Clasp designs / dentist technology

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Clasp designs / dentist technology

  1. 1. CLASPCLASP DESIGNSDESIGNS.. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2.  A removable partial denture mustA removable partial denture must havehave  SupportSupport  StabilizationStabilization  RetentionRetention www.indiandentalacademy.com
  3. 3. RETENTIONRETENTION FOR RPDFOR RPD  Is derivedIs derived mechanicallymechanically byby placing the retaining elements onplacing the retaining elements on the abutment tooth.the abutment tooth. www.indiandentalacademy.com
  4. 4. Direct retainerDirect retainer  Is that component of removableIs that component of removable partial denture used to retain andpartial denture used to retain and prevent dislodgement , consistingprevent dislodgement , consisting of clasp assembly or precisionof clasp assembly or precision attachment.attachment. -GPT.-GPT. www.indiandentalacademy.com
  5. 5.  Two types of direct retainers :Two types of direct retainers : 1) Intra coronal retainer (Attachments).1) Intra coronal retainer (Attachments). 2) Extra coronal retainer (clasps).2) Extra coronal retainer (clasps). www.indiandentalacademy.com
  6. 6. Intra coronal retainerIntra coronal retainer www.indiandentalacademy.com
  7. 7. Extra coronal retainer.Extra coronal retainer.  Two configurations areTwo configurations are 1) Manufactured retainers (Dalbo)1) Manufactured retainers (Dalbo) 2) Custom-made retainers:2) Custom-made retainers: a) Occlusally approaching (Circumferential ora) Occlusally approaching (Circumferential or Akers clasp)Akers clasp) b) Gingivally approaching (Bar or Roachb) Gingivally approaching (Bar or Roach clasp)clasp) www.indiandentalacademy.com
  8. 8.  Principle of extra coronal directPrinciple of extra coronal direct retainer.retainer. Resistance of the metal to theResistance of the metal to the deformation.deformation. www.indiandentalacademy.com
  9. 9. ClaspClasp  Is the component of the clasp assemblyIs the component of the clasp assembly that engages a portion of the tooth surfacethat engages a portion of the tooth surface and either enters an undercut for retentionand either enters an undercut for retention or remains entirely above the height ofor remains entirely above the height of contour to act as a reciprocating element.contour to act as a reciprocating element.  Generally, it is used to stabilize and retainGenerally, it is used to stabilize and retain a removable prosthesis.a removable prosthesis. -GPT.-GPT. www.indiandentalacademy.com
  10. 10. Clasp assembly.Clasp assembly.  The part of a removable partial dentureThe part of a removable partial denture that acts as a direct retainer and orthat acts as a direct retainer and or stabilizer for a prosthesis by partiallystabilizer for a prosthesis by partially encompassing or contacting an abutmentencompassing or contacting an abutment tooth.tooth. -GPT.-GPT. www.indiandentalacademy.com
  11. 11. ComponentComponent parts.parts. FunctionFunction LocationLocation RestRest SupportSupport Occlusal, Lingual, IncisalOcclusal, Lingual, Incisal MinorMinor connectorconnector StabilizationStabilization Proximal surfaces extendingProximal surfaces extending from the prepared marginalfrom the prepared marginal ridge to the junction of theridge to the junction of the middle and gingival third ofmiddle and gingival third of abutment crown.abutment crown. Clasp armsClasp arms StabilizationStabilization ReciprocationReciprocation RetentionRetention Apical portion of middle third ofApical portion of middle third of crown.crown. Apical portion of middle third ofApical portion of middle third of crowncrown Gingival third of crown inGingival third of crown in www.indiandentalacademy.com
  12. 12.  The critical areas of an abutment that isThe critical areas of an abutment that is responsible forresponsible for retention, stabilization,retention, stabilization, reciprocation and guide planesreciprocation and guide planes can onlycan only be identified with the use ofbe identified with the use of dentaldental surveyors.surveyors. www.indiandentalacademy.com
  13. 13.  General considerations:General considerations: A clasp should be located at the undercutA clasp should be located at the undercut area in relation to the determined path ofarea in relation to the determined path of insertion and removal of the prosthesis.insertion and removal of the prosthesis. www.indiandentalacademy.com
  14. 14. Prothero’s cone theory.Prothero’s cone theory. According to him , the tooth is considered as a pair of cones sharing a common base A clasp arm or tip that ends on a cervical cone would resist movement in the occlusal direction because to release from the tooth it would be forced to undergo deformation.www.indiandentalacademy.com
  15. 15.  The line which the two converging conesThe line which the two converging cones meet is called themeet is called the height of contourheight of contour, the, the term first coined byterm first coined by Kennedy.Kennedy.  DevanDevan referred to the surface of a toothreferred to the surface of a tooth that is occlusal to the height of contour asthat is occlusal to the height of contour as supra bulgesupra bulge, and the tooth surface that is, and the tooth surface that is cervical to its height of contour ascervical to its height of contour as infrainfra bulge.bulge. www.indiandentalacademy.com
  16. 16. Component parts of a clasp.Component parts of a clasp.  The component parts of a clasp assemblyThe component parts of a clasp assembly may be rigid or flexible.may be rigid or flexible.  The flexible components are designedThe flexible components are designed below the height of contourbelow the height of contour www.indiandentalacademy.com
