Abutment Selection
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This document discusses various options for connecting dental restorations to abutments and implants, including the biologic and technical issues involved. It compares screw-retained, cement-retained, and screwless systems. It also discusses arguments in favor of cementation, potential problems like cement accumulation, and the limits of cement retention related to factors like abutment angulation and axial wall height. Finally, it covers custom abutments, platform switching, and the next generation of the UCLA abutment using shape memory alloys.
Abutment Selection
- 1. 9. Abutment selection John Beumer III DDS, MS George Perri DDS Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA 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. Restoration connection to abutment and/or implant fixture Biologic and technical issues v Screw retained systems v Cement retained systems v Screwless - cementless system (UCLA II) v Platform reduction (ie platform switching)
- 3. Arguments commonly used in favor of cementation v It’s a common procedure in the dental office: No “Implant” knowledge necessary? v Implants for dummies v The screw access hole is through the labial or buccal v Other options - Lingual set screws-lab expense and lab expertise v Simple traditional impression techniques? v Packing gingival retraction cord vs screw retained impression copings v Better esthetics? v Permits the use of zirconium abutments. Predictability of Zirconium abutments? v Fit isn’t as critical v Really? The assumption is that a misfit is just a passive cement gap with no negative consequences
- 4. Major Problems v Cement accumulation v Lack of retrievability
- 5. Subgingival cement accumulation Prepable abutment These abutments can be prepared at the lab bench or intraorally. An impression is made and the restoration is cemented in the usual and customary fashion.
- 6. Subgingival cement accumulation Prepable abutment An impression was obtained with an impression coping and the prepable abutment was attached to the fixture analogue imbedded in the master cast.
- 7. Subgingival cement accumulation Prepable abutment v The abutment is prepared so that the margin is slightly sub gingival. v An impression is made and the porcelain fused to metal crown was completed in a customary fashion. v The abutment is secured to the implant fixture and the crown is then cemented.
- 8. Subgingival cement accumulation Prepable abutment v The patient was unhappy with the esthetic result and so a hole was drilled into the occlusal surface in order to access the abutment screw. The crown and abutment was then removed v Note the accumulation of cement subgingivally.
- 9. Subgingival cement accumulation Sulcus Epithelium Implant Surface Why is there a greater risk of cement accumulation in the sulcus of implant crowns? Peri-implant tissues are more easily displaced from Circumferential the surface of collagen fibers the restoration. Bone *
- 10. Anatomy & Biology of Peri-Implant Soft Tissue Similarities between periodontal & peri-implant soft tissues: v Oral epithelium v Sulcular epithelium v Junctional epithelium Differences in peri-implant soft tissues include: v Lack of CT attachment v Hypovascular, hypocellular CT zone adjacent to the implant v Absence of periodontal ligament blood supply Sclar AG, 2003
- 11. Cementation permits use of a ceramic abutment Excellent esthetic result v Subgingival cement accumulation can be limited by packing gingival retraction cord prior to cementation v Allows the creation of an all ceramic restoration from the implant to the incisal edge. Is there an esthetic advantage? Perhaps. v The main issue is positioning of the cement margin v Incidence of fracture of zirconium abutments is a concern but long term followup data is not yet available.
- 12. Preformed nonprepable abutments Issues of concern v Positionof the cement margin in relation to the gingival margin v Particularly significant in the anterior region v Impaction of cement into the gingival sulcus v Difficulty in seating the crown because of hydraulic pressure
- 13. Preformed nonprepable abutments Considerations for use: v Tissue height essentially the same 360 degrees around the abutment v Head of the implant or abutment cement margin just subgingival v Sufficient clearance for sufficient axial wall height for predictable cement retention v Angulation allows reasonable draw with adjacent teeth
- 14. Preformed nonprepable abutments v The margin between the crown and the abutment does not follow the gingival margin. v There is significant risk of trapping cement beneath the gingival tissues upon cementation.
- 15. Preformed nonprepable abutments This patient presented with severe peri-implantitis 3 years post insertion of the crown. The initial x-ray A subsequent appeared to x-ray, taken at indicate that the right angles to crown was the long axis of seated. the implant, revealed that the crown, was not seated. Inability to completely seat the crown onto the abutment is a common complication associated with preformed abutments. Lingual access holes may help relieve the hydraulic pressure and enable seating of the crown.
- 16. Preformed nonprepable abutments Note the inflammation associated with the peri- implant gingiva 2 1/2 years post insertion.
- 17. UCLA Abutment Indications: a) Lack of interocclusal space b) Restorations in the esthetic zone c) Angulation problems d) Soft tissue problems
- 20. Custom abutments with screw retained restorations Advantages v Control thickness of labial porcelain v Used when the Waxing implant is inclined sleeve excessively to the labial. v Retrievable Full contour wax pattern is developed
- 21. Custom abutments with screw retained restorations Wax cut back Sprued wax pattern Lingual retention screw channel
- 22. Custom abutments with screw retained restorations Cast custom abutment Note lingual retention screw orifice
- 23. Custom abutments with screw retained restorations Coping Completed and sprued wax pattern Lingual retention screw channel Labial index fabricated following the full contour wax pattern.
