Different PEEK qualities irradiated with light of different wavelengths: Impact on Martens hardness

ObjectivesTo assess the impact of irradiation on Martens hardness parameters of different PEEK qualities filled with titanium dioxide (TiO2), namely PEEK/0%, PEEK/20%, and PEEK/>30%.MethodsFor Martens hardness (HM) measurements, 40 specimens of each PEEK quality were fabricated and air-abraded with 50 μm Al2O3. HM parameters of PEEK specimens were measured initially and stepwise after irradiating for 5, 10, 20, 30, 40, 60, 80, 100, 180, 360 and 540 s using light units with different wavelength: Elipar S10 (430-480 nm), EyeVolutionMAX (385-390 nm + 465-470 nm), Translux CL (380-500 nm) and bre.Lux Power Unit (370-500 nm). HM parameters of 10 human teeth were measured initially on enamel and dentin. Data was analysed using 3-way ANOVA with partial eta-squared (ηP2) and post-hoc Tuckey-HSD-test (p < 0.05).ResultsPEEK qualities followed by the wavelength showed the highest effect on Martens hardness (p < 0.013). PEEK/>30% (197.35 ± 19.9 N/mm2), followed by PEEK/20% (191.45 ± 15.49 N/mm2) showed significantly higher values for HM than PEEK/0% (189.55 ± 16.89 N/mm2). PEEK/>30% (5.49 ± 0.4 kN/mm) and PEEK/20% (5.38 ± 0.26 kN/mm2) presented higher indentation modulus (EIT) than PEEK/0% (4.77 ± 0.36 kN/mm2). Irradiated with wavelength of 430-480 nm (PEEK/0%: 193.28 N/mm2, PEEK20%: 198.83 N/mm2, PEEK/>30%: 200.5 N/mm2) indicated higher HM compared to specimens irradiated with 380-500 nm (PEEK/0%: 186.63 N/mm2, PEEK20%: 191.05 N/mm2, PEEK/>30%: 196.13 N/mm2). Irradiation using 430-480 nm (PEEK/0%: 4.95 kN/mm2, PEEK20%: 5.52 kN/mm2, PEEK/>30%: 5.59 kN/mm2) and 370-500 nm (PEEK/0%: 4.92 kN/mm2, PEEK20%: 5.43 kN/mm2, PEEK/>30%: 5.53 kN/mm2) indicated higher EIT values compared to specimens irradiated with 380-500 nm (PEEK/0%: 4.72 kN/mm2, PEEK20%: 5.34 kN/mm2, PEEK/>30%: 5.47 kN/mm2). Duration of irradiation presented no impact on results. Enamel (HM: 2263.6 ± 405.16, EIT: 63.16 ± 19.24) and dentin (HM: 468.2 ± 30.77 N/mm2, EIT: 14.14 ± 4.59 kN/mm2) presented significantly higher HM and EIT than the tested PEEK qualities (p < 0.001).SignificanceIrradiation with different wavelength impacted HM parameter. The increase of TiO2 percentage in PEEK matrix improved the HM parameter. However, PEEK showed significantly lower HM parameter than human teeth.