Selection of Abutment Teeth Flashcards
What are the 7 critical factors for selecting abutment teeth
- Crown-root ratio
- Root configuration
- Periodontal ligament area
- Biomechanical consideration
- Periodontal health
- Endodntic consideration
- Pier abutments
As the level of bone moves apically, the crown/root ratio __, this __ the tooths prognosis
increases
compromises
What are 2 causes of increased crown/root ratio
Periodontal disease
tooth supereruption
Crow/root ratios above __ are unacceptable
1.0
Clinical crown > clinical root
(Look at picture of most favorable / acceptable)
What is the most favorable crown/root ratio
2/3 (0.66)
Root configuration:
Roots with greater __ are preferred than a circular root
labiolingual
(maxillary 1st premolar)
(holds onto bone better)
For multi-rooted teeth, __ roots are preferred
spread out
(Picture)
Are longer or shorter roots better for abutment teeth
Longer roots
(canine)
Periodontal Ligament Area:
What is Ante’s Law
States that the total root surface area of all supporting teeth must equal or exceed the total root surface area of the teeth being replaced
(There are root surface area numbers and you calculate this)
Biomechanical Considerations:
Relative deflection of pontics-
Mesio-distal :
Occluso-gingivally :
Mesio-distal : Directly proportional
(The bigger the span length, the bigger the deflection) (Bigger the pontic more likely to bend)
Occluso-gingivally : Inversely proportional
(The thicker the restoration, the lesser the deflection) (want a thicker tooth so it doesn’t bend)
(# of pontics)^3 =
FDPs deflection
Biomechanical Considerations:
Direction of force -
The dislodging forces on an FDP tend to act in a __ direction, as opposed to __ with a single crown
mesio-distal
bucco-lingually
Biomechanical Considerations:
Direction of force -
Preparations should be modified with __ to obtain a better retention and resistance form, ultimately better prognosis
retentive grooves (buccal/lingual)
Biomechanical Considerations:
Secondary abutments -
High risk of __ of secondary abutments due to tensile forces created on the retainers while the FDP is under load
margin leakage
(Look at pic of what margin leakage is)
Biomechanical Considerations:
Secondary abutments -
Sufficient crown height and space between adjacent abutments to prevent impingement of the __
gingiva under the connector
Are secondary abutments recommended
NO
Biomechanical Considerations:
Arch curvature -
When pontics lie outside the __ they act like a lever arm, which will produce a torquing force under load. Where is this most commonly seen?
interabutment axis (fulcrum line) line
Anterior teeth
Biomechanical Considerations:
Arch curvature -
What are required in these cases
secondary abutments (not ideal though, implant option is recommended if possible)
Biomechanical Considerations:
Arch curvature -
The retainers width span should be equal or bigger than the __
pontic lever arm
(look at pic)
Biomechanical Considerations:
Opposing arch nature -
What kind of occlusion will this new FDP be experiencing / how do forces increases with the type of appliance
(Forces increases as you go down the list)
Complete denture
Removable Dental Prosthesis
Natural dentition
Implant supported restoration (worst/ most force)
Other biomechanical consideration to consider (4)
Bruxism / clenching
parafunctional habits
neighbor teeth
occlusion on contralateral side
Periodontal Health:
__ periodontal tissues are prerequisite for all fixed restorations
If crown-root ratio is already questionable (1/1), __ and __ need to be excellent. If not, FDP will have a poor __
Healthy
periodontal health
oral hygiene
prognosis
Endodontic consideration:
If abutment tooth vitality is questionable, an __ prior to fabrication of FDP might be indicated
endodontic treatment
Endodontic consideration:
In many occasions an __ might be indicated in order to fabricate an FDP. For example, when preparing an FDP on teeth that are angled or supererupted, pulp will be exposed in order to obtain an appropriate path of insertion/clearance
elective endodontic treatment
(Note: ortho is perferred)
Pier abutments:
A natural tooth or implant abutment that is located between terminal abutments that serves to support a fixed or removable dental prosthesis
Intermediate abutment
A __ should be avoided if a pier abutment is present
conventional (long span) FDP
An intermediate abutment will create huge stress on __
terminal and pier abutments
(like a seesaw)
(look at pic and read possible complications)
Pier abutment:
Treatment options (4)
- (Ideal) implant restorations
- Implant crown on one side and FDP on other
- FDP with non-rigid connector which will work as a stress reliever
- Cantilever pontic (not ideal, occlusion should be evaluated very closely)
Cantilever pontic should be more mesial or distal
Mesial (mouth is like scissors, more force in the back)
