Biomechanical factors associated with mandibular cantilevers: analysis with three-dimensional finite element models.
OBJECTIVE
Although the risks of using a cantilever to treat missing teeth have been described, the mechanisms remain unclear. This study aimed to reveal these mechanisms from a biomechanical perspective. The effects of various implant sites, number of implants, and superstructural connections on stress distribution in the marginal bone were analyzed with three-dimensional finite element models based on mandibular computed tomography data. Forces from the masseter, temporalis, and internal pterygoid were applied as vectors.


METHODS
Two three-dimensional finite element models were created with the edentulous mandible showing severe and relatively modest residual ridge resorption. Cantilevers of the premolar and molar were simulated in the superstructures in the models. The following conditions were also included as factors in the models to investigate changes: poor bone quality, shortened dental arch, posterior occlusion, lateral occlusion, double force of the masseter, and short implant. Multiple linear regression analysis with a forced-entry method was performed with stress values as the objective variable and the factors as the explanatory variable.


RESULTS
When bone mass was high, stress around the implant caused by differences in implantation sites was reduced. When bone mass was low, the presence of a cantilever was a possible risk factor. The stress around the implant increased significantly if bone quality was poor or if increased force (eg, bruxism) was applied.


CONCLUSIONS
The addition of a cantilever to the superstructure increased stress around implants. When large muscle forces were applied to a superstructure with cantilevers or if bone quality was poor, stress around the implants increased.
Tomoya
T
Gonda
Daiisa
D
Yasuda
Kazunori
K
Ikebe
Yoshinobu
Y
Maeda
D016301:Alveolar Bone Loss / Q000503:physiopathology; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D003198:Computer Simulation; D003724:Dental Arch / Q000502:physiology; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods; D003779:Denture Design; D003826:Denture, Complete, Lower; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007575:Jaw, Edentulous / Q000503:physiopathology; D008334:Mandible / Q000502:physiology; D008406:Masseter Muscle / Q000502:physiology; D008953:Models, Anatomic; D011626:Pterygoid Muscles / Q000502:physiology; D013314:Stress, Mechanical; D013703:Temporal Muscle / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000379:methods
D015921:Dental Implants