Effects of sizes and designs on an immediate-load maxillary implant

Objectives: This study investigated the surrounding bone stress and the bone-implant interfacial sliding of implant designs and implant sizes of immediate-load implant with maxillary sinus augmentation using three-dimensional (3D) non-linear finite element analysis. Methods: Twenty-four FE models including four implant designs (cylindrical, threaded, stepped and step-thread implants) and three implant dimensions (standard, long and wide threaded implants) with a bonded and three levels of frictional contact of implant-bone interfaces were created. Non-linear contact simulation was adapted to analyze interfacial condition between immediate-load implant and bone. The maxillary model was constructed from computer tomography images of a human skull and all 3D implant models were created via the computer aided design software. Results: The use of threaded implants decreased the bone stress and sliding distance obviously about 30% as compared with non-threaded (cylindrical and stepped) implants. Increasing the implant's length or diameter reduced the bone stress by 13%-26%. Employing a immediately loaded implant with smooth machine surface (ì=0.3, ì represents frictional coefficient) increased the bone stress by 28-63% as compared with the osseointegrated (bonded interfaces) implants. Roughening the implant surface (ì>0.3) did not reduced the bone stress, however it did decrease the interfacial sliding between implant and bone. Conclusions: For an immediately loaded implant placed with sinus augmentation, using threaded implant could decrease both the bone stress and implant-bone sliding distance which may improve the implant initial stability and long-term survival. 0.45 frication coefficient of rough surface shows no benefit to reduce the bone stress but they could lower the interfacial sliding between implant and bone. On the contrary, employing long or wide implants decrease the bone stress but they can not diminish the interfacial sliding. Acknowledgement: This research was supported by China Medical University (CMU-96-143).