Abstract
The addition of different polymers, such as polytetrafluorethylene (PTFE), to denture base resins could be an option to modify acrylic resin mechanical properties. This study evaluated the surface hardness, impact and flexural strength, flexural modulus and peak load of 2 acrylic resins, one subjected to a long and another subjected to a short polymerization cycle, which were prepared with or without the addition of 2% PTFE. Four groups were formed according to the polymerization cycle and addition or not of PTFE. Forty specimens were prepared for each test (10 per group) with the following dimensions: hardness (30 mm diameter x 5 mm thick), impact strength (50 x 6 x 4 mm) and flexural strength (64 x 10 x 3.3 mm) test. The results of the flexural strength test allowed calculating flexural modulus and peak of load values. All tests were performed in accordance with the ISO 1567:1999 standard. Data were analyzed statistically by ANOVA and Tukey's test with the level of significance set at 5%. No statistically significant differences (p>0.05) were found for surface hardness. Flexural strength, impact strength and peak load were significantly higher (p<0.05) for resins without added PTFE. The flexural modulus of the acrylic resin with incorporated 2% PTFE polymerized by long cycle was significantly higher (p<0.05) than that of the other resins. Within the limits of this study, it may be concluded that the addition of PTFE did not improve the mechanical properties of the evaluated acrylic resins.
Highlights
Acrylic resins have been used for a long time as the best choice to fabricate full or partial dentures because of its esthetic qualities and ease of manipulation
Four groups were formed according to the polymerization cycle and addition or not of PTFE: LC: acrylic resin polymerized by long cycle; LE: acrylic resin plus 2% PTFE polymerized by long cycle; SC: acrylic resin polymerized by short cycle; and SE: acrylic resin plus 2% PTFE polymerized by short cycle
The surface hardness results showed that the addition of PTFE to the resins polymerized by either a long or a short cycle did not cause any change in this property
Summary
Acrylic resins have been used for a long time as the best choice to fabricate full or partial dentures because of its esthetic qualities and ease of manipulation. Their mechanical properties should be improved [1]. Alternatives to improve the mechanical properties of acrylic resins have been described, and include the addition of copolymers, cross-linking agents [3,4,5,6] and rubber substances in the form of butadiene styrene [7]. The addition of synthetic fluoropolymers, such as polytetrafluorethylene (PTFE) particles, to the polymeric matrix of acrylic resin in order to control microorganism adhesion, avoid unwanted creep and improve wear and friction is still unexplored. Little information is available about the use of PTFE for dental applications [9,10], it is known that PTFE is chemically inert, biocompatible, highly resistance to chemical reagents, and has high temperature tolerance, low surface energy and low coefficient of friction, which allows this material to act as a sealing and lubricant pellicle [11]
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