This document summarizes information from a lecture on removable partial dentures (RPDs), attachments, and rotational path RPDs. It discusses the advantages and disadvantages of different types of attachments, including ERA attachments, magnetic attachments, and overlay dentures. It also describes rotational path RPDs and lateral rotational path RPDs, highlighting how they can eliminate visible clasps while providing retention and stability. Examples are provided of different RPD designs incorporating various attachments and rotational paths of insertion.

1. Esthetics, Use of Attachments and Rotational Path RPD’s John Beumer III DDS, MS Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry UCLA School of Dentistry This program of instruction is protected by copyright ©. No portion of this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior permission.

2. Esthetics, Use of Attachments and rotational path RPD’s

3. “ I” bar vs Circumferential clasp Circumferential clasp on the cuspid

4. Esthetics “ I” bars vs Circumferential

5. Esthetics Low smile line Cuspid –lateral splinted Occlusion Anterior guidance Posterior – Lingualized with centric only contact

6. Esthetics – I” bars Note low smile line Widened major connector Positive cingulum rests Occlusion Anterior guidance using the cuspids Lingualized posterior occlusion with centric only contact 5 year post delivery followup.

7. Esthetics-”I” Bars

8. Esthetics – “I” Bars Extension Base RPD opposing implant supported fixed hybrid prosthesis Occlusion Anterior guidance with the anterior teeth Posterior occlusion-lingualized with centric only contact

9. RPD Attachments Advantages: Elimination of visible clasp arms Disadvantages: Additional expense Increased frequency of adjustment and failure Increased technical expertise required Unpredictable or unfavorable distribution of forces

10. Attachment Classification Rigid attachments No movement is possible between the parts. Used in situations where the abutment teeth fully support the occlusal forces (tooth borne RPD’s and fixed partial dentures) Resilient attachments Allows movement to take place between the parts, thus providing stress-breaking. An example is the ERA attachment

11. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment The ERA attachment permits the RPD to be displaced into the edentulous extension area by up to .4 mm

12. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment Plastic burnout pattern Metal housing ERA attachment Various levels of retention

13. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment Requirements for use Splinted abutments Rest distant from the attachment Close followup to consider relines ERA Attachment

14. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment ERA ERA + splinting Photoelastic analysis - Evaluating the following: Splinted vs unsplinted Rest vs no rest Rest position Berg and Caputo et al

15. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment ERA ERA+splinting Summary and conclusions Attachment best used when: Adjacent teeth splinted Positive rests Light retention (white and orange attachment)

16. Splinting the abutments helps distribute the forces Positive rests away from the extension area helps direct the forces vertically onto the abutment and into the edentulous bearing surfaces Less wear of ERA attachment Attachments - Resilient ERA attachment – Extra-coronal resilient attachment

17. Overlay denture attachments Advantages Improved esthetics Maintain support More favorable biomechanics - Improved crown-root ratio

18. Overlay denture attachments Problems Copings become loose Attachment wear, loss & breakage Alveolar resorption Overdenture breakage Pt. maintenance problems Pt. oral hygiene problems

19. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment This patient is status post partial palatectomy for a benign tumor of the left hard palate. The left tuberosity remains and it contains a third molar

20. Surveyor used to determine the path of insertion for the attachments

21. Surveyor used to prepare the path of insertion for the attachments

22. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment Note the bracing arm through the proximal of #5 and #6. It is non- retentive but keeps the RPD framework from being displaced lingually in this region and with the cingulum rest on #8, keeps the framework centered over the ERA attachment. ERA attachment Cingulum rest Bracing arm Rest

23. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment The two central incisors have been splinted together. A cingulum rest is positioned on the mesial side of #8. The ERA attachment is incorporated within the crown of #9. High smile Bracing arm

24. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment Note the attachment associated with third molar. This serves as an occlusal stop and has a retentive attachment incorporated within. The ERA should not be used unless a positive occlusal stop is present on the defect side, either from a tooth or an implant .

25. Attachments - Resilient ERA attachment – Extra-coronal resilient attachment Occlusion Right side – Anterior guidance Left side – Mutually protected occlusion

26. Magnetic Attachments Advantages : Ease of insertion and removal Simple laboratory work & economic cost Reduced lateral forces No leverage No fragile parts for fracture No activation necessary Do not need special equipment parallelometer etc.). Easy to maintain oral hygiene

27. Magnetic Attachments Applications Retained roots Implants Maxillofacial Prosthetic Applications

28. Magnetic Attachments Maxillofacial applications

29. Magnetic Attachments Maxillofacial applications

30. Magnetic Attachments Maxillofacial applications

31. Magnetic Attachments Maxillofacial applications

32. Inappropriate use of attachments Insufficient vertical movement allowed Cantilever forces delivered to the abutments Result High rate of periodontal breakdown and abutment tooth fracture

33. Inappropriate use of attachments Cantilever forces delivered to the abutments Result High rate of periodontal breakdown and fracture of the abutment teeth

34. Inappropriate use of attachments Nonresilient Attachments in Extension Based RPD’s No vertical movement permitted Cantilever forces delivered to the abutments Result High rate of periodontal breakdown and fracture

35. Inappropriate use of attachments Nonresilient Attachments in Extension Based RPD’s No vertical movement permitted Cantilever forces delivered to the abutments Result High rate of periodontal breakdown and fracture of the abutment teeth

36. Inappropriate use of attachments Nonresilient Attachments in Extension Based RPD’s No vertical movement permitted Cantilever forces delivered to the abutments Result High rate of periodontal breakdown and fracture of the abutment teeth

37. Kennedy Class IV RPD’s Rotational Path of Insertion RPD’s Courtesy Dr. GE King Courtesy Dr. GE King

38. Rotational Path of Insertion RPD’s One portion is inserted first permitting rigid portions of the RPD (proximal plates) to engage undercuts The prosthesis is then rotated into position In the posterior quadrants limited to tooth borne RPD’s Most often used to restore anterior extension defects where use of attachments or clasps is unfavorable

39. Rotational Path of Insertion RPD’s Advantage Elimination of unesthetic retainers (clasp arms) The clasp arms are replaced by rigid retainers These rigid retainers engage undercuts and consist of a positive rest and a minor connector (proximal plate).

