Indirect retainers / implant dentistry course/ implant dentistry course

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Indirect retainers / implant dentistry course/ implant dentistry course

  1. 1. Indirect retainersIndirect retainers INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  2. 2. CONTENTSCONTENTS  IntroductionIntroduction  DefinitionDefinition  Auxiliary functions of indirect retainersAuxiliary functions of indirect retainers  Factors determining effectiveness of indirectFactors determining effectiveness of indirect retainersretainers  Forms of indirect retainersForms of indirect retainers  ConclusionConclusion  BibliographyBibliography www.indiandentalacademy.comwww.indiandentalacademy.com
  3. 3. IntroductionIntroduction  A Removable partial denture that is supportedA Removable partial denture that is supported by healthy natural teeth posses adequateby healthy natural teeth posses adequate stability and retention to resist functionalstability and retention to resist functional displacement, but a denture base that isdisplacement, but a denture base that is supported at one end by a healthy naturalsupported at one end by a healthy natural abutment and at the other by movable softabutment and at the other by movable soft tissues will rotate toward or away from thetissues will rotate toward or away from the residual ridge when subjected to occlusal forcesresidual ridge when subjected to occlusal forces or the pull of sticky foods.or the pull of sticky foods. www.indiandentalacademy.comwww.indiandentalacademy.com
  4. 4.  This rotational movement occurring within aThis rotational movement occurring within a prosthesis supported by natural teeth and softprosthesis supported by natural teeth and soft tissue was first described bytissue was first described by F.H.BALKWILLF.H.BALKWILL inin 1880.1880.  In 1916,In 1916, J.H.PROTHEROJ.H.PROTHERO coined the termcoined the term FULCRUM LINEFULCRUM LINE to identify the primary axis ofto identify the primary axis of rotation.rotation. www.indiandentalacademy.comwww.indiandentalacademy.com
  5. 5.  When occlusal loadWhen occlusal load is applied to a distalis applied to a distal extension removableextension removable partial denture, thepartial denture, the prosthesis rotatesprosthesis rotates around a fulcrum linearound a fulcrum line that passes through thethat passes through the most posterior rests,most posterior rests, one on each side of theone on each side of the dental arch.dental arch.  This displacement isThis displacement is resisted by broad andresisted by broad and accurate adaptation ofaccurate adaptation of the denture base to thethe denture base to the supporting tissues.supporting tissues. www.indiandentalacademy.comwww.indiandentalacademy.com
  6. 6.  Forces acting to dislodge the prosthesis inForces acting to dislodge the prosthesis in occlusal direction occurs by sticky foods whichocclusal direction occurs by sticky foods which pull on the artificial teeth and move thepull on the artificial teeth and move the extension base away from the underlying ridges.extension base away from the underlying ridges.  Active tissues such as the tongue andActive tissues such as the tongue and buccinator muscle also displace the denturebuccinator muscle also displace the denture base during speech, mastication, or swallowing.base during speech, mastication, or swallowing. www.indiandentalacademy.comwww.indiandentalacademy.com
  7. 7.  During these forces, theDuring these forces, the associated fulcrum line passesassociated fulcrum line passes through the tips of the retentivethrough the tips of the retentive clasps and the anterior portionclasps and the anterior portion of the prosthesis rotates in anof the prosthesis rotates in an apical direction resulting inapical direction resulting in unwanted prosthesisunwanted prosthesis impingement into the softimpingement into the soft tissues of the floor of the mouth.tissues of the floor of the mouth.  This impingement of theThis impingement of the prosthesis into the floor of theprosthesis into the floor of the mouth is negated as the fulcrummouth is negated as the fulcrum line is transferred to the anteriorline is transferred to the anterior rest which acts as an indirectrest which acts as an indirect retainerretainer www.indiandentalacademy.comwww.indiandentalacademy.com
  8. 8. Indirect retainerIndirect retainer ““The component of a partial removableThe component of a partial removable dental prosthesis that assists the direct retainersdental prosthesis that assists the direct retainers in preventing displacement of the distalin preventing displacement of the distal extension denture base by functioning throughextension denture base by functioning through lever action on the opposite side of the fulcrumlever action on the opposite side of the fulcrum line when the denture base moves away fromline when the denture base moves away from the tissues in pure rotation around the fulcrumthe tissues in pure rotation around the fulcrum line.line. www.indiandentalacademy.comwww.indiandentalacademy.com
