الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The purpose of this study was to evaluate the influence of the spacer on reducing the stresses transmitted to abutment teeth retaining a RPOD for mandibular bilateral distal extension case with a resilient precison attachment (O-ring) through the aid of strain gage technology An educational acrylic resin model was fabricated resembling a mandibular bilateral distal extension case with the first premolars were the posterior remaining teeth as they were prepared to receive posts of O-ring attachment. The moldel were prepared to simulate the oral condition by reproducing an artificial mucosa and periodontal ligament using silicone soft lining material, and prepared to receive three straing gages (buccal, lingual, and distal) around each abutment on both sides Two designs were tested according to use of spacer between denture base and abutment teeth during picking up the O-ring attachment as follows: Design І used without a spacer Design ІІ same as design one but used with spacer between the denture base and the abutment teeth The two designs were loaded with a controlled vertical static load of 60 N for 15 seconds in two positions unilaterally and bilaterally and micro strains were measured from three surfaces (distal, buccal, and lingual) of the abutment teeth for the two designs in each loading position. The statistical analysis for the results revealed that: 1- The stresses were significantly reduced in the second design which was used with a spacer in both loading positions on the loaded and unloaded side. 2- The lateral forces were markedly directed toward the buccal side more than lingual side in both designs in spite of being reduced in value when a spacer is used. Conclusion: 1- It is very important to use spacer with resilient attachments retaining a partial overdenture in order to minimize the forces exerted on the abutment teeth. 2-Most of the lateral forces were directed to the buccal side of the abutment teeth in case of Recommendation:- 1- Periodic monitoring of the buccal side of the abutment teeth using a resilient attachment either 2-Further investigation is needed to evaluate the stresses directed to the residual ridge of with or without spacer.