- 24. Custom abutments with screw retained restorations Completed crown Retention screw Abutment screw Custom abutment
- 25. Custom abutments with screw retained restorations Completed restoration Lingual retention screw
- 26. Custom abutments with screw retained restorations
- 27. Custom abutments with screw retained restorations Healing Full contour abutment wax pattern Completed Wax pattern of custom abutment custom abutment
- 28. Custom abutments with screw retained restorations Completed restoration. Note the level of the gingiva
- 29. Custom abutments with screw retained restorations Gingival levels do not match but the the patient does not display his gingiva during a high smile.
- 30. Custom abutments allows the use of pink porcelain Porcelain has been baked onto the custom abutment
- 31. Custom abutments with screw retained restorations Excessive labial inclinations The axial wall lengths are frequently inadequate for effective cement retention
- 32. Custom abutments with screw retained restorations Labial axial walls are insufficient to retain a cemented restoration.
- 33. Custom abutments with screw retained restorations
- 34. Custom abutments with screw retained restorations
- 35. Limits of Cement Retention Implants angled excessively to the labial or buccal v Axialwall height limits the retention v Shortest wall determines retention v Minimum height of axial wall – 4 mm.
- 36. Fit isn’t as critical ? Really? The assumption is that a misfit is just a passive cement gap with no negative consequences The restoration appears to precisely fit the master cast. However, will it fit the patient?
- 37. Fit isn’t as critical ? Really? The assumption is that a misfit is just a passive cement gap with no negative consequences Unfortunately, this was not the case. If you cement this case there will be a sizable cement margin and you may overload the implants.
- 38. Fit isn’t as critical ? Really? The assumption is that a misfit is just a passive cement gap with no negative consequences When the impression is made with linked open tray impression copings and the original restoration placed on the master cast the misfit is profound
- 39. Fit isn’t as critical ? Really? The assumption is that a misfit is just a passive cement gap with no negative consequences New Bridge on accurate model.
- 40. Emergence Profile Compromises Screw vs Cement Retained v Cemented crown contour v Screw retained crown begins ideally just apical to the can carry ideal contour marginal soft tissue, which can all the way to the head produce the classic “pancake” crown. of the implant (arrow)
- 41. Summary: Limits of Cement Retention v Axialwall height limits the retention v Shortest wall determines retention v Minimum height – 4 mm.
- 42. Cementation The main issues are: v Cement retention (pack retraction chord before cementation) v Quality of retention (axial wall length) v Lack of retrievability
- 43. Arguments in favor of screw retained restorations v Carry restoration more subgingivally than we can predictably remove cement. v Formore ideal emergence profile and contour. v Avoid trapping cement subgingivally v More predictable seating of bridge pontic or even single tooth given the gingival contour. v Better retention particularly when a cemented restoration would have a very short axial wall. v Easier to restore when there is limited inter- occlusal or restorative space
- 44. Next Generation of the UCLA Abutment Shape Memory Sleeve (Seo and Wu) ❖ The treatment procedure is similar to current methods
- 45. The Next Generation of the UCLA Abutment Shape Memory Sleeve “Nitinol” (Nickel titanium alloy)
- 46. Next Generation of the UCLA Abutment (Seo and Wu) Issues v Is Nitinal biocompatible? v Will the increase in temperature during activation be transmitted to the fixture, abutment and underlying tissues? v What is the quality of the retention? v Will it stand up to repeated occlusal loading v Galvanic reactions?