  17. 17. Component parts of a claspComponent parts of a clasp  Retentive clasp armRetentive clasp arm  Retentive terminalRetentive terminal  Reciprocal armReciprocal arm  Occlusal restOcclusal rest  ShoulderShoulder  BodyBody  Minor connectorMinor connector www.indiandentalacademy.com
  18. 18. Retentive armRetentive arm  A flexible segment of a removable partialA flexible segment of a removable partial denture which engages a under cut on andenture which engages a under cut on an abutment which is designed to retain theabutment which is designed to retain the denture – GPTdenture – GPT Retentive arm retentive clasp armRetentive arm retentive clasp arm ++ retentive terminalretentive terminal www.indiandentalacademy.com
  19. 19. Retentive armRetentive arm  Retentive clasp arm - not flexibleRetentive clasp arm - not flexible - located above the- located above the height of contourheight of contour Retentive terminal - flexibleRetentive terminal - flexible - located below the- located below the height of contourheight of contour www.indiandentalacademy.com
  20. 20. Reciprocal armReciprocal arm A component of a clasp assemblyA component of a clasp assembly specifically designed to providespecifically designed to provide reciprocation by engaging a reciprocalreciprocation by engaging a reciprocal guiding plane andguiding plane and it counteracts the action of the clasp duringit counteracts the action of the clasp during the removal and insertion of the partialthe removal and insertion of the partial denture - GPTdenture - GPT www.indiandentalacademy.com
  21. 21. Reciprocal armReciprocal arm  Location - on the side of the toothLocation - on the side of the tooth opposite to the retentive armopposite to the retentive arm  - always placed in the supra- always placed in the supra bulge areabulge area www.indiandentalacademy.com
  22. 22. Reciprocal armReciprocal arm  Function - resists the lateral forcesFunction - resists the lateral forces exerted by the retentive armexerted by the retentive arm when it passes through thewhen it passes through the height of contourheight of contour  - acts as an indirect retainer- acts as an indirect retainer when placed on an abutmentwhen placed on an abutment located anterior to thelocated anterior to the fulcrum linefulcrum line www.indiandentalacademy.com
  23. 23. ShoulderShoulder  Part of the clasp thatPart of the clasp that connects the body to theconnects the body to the clasp terminalclasp terminal  Lies above the height ofLies above the height of contourcontour  Provides stabilizationProvides stabilization against horizontalagainst horizontal displacementdisplacement www.indiandentalacademy.com
  24. 24. BodyBody  Part of the clasp that connects the rests andPart of the clasp that connects the rests and shoulders of the clasp of the minor connectors.shoulders of the clasp of the minor connectors.  It is rigid and lies above the height of contourIt is rigid and lies above the height of contour  It contacts the guide plane of the abutment duringIt contacts the guide plane of the abutment during the insertion and removalthe insertion and removal  Part of the body that contacts the guiding plane -Part of the body that contacts the guiding plane - proximal plateproximal plate www.indiandentalacademy.com
  25. 25. restrest  A rigid extension of a removableA rigid extension of a removable partial denture which contacts apartial denture which contacts a remaining tooth or teeth toremaining tooth or teeth to dissipate vertical or horizontaldissipate vertical or horizontal forcesforces  part of the clasp assembly thatpart of the clasp assembly that lies on the occlusal or lingual orlies on the occlusal or lingual or incisal edge or surfaces of theincisal edge or surfaces of the teethteeth  Resist tissue ward movement ofResist tissue ward movement of the clasp by acting like a verticalthe clasp by acting like a vertical stopstop www.indiandentalacademy.com
  26. 26. Minor connectorMinor connector  It joins the clasp with the remaining part ofIt joins the clasp with the remaining part of the frameworkthe framework  In gingivally approaching clasp –In gingivally approaching clasp – Approach armApproach arm www.indiandentalacademy.com
  27. 27. BASIC PRINCIPLES OF CLASPBASIC PRINCIPLES OF CLASP DESIGNDESIGN  Any clasp assembly must satisfy the basicAny clasp assembly must satisfy the basic prin­ciple of clasp design, isprin­ciple of clasp design, is ENCIRCLEMENTENCIRCLEMENT  which is that more than 180 degrees ofwhich is that more than 180 degrees of the greatest circumference of the crown ofthe greatest circumference of the crown of the tooththe tooth  passing from diverging axial surfaces topassing from diverging axial surfaces to converging axial surfacesconverging axial surfaces www.indiandentalacademy.com
  28. 28.  In the form of continuous contact whenIn the form of continuous contact when circumferential clasp arms are used.circumferential clasp arms are used.  When bar clasp arms are used, at leastWhen bar clasp arms are used, at least three areas of tooth contact must bethree areas of tooth contact must be embracing more than one half of toothembracing more than one half of tooth circum­ferencecircum­ference  These are the occlusal rest the retentiveThese are the occlusal rest the retentive terminal area, and the reciprocal terminalterminal area, and the reciprocal terminal area.area. www.indiandentalacademy.com
