Minor Connectors & Rests

1. Minor Connectors & Rests Rola M. Shadid, BDS, MSc

2. Lecture Outline • Discuss functions of minor connector • Discuss types of minor connectors • Discuss functions of rests • Discuss forms of rests & prep of rest seats

3. Minor Connectors • Connects components to the major connector • Direct retainer • Indirect retainer • Denture base

4. Functions of Minor Connectors • Unification and rigidity • Stress distribution * • Bracing through contact with guiding planes • Maintain a path of insertion via contact with guiding planes

5. Types of Minor Connectors • Embrasure Minor Connectors • Between two adjacent teeth

6. Embrasure Minor Connectors • Should have sufficient bulk to be rigid but in the same time unobjectionable as possible • Should be located in an embrasure not be located on a convex surface • Should be tapering toward the contact area

7. Embrasure Minor Connectors • Joins major connector at right angles • Relief placed so connector not directly on soft tissue

8. Embrasure Minor Connectors • It should be thickest toward the lingual surface, tapering toward the contact area • Triangular shaped in cross section

9. Embrasure Minor Connectors • Contact teeth above height of contour • Prevents wedging & tooth mobility

10. Gridwork Minor Connectors • Connect the denture base and teeth to the major connector

11. Gridwork Minor Connectors • Adjacent edentulous spaces • Usually connect major connector to direct retainers • Open lattice work or mesh types

12. Gridwork Minor Connectors Minor connector for mandibular distal extension base should extend posteriorly about 2/3 the length of the edentulous ridge Never on the ascending portion of the ridge

13. Gridwork Minor Connectors Minor connectors for maxillary distal extension denture bases should extend the entire length of the residual ridge

14. Gridwork Minor Connectors • Mesh type • Flatter • Potentially more rigid • Less retention for acrylic if openings are small

15. Gridwork Minor Connectors • Lattice Type • Potentially superior retention • Interferes with setting of teeth, if struts are too thick • Both types are acceptable if correctly designed

16. Gridwork Relief • Mechanical retention of denture base resin • Allows the acrylic resin to flow under the gridwork

17. Gridwork Relief • Relief wax is placed in the edentulous areas • 1 mm of relief

18. Relief Under the Gridwork • Should begin 1.5 - 2 mm from the abutment tooth

19. Relief Under the Gridwork • Creates a metal to tissue contact • Preferable since it wears less • Less porous, (hygiene)

20. Junction With Major Connector • Butt joint with slight undercut in metal • Maximum bulk of the acrylic resin • Prevents thin, weak edges fracturing

21. Gridwork Design Facially just over the crest of the residual ridge

22. Position of Major Connector Junction • Should be ≈ 2 mm medial to lingual surface of denture teeth • Ensures bulk of resin around teeth

23. Mandibular Tissue Stops • Contact of metal with cast at posterior of distal extension gridwork • Prevents distortion at free end during hydraulic pressure of processing

24. No Tissue Stops In Maxilla • Maxillary major connector acts as a tissue stop (no relief)

25. Proximal Plates • Minor connectors originating from the gridwork in an edentulous area • Broad contact with guiding planes • May or may not terminate in an occlusal rest

26. Proximal Plates

27. Proximal Plates • Shifted slightly lingually • Increases rigidity • Enhances reciprocation • Improves esthetics • Often a triangular space below the guiding plane (an undercut)

28. Proximal Plates • Rigid, cannot be placed in undercut • Block-out placed in undercuts prior to waxing and casting the framework

29. Rests & Rest Seats

30. The most effective resistance can be provided if the tooth is stressed along its long axis • Prosthesis should engage the tooth in a manner that encourages axial loading

31. Rest • A rigid component of RPD resting in a recessed preparation on the occlusal, lingual or incisalsurface of a tooth. • Provides vertical support

32. Rest Seat • Portion of a tooth prepared to receive a rest *

33. Functions • Direct occlusal forces along long axis of abutment

34. Slides down incline Functions • SUPPORT - Prevents impingement of soft tissue * Fractured abutment, no rest seat

35. Major connector imbeds into tissue

36. Functions • Maintains established occlusal relationships by preventing settling of the denture *

37. Functions • Maintain components in their planned positions (maintains a clasp -tooth relationship)

38. Functions • Provide reference for relines or impressions

39. Functions • Act as indirect retainer • Prevents rotation (Class I or II RPD’s only)

40. Form of Occlusal Rest • Rounded triangular shape with the apex toward center of occlusal surface • As long as it is wide

41. Occlusal Rest Seat Form • Base of triangle should be one third the bucco-lingual width of the tooth *

42. Rest Seat Form • Smooth flowing outline form (i.e. no sharp line angles)

43. Occlusal Rest Seat • Deepest portion is central

44. Occlusal Rest Seat • Floor should be apical to marginal ridge • Angle formed by occlusal rest & vertical minor connector from which it originates should be less than 90°

45. “Positive” Rest Seats • An explorer tip will not slide off the rest seat

46. Occlusal Rest Seat • Directs the occlusal forces along the long axis of the tooth • Prevent orthodontic movement

47. Occlusal Rest Seat • Floor should be concave or spoon shaped (ball-&-socket joint) • Prevents horizontal stresses & torque

48. Occlusal Rest Seat • Marginal ridge must be lowered and rounded 1-1.5mm • Bulk of metal to prevent fracture *

49. Occlusal Rest Seat • Adjacent Tooth • Rest not flared to facial line angle • Lingual flared more - space for minor connector

50. Secondary Occlusal Rest * • To prevent slippage of the primary rest • To prevent orthodontic movement of abutment tooth • To direct forces over greatest root mass of abutment