Biomechanics Flashcards
- Application of mechanical engineering principles in the living organism
- Mechanical forces exerted on RPD during functional & parafunctional mandibular movements should be properly directed to the supporting tissue to elicit the most favorable response.
Biomechanics
Teeth better able to tolerate vertical forces: down ____ of tooth
–More PDL fibers activated to resist force
long-axis
Excess force to alveolar bone may result in what 2 things?
Mucosal ulcerations
Bone resorption
What are the 3 RPD components involved in retention?
Direct retainer: Retentive clasp
Indirect retainer
Proximal plates
What 4 RPD components involved in stability?
Minor connectors
Proximal plates
Lingual plates
Denture bases
What are the 3 RPD components involved in support?
Rests
Major connectors (Max tooth tissue supported)
Denture bases
:is the means by which one part of a restoration is made to counter the effects created by another part.
Reciprocation
RPD’s true reciprocation can only be achieved if the reciprocating element touches the tooth before or after the retentive clasp?
Before
What class of RPDs best resist functional forces
Class III
What are the 3 cases of RPD that are Tooth tissue supported
Class 1, 2 and long span IV
What are the tooth supported classes of RPD?
Class III and short span class IV
Tooth tissue or tooth supported?
–Subject to greater stress
–Combination of tooth & soft tissue support
–RPD extension movement permits rotational movement around fulcrums in 3 planes
Tooth tissue supported
What motion occurs through the sagittal plane through the horizontal plane fulcrum?
Rotation causing vertical dislodgement
What motion occurs through the vertical plane through the longitudinal fulcrum?
Rocking side to side
What motion occurs through the horizontal plane through the vertical fulcrum?
Horizontal twisting resulting in BL movement of RPD
What class of lever do you need for an RPD?
Class 2
What type of clasp causes a class 1 lever in distal extension cases?
Distal rest with circumferenial class
What type of clasp causes class 2 lever in distal extension cases?
RPI or RPC with mesial rest
Class ____ lever occurs when abutment with retentive clasp anterior to horizontal fulcrum line/axis of rotation (AR) in Class II arch with posterior modification space.
Class I Lever
Is a broad or thin ridge provide better resistance to vertical and horizontal forces?
Broad ridge
If the clasp is more flexible, how will it relate to stress on the abutment teeth, residual ridge, and horizontal stability?
Less stress to abutment
More stress to ridge
Less horizontal stability
Does the retentive or reciprocal clasp arm contact the tooth first?
Reciprocal clasp
