Bicortical Stabilized Implant Load Transfer

Bicortical Stabilized Implant Load Transfer
September 2003
Cagna, David R. DMD
Implant Dentistry: Volume 12(3) September 2003 p 198
Lippincott Williams & Wilkins
Department of Prosthodontics
University of Texas Health Science Center at San Antonio
7703 Floyd Curl Drive
San Antonio, TX 78284-7894
Editors' Note: Please be aware that articles reviewed in this segment of Implant Dentistry are selected by the Editors and are assigned to be reviewed by knowledgeable individuals. These are not fillers. Each article has been carefully analyzed and diligently reviewed.
: David R. Cagna, DMD,* Scott R. Dyer, DMD,** Gary A. Hartman, DDS, MS,*** Robert M. Loughlin, DDS,ÇƒÜ; Michael P. Mills, DMD, MSÇƒ?;
Bicortical Stabilized Implant Load Transfer C. M. Jeong, A. A. Caputo, R. S. Wylie, S. C. Son, Y. C. Jeon, Int J Oral Maxillofac Implants, 2003;18:59-65
The biomechanical advantage of engaging more than one cortical plate when placing dental implants is often listed as a desirable surgical goal. Although somewhat intuitive, clear, and convincing, scientifically credible evidence is lacking. Originally described as an objective during placement of implants in the anterior mandible, effective bicortical stabilization may be difficult to achieve in the posterior mandible due to obvious anatomical restrictions. However, in selected instances, it is possible to engage both the superior cortical plate and the lingual cortical plate when placing implants in the posterior mandible.
To evaluate load transfer to the osseous structures of the posterior mandible through a single implant, Jeong et al developed photoelastic models housing a single, 15-mm threaded implant. Each of the models contained polymers of varying elastic moduli representing the diverse physical properties of cortical and cancellous bone. Implants were positioned within the models in one of two locations: (1) centrally located so that the implant engaged only the superior cortical plate, or (2) eccentrically located so that the implant engaged both the superior cortical plate and had the apical three threads engaging the lingual cortical plate. Crowns with 5-mm buccal cantilevers were screw retained to the implants. Models were thermally stress relieved before experimentation. Fifteen-pound vertical loads were applied to the crowns along the central implant axes, on the cantilevers 3 mm from the central axes, and on the cantilevers 5 mm from the axes. The models were then modified to simulate a saucer-shaped peri-implant bone defect extending through the superior cortical plate. Modified models were subjected to the same loading regimen.
The results suggest that bicortical engagement, without peri-implant defects, reduces maximum stress in the superior cortical plate approximately 20%. In the presence of peri-implant defects, stress is transferred to the cancellous bone. Cantilever loading elevated stress transfer in all modeled scenarios. The authors cautioned that any biomechanical advantages implied by this study must be carefully considered. Reduced stress transfer to the superior cortical plate may not be clinically significant when considering the increased surgical risks necessary to achieve bicortical implant placement. The ultimate advantages of bicortical stabilization must be balanced against potential postoperative complications and sequelae.
¨© 2003 Lippincott Williams & Wilkins, Inc.