  29. 29. Other principles to be considered inOther principles to be considered in the design of a clasp are asthe design of a clasp are as follows:follows:  1. The occlusal rest must be designed so that1. The occlusal rest must be designed so that movement of the clasp arms cervically ismovement of the clasp arms cervically is prevented.prevented.  2. Each retentive terminal should be opposed by2. Each retentive terminal should be opposed by a reciprocal arm or element capable of resistinga reciprocal arm or element capable of resisting any orthodontic pressures exerted by theany orthodontic pressures exerted by the retentive arm.retentive arm.  Reciprocal and stabilizing elements must beReciprocal and stabilizing elements must be rigidly connected bilaterallyrigidly connected bilaterally www.indiandentalacademy.com
  30. 30.  3. Retentive clasps should be bilaterally3. Retentive clasps should be bilaterally opposed,opposed,  that is, buccal retention on one side of the archthat is, buccal retention on one side of the arch should be opposed by buccal retention on theshould be opposed by buccal retention on the other, or lingual on one side opposed by lingualother, or lingual on one side opposed by lingual on the other.on the other.  In Class II situations the third abutment mayIn Class II situations the third abutment may have either buccal or lingual retention.have either buccal or lingual retention.  In Class III situations, retention may be eitherIn Class III situations, retention may be either bilaterally or diametrically opposedbilaterally or diametrically opposed www.indiandentalacademy.com
  31. 31. . A, Retentive clasps should be bilaterally opposed. B, In Class II situations the retention on the third abutment may be on the buccal or the lingual . C, In Class III situations retention may be either (a) bilateral or (b) diametrically opposed. www.indiandentalacademy.com
  32. 32.  4. The path of escapement of each retentive4. The path of escapement of each retentive clasp terminal should never coincide with theclasp terminal should never coincide with the path of removalpath of removal  5. Amount of retention should be the minimum,5. Amount of retention should be the minimum, necessary to resist reasonable dislodgingnecessary to resist reasonable dislodging forces.forces.  6. Clasp retainers on abutment teeth adjacent to6. Clasp retainers on abutment teeth adjacent to distal extension bases should be designed sodistal extension bases should be designed so that, it should never exert tipping forces on thethat, it should never exert tipping forces on the abutment teeth.abutment teeth. www.indiandentalacademy.com
  33. 33.  7. Reciprocal elements of the clasp7. Reciprocal elements of the clasp assembly should be located at the junctionassembly should be located at the junction of the gingival and middle thirds of theof the gingival and middle thirds of the crowns of abutment teeth.crowns of abutment teeth.  The terminal end of the retentive arm isThe terminal end of the retentive arm is optimally placed in the gingival third of theoptimally placed in the gingival third of the crowncrown www.indiandentalacademy.com
  34. 34. Functional requirements of a clasp.Functional requirements of a clasp.  RetentionRetention  StabilityStability  SupportSupport  ReciprocationReciprocation  EncirclementEncirclement  Passivity.Passivity. www.indiandentalacademy.com
  35. 35. Retention.Retention.  The function of retentive clasp arm is toThe function of retentive clasp arm is to provide retention.provide retention.  The retentive clasp is divided into threeThe retentive clasp is divided into three parts.parts.  The terminal third – engages the undercutThe terminal third – engages the undercut area.area. Middle third - engages a minimalMiddle third - engages a minimal amount of undercut.amount of undercut. www.indiandentalacademy.com
  36. 36.  The proximal third - is positioned aboveThe proximal third - is positioned above or shoulder the height of contour.or shoulder the height of contour. www.indiandentalacademy.com
  37. 37. Three dimensions of a retentiveThree dimensions of a retentive undercut.undercut. www.indiandentalacademy.com
  38. 38. The following factors determine theThe following factors determine the amount retention a clasp is capable ofamount retention a clasp is capable of generating.generating.  1) Size of angle of cervical convergence.1) Size of angle of cervical convergence.  2) How far into the angle of cervical2) How far into the angle of cervical convergence the clasp terminal is placed.convergence the clasp terminal is placed.  3) Flexibility of the clasp arm, which is the3) Flexibility of the clasp arm, which is the product of -product of - a) Its length which is directly proportionala) Its length which is directly proportional to the flexibility.to the flexibility. www.indiandentalacademy.com
  39. 39.  b) Its diameter is inversely proportionalb) Its diameter is inversely proportional to the flexibility of the clasp arm.to the flexibility of the clasp arm.  c) Its cross-sectional form or shape, thatc) Its cross-sectional form or shape, that is, whether it is round, half-round, or some otheris, whether it is round, half-round, or some other form.form. round clasp - flex in all spatial planes.round clasp - flex in all spatial planes. half-round clasp-flex only in a single plane.half-round clasp-flex only in a single plane. www.indiandentalacademy.com
  40. 40. d) The material of which the clasp is made,d) The material of which the clasp is made, that is whether it is made of a gold alloy,that is whether it is made of a gold alloy, or chrome alloy.or chrome alloy. Chrome alloy have a higher modulus ofChrome alloy have a higher modulus of elasticity and is less flexible.elasticity and is less flexible. www.indiandentalacademy.com
  41. 41. A smaller cross sectional form of the clasp and less depth of the retentive undercut is engaged when chrome alloy is used and vice versa while using gold alloy. www.indiandentalacademy.com
  42. 42. Cast vs. wrought alloy.Cast vs. wrought alloy. www.indiandentalacademy.com
