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BIOMECHANICS OF REMOVABLE PARTIAL DENTURE new.pptx
- 1. BIOMECHANICS OF REMOVABLE PARTIAL DENTURE Dr. Wajiha Zia Resident of Prosthodontics AIDM
- 2. CONTENT • Definition of biomechanics • Biomechanical consideration • Forces acting on partial denture • Types of machine • Types of simple machine • Types of lever • Fulcrum line • Movement of Rpd • Factors Influencing Stresses Transmitted to Abutment Teeth
- 3. DEFINITION OF BIOMECHANICS: Application of biomechanical principles act on biological tissues and use these principles to design a stable prosthesis
- 4. WHY BIOMECHANICS IS IMPORTANT: Maximize stability in removable dentures control movement of rpd under functional load
- 5. BIOMECHANICAL CONSIDERATIONS Forces require resistance Duration, magnitude and intensity of forces Teeth or mucosa capacity to resist these forces How material influence resistance
- 6. Fibers of the periodontal ligament are arranged to resist vertical (i-e, axial) forces more effectively than horizontal or torsional force
- 7. FORCES ACTING ON PARTIAL DENTURE • Transvere plane • Saggital plane • Coronal plane
- 8. AXES OF THE BODY: The planes which are mutually perpendicular and therefore intersect one another at right angles. The intersection of any two planes forms a linear axis
- 10. SIMPLE MACHINE:
- 11. COMPLEX MACHINE: Complex machine is the combination of one or more simple machine •Lever •Inclined plane Mechanical principle in RPD
- 12. FULCRUM LINE:
- 13. FULCRUM LINE: Fulcrum line is the center of rotation or imaginary line around which the denture rotates.
- 14. LEVER: A simple machine consists of rigid bar on fixed point and used to transmit forces at one end by pushing down on the other
- 15. TYPES OF LEVER:
- 16. • First class lever • Most efficient(with modification) • Second class lever • Less efficient • Third class lever • Least efficient Types of lever
- 17. A cantilever is a beam supported at one end that can act as a first-class lever. A cantilever design should be avoided.
- 18. INCLINED PLANE: Forces acting against inclined plane may result in movement to the inclined plane in opposite direction that’s not desirable
- 19. 1) MOVEMENT AROUND TRANSVERE AXIS: Movement of denture base towards and away from the denture FORCES ON TRANSVERSE AXIS: • Sticky food • Pulling of food • Gravity in maxillary denture MOVEMENT OF RPD:
- 20. Stabilizing component for denture movement: Movement away from denture base • Retentive clasp arm(direct retainer) • Minor connector Movement towards tissue • Rest on abutment • Accuracy of fit of denture • Quality of tissue • Amount of occlusal force
- 22. 2.MOVEMENT AROUND LONGITUDINAL OR SAGGITAL AXIS: Movement around the distal extension base in a rotary direction about the residual ridge •Rigidity of major and minor connector •Rigidity of direct retainer STABILIZING COMPONENT:
- 24. 3.MOVEMENT AROUND VERTICAL AXIS: Movement of denture is near the center of the dental arch FORCES ON VERTICAL AXIS STABILIZING COMPONENT Lateral stresses: Mastication, bruxism, clenching Reciprocal clasp arm Minor connector
- 26. Factors Influencing Stresses Transmitted to Abutment Teeth: Length of edentulous span Quality of ridge support Clasp flexibility Clasp design Length of clasp Material used in clasp Occlusal harmony Surface characteristics of abutment
- 28. THANK YOU
Editor's Notes
- AOA, waji … fcps resident in depth of prostho, my topic of presen. In book club
- As we know that Most common problem is movement of rpd and to prevent this movment we have to study about biomechanics and its principals..
- Why we uses it to design rpd, To gain max.
- Which things need consideration in desiging rpd Forces on rpd Material thru which we make rpd
- In a normal tooth , pdl arrangement in the tooth are…
- Lets discuss the forces on rpd. This is human body, in which we have coronal and frontal is same/ rpd rotate in 3 these plane so its imp. So its imp. to understand these plane
- As we discussed that we have 3planes so we also have 3 axes/ frontal means saggital axes, u can see in the picture/ so on these planes forces are going to be act and displace the rpd,
- iN order to resist these forces, simple machines are applied to the design of removable partial dentures
- We study lver and inclined plane
- Before the discussion of lever, lets discuss about the fulcrum which is the Imaginary line around which denture rotates & present on distal abutments
- Class 3 fulcrum is non existent b/c it is tooth supported and no rotation b/c of soft tissue
- Fixed point is fulcrum
- F is in middle/ e is on one end while r is on another end Types depend on the sequence based on location of fulcurm 1..fclrum in center e.g is sesaw Clinical e.g of 1st class is distal extension…………. F is occlusal rest/ R is clasp 2… r in center e.g wheel barrow, f is mesial rest r is retentive arm of I bar 3… e in center e.g is fising,stapler, in class3 rpd/ f because from here the denture is moved How to deal with these forces …attach imdirect retainer
- Its e.g is rest…….If rest is on inclined plane then forces will dislodge the rest so we place it on less than 90 degree to prevent this
- I am going to discuss movement of rpd in 3 plane
- So this is the clinical e.g of movement of denture in transvere axis, denture move in transverse axis
- Buccolingual movement of denture
- Mediolateral/ horizontal movement of denture F is in midline