Chlorhexidine loading of acrylic reline resins - Microhardness and flexural strength after thermal aging

Objectives: To evaluate the effect of chlorhexidine loading in microhardness and flexural strength of acrylic reline resins, after thermal aging. Methods: Several concentrations of chlorhexidine were selected to load three acrylic reline resins: 1%, 2.5%, 5%, and 7.5% in Kooliner, 1%, 2.5%, 5%, 7.5% and 10% in Ufi Gel Hard and 1%, 2.5% and 5% in Probase Cold. In the control group the reline resin was not loaded with chlorhexidine. Eight specimens per group (n=8) were fabricated (64×10×3.3 mm) and submitted to thermal aging (1000 cycles, 5°C-55°C). Knoop microhardness (30 s, 98 mN) and 3-point flexural strength (5 mm/min) tests were performed in each specimen. Results were submitted to nonparametric tests Kruskall-Wallis e Mann-Whitney (α=0.05). Results: No differences (p>0,05) were found among microhardness of Kooliner and Probase Cold loaded with the tested chlorhexidine concentrations. Ufi Gel Hard with 2.5% of chlorhexidine yielded higher (p<0,05) microhardness than the control and 7.5% chlorhexidine groups. Regarding to flexural strength, no differences (p>0,05) were observed for Kooliner and Ufi Gel Hard. Loading Probase Cold with 5% of chlorhexidine lead to lower (p=0.033) flexural strength values than control group. Conclusions: Loading Kooliner and Ufi Gel Hard with the studied concentrations of chlorhexidine does not negatively affect microhardness or flexural strength, after thermal aging. Loading Probase Cold with 5% of chlorhexidine does not affect microhardness, but leads to a decrease of the flexural strength.