  43. 43. Support.Support.  Is the property of a clasp that resistsIs the property of a clasp that resists displacement of the clasp in a gingivaldisplacement of the clasp in a gingival direction.direction.  The support units of a clasp are occlusal,The support units of a clasp are occlusal, lingual, or incisal rests.lingual, or incisal rests. www.indiandentalacademy.com
  44. 44. Stability.Stability.  All clasp components except the retentiveAll clasp components except the retentive clasp terminals contribute to this propertyclasp terminals contribute to this property in varying degrees.in varying degrees.  Cast circumferential –offers greatestCast circumferential –offers greatest clasp amount of stability.clasp amount of stability. www.indiandentalacademy.com
  45. 45. Reciprocation.Reciprocation.  Each retentive clasp terminal must beEach retentive clasp terminal must be opposed by a reciprocal clasp arm oropposed by a reciprocal clasp arm or another element of the partial dentureanother element of the partial denture capable of resisting horizontal forcescapable of resisting horizontal forces exerted on the tooth by the retentive arm.exerted on the tooth by the retentive arm. www.indiandentalacademy.com
  46. 46. Reciprocation.Reciprocation.  The reciprocal arm of the clasp isThe reciprocal arm of the clasp is positioned on the opposite side of thepositioned on the opposite side of the tooth from the retentive arm.tooth from the retentive arm.  It also stabilizes the denture againstIt also stabilizes the denture against horizontal movement.horizontal movement.  It should be placed preferably at theIt should be placed preferably at the junction of the gingival and middle thirds ofjunction of the gingival and middle thirds of the abutment tooth (always positionedthe abutment tooth (always positioned above the height of contour.)above the height of contour.) www.indiandentalacademy.com
  47. 47.  It should contact the abutmentIt should contact the abutment tooth along with or before thetooth along with or before the retentive arm during insertion orretentive arm during insertion or removal.removal.  Other parts which offerOther parts which offer reciprocation are:reciprocation are:  Lingual plate major connector.Lingual plate major connector.  An additional occlusal restAn additional occlusal rest placed on the opposite side of theplaced on the opposite side of the tooth along with the minortooth along with the minor connector.connector. Reciprocation.Reciprocation. www.indiandentalacademy.com
  48. 48. Reciprocation.Reciprocation.  The reciprocal arm of the clasp isThe reciprocal arm of the clasp is positioned on the opposite side of thepositioned on the opposite side of the tooth from the retentive arm.tooth from the retentive arm.  It also stabilizes the denture againstIt also stabilizes the denture against horizontal movement.horizontal movement.  It should be placed preferably at theIt should be placed preferably at the junction of the gingival and middle thirds ofjunction of the gingival and middle thirds of the abutment tooth (always positionedthe abutment tooth (always positioned above the height of contour.)above the height of contour.) www.indiandentalacademy.com
  49. 49. Encirclement.Encirclement.  It is the property ofIt is the property of the clasp assembly tothe clasp assembly to encompass moreencompass more than 180 degree ofthan 180 degree of the abutment tooththe abutment tooth either by continuouseither by continuous or broken contact toor broken contact to prevent dislodgementprevent dislodgement during function.during function. www.indiandentalacademy.com
  50. 50.  It can be either a continuous contact as inIt can be either a continuous contact as in circumferential clasp or a broken contactcircumferential clasp or a broken contact as in bar clasp with at least 3 differentas in bar clasp with at least 3 different areas of contact.areas of contact.  The three points of contact are:The three points of contact are:  retentive terminalretentive terminal  occlusal contactocclusal contact  reciprocal armreciprocal arm www.indiandentalacademy.com
  51. 51. Passivity.Passivity.  A clasp in place should be completelyA clasp in place should be completely passive.passive.  The retentive function is activated onlyThe retentive function is activated only when dislodging force are applied towhen dislodging force are applied to the partial denture.the partial denture.  A clasp must be completely seated onA clasp must be completely seated on a tooth to be completely passive.a tooth to be completely passive.  If a clasp designed to reach a retentiveIf a clasp designed to reach a retentive undercut of 0.010 inch cannot reachundercut of 0.010 inch cannot reach that depth, it will exert a constant forcethat depth, it will exert a constant force on tooth. Over time this can produceon tooth. Over time this can produce pain or tooth movementpain or tooth movement www.indiandentalacademy.com
  52. 52.  The types of clasps are:.The types of clasps are:.  Circumferential or Aker ' s clasps.Circumferential or Aker ' s clasps.  Vertical projection or Bar or RoachVertical projection or Bar or Roach clasps .clasps . www.indiandentalacademy.com
  53. 53. Cast circumferential claspCast circumferential clasp  A clasp that encircles a tooth by moreA clasp that encircles a tooth by more than 180 degrees, including oppositethan 180 degrees, including opposite angles, and which usually has totalangles, and which usually has total contact with the tooth (throughout thecontact with the tooth (throughout the extent of the clasp), with at least oneextent of the clasp), with at least one terminal being in the infra bulge (gingivalterminal being in the infra bulge (gingival convergence) area"convergence) area" - GPT- GPT www.indiandentalacademy.com
