Bicortically stabilized implant load transfer.
OBJECTIVE
Questions exist as to the potential advantages of bicortical stabilization of implants in the mandible through engagement of the lingual cortical plate. The purpose of this investigation was to determine photoelastically the effect of lingual cortical plate engagement on implant load transfer.


METHODS
Composite photoelastic models of an edentulous posterior segment of a mandible were fabricated using plastics of different modulus to simulate cortical and trabecular bone. One model included a 3.75 x 15-mm threaded implant that engaged the simulated lingual cortical plate, while in the other model the implant was centrally located within the simulated trabecular bone. A metal superstructure was cast using an abutment cylinder. Simulated vertical occlusal loads were applied to the superstructure over the implant and at fixed buccal cantilever lengths. Stresses that developed within the model were monitored photoelastically and recorded photographically. Peri-implant defects were then formed in the models and the loading and recording procedures were repeated.


RESULTS
Lingual cortical plate engagement generated the highest stresses at the lingual cortical plate and the buccal crestal cortical layer at the implant neck. Stress intensity within the buccal plate at the implant neck was lower than that in the centrally placed implant. In the presence of a peri-implant defect, for all load conditions, more load was borne by the trabecular bone. Increasing cantilever lengths caused asymmetric load transfer with higher maximum stresses.


CONCLUSIONS
For both implant placements, a large portion of the applied load was taken by the crestal cortical bone simulant. Engagement of the lingual cortical plate reduced maximum stress in the crestal cortical bone by approximately 25%. With peri-implant defects, the simulated trabecular bone provided the main support of the applied load. Longer buccal cantilever lengths increased maximum stresses for all placement and crestal bone conditions.


CONCLUSIONS
The results of this investigation do not indicate a clear load transfer advantage to apical engagement of the lingual cortical plate in this model.
Jeong
Chang Mo
CM
Department of Prosthodontics, School of Dentistry, Pusan National University, Pusan, Korea.
Caputo
Angelo A
AA
Wylie
Robert S
RS
Son
Seung C
SC
Jeon
Young Chan
YC
D000539:Alveolar Process / Q000473:pathology / Q000503:physiopathology; D001732:Bite Force; D000044:Dental Abutments; D015921:Dental Implants; D017267:Dental Prosthesis Design; D004548:Elasticity; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007575:Jaw, Edentulous / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D008027:Light; D008334:Mandible / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D008953:Models, Anatomic; D008954:Models, Biological; D010781:Photography; D010969:Plastics; D013314:Stress, Mechanical; D013499:Surface Properties; D016474:Weight-Bearing / Q000502:physiology*
D015921:Dental Implants; D010969:Plastics