40. Rotational Path of Insertion RPD’s Caution Little tolerance for error. It requires a high level of sophistication on the part of both the dentist and the lab technician Requires well prepared positive rests seats. May require restorations to develop an acceptable rest seat Undercuts in posterior rest seats will prevent proper seating

41. Rotational Path of Insertion RPD’s They can also be used to restore Kennedy Class III RPD’s with missing posterior teeth Disadvantage Bracing from guide planes is compromised

42. Rotational Path of Insertion RPD’s Treatment planning Patient presents with moderate periodontal bone loss with recent loss of the incisors Options Fixed partial denture Implant supported fixed partial denture Rotational path of insertion RPD Courtesy Dr. GE King Courtesy Dr. GE King

43. Rotational Path of Insertion RPD’s Treatment planning Patient presents with moderate periodontal bone loss with recent loss of the incisors Options Fixed partial denture – Problems Length of span Amount of tooth reduction for PFM’s Long pontics – Compromised esthetic result Courtesy Dr. GE King Courtesy Dr. GE King

44. Rotational Path of Insertion RPD’s Treatment planning Patient presents with moderate periodontal bone loss with recent loss of the incisors Options Implant supported fixed partial denture – Problems Difficult to predictably restore vertical and horizontal boney contours with grafting Esthetic result will not be acceptable without restoration of bone and soft contours Cost Courtesy Dr. GE King Courtesy Dr. GE King

45. Rotational Path of Insertion RPD’s Treatment planning Patient presents with moderate periodontal bone loss with recent loss of the incisors Options Rotational path of insertion RPD -Best solution Minimal reduction of tooth structure Best esthetic result Least costly Courtesy Dr. GE King Courtesy Dr. GE King

46. Tentative RPD design Rotational Path of Insertion RPD’s Courtesy Dr. GE King

47. Rotational Path of Insertion RPD’s Surveying the cast Identify the cast orientation that results in at least a .25 mm undercut on each of the anterior abutments Courtesy Dr. GE King Courtesy Dr. GE King

48. Rotational Path of Insertion RPD’s Surveying the cast Tilt cast to determine initial path of insertion. Courtesy Dr. GE King Courtesy Dr. GE King

49. Rotational Path of Insertion RPD’s Surveying the cast Verify that at this cast inclination, proper rests can be developed consistent with the initial path of insertion. The rests must not be undercut in relation to the path of insertion Courtesy Dr. GE King Courtesy Dr. GE King

50. Prepare the anterior and posterior rests. The rests must be positive Beware of excessive buccal inclination of the maxillary molars. The rests must be positive but should not be undercut in relation to the path of insertion Rotational Path of Insertion RPD’s

51. Fabricate the RPD casting and verify the adaptation Rotational Path of Insertion RPD’s Courtesy Dr. GE King Courtesy Dr. GE King

52. Rotational Path of Insertion RPD’s Completed RPD Important factors for long term success Positive rests Survey for appropriate undercuts and proper rotational path of insertion Courtesy Dr. GE King Courtesy Dr. GE King

53. Rotational Path of Insertion RPD’s In this patient circular concave rests were used on the cuspids Guidance in lateral excursion provided by the cuspids and premolars Courtesy T Berg Courtesy Dr. GE King Courtesy Dr. GE King

54. Rotational Path of Insertion RPD’s Cingulum rests prepared on the cuspids Positive rests prepared on the distal side of the molars Courtesy Dr. GE King Courtesy Dr. GE King

55. Rotational Path of Insertion RPD’s Positive rests on the cuspids and the molars Lingual “I” bars used for reciprocation and encirclement of the molars Guidance in lateral excursion provide by the cuspids and premolars Courtesy Dr. GE King Courtesy Dr. GE King

56. Rotational Path of Insertion RPD’s Cingulum rest prepared on the cuspid Positive rest on the premolar and molars Courtesy Dr. GE King Courtesy Dr. GE King

57. Rotational Path of Insertion RPD’s Guidance provided by the cuspid and lateral incisor on the left the premolar and molar on the right Courtesy Dr. GE King

58. Lateral Rotational Path on Insertion Patient presents status post anterior mandibular resection The posterior segments of mandible are rotated to the lingual

59. Lateral Rotational Path on Insertion Retention provided by the lingual surfaces of the right molars and the “I” bar on the left Reciprocation and encirclement for the right molar provided by the trans-occlusal rest

60. Lateral Rotational Path on Insertion Trial denture Completed RPD is inserted right to left

61. Lateral Rotational Path on Insertion Courtesy Dr. GE King Courtesy Dr. GE King

62. Lateral Rotational Path on Insertion Surveying the cast. Note the lingual undercuts Courtesy Dr. GE King Courtesy Dr. GE King

63. Lateral Rotational Path on Insertion Completed RPD with lingual retention Insertion path is from right to left Courtesy Dr. GE King Courtesy Dr. GE King

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