  54. 54. Vertical projection claspVertical projection clasp // BarBar claspclasp // Roach clasp:Roach clasp:  A clasp having arms which are bar typeA clasp having arms which are bar type extensions from major connectors or fromextensions from major connectors or from within the denture base;within the denture base;  the arms pass adjacent to the soft tissuesthe arms pass adjacent to the soft tissues and approach the point or area of contactand approach the point or area of contact on the tooth in a gingivo- occlusalon the tooth in a gingivo- occlusal direction"direction" - GPT.- GPT. www.indiandentalacademy.com
  55. 55. Continuous claspContinuous clasp  A metal bar usually resting on the lingualA metal bar usually resting on the lingual surface of teeth to aid in their stabilizationsurface of teeth to aid in their stabilization and to act as an indirect retainer"and to act as an indirect retainer"  - GPT.- GPT. www.indiandentalacademy.com
  56. 56. Cast Circumferential ClaspCast Circumferential Clasp  TheyThey are popularly known as Aker’sare popularly known as Aker’s clasps.clasps.  These clasps embrace more than half ofThese clasps embrace more than half of the abutment tooth.the abutment tooth.  This architecture helps the clasp to holdThis architecture helps the clasp to hold the abutment firmly enough to prevent thethe abutment firmly enough to prevent the rotation of the denture.rotation of the denture.  They approach the undercut from anThey approach the undercut from an occlusal direction.occlusal direction. www.indiandentalacademy.com
  57. 57.  Advantages:Advantages:  Easiest clasp to make and repair.Easiest clasp to make and repair.  Less food retentionLess food retention  Best when applied in a tooth supportedBest when applied in a tooth supported partial denture.partial denture.  Derives excellent support, bracing andDerives excellent support, bracing and retentionretention www.indiandentalacademy.com
  58. 58.  Disadvantages :Disadvantages :  It covers a large tooth surface area.It covers a large tooth surface area.  It also alters the Bucco lingual width of the crownIt also alters the Bucco lingual width of the crown  This affects the normal food flow pattern leadingThis affects the normal food flow pattern leading to food accumulation.to food accumulation.  This causes decalcification of the toothThis causes decalcification of the tooth structure.structure.  Damage to soft tissue will occur due to lack ofDamage to soft tissue will occur due to lack of physiological stimulation.physiological stimulation.  Difficult to adjust with pliers because of it'sDifficult to adjust with pliers because of it's half-half- round configuration.round configuration. www.indiandentalacademy.com
  59. 59.  If these clasps are placed high (more occlusally)If these clasps are placed high (more occlusally) on the tooth, the width of the food tableon the tooth, the width of the food table increases leading to generation of greaterincreases leading to generation of greater occlusal forces.occlusal forces.  All cast circumferential claspsAll cast circumferential clasps should nevershould never bebe used to engage the mesio buccal undercut of anused to engage the mesio buccal undercut of an abutment adjacent to the distal edentulousabutment adjacent to the distal edentulous space (Fig. 18.167). Hence they cannot be usedspace (Fig. 18.167). Hence they cannot be used for cases with an undercut away from thefor cases with an undercut away from the edentulous space.edentulous space. www.indiandentalacademy.com
  60. 60. Types of Cast CircumferentialTypes of Cast Circumferential ClaspsClasps  11. Simple circlet clasp.. Simple circlet clasp.  Most versatile and widely used.Most versatile and widely used.  Best for tooth supported partial denture.Best for tooth supported partial denture.  It approaches the undercut from theIt approaches the undercut from the edentulous space.edentulous space.  It engages the undercut, located awayIt engages the undercut, located away from the edentulous space.from the edentulous space. www.indiandentalacademy.com
  61. 61.  Clasp can be adjusted only in oneClasp can be adjusted only in one direction.direction.  They cannot be used for distal extensionThey cannot be used for distal extension cases as they engage a mesio buccalcases as they engage a mesio buccal undercut.undercut. www.indiandentalacademy.com
  62. 62.  2. Reverse circlet clasp or reverse2. Reverse circlet clasp or reverse approach clasp:approach clasp:  This clasp is used when the retentiveThis clasp is used when the retentive undercut on the abutment tooth is locatedundercut on the abutment tooth is located adjacent to the edentulous space.adjacent to the edentulous space.  Used in distal extension denture base toUsed in distal extension denture base to control the stresses acting on the terminalcontrol the stresses acting on the terminal abutment teeth.abutment teeth. www.indiandentalacademy.com
  63. 63.  Disadvantages.Disadvantages.  If sufficient occlusal clearance is notIf sufficient occlusal clearance is not present, the thickness of the clasp has to bepresent, the thickness of the clasp has to be reduced. This will affect the strength of thereduced. This will affect the strength of the clasp.clasp.  An occlusal rest away from the edentulousAn occlusal rest away from the edentulous space does not protect the marginal gingivaspace does not protect the marginal gingiva adjacent to the abutment tooth.adjacent to the abutment tooth.  Poor esthetics as the clasp runs from thePoor esthetics as the clasp runs from the mesial to the distal end of the facial surfacemesial to the distal end of the facial surface  Wedging may occur between the abutmentWedging may occur between the abutment and its adjacent tooth if the occlusal rest isand its adjacent tooth if the occlusal rest is not well prepared.not well prepared.www.indiandentalacademy.com
