الفهرس 
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Abstract
This in vitro study was carried out on epoxy resin models to compare the microstrains induced by two different diameters of short implants in restoring maxillary bilateral distal extension bases. The models were prepared to simulate the oral cavity. Oral mucosa simulation was carried out by adding an even layer of 2 mm silicone material over the ridge area. On the epoxy resin models, two different short implant diameters were used as follow: group A: One side of the model, two implants with 4.8 mm diameter and 5 mm length were used. One implant was placed in the second premolar region and the other in the second molar region. Ceramo-metal screw retained partial denture was constructed on both implants. group B: On the other side of the model, two implants with 6.2 mm diameter and 5 mm length were used. One implant was placed in the second premolar region and the other in the second molar region. Ceramo-metal screw retained partial denture was constructed on both implants. The transmucosal abutments that used, were for screw retained superstructure and had the same lengthes. Grooves and tunnels were made in the models to facilitate strain gauge measurements. Strain gauges were installed, opposing to the buccal and palatal surfaces of each implant. A digital loading device was used to apply 200 N vertical load and 40 N oblique load at 45 degree on the fixed partial denture of each group on the model. The strain was measured and recorded with digital strain-meter and recorded. The results of this study had revealed that:- 1- Microstrains recorded at the palatal sides of the implants on vertical and oblique loads were higher than the microstrains recorded at the buccal sides for both groups. 2- Microstrains recorded at the palatal sides of the implants in group A on vertical and oblique loads were higher than the microstrains that recorded for group B. 3- Microstrains recorded at the buccal sides of the implants in group A on vertical and oblique loads were higher than the microstrains that recorded for group B. 4- Microstrains recorded on vertical and oblique loads for group A were higher than microsrains recorded for group B which had wide diameter.