Minor connectors


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Minor connectors

  1. 1. Bibin bhaskaran
  2. 2. Minor connectors Definition-  Components that serve as the connecting link between major connector or base of a removable partial denture and other components of the prosthesis,such as the clasp assembly,indirect retainers,occlusal rests,or cingulum rests.
  3. 3.  Continuous with some other part of the denture.  Eg An occlusal rest at one end of a linguo plate is actually the terminus of a minor connector even though the minor connector is continuous with the linguoplate.
  4. 4.  The portion of a partial denture frame work that supports the clasp and occlusal rest is a minor connector.  Portion of removable partial denture frame work that retain the denture bases are also minor connectors.
  5. 5. Functions  Primary function-joining other units of the prostheses and denture bases to the major connector.  Transfer functional stresses to the abutment teeth.  Transfer the effect of retainers,rests,stabilizing components throughout the prostheses.
  6. 6.  Distributes the stresses that occur against certain components of partial denture to other components.  Distributes forces on the edentulous ridge to the ridge and the remaining teeth. This broad distribution of force prevents any one tooth or one portion of the edentulous ridge from bearing a destructive amount of stress.
  7. 7. Form and location  Sufficient bulk to be rigid.  Minor connector contacting axial surface of abutment teeth should not be located on convex surface,instead should be located on the embrasure.  Should conform to the interdental embrassure.  Should be thickest towards the lingual surface,tapering towards the contact area.
  8. 8.  Deepest part of interdental embrassure should have been blocked out to avoid interference during placement and removal.  When a minor connector contacts tooth surfaces on either side of the embrassure in which it lies,it should be tapered to the teeth.  Minor connector should be wide enough to use the guiding plane to the fullest advantage.  When it gives rise to clasp arm it should be tapered.
  9. 9.  Whenever possible, the minor connector of a removable partial denture is located in the interdental embrasure.  Recent evidence suggests that gingival attachment loss is more probable on the proximal aspect, thus minor connectors located in embrasures cover susceptible sites. “A variation in minor connector design for partial dentures,Radford DR, Walter JD Int J Prosthodont. 1993 Jan-Feb;6(1):50-4.”
  10. 10.  The framework designs offering strong retention for acrylic resin bases allowed the use of a greater bulk of acrylic resin projecting through openings in the metal retention design. “Dunny J A, King G E, Minor connector designs for anterior acrylic resin bases: a preliminary study. J Prosthet Dent 1975,34:496-502.”
  11. 11. Types 4 types –  Join the clasp assembly to the major connector.  Join direct retainers or auxillary rests to the major connector.  Join the denture base to the major connector.  Serve as an approach arm for a vertical projection or bar type.
  12. 12. Minor connectors that join the clasp assembly to the major connector.  Should be rigid to support the active component of the partial denture,the retentive clasp.  Support the component of the prosthesis that prevents vertical movement towards the tissue(Rest).  Located on proximal surfaces of teeth adjacent to edentulous areas.
  13. 13.  Should be broad buccolingually but thin mesiodistally.  If clasp assembly is not being placed on a tooth adjacent to an edentulous space,minor connector must be positioned in embrassure between two teeth.  Never position on convex lingual surface of a tooth.
  14. 14. Minor connectors that join indirect retainers or auxillary rests to major connectors.  Arises from the major connector.  Form a right angle with major connector.  Designed to lie in the embrassure between teeth to disguise its bulk as much as possible.
  15. 15. Minor connector that join denture base to major connector May be –  Of latticework construction  Of mesh construction  Bead ,wire,or nail head minor connectors
  16. 16.  Must be strong enough to anchor the denture base.  Rigid enough to resist breakage or flexing.  In maxillary arch-distal extension base-minor connector – tuberosity.  Mandibular distal extension base-two thirds the length of edentulous ridge
  17. 17. Open latticework construction  Consists of 2 struts of metal(12-16guage).  In mandibular arch – one strut buccal other – lingual.
  18. 18.  In maxilla one strut buccal – border of major connector – second strut.  Smaller struts connect the two struts and form the lattice work.
  19. 19.  Longitudinal struts avoided– artificial teeth arrangement.  Relief space given for both lattice work and mesh work minor connectors.  Acrylic denture base will be formed in this space.  Locking of acrylic resin provides retention of denture base.  Used – multiple teeth replacements.
  20. 20. Mesh construction  Thin sheet of metal with multiple small holes that extends over crest of residual ridge to the buccal,lingual and posterior limits.  Used for replacement of multiple teeth.  Major drawback– difficult to pack acrylic resin.  Does not provide a strong attachment for denture base.
