The influence of mandibular deformation, implant numbers, and loading position on detected forces in abutments supporting fixed implant superstructures.
BACKGROUND
Forces may arise in association with the use of implant stabilized mandibular fixed partial dentures as a result of functional jaw deformation, yet the phenomenon has received little attention and is rarely included as a variable when investigating implant biomechanics.


OBJECTIVE
This in vitro investigation tested the hypothesis that functional mandibular deformation influences force distribution in the jaw/implant/superstructure complex.


METHODS
Six Brånemark implants were mounted in an acrylic resin replica of an edentulous human mandible. Applied forces were measured with 4-element resistance strain gauges mounted on each of 6 standard titanium abutments. The mandible was supported either on its lower border or suspended in a frame that simulated the natural situation. A cast gold superstructure was a mounted on varying combinations of implants, loaded occlusally in different locations, and the resultant forces at each supporting transmucosal abutment measured.


RESULTS
The suspended ("natural") support configuration was associated with considerable differences in patterns of force transmission as compared with bench support. Loads were more widely spread, and large extrusion forces were detected, particularly where several implants were connected.


CONCLUSIONS
Functional mandibular deformation is a significant factor in the design of mandibular implant stabilized prostheses, and calls into doubt the value of modeling techniques that do not allow for this phenomenon.
Hobkirk
J A
JA
Department of Prosthetic Dentistry, Eastman Dental Institute, University of London, United Kingdom.
Havthoulas
T K
TK
D000180:Acrylic Resins; D001696:Biomechanical Phenomena; D000044:Dental Abutments; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D003766:Dental Occlusion; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003779:Denture Design; D003830:Denture, Partial, Fixed; D006047:Gold Alloys; D006801:Humans; D007575:Jaw, Edentulous / Q000503:physiopathology; D008334:Mandible / Q000502:physiology*; D008953:Models, Anatomic; D013314:Stress, Mechanical
D000180:Acrylic Resins; D015921:Dental Implants; D006047:Gold Alloys