_____ FPD:
- -1 or 2 missing teeth
- -2 abutments
Simple FPD
\_\_\_\_\_\_ FPD: --3 or more missing teeth --Missing Canine --1,3, or greater than three abutments Splinted, pier, cantilever --Non-parallel abutments --Combined anterior and posterior FPD
Complex FPD
Abnormal stress created by_____ and _______ create material
failure and tooth failure
torque and leverage
What are the 4 Problems caused by bending and deflection?
- Fracture of Porcelain
- Connector breakage
- Retainer loosening and subsequent caries
- ”Unfavorable” tooth or tissue response
The ______ is directly proportional to the cube of
the length of its span.
deflection
The deflection is directly _______to the cube of
the length of its span.
proportional
Greater span/ interabutment space = _____ deflection
Greater deflection
_______ varies inversely by the cube of its
height (thickness).
Deflection
Deflection varies inversely by the cube of its
________
height (thickness).
The higher the occluso-cervical thickness of the connector, the _____ the FPD flexure
Less flexure
–FPD flexure is ______ to connector width
proportional
Is the width or height of connector more important to decreasing FPD flexure?
height
For PFM, what is the minimum height for connector?
3-4 mm
For ceramic FPDs, what is the minimum connector height needed?
4 mm
Use a bridge material with _____ yield strength (Yield strength refers to an
indication of maximum stress that can be developed in a material without
causing plastic deformation.)
high
_______ refers to an
indication of maximum stress that can be developed in a material without
causing plastic deformation.)
(Yield strength
Abutments and retainers in FPD receive ____ dislodging forces
than a single crown
greater
Occlusal force on
pontics can cause
______
torque.
Mesial-Distal
Forces at an oblique
angle or outside the
center of the restoration
cause _______
F-L torque (around
M-D axis of rotation) .
Grooves / boxes ______ to dislodgement.
increase resistance
Is stress more favorable on the max or mand arch to stabilize and decrease likelihood of fracture?
Mand arch
Canine replacing FPD is not a good idea in ____ arch?
Max arch
\_\_\_\_\_\_\_ help stabilize the prosthesis by distributing forces over more teeth (do not necessarily increase retention).
Double abutments
Double abutments help stabilize the prosthesis by distributing forces over more teeth (do not necessarily \_\_\_\_\_\_\_ )
increase retention).
An edentulous space on both sides of a lone free-standing abutment
Pier Abutment:
Cause of failure in Peir Abutments is most often a _______
-Prosthesis flexure creating movement of teeth
-Tensile stresses between terminal retainers and abutments; intrusion of abutments under
loading
-Differences in retentive capacities between abutments (relative to size)
loosened retainer
-Stresses can be concentrated around the abutment teeth
and between retainers and abutment preps
-Slight movement in non-rigid connectors can minimize the
transfer of stress from the particularly loaded segment to the
rest of the FPD
Non-rigid connectors
If a non-rigid connector is placed on the \_\_\_\_\_ side of the retainer on a middle abutment, movement in a mesial direction will seat the key into the keyway.
distal
If a non-rigid connector is placed
on the _____ side of the middle
abutment, mesially-directed
movement will un-seat the key.
mesial
- Indications:
- Pier abutment FPD
- Long span FPD with multiple abutments
- Non-parallel abutments – Tipped molar
- Planning for failure
Non-Rigid Connectors
- Contraindications:
- Long span FPD with two abutments
- Excessively mobile teeth
- Unopposed teeth
Non-Rigid Connectors
-Long axes of abutment teeth should converge by no more than _____ (maximum
angle of tilting) if FPD is made.
25o - 30o
-Generally poor abutments
-Mesial wall must be over-reduced / overtapered (↓ resistance)
-Distal adjacent tooth may intrude on the path of insertion
Mesial surface may need re-contouring or restoration or extraction
Consider orthodontic uprighting (3rd molar extraction)
Tilted molars
-Non-axial loading (horizontal) because of a tilted molar often leads to ________
proximal crestal bone loss
-Places abutment in better position for preparation
-Distributes forces under loading through long axis of tooth (helps
prevent/eliminate mesial bony defects)
-Enables replacement of optimum occlusion
-Requires EXCELLENT communication and treatment planning skills to
educate patient. Often extra 1-2 years of ortho prior to bridge
placement. And then maybe an implant would be better?
Molar uprighting (orthodontic movement)
If a molar is tilted, where would you have to reduce more occlusally for occlusion to be harmonious?
Distal
-Allows slight movement - short span -Keyway in distal of premolar to avoid intrusion of molar (mesial seating action) -Must prepare box in distal of premolar preparation
Non rigid connector used to accommodate a tilted molar
If a non rigid connector is used, where should grooves/boxes be placed for retention of the FPD?
Facial and lingual surfaces
– does not involve distal wall -3/4 crown rotated 90o Used in case of tilted molars Requirements: -Caries-free distal surface -Low incidence of caries -Even marginal ridge height -Short span length
Proximal Half Crown
Full crown preparation and coping with path of insertion in long axis of tooth. Full coverage crown compensates for discrepancy in paths of insertion. Must over-reduce molar to accommodate the thickness of coping and crown. WHY would you do this? Design for failure Protect tooth (reduced fracture of crown of tooth with bridge stresses
Copings
Primarily only for patients contraindicated for implants. Why? -Removing tooth structure on two teeth. -Occlusal forces create guarded prognosis Criteria : -Replace only 1 tooth, and have at least 2 abutments Criteria for abutment teeth: -Long roots w/ good configuration -Long clinical crown -Resistance form for preparations O-C height for connectors w/o impinging on interdental papilla -Favorable crown:root ratio and healthy periodontium
Cantilever
What are the 3 types of forces that can result from a cantilever placed in high occlusion?
Down, toward abutment or oblique twisting forces
-Only the canine should be used as a solo abutment
(Why?) Long Root, Esthetics easier, occlusal forces more lateral and therefore protective of
pontic.
-A Rest can be placed on mesial of pontic against a rest prep in a restoration in the distal of
the central incisor or slight wrap-around of proximal contact.
-Good clinical crown length / orthodontic position is necessary
Replacing lateral incisor
Replacement of _______ using cantilever
- Use full veneer retainers on the 2nd premolar and 1st molar.
- Limit occlusion on the pontic.
First Premolar
-For premolar cantilevers for premolars, \_\_\_\_\_\_ used to support premolar cantilever pontic -Either cemented or bonded.
Mesial rest
What’s the 2
biggest problems
with this type of
restoration (mesial rest for PM cantilever?? -
OCCLUSION and Caries
-Unfavorable prognosis!!
-Extreme leverage forces
generated by posterior position
-Occlusal forces place tensile stress
on 2o retainer
First molar cantilever
If absolutely necessary: -Pontic size small (premolar) -Light occlusal contact; no excursive contact -Pontic and connector need maximum O-G height for rigidity -Good crown:root ratio of abutments -Clinical crowns - maximum preparation length and resistance form
Cantilever first molar indications
-Lateral incisor abutment
-Why is this negative?
-Severe vertical overlap
-Why is this negative?
-Repeated de-cementation with
this particular case.
-Why would this keep
happening?
What other options could you have
done here to replace #9?
-Conventional bridge from #8-#10
-Single implant
-What else??
Central incisor cantilever