Biomechanical analysis of immediately loaded implants according to the "All-on-Four" concept.
OBJECTIVE
The purpose of this study was to investigate the biomechanical behavior of immediately loaded implants in an edentulous mandible according to the "All-on-Four" concept.


METHODS
A 3D-finite element model of an edentulous mandible was constructed. Four implants were placed between the bilateral mental foramen according to "All-on-Four" concept. A framework made of titanium or acrylic resin between the bilateral first molars was modeled. Immediate loading and a delayed loading protocol were simulated. A vertical load of 200N was applied at the cantilever or on the abutments region of the distal implants, simulating the absence of a cantilever.


RESULTS
The peak principal compressive strains in the immediate loading models resulted in 24.0-35.8% and 26.4-39.0% increases compared with the delayed loading models under non-cantilever loading and cantilever loading, respectively. The loading position greatly affected the principal compressive and tensile strain values. The peak principal compressive strains in non-cantilever loading resulted in a 45.3-52.6% reduction compared with those in cantilever loading. The framework material did not influence the peak compressive and tensile strain. The maximum micromotion at the bone-implant interface in the immediate loading models was 7.5-14.4μm.


CONCLUSIONS
Mandibular fixed full-arch prostheses without cantilevers may result in a favorable reduction of the peri-implant bone strain during the healing period, compared with cantilevers. The maximum micromotion was within the acceptable limits for uneventful implant osseointegration in the immediate loading models. Framework material did not play an important role in reducing the peri-implant bone strain and micromotion at the bone-implant interface.
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan. Electronic address: horisato@naramed-u.ac.jp.
Satoshi
S
Horita
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan.
Tsutomu
T
Sugiura
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan.
Kazuhiko
K
Yamamoto
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan.
Kazuhiro
K
Murakami
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan.
Yuichiro
Y
Imai
Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan.
Tadaaki
T
Kirita
D001696:Biomechanical Phenomena; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D003764:Dental Materials; D004548:Elasticity; D020342:Finite Element Analysis; D006801:Humans; D057893:Immediate Dental Implant Loading; D007575:Jaw, Edentulous; D008334:Mandible; D003765:Models, Dental; D016348:Osseointegration
D015921:Dental Implants; D003764:Dental Materials
All-on-Four concept; Cantilever loading; Finite element analysis; Framework material; Immediate loading