الفهرس 
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Abstract
The aim of this study was to compare the effect of the position of the implant on stress distribution in bilateral distal extension free end saddle (Kennedy class I). A single posterior implant was used to support a RPD. Three identical models were constructed and the only difference between them was the position of the implant in the edentulous ridge. In these 3 models that represented a case of mandibular Kennedy class I; the last standing natural abutment was the canine bilaterally. The model was created from CT scan data of a subject and modified by drawing of the additional components. An implant was drawn to support the simulated RPD at the free end saddle area of each of the 3 models. The implant position was at the area of 2nd premolar, 1st molar and the 2nd molar respectively. An extra-coronal attachment was used to retain the RPD to the natural abutment. The remaining anterior teeth were modified to represent a splinting condition with a bridge from canine to canine.
The stress induced in each model was evaluated using a three-dimensional Finite Element Analysis (FEA). A distribute unilateral load of 150 N was applied to the central fossae of artificial teeth of the right side.
After running the analysis; collecting the data and comparing the results, it was found that:
1. The highest stress on implant and the surrounding structures was when the implant placed in the 2nd premolar site.
2. The stress readings recorded for compact and spongy bone when using the implant at 1st molar were better when compared to second molar implant position, however, the stresses at the bridge and the body of the implant were higher.
3. The best stresses readings of the implant and the surrounding structures where at the 2nd molar region , except for the periodontal ligament at bucco-cervical point of the right canine ; (same side of load application)
To summarize, different stress pattern were generated in conjunction with changing the implant position. The effect of changing implant position was greatly marked on stresses around the implant of loaded side and its bone cylinder, attachment and the implant of the contralateral side. The homogenous stress pattern generated when inserting the implant at the second molar area would suggest its use as a cost effective solution. The results in this case may be promising and predictable.
Conclusions:
1. Within the limitations of the current study it can be concluded that the inserting an implant at the position of second molar may be the best situation in long span distal extension RPDs, regarding stress distribution on the implant, the cortical bone, residual ridge and remaining natural teeth.
2. If this is anatomically not possible, a more mesial position of the implant is recommended. Accordingly, the position of the 1st molar would be the second best applicable option.
3. Additional research is recommended and further verification should be carried out in clinical cases in order to gain a more accurate clinical guideline.