Purpose: The aim of the study is in vitro stress analysis of force transmitted by mandibular bilateral free end saddle using  extra short dental implant (four millimeters ) retained removable partial overdenture. Material and methods: :For this study ten educational epoxy resin models were made representing mandibular bilateral distal extension edentulous area with the only six anterior teeth remaining and the mandibular canine as the main abutment,the implant were placed at the site of the second molar ,A self-protected linear strain gauge was used for this study to measure the micro-strain induced on the buccal , lingual ,mesial and distal sides of the implant. Results: during unilateral loading on the loading side,There was a significant difference in total stresses between groups combination clasp recorded significant higher total stress than RPI.and there was a significant difference in peri-implant stresses between groups for all gauge positions .during unilateral loading on the non-loading side,There was a significant difference in total stresses between groups combination clasprecorded significant higher total stress than RPI.. Conclusion:Implant retained mandibular partial overdenture with combination clasp transfere more stress than RPI clasp because of the flexibility of the combination clasp more than rigid connection of RPI clasp and therefore transmit more stress during loading than RPI.and there was asignficient difference in stress between strain gages position in both groups.