الفهرس 
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Abstract
Objectives : The purpose of this study was to measure the effect of loads on the implants of different angulations experimentally and to evaluate the effect of angulated implant placement in posterior maxilla by finite element analysis. Materials and Methods: Two simplified models were designed to simulate a clinical situation where a dental implant placed into posterior maxilla in two different ways. One implant placed vertical piercing the maxillary sinus and the other tilted 25° inside the bone not piercing the maxillary sinus. Geometric modeling was prepared on Autodesk Inventor then assembled in ANSYS for finite element analysis. The results of finite element analysis were verified against experimental trial, where two groups each of three bovine bone ribs contain implant-abutment complexes. group A received three straight implants inside the bone with straight abutments on it and group B received three tilted 25° implants inside the bone with angulated abutments, then they were gradually loaded up to failure in a universal testing machine. The forces were applied vertically. Results were statistically analyzed by computer software using student t-test (level of significance p < 0.05). Results : Revealed that the maximum Von Mises stress on cortical bone was found where implant was placed at 25° in comparison to vertically inserted. On the other hand, the maximum Von Mises stress for titanium components ; the implant, abutment and screw in the second run were lower than those of the first run. The results of the fracture resistance test of the two studied groups showed that there was a highly significant difference between the mean compressive loads of them. Conclusions : When axial loading was applied, the highest level of stress was observed on the implant-bone interface and peri-implant bones in an angulated implants and the lowest stress distribution was exhibited in the implant-bone interface and peri-implant bones in straight implant conditions. The highest level of stress was distributed on the implant complex of the axial implant and the lowest level of stress was on the implant complex of the angulated implant. Implant angulation and position had a large effect on stress distribution. Comparing results between finite element analysis and experiment showed very good agreement. Thus, it can be emphasized that the tilted implant 25° can be utilized in the posterior region of the maxilla to replace maxillary first molar avoiding sinus penetration. Recommendations : Further research concerning bicortical dental implantation and angulatoin in the posterior maxilla is required.