الفهرس 
Types of removable partial denturesOnly 14 pages are availabe for public view
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Abstract
Statement of problem: Thermoplastic resin clasps have been used recently in the partial removable dental prosthesis’s construction. However, little is known about the long-term retentiveness of these clasps under clinical conditions. Objectives: The study aimed to evaluate some of the mechanical properties (Retentive strength, Flexural strength and Modulus) of Acetal resin, Valplast. Materials and methods: Retention test: Two metallic premolar models were made (the first with 0.02 inch undercut and the second with 0.03 inch undercut). Sixty-four clasps were prepared. The clasp specimens include: group 1: Thirty-two clasps made from Acetal. Each model received sixteen Acetal Akers clasps (eight clasps with 2mm thickness and eight with 3mm thickness). group 2: Thirty-two clasps made from Valplast. Each model received sixteen Valplast Akers clasps (eight clasps with 2mm thickness and eight with 3mm thickness). This test allowed the placement (insertion) of the clasp to its predetermined terminal position and its subsequent removal from this position, thus simulating the placement and removal of a RPD. The cyclic loading applied to remove the clasp was (0, 1500, 3000, 4500, 6000, and 7500). Lloyd instruments recorded continuous cycles corresponding to (0, 1, 2, 3, 4 and 5 years of simulated clinical use of a RPD). The recorded data were collected and statistically analyzed using student T- test. Flexural strength test: It was consisted of eight specimens for Acetal, eight specimens for Valplast. For the study, preformed metal mold for denture base specimen strength test were fabricated having 65mm x 10mm x 3mm as given by ISO 1567 for testing denture base resin to construction of specimens. All specimens were individually and horizontally mounted on custom made fixture [three-point bending test] on a computer controlled materials testing machine with a load cell of 5 KN. The recorded data were collected and statistically analyzed. Results: The result of this study showed that the first group (Acetal) recorded higher retentive force mean value than the second one (Valplast). The result of this study showed that Acetal recorded higher flexural strength and modulus than Valplast.