  9. 9. Indirect retentionIndirect retention ““ The effect achieved by one or moreThe effect achieved by one or more indirect retainers of a partial removable dentalindirect retainers of a partial removable dental prosthesis that reduces the tendency for aprosthesis that reduces the tendency for a denture base to move in an occlusal direction ordenture base to move in an occlusal direction or rotate about the fulcrum line”rotate about the fulcrum line” The concept of indirect retention wasThe concept of indirect retention was originally described byoriginally described by Dr.W.D.CUMMERDr.W.D.CUMMER www.indiandentalacademy.comwww.indiandentalacademy.com
  10. 10. Action of indirect retainersAction of indirect retainers www.indiandentalacademy.comwww.indiandentalacademy.com
  11. 11.  Auxiliary functions of indirect retainersAuxiliary functions of indirect retainers  When in positive contact with rest seat, an indirectWhen in positive contact with rest seat, an indirect retainer contributes to the overall support andretainer contributes to the overall support and stability of the prosthesis.stability of the prosthesis.  For long span lingual bar, it can provide additionalFor long span lingual bar, it can provide additional support and rigidity to the major connector.support and rigidity to the major connector.  It tends to reduce anteroposterior-tilting leveragesIt tends to reduce anteroposterior-tilting leverages on the principal abutments, particularly whenon the principal abutments, particularly when isolated tooth is being used as an abutment.isolated tooth is being used as an abutment. www.indiandentalacademy.comwww.indiandentalacademy.com
  12. 12.  Contact of its minor connector with axial toothContact of its minor connector with axial tooth surfaces aids in stabilization and also acts assurfaces aids in stabilization and also acts as auxiliary guiding plane when the tooth surface isauxiliary guiding plane when the tooth surface is made parallel to the path of placement.made parallel to the path of placement.  Anterior teeth supporting indirect retainers areAnterior teeth supporting indirect retainers are stabilized against lingual movement.stabilized against lingual movement.  It provides the first visual indications for the need toIt provides the first visual indications for the need to reline an extension base partial denture by thereline an extension base partial denture by the dislodgement of indirect retainers from theirdislodgement of indirect retainers from their prepared rest seats when the denture base isprepared rest seats when the denture base is depressed and rotation occurs around the fulcrum.depressed and rotation occurs around the fulcrum. www.indiandentalacademy.comwww.indiandentalacademy.com
  13. 13.  Fulcrum lines inFulcrum lines in various types ofvarious types of partial edentulouspartial edentulous arches and location ofarches and location of indirect retainers.indirect retainers. www.indiandentalacademy.comwww.indiandentalacademy.com
  14. 14. Factors influencing effectiveness ofFactors influencing effectiveness of the indirect retainers.the indirect retainers. 1. The principal occlusal rests on the primary1. The principal occlusal rests on the primary abutment teeth must be reasonably held in theirabutment teeth must be reasonably held in their seats, rotation about an axis should occur, whichseats, rotation about an axis should occur, which activates the indirect retainers. If totalactivates the indirect retainers. If total displacement of the rests occurs, there would bedisplacement of the rests occurs, there would be no rotation about the fulcrum, and the indirectno rotation about the fulcrum, and the indirect retainers would not be activated.retainers would not be activated. www.indiandentalacademy.comwww.indiandentalacademy.com
  15. 15. 2. Distance from the fulcrum line. The following2. Distance from the fulcrum line. The following three areas must be considered:three areas must be considered: a. length of the distal extension basea. length of the distal extension base b. location of the fulcrum line & indirect retainer.b. location of the fulcrum line & indirect retainer. c. how far beyond the fulcrum line the indirectc. how far beyond the fulcrum line the indirect retainer is placed.retainer is placed. 3. All connectors supporting the indirect retainer3. All connectors supporting the indirect retainer must be rigid .must be rigid . 4. The indirect retainer must be placed on a4. The indirect retainer must be placed on a definite rest on which slippage or toothdefinite rest on which slippage or tooth movement will not occur. Tooth inclines andmovement will not occur. Tooth inclines and weak teeth should never be used.weak teeth should never be used. www.indiandentalacademy.comwww.indiandentalacademy.com
  16. 16.  Forms of indirect retianersForms of indirect retianers  Auxiliary occlusal rests.Auxiliary occlusal rests.  Cingulum rests.Cingulum rests.  Incisal rests.Incisal rests. www.indiandentalacademy.comwww.indiandentalacademy.com
  17. 17. Occlusal restOcclusal rest Occlusal rest isOcclusal rest is most preferredmost preferred because of itsbecause of its location and verticallocation and vertical orientation, permitsorientation, permits forces to be directedforces to be directed within the long axis ofwithin the long axis of the abutment.the abutment. www.indiandentalacademy.comwww.indiandentalacademy.com
