9Tooth-tissue supported partial dentures are subjected to vertical displacing forces acting in an occlusal direction. These forces may totally displace the denture if the direct retainers are not functioning adequately. However if the direct retainers are adequate, rotation of the denture around a fulcrum axis rather than total displacement occurs. This rotation is counteracted by the unit of the partial denture called "Indirect retainer".
10In tooth supported partial dentures; tissue away movement of the prosthesis is prevented by the action of direct retainers and rests placed on the abutment teeth (self indirect retainer).In mucosa supported partial dentures;(full palatal coverage) tissue away movement of the prosthesis is prevented by mechanical means (clasps) and by the action of physical means of retention on a well fitting denture base and the connector (direct indirect retention).
11Indirect Retainers are “components of removable partial denture that are used to reduces the tendency of the denture to rotate in an occlusal direction about the fulcrum axis”
12Fulcrum LinesRetentive fulcrum line is the line joining the retentive tips of the clasps holding the principal abutments (Diagonally placed).Supportive Fulcrum Line Is the Line Joining the Occlusal Rests Supported by Principal Abutments.
16FThis Movement Is Related To Quality Of The Tissue, Extent Of Denture Base And Its Fit And The Amount Of Force Applied
17Indirect RetentionComponents of RPD That Are Used to Reduces Its Tendency to Rotate in an Occlusal Direction About the Fulcrum AxisSupportive Elements (Rests) Used to Retain Far Ends of Partial Dentures
18DIRECT RETAINERSRetaining Elements (Clasps) Used to Retain Near Ends of Partial Dentures
19FThis Movement Is Related To Quality Of The Tissue, Extent Of Denture Base And Its Fit And The Amount Of Force Applied Support
21Tooth-tissue Supported Partial Dentures Are Subjected to Vertical Displacing Forces Acting in an Occlusal Direction. If the Direct Ret. Are Adequate, Rotation of the Denture Around a Fulcrum Axis Rather Than Total Displacement Occurs
27Factors Influencing the Effectiveness of Ind.Ret. 1-Effectiveness of the Direct R.
282- Proper Location of I.RWell-supported I. R. Should Be Placed As Far From the Fulcrum Line As Possible. The Greater the Distance, the More Effective Is the Indirect RetentionA Perpendicular Line Projecting Anteriorly From the Fulcrum Axis Is the Most Effective Location of I. R. And Affords the Best Resistance Against Vertical Dislodging Forces
35I.R. In the Form of Rest Should Be Placed in a Definite, Properly Prepared Rest Seat That Allows Transmission of the Forces Along the Long Axis of the Tooth Without Slippage of the Rest or Movement of the Tooth
474- Auxiliary Rests at the Terminal Ends of Ling. Plate or Kennedy Bar
48A- R. Used In Mandibular P. D. Forms of Ind.RetainersA- R. Used In Mandibular P. D.1-Auxiliary Occlusal or Canine Rests2- Principal Occlusal Rest of Modification Area3- Embrasure Hooks4- Auxiliary Rests at the Terminal Ends of Ling Plate or Kennedy Bar
49B- Indirect Retainers Used in Maxillary Partial Dentures 1) Cummer Arm2) Palatal Arm3) Anterior Palatal Bar4) Posterior Palatal Bar
505) Palatal Strap and Rugae Support 6) Direct-indirect Retainer (Full Palatal Coverage)7) Auxiliary Occlusal or Canine Rests8) Principal Occlusal Rest of Modification Area