الفهرس 
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Abstract
The aim of the study was to evaluate the axial and off axial loading on implants of different diameters for replacing first mandibular molar using strain gauge. Fifteen epoxy resin blocks in which implants of different diameters were fixed were used in this study. The blocks were divided into 3 parallel groups, 5 specimens each according to the implant diameter. group l: Crown restorations supported on 6mm dummy implants diameter. group II: Crown restorations supported on 4.7mm dummy implants diameter design. group III: Crown restorations supported on 3.7-3.7mm double- dummy implants diameter design. Four strain gauges were fixed for each implant facially, lingually, mesially and distally on the epoxy resin model adjacent to the implant site. They were connected afterwards to a strain meter in order to record the developed strain. A universal testing machine was used for load application (100 N) to test the micro-strain developed around the implants at five points: the central fossa (CF) of the crown, the buccolingual (BL) midpoint of the mesial marginal ridge (MMR), the buccolingual midpoint of the distal marginal ridge (DMR), the mesiobuccal cusp tip (MBC tip) and the distobuccal cusp tip (DBC tip).
The results were then recorded, tabulated, and statistically analyzed. group III exhibited lower mean micro-strain values (89.05±27.58) followed by group I (151.15±59.75) then group II (381.11±191.99). There was statistically significant difference between the three groups (p > 0.05).
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It was concluded that for single molar implant designs, an increase in implant number and diameter may effectively reduce experimental implant abutment strains. Double (3.75-3.75mm) implants were better in eliminating stresses and strains than 6mm diameter implant and 4.7 mm diameter implant. The double implants give wider support to a molar restoration leading to preservation of crestal bone and elimination of the mesiodistal cantilever.