  18. 18. Cingulum restCingulum rest  A cingulum rest isA cingulum rest is commonly limited tocommonly limited to maxillary caninesmaxillary canines because of its normalbecause of its normal morphology whichmorphology which lends itself tolends itself to appropriate rest seatappropriate rest seat preparation withpreparation with minimal recontouring.minimal recontouring. www.indiandentalacademy.comwww.indiandentalacademy.com
  19. 19. Incisal restIncisal rest  An incisal rest used as indirect retainer onlyAn incisal rest used as indirect retainer only when all other rests are contraindicated.when all other rests are contraindicated.  It is given in maxillary and mandibular incisorsIt is given in maxillary and mandibular incisors and mandibular canines.and mandibular canines.  Incisal rests are esthetically objectional andIncisal rests are esthetically objectional and exhibit long approach arms that may transferexhibit long approach arms that may transfer harmful tipping forces to abutmentsharmful tipping forces to abutments www.indiandentalacademy.comwww.indiandentalacademy.com
  20. 20.  Most effective indirectMost effective indirect retention is achievedretention is achieved by preparing theby preparing the incisor to receiveincisor to receive either full coverageeither full coverage restoration or a castrestoration or a cast metal rest seat that ismetal rest seat that is bonded to the lingualbonded to the lingual surface of the tooth.surface of the tooth. www.indiandentalacademy.comwww.indiandentalacademy.com
  21. 21.  Canine extensionsCanine extensions from occlusal rests.from occlusal rests. A finger like extensions from aA finger like extensions from a premolar rest is placed on a lingualpremolar rest is placed on a lingual slope of the adjacent canine tooth.slope of the adjacent canine tooth. It is particularly applicable when aIt is particularly applicable when a first premolar serves as a primaryfirst premolar serves as a primary abutment.abutment. No preparation is required onNo preparation is required on cuspid. Such a design exploits thecuspid. Such a design exploits the excellent indirect retention that theexcellent indirect retention that the cuspid is capable of supplying andcuspid is capable of supplying and combines it with the equallycombines it with the equally excellent vertical support offered byexcellent vertical support offered by the bicuspid.the bicuspid. www.indiandentalacademy.comwww.indiandentalacademy.com
  22. 22.  Cingulum barsCingulum bars ( continuous bars )( continuous bars ) and linguoplatesand linguoplates .. Technically these are notTechnically these are not indirect retainers, becauseindirect retainers, because they rest on unpreparedthey rest on unprepared lingual inclines of anteriorlingual inclines of anterior teeth, but proves to beteeth, but proves to be effective if it is used with aeffective if it is used with a terminal rest at each end.terminal rest at each end. www.indiandentalacademy.comwww.indiandentalacademy.com
  23. 23.  Rugae supportRugae support www.indiandentalacademy.comwww.indiandentalacademy.com
  24. 24. ConclusionConclusion The distal extension partial denture tends to rotate aroundThe distal extension partial denture tends to rotate around the fulcrum lines, this movement away from the tissues can bethe fulcrum lines, this movement away from the tissues can be resisted by the activation of the direct retainer, stabilizingresisted by the activation of the direct retainer, stabilizing components of clasp assembly. Ultimately it is a indirectcomponents of clasp assembly. Ultimately it is a indirect retainer, a part of the rigid component of the partial dentureretainer, a part of the rigid component of the partial denture frame work that are located on the definitive rests on theframe work that are located on the definitive rests on the opposite side of the fulcrum line away from the distal extensionopposite side of the fulcrum line away from the distal extension base which is responsible to resist the movements away frombase which is responsible to resist the movements away from the tissue .the tissue .  Hence the choice of the indirect retainer should be based onHence the choice of the indirect retainer should be based on biologic as well as mechanical principles.biologic as well as mechanical principles.  The dentist responsible for the treatment rendered must beThe dentist responsible for the treatment rendered must be able to justify the indirect retention used for each abutmentable to justify the indirect retention used for each abutment tooth in keeping with these principles.tooth in keeping with these principles.www.indiandentalacademy.comwww.indiandentalacademy.com
  25. 25.  BibliographyBibliography  Mc Cracken’s –Removable partialMc Cracken’s –Removable partial prosthodontics.prosthodontics.  Stewart’s – Clinical Removable partialStewart’s – Clinical Removable partial prosthodontics- third editionprosthodontics- third edition  Ernest L. Miller – Removable partialErnest L. Miller – Removable partial prosthodontics.prosthodontics.  Osborne & Lammie’s – RemovableOsborne & Lammie’s – Removable prosthodonticsprosthodontics www.indiandentalacademy.comwww.indiandentalacademy.com
  26. 26. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com

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