To evaluate the effect of chlorhexidine incorporation on the microhardness and flexural strength of three reline acrylic resins, after a 28-day chemical aging process. Methods: Forty-eight specimens were fabricated according to the several possible combinations of acrylic reline resin and concentrations of incorporated chlorhexidine (Kooliner-0% vs. 2.5%; Ufi Gel Hard-0% vs. 5%; and Probase Cold-0% vs. 5%), to set 6 experimental groups (n=8). After a 4-week chemical aging process (pH fluctuation in artificial saliva, with cycles of 6 hours at pH=3 and 18 hours at pH=7), the Knoop microhardness (98.12 mN, 30 seconds) and flexural strength (1 kN, 5 mm/min) of all specimens were evaluated. Data were submitted to non-parametric statistical tests, according to Kruskal-Wallis and Mann-Whitney (α=0.05). Results: Chlorhexidine incorporation did not significantly affect the microhardness of the three tested resins (Kooliner-p=0.798; Ufi Gel Hard-p=0.798; and Probase Cold-p=0.195). Although chlorhexidine incorporation did not influence the flexural strength of Kooliner (p=0.959) and Ufi Gel Hard (p=0.645), the incorporation of 5% chlorhexidine in Probase Cold led to a statistically lower flexural strength than that obtained without incorporation (p=0.021). Conclusion: After chemical aging, the microhardness of chlorhexidine-incorporated acrylic resins is not affected. However, the incorporation of 5% chlorhexidine into Probase Cold negative

To evaluate the effect of chlorhexidine incorporation on the surface free energy and microtensile bond strength of three reline acrylic resins, after chemical aging. Methods: For each of the studies, six experimental groups were set according to reline resin and chlorhexidine incorporation [Kooliner-0% vs. 2.5% chlorhexidine; Ufi Gel Hard and Probase Cold-0% vs. 5% chlorhexidine]. The specimens were submitted to a chemical aging process for 4 weeks (pH fluctuation in artificial saliva, cycles of 6 hours at pH=3 and 18 hours at pH=7). For the first study, 42 specimens were prepared (n=7) and, after chemical aging, the surface free energy was calculated. For the adhesive strength study, 36 denture base resin cubes were prepared and reline resin was applied to them according to the experimental group (n=6). Five sticks (1×1 mm section) were obtained from each specimen and submitted to chemical aging followed by microtensile test (1 kN; 1 mm/min). Data were analyzed with Kruskal-Wallis and Mann-Whitney non-parametric tests (α=0.05). Results: Differences (p<0.05) were observed between resins, both in surface energy and in bond strength. The chlorhexidine incorporation did not affect the surface energy of neither of the resins and also did not affect the bond strength of Kooliner and Ufi Gel Hard (p>0.05). Incorporating 5% chlorhexidine (p=0.004) decreased the Probase Cold bond strength to the denture base resin. Conclusions: After chemical aging, chlorhexidine incorporation only negatively affected the