  64. 64.  3.Multiple circlet3.Multiple circlet clasp.clasp.  It is a combination ofIt is a combination of two simple circlettwo simple circlet clasps joined at theclasps joined at the terminal end of theterminal end of the reciprocal arms.reciprocal arms. www.indiandentalacademy.com
  65. 65.  It is used for sharing the retention withIt is used for sharing the retention with additional teeth on the same teeth on theadditional teeth on the same teeth on the same side of the arch when the principlesame side of the arch when the principle abutment tooth has poor periodontalabutment tooth has poor periodontal support.support.  It is a mode of splinting weakened teeth.It is a mode of splinting weakened teeth.  It’s disadvantages are similar to that ofIt’s disadvantages are similar to that of simple and reverse circlet clasps.simple and reverse circlet clasps. www.indiandentalacademy.com
  66. 66.  4. Embrasure clasp or4. Embrasure clasp or modified crib clasp.modified crib clasp.  It is a combination ofIt is a combination of two simple circlet claspstwo simple circlet clasps joined at the body.joined at the body.  It is used on the sideIt is used on the side of the arch where thereof the arch where there is no edentulous space.is no edentulous space. www.indiandentalacademy.com
  67. 67.  The clasp must cross the marginal ridges of twoThe clasp must cross the marginal ridges of two teeth, emerge to cross the facial surfaces ofteeth, emerge to cross the facial surfaces of both teeth, and engage undercuts on theboth teeth, and engage undercuts on the opposing line angles of these teeth.opposing line angles of these teeth.  Occlusal rest seat preparation must be made onOcclusal rest seat preparation must be made on both teethboth teeth  Tooth structure must be removed from theTooth structure must be removed from the buccal inclines of both teeth to provide space forbuccal inclines of both teeth to provide space for adequate thickness of the metal.adequate thickness of the metal. www.indiandentalacademy.com
  68. 68.  Indications: It is used in kennedy’s class 2Indications: It is used in kennedy’s class 2 and class 3 cases without anyand class 3 cases without any modifications.modifications.  Occasionally, a very small edentulousOccasionally, a very small edentulous space can be closed by a modifiedspace can be closed by a modified embrasure clasp called a pontic claspembrasure clasp called a pontic clasp www.indiandentalacademy.com
  69. 69.  5. Ring clasp5. Ring clasp  Indicated in tipped molarsIndicated in tipped molars  In Distal edentulous conditions withIn Distal edentulous conditions with distolingual undercut - the retentive armdistolingual undercut - the retentive arm is extended all around the tooth from theis extended all around the tooth from the disto buccal end to terminate in thedisto buccal end to terminate in the distolingual undercut across the mesialdistolingual undercut across the mesial side of the toothside of the tooth www.indiandentalacademy.com
  70. 70.  As clasp is long – additional support isAs clasp is long – additional support is provided by auxiliary bracing armprovided by auxiliary bracing arm www.indiandentalacademy.com
  71. 71.  DisadvantagesDisadvantages  Alteration in food flow patternAlteration in food flow pattern  Increased tooth surface coverageIncreased tooth surface coverage  Difficult to adjust or repairDifficult to adjust or repair  Contra indicationsContra indications  Not considered in mandibular molar whereNot considered in mandibular molar where attachment of the buccinator is close toattachment of the buccinator is close to tooth that the auxiliary arm encroaches ontooth that the auxiliary arm encroaches on itit www.indiandentalacademy.com
  72. 72.  6. fishhook or hairpin or reverse action6. fishhook or hairpin or reverse action claspclasp  Type of simple circlet clasp.Type of simple circlet clasp.  retentive armretentive arm – crosses the facial– crosses the facial surface of the tooth from its point of origin,surface of the tooth from its point of origin, loops back in a hairpin turn to engage aloops back in a hairpin turn to engage a proximal undercut below its point of originproximal undercut below its point of origin www.indiandentalacademy.com
  73. 73.  Upper arm - rigidUpper arm - rigid  Lower arm - flexibleLower arm - flexible  Sufficient space should be presentSufficient space should be present between the two arms – to avoid foodbetween the two arms – to avoid food accumulation & for properaccumulation & for proper finishing and polishingfinishing and polishing www.indiandentalacademy.com
  74. 74.  IndicationIndication  Crown with sufficient occluso gingivalCrown with sufficient occluso gingival heightheight  The undercut is adjacent to edentulousThe undercut is adjacent to edentulous areaarea  Presence of a soft tissue undercutPresence of a soft tissue undercut  Reverse circlet can’t be used – lack ofReverse circlet can’t be used – lack of occlusal spaceocclusal space www.indiandentalacademy.com
  75. 75.  DisadvantagesDisadvantages  Poor estheticsPoor esthetics  Tends to trap and accumulate food debrisTends to trap and accumulate food debris www.indiandentalacademy.com
  76. 76.  Onlay clasp ;Onlay clasp ;  Extension of a metal crown or onlay withExtension of a metal crown or onlay with buccal and lingual clasp arms.buccal and lingual clasp arms.  Used in occlusal surfaces of submergedUsed in occlusal surfaces of submerged abutment teeth – thus restoring theabutment teeth – thus restoring the occlusal plane with an onlay.occlusal plane with an onlay. www.indiandentalacademy.com