  21. 21. Tissue stops  Integral parts of minor connectors– retention of acrylic resin bases.  Provide stability for frame work during the stages of transfer and processing.  Prevents distortion of framework during acrylic resin processing  Engage buccal and lingual slopes for stability.
  22. 22.  Another integral part of minor connector designed to retain acrylic denture base is similar to tissue stop but serves different purpose.  Located distal to the terminal abutment and is continuation of the minor connector contacting the guiding plane.  To establish a definitive finishing index stop for acrylic resin base after processing.
  23. 23. Fabrication  Removing approximately 2 square mm of the relief wax used to create space beneath the lattice work or mesh from the point where the posterior end of minor connector crosses the centre of the ridge.  During waxing this little depression is waxed as a projection of latticework or mesh.
  24. 24.  After casting this projection contacts the edentulous ridge of the cast and prevents frame work from being distorted during acrylic packing.
  25. 25. Bead wire,or Nail head retention (Minor connector)  Metal denture base  No relief provided.  Attached to outer or superior surface of metal base.  Retention by projections of metal on this surface.  Projections may be – beads,wires,or nail heads.  Denture base – hygenic because of better soft tissue response to metal.
  26. 26. Shortcomings –  Difficult to adjust metal base.  Cannot be adequately relined.  Weakest attachment of 3 types. “Should be used on tooth-supported,well healed ridges when interarch space is limited.”
  27. 27. Attachment to major connector  Acrylic resin minor connector must be joined to major connector with sufficient bulk to avoid fracture.  Must join in a smooth,event joint.  Irregularity b/w surface irritates tongue or mucosa of the ridge.  Acrylic resin– butt joint must be made on both internal and external surfaces of the major connector.
  28. 28.  For metal base minor connector – single butt joint .  Butt joints – finish lines.  Outer aspect – external finish line.  Internal or tissue side – internal finish line.
  29. 29. Finish lines  Finishing line junction with major connector– angle not greater than 90 degree.  Finish line located too far medially– natural contour of palate altered by thickness of acrylic resin.
  30. 30.  Too far buccally– difficult to create a natural contour of acrylic resin on lingual surface of artificial teeth.  90 degree butt-type joint given for junction of minor connectors and bar-type direct retainers.
  31. 31. Internal finish lines  Formed from relief waxes used over edentulous ridge on master cast.  24-26 guage thick.  Margins of relief wax – internal finish line.  Ledge created by wax – sharp and define
  32. 32. External finish lines  Sharp and definite and should be slightly undercut to help lock acrylic resin securely to major connector.  Angle the finish line forms with major connector – less than 90 degree.
  33. 33.  Should extend on to the proximal surface of teeth adjacent to edentulous space.  Finish line begins at lingual extent of rest seat and continues down the lingual aspect of minor connector on proximal surface of the tooth.
  34. 34. Minor connector that serve as approach arm for vertical projection or bar-type clasp.  Only non rigid minor connector.  Supports a direct retainer that engages an undercut on a tooth from below.  Approaches tooth from gingival margin.  Should be smooth,even and taper from its origin to its terminus.
  35. 35.  Must not cross a soft tissue undercut.  Considered in great depth when direct retainers are used.
  36. 36. References  Carr A B, Mc Givney G P, Brown D T, Minor connector in McCraken’s Removable partial Prothodontics. 11th ed, st louis: Mosby; 2008, 35-53.  Stewart K L, Rudd K D, Kuebker W A, Minor connector in Stewart’s Clinical Removable Partial Prosthodontics. 2nd ed, 2004, 22-42.  Miller E L, Grasso J E, Major connector in Removable Partial Prosthodontics. 2nd ed, Baltimore: Williams & Wilkins; 1979, 175-94.
  37. 37.  Dunny J A, King G E, Minor connector designs for anterior acrylic resin bases: a preliminary study. J Prosthet Dent 1975,34:496-502.  Brown D T, Desjardins R P, Chao EY.Fatigue failure in acrylic resin retaining minor connections. J Prosthet Dent 1987;58:329-35.
  38. 38.  A variation in minor connector design for partial dentures,Radford DR, Walter JD Int J Prosthodont. 1993 Jan-Feb;6(1):50-4.  Davenport JC, Basker RM, Heath JR, Ralph JP, Glantz P-O, Hammond P. Connectors. British Dental Journal 2001; 190: 184–191.