soldered connectorsare made by fusion of an intermediate metal alloy
to the previously made castings. These days, the one piece casting goes
a long way towardsovercoming rigid connector failure in bridgework.
The connector thatpermitslimited movementbetween the otherwise

4. rigid membersof the FPDs, is the Non- Rigid Connector or NCR.
The NRC could be made by an incorporation of prefabricated
precision inserts, by use of a custom-milling machine or by use of the
prefabricated plastic patterns.
Ref. Pissiotis AL, MichalakisKX. An esthetic and hygienic approach to the
use of
intracoronalattachmentsasinterlocksin fixed prosthodontics. J Prosthet
Dent
Non-rigid conncetors

5. The indicationsfor the use of the NRC in fixed prosthodonticsare :
1. The existence of a Pier abutment, which promotesa fulcrum-like
situation that can cause the weakest of the terminalabutmentsto fail
and may also cause intrusion of the pier abutment. But should Pier
Abutmentsbe used at all considering their high failure rate ??? (Ziada
et al. 1998.)
2. The existence of a malaligned abutment, where parallelling
preparationsmightresultin excessive tooth preparation and
devitalisation. Such situations can be solved through the use of
intracoronalattachmentsasconnectors.
3. The presence of mobile teeth , which need to be splinted together
with the fixed prosthesis. In such situations, it is not practicalto
cementa splinting type restoration with numerousteeth involved.
Through the use of interlocks, smaller segments can be cemented with
the splinting effectprovided by the interlocks

6. 4. Long span FPDs: which can distort due to shrinkage and pullof
porcelain on thin sections of framework and thusaffectthe fitting
of the prosthesison the teeth. Again, should long span bridgesbe
favored considering their failure rate and considering the success
rate of implants ???
5. In situations where a questionable distal abutmentexists and
fabrication of the fixed partialdenture is considered to be the best
interim treatment, the use of the NRC may solve the problem of not
having to repeatthe restoration of the remaining abutment(s) after
final failure of the questionable abutment.
6. It could also be used with osseointegrated implants.
So, the NRCs are mainly used to reduce stress on the
abutmentand to accommodate malaligned FPD
abutments.
The four typesof NRCs are the
1. Dovetail (key-keyway)or (Tenon-Mortise) connectors.
2. Loop connectors.
3. Split connectors.
4. Cross pin and wing connectors.
Align the path of the keyway to thatof the mesial abutment. A
deep wax boxis carved into the distal of the waxpattern for the
incorporation of a keyway, which in turn requiresan intracoronal
preparation of adequate depth and a parallelpath of insertion.

7. Ref: Badwalk PV, Pakhan AJ. Non-rigid connectorsin Fixed
Prosthodontics: currentconcepts. J Indian DentAssoc. 2005;5:2,99-102
Banjaree S. et al Non-rigid connectors- the wand to reduce stresseson
the
abutmentteeth. Contemp Clin Dent2011,2:351.
Sutherland etal. (1980) suggested thata rigid bridge
resolves more of its stress internally before the
remaining stress can reach the bone, and it has been
found thatthe greatest stress concentrationsin a rigid
bridge occur in the connectors.With a non-rigid
design, the stress may be directed through the
abutmentteeth to the supporting bone rather than
being concentrated in the connector itself.
_ This meansthat the prosthetic material and the luting
cementin a rigid design must withstand much greater
stress than in the non-rigid design.
Another problem thatexists in the posterior mouth is the
inequality of the abutmenttooth size.
_ In a bridge replacing a first molar for example, the smaller
abutment(second premolar) may develop a thicker pericemental
cushion following frequentstress, as a compensating measure for
this stress. As a result, weaker abutmentsmay move more than
the larger sturdier abutment. Thisresults in large lever strains on
the weaker abutmentwhich tendsto shear the luting bond.

8. _ However, when a stress-breaker isused on the smaller abutment,
it will tend to dissipate much of the leverage force.
_ Stress-breakerscan also be required in long-span bridgesas
satisfactory tooth alignmentbecomesmore difficult to achieve.
_ Even in short-span bridgeswith divergentabutmentteeth,
abutmentpreparationsdo nothave to be parallelto each other.
Each preparationscan be designed to MAXIMIZEindividual
retention, independentof a common path of insertion.
The use of stress-breakersalso tends to break up bridge length to more
manageable portionsand makessubsequentrepair/replacementeasier.
Fixed-fixed
Rigid connectors