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Modified Drilling Sequence for Immediate Loading of Non-Conical Single Implants Placed in Extraction Sockets

Dental implant manufacturers have developed specific drilling sequences to ensure optimum results with respect to osseointegration. The recommended drilling procedure, however, accounts for clinical applications where traditional implant loading protocols (which include a healing period prior to restoring the implant and subsequent exposure to occlusal forces) will be followed.

Several authors have demonstrated high success rates in situations where multiple implants are immediately loaded and splinted with a full-arch fixed prosthesis.1-3 The rationale for this procedure is grounded in the fact that the cross-arch stabilization provided by the splinted prosthesis limits implant movement, thus preventing fibrous proliferation along the implant surface and allowing osseointegration to result in adequate bone-to-implant contact.

While immediate loading of a full-arch prosthesis has been shown to be a viable approach,1,4,5 the immediate loading of single implants requires additional considerations. Since splinting cannot be counted on to control occlusal forces under these circumstances, implants placed into extraction sockets that are immediately loaded may require a higher degree of stability to prevent micromotion and fibrous tissue proliferation along the implant surface, which may result in decreased bone-to-implant contact and potential fixture failure. Nevertheless, minimum insertion torque requirements for the successful integration of immediately loaded single-tooth implants placed into fresh extraction sockets remain to be determined. Reports by Wörhle6 and Cannizaro et al7 suggest that insertion torques of 45 Ncm seem adequate in terms of achieving sufficient primary stability for immediate loading of single-tooth implants. Conversely, Pinheiro Ottoni et al reported a high degree of failures when implants where placed at 20 Ncm and immediately loaded.8

The following protocol was developed with the purpose of increasing the insertion torque and stability of implants exhibiting a non-conical apical design placed into fresh extraction sockets. Additionally, it should enable clinicians to pursue immediate loading with a provisional restoration.

Surgical Guidelines

Implant osteotomy preparation in fresh extraction sockets may present technical challenges. Often times, the clinician may choose not to follow the orientation of the extracted tooth, which requires the surgical preparation of an alveolar wall. Additionally, immediate postextraction placement in the aesthetic zone often requires that the implant be placed in a more lingual (ie, palatal) position. Either of the former scenarios includes osteotomy drilling that must be performed on the inclined plane of a socket wall. Traditionally shaped initial drills and pilot burs are not designed for this application and may tend to drift during the drilling procedure, therefore making adequate implant placement more difficult in these situations.

The authors’ preference is to utilize a precision initial drill that allows accurate positioning of the osteotomy within the palatal alveolar wall. Once the osteotomy site has been clearly established, a number of drills are followed in sequence to accommodate the desired implant length and subsequently prepare the osteotomy site to its required diameter. Efforts must be made to apply pressure towards the palatal aspect during drilling to preclude the osteotomy preparation from migrating labially as the drilling sequence is completed (Figures 1-2-3-4-5-6-7-8).

A common method of achieving increased insertion torques is to undersize the osteotomy preparation relative to the diameter of the implant that will be placed.9 This approach, however, is not universally applicable to all implant types. Tapered implants and implants with a conical apex design exhibit a narrower apical diameter that may be fitted into an undersized ostetotomy. Some popular implant designs, however, incorporate the use of parallel walls and a square or blunt apex, which do not lend themselves to common undersizing techniques.

The authors have developed a modified drilling technique to achieve higher insertion torques in implants exhibiting a non-conical design. The protocol follows the traditional drilling sequence recommended by the manufacturer except for the last drill, which must be utilized in order to properly size the osteotomy so that it will allow placement of the non-conical implant apex. Increased primary stability is achieved by drilling only to a distance corresponding to two thirds (2/3) of the implant length. The objective herein is to drill beyond the socket while preserving an underprepared portion of the osteotomy within the cancellous bone (Figures 9-10-11).

Implant placement is subsequently performed at 15 rpm, with complete seating taking place at a minimum insertion torque of 45 Ncm. In the authors’ experience, the implant stability resulting from this amount of insertion torque appears to be sufficient to allow immediate placement of a provisional restoration. Depending on bone quality, excessive resistance may be encountered during implant insertion, which poses a risk of stripping the osteotomy threads. In this case, the implant must be reversed out and the osteotomy must be further prepared utilizing the final drill to a longer distance.

The osteotomy preparation is oriented to allow implant placement that will result in a gap of approximately 1 mm to 2 mm between the buccal socket wall and the corresponding implant surface. This ensures that no trauma is placed on the buccal alveolar socket wall as a result of the implant procedure. The authors advocate grafting this gap with a bovine-derived xenograph regardless of periodontal biotype. The rationale is to utilize a slow-resorbing material that will provide adequate support to the gingival tissues during the postextraction bone remodeling process.10,11

(Continued from page 1 )

Prosthetic Guidelines

There are many techniques to fabricate an implant-supported provisional crown. The authors recommend utilizing a transitional custom abutment,12 whereby composite resin is added to a metallic temporary cylinder to achieve an emergence profile that mimics the corresponding cross-sectional portion of the root (Figures 12 and 13).