- 47. Next Generation of the UCLA Abutment Safety of Shape Memory Alloy, “Nitinol” (Nickel titanium alloy) ‣ Nitinol is safe and bio-compatible ‣ Many devices are approved by FDA ‣ Economical to manufacture Heart balloon Arch bars Heart stent
- 48. Release of the crown Shape memory device is activated by heat Activation brings the temperature up to 55 degrees Centigrade. It’s a shape change
- 49. Next Generation of the UCLA Abutment Measurement of Temperature Rise in Abutment and Implant Fixture During Heat Activation
- 50. Next Generation of the UCLA Abutment Measurement of Temperature Rise in Abutment and Implant Fixture During Heat Activation ΔT, implant fixture (°C) ΔT, abutment (°C) Passive air cool 1.4 2.8 Forced air cool 0.3 2.1
- 51. Next Generation of the UCLA Abutment Measurement of Retention Strength Temperature Chamber
- 52. Next Generation of the UCLA Abutment Measurement of Retention Strength - Set up - Assembly: implant Saline chamber: body temperature fixture + abutment + RODO sleeve
- 53. Measurement of Retention Strength Results Min - Max. (N) Provisional cement 30 - 250 Zinc phosphate 330 - 346 RODO Device! 275 - 1,500! Shape memory sleeve after the test
- 54. Measurement of Maximum Compressive Strength ISO 14801 Guideline - Set up - Assembly: implant fixture + Saline Chamber abutment + RODO sleeve (Body Temperature)
- 55. Measurement of Maximum Compressive Strength Results Maximum Abutment Strength Failed at abutment- *No failure in the RODO Device implant fixture interface 750 N Failure of Conventional Abutments : 800 ~ 1,000 N Screw fractured
- 56. Next Generation of the UCLA Abutment ISO 14801:2007-11-15 Dynamic Fatigue Test for Endosseous Dental Implants Failed at abutment- Displacement controlled fatigue performance implant fixture interface *No failure in the RODO Device 50 - 400 Screw failed at 6000 cycles Minimum # of cycles
- 57. Next Generation of the UCLA Abutment (Seo ,Wu and Shah) Upcoming Studies v Galvanic testing v Short term IRB trial at UCLA School of Dentistry (Kumar Shah and Neil Garrett) v Long term IRB trials at UCLA, other universities and private clinics in the US commenced summer 2011. Patients with known nickel allergies not candidates
- 58. Platform Reduction and Etiology of Marginal Bone Loss around Implants Original Branemark design lost bone down to the first thread. Why? v Thread design? v Surface topography? v Conical implant seal? v Design of the neck? v Platform reduction? (switching)
- 59. Etiology of the initial bone loss around implants v Almost immediately the original “Branemark” design lost bone down to the first thread. v Other designs such as the “Astra” design appear to retain their bone levels v What is the evidence? What are the likely explanations for this difference?
- 60. Etiology of initial bone loss around implants Angulation of the neck v An implant is torqued into position with 45 Newtons v However, the torque values around the neck of the implant imbedded in the cortical bone is probably closer to 100 Newtons. v Will these values predispose to resorption to the cortical bone around the neck of the implant when the angle of the implant is acute?
- 61. Etiology of initial bone loss around implants v Angulation of the neck v Whenocclusal loads are applied will the implants with acute angles atop of the implant overload the bone in this area precipitating a resorptive remodeling response and bone loss?
- 62. Platform reduction (platform switching) Courtesy G. Perri Courtesy C. Stanford v Note the bone levels atop the implant. v Is it the result of the horizontalization of the biologic width (platform reduction)?
- 63. Platform reduction (platform switching) Courtesy G. Perri Courtesy C. Stanford The evidence is far from clear. v In these examples the angulation of the top of the implant may be the more important factor v In addition in both these implant systems the micro-rough surface was extended to the top of the implant. This also, may contribute to the maintenance of bone levels atop the implant.
- 64. Angulation of the neck v Some authors have maintained that the angulation atop the implant is the most important factor. (Braun, et al, 2006; Iacono et al , 2006) v They attribute the maintenance of bone atop of the implant to the so-called “negative” slope (dotted lines).
- 65. The presence of micro-threads Courtesy G. Perri Courtesy C. Stanford Is it the result of the microthreads around the neck of the implant?
- 66. Internal interlocking vs external hex system Conical seal v Allabutment – implant fixture interfaces demonstrate gaps upon loading from 10-50 microns. The original external hex systems demonstrates the largest gaps during flexure. v Do these gaps harbor micro-organism which in turn precipitate an inflammatory response leading to bone loss around the neck of the implant?
- 67. Marginal Bone Loss Based on a Med Line search, a review of the literature indicated that no implant system, surface or design was found superior with regards to marginal bone loss (Abrahamsson and Berhlundh, 2009)
- 68. Platform Switching (Reduction) Will this type of implant fixture – abutment configuration minimize the bone loss around the neck of implants? v Basedon a review by Bateli and Strub (2011) “the current literature provides insufficient evidence about the effectiveness of any specific modification in the implant neck area in preserving marginal bone or preventing marginal bone loss”
- 69. One piece systems Nobel direct and similar one piece systems There are no gaps developing between an abutment and fixture. Why the bone loss? Most have modern surfaces. Many were immediately provisionalized and loaded with cement retained restorations. In many cases the cement extended down to the boney levels v Aninflammatory response was initiated which was progressive and irreversible leading to extensive bone loss.
- 70. Zirconium Implant Fixtures (Strub et al, 2010) v Has been promoted for use in the esthetic zone v Biocompatible " Histology similar to titanium – about 60% bone implant contact area " Anchorage is similar to titanium v Microrough surfaces the best v Success rates equivalent to titanium v UV exposure makes the surface more bioreactive v Fractures " One piece system – fractures at ¼ the load compared to titanium " Two piece systems fracture at 1/6th the load compared to titanium " Alumina reinforced zirconium is stronger Not ready for clinical use. Some people believe that zirconium implants will eventually disappear from the market.
- 71. Zirconium abutments and frameworks Used in the esthetic zone Abutments l Less plague adherence l More esthetic l Higher fracture rate Frameworks l High incidence of chipping of porcelain off the zirconium frameworks l Not recommended for posterior teeth Courtesy Dr. A. Sharma
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