ABSTRACT
Objective: This study was conducted to evaluate the clasp retentive force and deformation of RPD frameworks made from cobalt chromium and acetal Subjects and Methods: Ten premolars natural teeth were collected and divided into two groups according to the framework material. Each tooth was embedded vertically till the cement enamel junction in one side of acrylic block. RPA clasps were constructed on each model utilizing 0.25mm undercut. Modeles were divided into two equal group. Group I contained five testing model for Cr-Co while Group II contained five testing models for acetal resin. Retention was measured by applying withdrawal force to frameworks by a universal testing machine at 5 mm/min. Deformation of clasps was evaluated by measuring the distance between 2 reference points on the tips of the retentive and reciprocal arms before and after repeated insertion/removal cycles by a chewing simulator. Results: Clasp deformation and retentive force showed significant difference between the two groups, cobalt chromium was greater than acetal clasp. Conclusion: Within the limitations of this study, it could be concluded that cobalt-chromium clasps had significant clasp deformation and retentive force more than acetal resin clasps