Stewarts Flashcards
Six requirements of direct retainers (clasp assemblies)
- Support
- Retention
- Stability
- Reciprocation
- Encirclement
- Passivity
Three factors affecting the magnitude of retention of clasp arms
- Angle of convergence
- Placement of clasp into angle of convergence
- Flexibility of clasp arm
Six factors of clasp flexibility
- Length
- Cross-sectional form
- Longitudinal taper
- Cross-sectional diameter
- Clasp curvature
- Alloy characteristics
Four factors of indirect retainer effectiveness
- Distance from fulcrum line
- Status of abutment tooth
- Full seating
- Rigidity of minor connector
Altered cast purpose (3)
- Improve adaptation of denture base to the ridge
- Equalize stress between ridge and abutments
- Capture periphery
Why is altered cast not necessary for maxillary arch?
The palate contacts with the major connector
Two potential issues with altered cast
- Not fully seating RPD
2. Newly poured stone onto teeth surfaces preventing articulation
Applegate’s modifications 1-4
- Classification made after extractions
- If third molar is missing and not to be replaced, it is not included in classification
- If third molar is part of restoration, it is considered
- If second molar is missing and not to be replaced, it is not included in classification
Applegate’s modifications 5-8
- Most posterior edentulous region determines classification
- Edentulous regions other than most posterior are deemed modifications
- Extent of modification is not considered, just number
- Class IV’s cannot have a ny modifications
For an RPD, how much in mm can teeth and soft tissue be displaced?
Teeth: 0.2 mm
Soft tissue: 1.0 mm
Major connector requirements (5)
- Rigidity
- Protect soft tissues
- Provide a means for indirect retainers
- Provide a means for denture bases
- Promote patient comfort
Why is amalgam not preferred for rest seats?
- Unfavorable flow and poor tensile characteristics
2. Replacement of defective restoration under RPD is difficult
Define angle of cervical convergence
Angle created by the analyzing rod and tooth surface apical to the height of contour
The greater the angle, the greater the force to remove a clasp from the abutment
What two strategies to utilize if severe angle of convergence?
- Engage only 0.1 undercut instead of 0.2
2. Recontour tooth surface
Purpose of rest seats (2)
- Resist displacement / movement of RPD
2. Direct forces down long axis of abutment tooth
Who introduced the cast circumferential clasp?
Wrought wire circumferential clasp?
I-bar?
- Nesbitt in 1916
- Applegate in 1965
- Krol
What are the three fulcrums in RPD?
- Vertical - From rest to rest of abutment teeth (movement in sagittal)
- Sagittal - Rest seats through crest (movement in frontal plane - two in a KC 1 red)
- Horizontal - Fulcrum is near midline - Most dangerous (horizontal plane)
RPI - having the rest of the mesial leads to what kind of lever system whenever there is occlusal load on a distal extension?
Class II level system
Beyron’s point
13 mm anterior to the tragus on a line from the tragus to the cantus of the eye
What third reference point does the Hanau springbow utilize?
Infraorbital notch
How long to keep Iowa or Korecta wax intramurally for fluid wax technique?
5-7 minutes
If tissue contact during fluid wax technique, will wax be shiny or dull?
If contact with tissue - shiny
If no contact, wax is dull
Hanau’s formula?
What is it for?
L = H/8 + 12
Set lateral condyle setting from protrusive record
Five factors of Hanau’s quint
- Condylar guidance
- Incisal guidance
- Occlusal plane
- Compensating curve
- Height of cusps
Composition of tissue conditions? (powder and liquid)
Powder - Polyethylmethacrylate
Liquid - Ethyl alcohol and ester
Clinical impact of arcon vs nonarcon
When you increase the OVD, non-arcon will not maintain the relationship between the occlusal plane and horizontal condylar guidance