  77. 77.  If onlay clasp is made of chrome alloy –If onlay clasp is made of chrome alloy – the opposing tooth should be protectedthe opposing tooth should be protected with a gold crown to avoid attrition ofwith a gold crown to avoid attrition of enamel.enamel.  Used in caries resistant mouth.Used in caries resistant mouth. www.indiandentalacademy.com
  78. 78.  8. combination clasp8. combination clasp  A cast circumferential clasp can’t be usedA cast circumferential clasp can’t be used – when an undercut is adjacent to the– when an undercut is adjacent to the edentulous space since it produceedentulous space since it produce destructive rotatory forces on the distaldestructive rotatory forces on the distal abutmentabutment  A flexible wrought wire retentive arm isA flexible wrought wire retentive arm is used to replace the rigid cast alloyused to replace the rigid cast alloy retentive arm.retentive arm. www.indiandentalacademy.com
  79. 79.  It has greater flexibility it can be placed inIt has greater flexibility it can be placed in a deeper undercut – without any hazard toa deeper undercut – without any hazard to the abutment tooththe abutment tooth  It is used in maxillary canines andIt is used in maxillary canines and premolars due to its superior esthetics.premolars due to its superior esthetics. www.indiandentalacademy.com
  80. 80.  AdvantagesAdvantages  The round configuration of the wroughtThe round configuration of the wrought wire – has a thin line contact whichwire – has a thin line contact which collects less debris and is easy tocollects less debris and is easy to maintain.maintain.  flex in all planesflex in all planes www.indiandentalacademy.com
  81. 81.  DisadvantagesDisadvantages  Tedious lab proceduresTedious lab procedures  Easily breaks or distortsEasily breaks or distorts  Poor stabilityPoor stability www.indiandentalacademy.com
  82. 82. Half and half claspHalf and half clasp  It has a retentive arm arising from one directionIt has a retentive arm arising from one direction and a reciprocal arm arising from anotherand a reciprocal arm arising from another direction.direction.  Two minor connectors are needed for thisTwo minor connectors are needed for this design. The first minor connector attaches thedesign. The first minor connector attaches the occlusal rest and the retentive arm to the majorocclusal rest and the retentive arm to the major connector. The second minor connectorconnector. The second minor connector connects the reciprocal arm which is similar toconnects the reciprocal arm which is similar to the bar clasp with or without an auxiliary rest.the bar clasp with or without an auxiliary rest. www.indiandentalacademy.com
  83. 83.  This design produces large toothThis design produces large tooth coverage which can be reduced bycoverage which can be reduced by converting the reciprocal arm into a shortconverting the reciprocal arm into a short bar with an auxiliary occlusal rest.bar with an auxiliary occlusal rest.  This design is intended to provide dualThis design is intended to provide dual retention.retention. www.indiandentalacademy.com
  84. 84.  Back-action claspBack-action clasp  It is a modification of the ring claspIt is a modification of the ring clasp  Here the minor connector is connected to theHere the minor connector is connected to the end of the clasp arm and the occlusal rest is leftend of the clasp arm and the occlusal rest is left unsupported.unsupported.  Disadvantages :Disadvantages :  Lack of support to the occlusal rest reduces itsLack of support to the occlusal rest reduces its function.function.  It has both biological and mechanical unsoundIt has both biological and mechanical unsound principles.principles. www.indiandentalacademy.com
  85. 85.  Grasso’s clasp or VRHR claspGrasso’s clasp or VRHR clasp  Developed by Grasso,Developed by Grasso,  This clasp consists of :This clasp consists of :  A vertical reciprocal arm,A vertical reciprocal arm,  an occlusal rest andan occlusal rest and  a horizontal retentive arm arisinga horizontal retentive arm arising separately from the major connector.separately from the major connector. www.indiandentalacademy.com
  86. 86. Grasso’s clasp or VRHR claspGrasso’s clasp or VRHR clasp  Advantages :Advantages :  Minimizes tooth contact without compromise in efficacy.Minimizes tooth contact without compromise in efficacy.  Does not require the preparation of guide planes.Does not require the preparation of guide planes.  Suitable for posterior teeth with high survey lines.Suitable for posterior teeth with high survey lines.  The placement of the retentive arm is more aesthetic.The placement of the retentive arm is more aesthetic. www.indiandentalacademy.com
  87. 87. Grasso’s clasp or VRHR claspGrasso’s clasp or VRHR clasp  Disadvantages :Disadvantages :  Difficult to maintain as the block out zoneDifficult to maintain as the block out zone between the base of the reciprocal armbetween the base of the reciprocal arm and the tooth tends to collect food debris.and the tooth tends to collect food debris. www.indiandentalacademy.com
  88. 88. Rest-proximal plateRest-proximal plate –– AkersAkers retentive arm (RPA) claspretentive arm (RPA) clasp  The RPA clasp is a modified circumferentialThe RPA clasp is a modified circumferential claspclasp  The circumferential arm arises from the proximalThe circumferential arm arises from the proximal plate adjacent to the edentulous base area.plate adjacent to the edentulous base area.  The retentive component of this directThe retentive component of this direct retainerretainer - engages a retentive undercut located- engages a retentive undercut located on the facial surface of the abutment tooth awayon the facial surface of the abutment tooth away from the edentulous area.from the edentulous area. www.indiandentalacademy.com
