Bridges I - Adhesive bridges Flashcards
What can adhesive bridges also be called?
Resin bonded bridge
Bonded bridge
Maryland bridge
How to retain a FPD?
Full coverage crowns - Prep of the abutment tooth is a full coverage crown e.g. FGC, PFM, all ceramic
Adhesive retainers - Prep of abutment tooth is minimal and involves palatal and proximal surfaces only
Use of abutments?
Fixed-fixed - The bridge spans from
one abutment to another, with the pontic
in between.
I.e.: Abutment – Pontic – Abutment
Cantilevered - bridge is retained by one abutment only e.g. abutment - pontic
Design criteria for adhesive bridges?
- Perio support
- Occlusal loading - magnitude and direction of force vectors
- . Conservation of tooth tissue
- Cleansability
- Appearance
- Rigidity (of retainer and connector)
- Qual of abutments
- No of abutments
- Choice of adhesive lute
- Contingency planning - what if it debonds, what if the tooth becomes non-vital
Features of single tooth and fixed cantilevered bridges?
More retentive than fixed fixed Pontic can move with the abutment Reduced shear forces on the pontic Debond leads to cleansable surfaces Risk of caries eliminated
When are adhesive bridges wanted? When do they work best?
Single tooth replacement
Work best when cantilevered from a good abutment tooth
What to consider with the framework design of adhesive bridges?
Retainer thickness and configuration Bonding area Wrap around Occlusal extension of metalwork Connector design Length of span
What to consider with retainer thickness and configuration?
Retainers for molars - 0.8mm thick
Greater if the retainer is not joined over the occlusal surface
What to consider with the bonding area?
Max enamel bonding
Extension of the metal work as far occlusogingivally and circumferentially around the tooth as possible
What is the max wrap around?
Max = 180 degrees (mesial and distal groove)
What is the occlusal extension of the metalwork?
- Full palatal coverage with no tooth prep
2. Reduced palatal coverage with tooth prep (finish 1-3mm short of incisal edge)
What is posterior occlusal coverage for?
Resistance to displacement apically or laterally
Increased rigidity of the framework
Greater surface area for bonding
What must the connector (metal wing joined to the pontic) design be?
Significant width and height required - at least 50% of the height of the pontic
Need to resist bending of the alloy
Must avoid putting adhesive lute under tensile loading
Length of span?
Ideally one tooth replacement
Longer spans are not contra-indicated, but the tooth prep and framework design should be planned to reduce potential debonding stresses on the retainer
What is needed to prep the tooth?
Axial tooth prep Grooves Occlusal rest seats Intracoronal prep Cantilevered resin bonded bridges
Why do axial tooth prep?
Increases area for bonding
Increases resistance and retention
Minimal reduction with chamfer finish
Why are grooves needed?
– Provide increased resistance form to lateral
displacement
– May help increase retention form.
– They also increase the structural rigidity of
the metal framework after cementation.
– The use of 2 grooves (1mm deep) per
abutment, significantly increases resistance
to debonding
Why have occlusal rest seats?
Allows transmission of occlusal forces along the long axis of the tooth
Provides resistance form and possibly limit shear forces to the cement lute
Why do an intracoronal prep?
Joining of mesial and distal rest seats of the retainer over the occlusal surface to form an occlusal bar to improve the rigidity of the retainer
Reduces deformation of retainer
Improves the resistance form
Increases surface area for bonding
What cements to use?
ADHESIVE LUTE
Self-cure composite lute
- Non-adhesive
- In combo with bonding system
- Requires an etched mesial substrate
- Needs bonding system
Anaerobic adhesive lutes - panavia:
- Opaque
- Specific adhesion to metal retainers
4-meta adhesive lutes
- Specific bonding to metal and ceramic retainers
Alloys used - nickel chromium features?
Can be electrolytically etched
V rigid
Works well with composite luting systems
Gold alloy features?
Cannot be etched
Not as rigid as Ni/Cr
Need sandblasting
Need specific adhesive systems
Ceramic alloy features?
Experimental
More aesthetic
What does the choice of the abutment teeth depend on?
Tooth position
Crown shape
Restorative status - proximal restorations
Endodontic status
What does the quality of the abutment tooth depend on?
Endo status and prognosis Restorative status Qual of bonding substrate Anatomical shape Retention/resistance form
What make poor abutments?
Maxillary lateral incisors
Tilted incisor teeth - have an unfavourable pulp chamber morphology
Root filled teeth
Do adhesive bridges work?
Resin bonded bridges survival rate 87.7% over 5 yrs
How can bridges fail?
Debonding
- Failure of bond
- Lack of rigidity leading to peeling effect
Caries under retainer
Aesthetic failure - show through of retainer - grey tint to tooth
Double abutments?
2 adjacent teeth as abutments - not required
e.g UR5 and UR4 linked to replace UR3
Fixed fixed adhesive bridges?
Adhesive retainers with intermediate pontics
Generally not recommended
Only exception is the mandibular incisors, where the peel dislodgement effect is less
E.g. UR2 and UL1 to replace UR1
Why are fixed fixed adhesive bridges likely to fail?
Not a good idea
Significant stresses are applied to the retainers of fixed fixed resin bonded bridges due to differential tooth movements between the abutments during func and parafunc contacts
Forces can push one of the abutments away from the pontic
Tensile stress of cement lute
Debonding of an abutment and caries under the retainer
What should a single tooth fixed cantilevered adhesive bridge abutment have in the bridge prep?
180 degree wrap around palatal chamfer
Proximal parallel grooves
Cingulum rest seat
