Methods: Experimental resin blends ranked on increasing hydrophilicity were prepared: R2 (70% BisGMA + 28.75% TEGDMA); R3: (70% BisGMA + 28.75% HEMA); R5: (40% BisGMA + 30% BisMP + 28.75% HEMA). All blends contained 0.25 wt% camphorquinone and 1.0 wt% 2-ethyl-dimethyl-4-aminobenzoate. Tested groups were: (1) R2+1%CDA; (2) R2; (3) R3+1%CDA; (4) R3; (5) R5+1%CDA; (6) R5. Discs of 8mm in diameter and 2mm thick were immersed in 1mL saline solution and the elution kinetics of CDA was assayed by means of High Performance Liquid Chromatography (HPLC) with or without chewing simulation (load=82.4N; number of cycles= 86400; frequency=1Hz; test duration=24h). Statistical analysis was performed with two-way ANOVA and Tukey post-hoc test.
Results: Not Cycled Cycled R2+1%CDA= 0.9(0.3)a ; R2+1%CDA=2.4(0.2)b R2 neat= 0; R2 neat=0 R3+1%CDA= 2.3(0.2)b ; R3+1%CDA= 2.9(0.3)bc R3 neat= 0; R3 neat=0 R5+1%CDA= 3.4(0.3)c ; R5+1%CDA= 5.4(0.3)d R5 neat= 0; R5 neat=0
Conclusions: The tested hypothesis was rejected since chewing simulation increased CDA release. The most hydrophilic experimental resin (R5) exhibited the highest CDA release, while the most hydrophobic resin (R2) exhibited the lowest rate. Further studies are needed to clarify if CDA release during chewing can be beneficial for the durability of the adhesive interface.