  89. 89. Rest-proximal plateRest-proximal plate –– AkersAkers retentive arm (RPA) claspretentive arm (RPA) clasp  The shoulder of the clasp arm - contacts theThe shoulder of the clasp arm - contacts the tooth at the height of contour at the junction oftooth at the height of contour at the junction of the middle and gingival thirds of the tooth.the middle and gingival thirds of the tooth.  This direct retainer satisfies all the requirementsThis direct retainer satisfies all the requirements for use in distal-extension RPD situations.for use in distal-extension RPD situations.  Allows for mesially oriented support, which isAllows for mesially oriented support, which is preferable in distal-extension RPDs.preferable in distal-extension RPDs. www.indiandentalacademy.com
  90. 90. Rest-proximal plateRest-proximal plate –– AkersAkers retentive arm (RPA) claspretentive arm (RPA) clasp  Excellent bracing is derived from theExcellent bracing is derived from the contact of the minor connector supportingcontact of the minor connector supporting the rest, the proximal plate contacting thethe rest, the proximal plate contacting the tooth surface adjacent to the edentuloustooth surface adjacent to the edentulous base area, and the shoulder part of thebase area, and the shoulder part of the clasp arm.clasp arm.  Acceptable retention is derived fromAcceptable retention is derived from retentive areas located on surfaces of theretentive areas located on surfaces of the tooth away from the edentulous area.tooth away from the edentulous area. www.indiandentalacademy.com
  91. 91. Rest-proximal plateRest-proximal plate –– AkersAkers retentive arm (RPA) claspretentive arm (RPA) clasp  Requirements for adequate encirclement andRequirements for adequate encirclement and passivity can easily be accommodated by thispassivity can easily be accommodated by this direct retainer.direct retainer.  This type of clasp appears best suited for distal-This type of clasp appears best suited for distal- extension RPDs - where the undercut is locatedextension RPDs - where the undercut is located away from the edentulous area andaway from the edentulous area and  for situations in which it has been determinedfor situations in which it has been determined that the tooth need not be modified tothat the tooth need not be modified to accommodate a different type of clasp.accommodate a different type of clasp. www.indiandentalacademy.com
  92. 92. Mesiodistal clasp.Mesiodistal clasp.  This direct retainer might be consideredThis direct retainer might be considered for a tooth-borne RPD when maxillaryfor a tooth-borne RPD when maxillary incisors remain as the anterior abutmentincisors remain as the anterior abutment teeth.teeth.  Although the design exhibits goodAlthough the design exhibits good supporting and bracing qualities,supporting and bracing qualities,  it may be excessively traumatic to theit may be excessively traumatic to the supporting abutment teeth when used onsupporting abutment teeth when used on distal-extension RPDs.distal-extension RPDs. www.indiandentalacademy.com
  93. 93. Mesiodistal clasp.Mesiodistal clasp.  Retention for this direct retainer is gainedRetention for this direct retainer is gained through parallelism and frictional resistance ofthrough parallelism and frictional resistance of the clasp assembly against the natural teeth.the clasp assembly against the natural teeth.  The teeth must be prepared so that theirThe teeth must be prepared so that their proximal surfaces are parallel or have a slightproximal surfaces are parallel or have a slight convergence to one another.convergence to one another.  This direct retainer, like the other circumferentialThis direct retainer, like the other circumferential designs, poses the same problems of coveringdesigns, poses the same problems of covering excessive tooth structure and impairingexcessive tooth structure and impairing esthetics.esthetics. www.indiandentalacademy.com
  94. 94. Mesiodistal clasp.Mesiodistal clasp. www.indiandentalacademy.com
  95. 95. Bar or vertical projection or roachBar or vertical projection or roach clasp.clasp.  Approaches the undercut or retentive areaApproaches the undercut or retentive area on the tooth from a gingival direction,on the tooth from a gingival direction, resulting in a push type of retention.resulting in a push type of retention.  Flexibility of the bar type of clasp can beFlexibility of the bar type of clasp can be controlled by the taper and length of thecontrolled by the taper and length of the approach arm.approach arm.  More esthetic than the circumferentialMore esthetic than the circumferential clasp.clasp. www.indiandentalacademy.com
  96. 96.  Disadvantages.Disadvantages.  1. Greater tendency to collect and hold1. Greater tendency to collect and hold food debris.food debris.  2. Due to its increased flexibility of the2. Due to its increased flexibility of the retentive arm, it does not contribute asretentive arm, it does not contribute as much to bracing and stabilization as mostmuch to bracing and stabilization as most circumferential clasps do.circumferential clasps do. www.indiandentalacademy.com
  97. 97.  Rules to use.Rules to use.  The approach arm must always beThe approach arm must always be tapered uniformly from its point oftapered uniformly from its point of attachment at the frame work to the caspattachment at the frame work to the casp terminal.terminal. www.indiandentalacademy.com
  98. 98. Thank you For more details please visit www.indiandentalacademy.com www.indiandentalacademy.com

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