Concepts new/ dental technician training online


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Concepts new/ dental technician training online

  1. 1. • INTRODUCTION: INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. • In contrast with the Kratochvil’s basic design, which necessitates heavy preparation, Krol developed a modification that avoids tooth preparation.
  3. 3. • The state emphasis in Krol’s system is stress control with minimal tooth coverage and minimal gingival coverage.
  4. 4. • The clasp system includes the three elements of Kratochvil’s system: - mesial rest, proximal plate and I-bar. • Each element, however, has undergone significant change to meet Krol’s criteria.
  5. 5. • In RPI system: R = Rest P = Proximal plate I = I-bar
  6. 6. REST • Rest preparations are less extensive in the RPI system. • The mesial rest extends only into the triangular fossa, even in molar preparations, and canine rests are often circular concave depressions prepared in the mesial marginal ridge
  7. 7. • Mesio occlusal rest with the minor connector placed into the mesiolingual enbrassure, but not contacting the adjacent tooth.
  8. 8. PROXIMAL PLATE: • The proximal plate makes greatest departure from Kratochvil’s design. • The prepared guide plane is 2 to 3 mm high occlusogingivally and the proximal plate contacts only 1 mm of the gingival portion of the guide plane
  9. 9. • . Relief is provided at the tooth – tissue junction to allow the proximal plate to disengage into the proximal undercut under occlusal loading.
  10. 10. • This proximal plate, in conjunction with the minor connector supporting the rest, provides the stabilizing and reciprocal aspects of the clasp assembly.
  11. 11. I – bar: • The I-bar should be located in the gingival thirds of the buccal or labial surface of the abutment in a 0.001 inch undercut. • The whole arm should be tapered into the terminus, with no more than 2 mm of its tip contacting abutment.
  12. 12. • The retentive tip contacts the tooth from the undercut to the height of contour. • This area of contact along with the rest and proximal plate contact provides stabilization through encirclement. • The horizontal portion of the approach arm must be located at least 4 mm from the gingival margin and even farther if possible.
  13. 13. • There are three basic approaches to the application of the RPI system. • The location of the rest, the design of the minor connector (proximal plate) as it relates to the guiding plane, and the location of the retentive arm are factors that influence how this clasp system functions.
  14. 14. • All advocate the use of a rest located mesially on the primary abutment tooth adjacent to the extension base area.
  15. 15. I approach : • This approach recommends that the guiding plane and corresponding proximal plate minor connector extend the entire length of the proximal tooth surface, with physiological tissue relief to eliminate impingement of the free gingival margin
  16. 16. • Bar clasp assembly in which guiding plane (GP) and corresponding proximal plate (PP) extend entire length of proximal tooth surface to contact greater surface area of guide plane which directs functional forces in horizontal direction , thus tooth {teeth} are loaded more than edentulous ridge.
  17. 17. II approach: • This approach suggests that the guiding plane and corresponding proximal plate minor connector extend from the marginal ridge to the junction of the middle and gingival thirds of the proximal tooth surface
  18. 18. • Both approaches recommend that the retaining clasp arm be located in the gingival third of the buccal or labial surface of the abutment in a 0.001 inch undercut
  19. 19. • Bar clasp assembly in which guiding plane and corresponding proximal plate extend from marginal ridge to junction of middle and gingival thirds of proximal tooth surface. • This decrease amount of surface area contact of proximal plate on guide plane more evenly distributes functional force between tooth and edentulous ridge
  20. 20. III approach: • This approach favours a proximal plate minor connector that contacts approximately 1mm of the gingival portion of the guiding plane and retentive clasp arm located in a 0.001 inch undercut in the gingival third of the tooth at the greatest prominence or to the mesial away from the edentulous area
  21. 21. • Bar clasp assembly in which proximal plate contacts approximately 1 mm of gingival portion of guiding plane . • During function, proximal plate and I-bar clasp arm are designed to move in mesiogingival direction, disengaging tooth. Lack of sustained contact between proximal plate and guide plane distributes more functional force to edentulous ridge. •
  22. 22. • Application of each approach is predicated on the distribution of load to be applied to the tooth and edentulous ridge.
  23. 23. • The stated purpose of reducing the proximal plate is to improve gingival health by opening up embrasure spaces as much as possible.
  24. 24. MODIFICATION TO RPI SYSTEM: • Kroll in 1976 has given modification to RPI system. That is • RPA in which R = rest P = proximal plate A = Akers clasp
  25. 25. contraindications for a bar- type clasp  exaggerated buccal or lingual tilts,  severe tissue undercut  or a shallow buccal vestibule  and the desirable undercut is located in the gingival third of the tooth away from the extension base area, • this modification to RPI i.e., RPA should be considered.
  26. 26. Tipped abutments and tissue impingements are • treated with RPA clasp. • When Akers clasp arm is used, careful attention is paid to relieve all undercuts except at the retentive tip
  27. 27. The removable partial denture design: british dental journal: vol-189; n0-7 pg-414 • In the study they concluded that there a plaque accumulation in terms of quality and quantity on alloplastic materials and there is some components are leached into oral cavity from this alloplastic material • And this will cause tissue injury • This can be prevented with the equillibrium in 3 components • 1- operator • 2- patient • 3- laboratory perosenell
  28. 28. 10yr old eveluation of r.p.d’s ,survival rates based in re treatment j.p.d- vol-76: no-1, 1996 • In this survey 784 patients were given with metal dentures and their feed back was taken • In the survey it was found that 88% - with 96% of success 10 people died that is 8% Remaining people didnt wear the r.p.d
  29. 29. A randomised clinical trial of 2 basic r.p.d’s- comparision of masticatory efficiency- j.p.d- 1997: 78; 15-21 • Statement of problem: there is no clinical data about the functional efficiency of different r.p.d designs. • For this 118 patients were selected with unilateral or bi lateral r.p.d’s • Conclusion: despite some performance difference at entry the mean performance scores for the 2 different groups became similar
  30. 30. conclusion • Successful use of the system requires careful analysis of each component for the function that it provides and thoughtful execution of the system in the abutment preparation and precise fitting of framework
  31. 31. Thank you For more details please visit