Biomechanical comparison of axial and tilted implants for mandibular full-arch fixed prostheses.
OBJECTIVE
Controversy exists regarding the "All-on-Four" concept for a mandibular full-arch fixed prosthesis. The purpose of this study was to examine photoelastically the effect of the inclination of the two distal implants according to the All-on-Four concept on the stress distribution within the supporting structure.


METHODS
Two photoelastic models of a human edentulous mandible were fabricated. Each model had four screw-type implants embedded in the interforaminal area. The two distal implants were placed axially in one model and tilted 30 degrees distally in the other model. Two cantilevered acrylic resin prostheses, which used angulated abutments for the distal tilted implants and straight abutments for the axial implants, were fabricated and delivered. Vertical loads of 13 kg were applied at three loading points on the prosthesis: the central fossa of the first molar, the distal fossa of the first premolar, and the distal fossa of the second premolar. Stresses that developed in the supporting structure were monitored photoelastically and recorded photographically.


RESULTS
Whereas all cantilever loadings concentrated the stresses at the distal crest of the distal implant sites in both models, the posterior tilting of distal implants splinted in a full-arch fixed prosthesis did not increase the stresses in bone around the distal implants versus the axial-implant model.


CONCLUSIONS
Within the limitations of this photoelastic stress analysis, the use of tilted implants reduced the maximum stress in the distal crestal bone of the distal implant by approximately 17% relative to the axial implants.
Department of Prosthetic Dentistry, College of Dentistry, Wonkwang University Iksan, Korea.
Kyea-Soon
KS
Kim
Yu-Lee
YL
Kim
Ji-Myung
JM
Bae
Hye-Won
HW
Cho
D001641:Bicuspid; D001696:Biomechanical Phenomena; D003196:Computer Graphics; D000044:Dental Abutments; D003724:Dental Arch / Q000502:physiology; D059605:Dental Implant-Abutment Design; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000295:instrumentation; D003826:Denture, Complete, Lower; D055119:Elastic Modulus; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007575:Jaw, Edentulous / Q000503:physiopathology; D008334:Mandible / Q000502:physiology*; D008422:Materials Testing; D008953:Models, Anatomic; D008963:Molar; D010781:Photography; D013314:Stress, Mechanical
D015921:Dental Implants