Once the transitional custom abutment is fabricated, proper placement is facilitated by the fact that it is screw-retained, which allows the clinician to achieve complete seating in the presence of gingival tissue resistance. Once seated, the preparation of the transitional custom abutment is completed and a finish line is established 0.5 mm below the gingival margin. A provisional crown is subsequently fabricated and placed with temporary cement. This approach avoids the presence of a cement line within the alveolus, or in an excessively subgingival location. Additionally, it eliminates the possibility of the abutment screw exiting through the labial surface (Figures 14-15-16-17).

Occlusal management includes relieving all centric and excursive contacts, so as to eliminate and/or minimize occlusal loading as much as possible. Patients exhibiting parafunctional habits and excessive overbite with inadequate interocclusal space are poor candidates for this technique due to the difficulty in controlling excessive loading. Following implant integration, an impression technique that utilizes the transitional custom abutment as a pick-up impression coping may be utilized to accurately replicate the peri-implant soft tissue contours.12 A custom abutment may then be fabricated via casting or computer-milling techniques, over which the definitive restoration may be manufactured and placed (Figures 18-19-20-21-22).

Future Research

Six cases were utilized in a preliminary pilot study, utilizing the modified drilling technique described above, for immediate loading of implants placed into fresh extraction sockets. No implant losses have been reported following a two-year observation period, and complete maintenance of proximal bone levels has been verified with periapical radiographs. Additionally, the peri-implant soft tissues remained stable, with postoperative changes in the labial gingival margin of less than 1 mm over the same observation period.

Conclusion

Implants exhibiting a non-conical apex may be placed into fresh extraction sockets utilizing a flapless approach and immediately loaded to successfully replace individual teeth. A modified drilling sequence has been proposed to increase torque insertion and improve implant stability. Immediate placement of a provisional restoration may be essential to adequately support the peri-implant tissues. This approach may be particularly advantageous in the anterior maxilla, where maintenance of gingival margin levels is required to achieve a predictable aesthetic result.

*Director, Postdoctoral Periodontal Prosthesis Program and Clinical Professor, Department of Periodontics, University of Pennsylvania School of Dental Medicine, Philadelphia, PA; private practice, Bryn Mawr, PA.

†Former Resident, Postdoctoral Periodontal Prosthesis, University of Pennsylvania School of Dental Medicine, Philadelphia, PA; private practice, Seattle, WA.

‡Former Resident, Postdoctoral Periodontal Prosthesis, University of Pennsylvania School of Dental Medicine, Philadelphia, PA; ITI fellow, Geneva, Switzerland.

 

References

  1. Schnitman P, Wöhrle PS, Rubenstein JE, et al. Ten-year results for Brånemark implants immediately loaded with fixed prostheses at implant placement. Int J Oral Maxillofac Impl 1997;12(4):495-503.
  2. Tarnow DP, Emtiaz S, Classi A. Immediate loading of threaded implants at stage 1 surgery in edentulous arches: Ten consecutive case reports with 1- to 5-year data. Int J Oral Maxillofac Implants 1997;12:319-324.
  3. Balshi TJ, Wolfinger GJ. Immediate loading of Brånemark implants in edentulous mandibles: A preliminary report. Implant Dent 1997;6:83-88.
  4. Ganeles J, Wismeijer D. Early and immediately restored and loaded dental implants for single-tooth and partial-arch applications. Int J Oral Maxillofac Impl 2005;20:769-776.
  5. Testori T, Meltzer A, Del Fabbro M, et al. Immediate occlusal loading of Osseotite implants in the lower edentulous jaw: A multicenter prospective study. Clin. Oral Impl Res 2004;15:278-284.
  6. Wohrle PS. Single-tooth replacement in the aesthetic zone with immediate provisionalization: Fourteen consecutive case reports. Pract Periodont Aesthet Dent 1998;10:1107-1114.
  7. Cannizaro G, Leone M, Esposito M. Immediate functional loading of implants placed with flapless surgery in the edentulous maxilla: 1-year follow-up of a single cohort study. Int J Oral Maxillofac Implants. 2007 Jan-Feb;22(1):87-95
  8. Pinheiro Ottoni JM, Lima Oliveira ZF, Mansini R, Cabral AM. Correlation between placement torque and survival of single-tooth implants. Int J Oral Maxillofac Impl 2005;20:769-776.
  9. Skalak R, Zhao Y. Interaction of force-fitting and surface roughness of implants. Clin Impl Dent Relat Res 2000;2:219-224.
  10. Araújo M, Linder E, Wennström J, Lindhe J. The influence of Bio-Oss collagen on healing of an extraction socket: An experimental study in the dog. Int J Periodont Rest Dent 2008;28(2):123-35.
  11. Nevins M, Camelo M, De Paoli S, et al. A study of the fate of the buccal wall of extraction sockets of teeth with prominent roots. Int J Periodont Rest Dent 2006;26(1):19-29. 
  12. Lee EA. Transitional custom autments: Optimizing aesthetic treatment implant-supported restorations. Pract Periodont Aesthet Dent 1999;11(9):1027-1034.
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