J Adhes Dent 19 (2017), No. 6 12. Jan. 2018
J Adhes Dent 18 (2016), No. 2 (15.04.2016)
Page 161-171, doi:10.3290/j.jad.a35842, PubMed:27022645
Influence of Light Irradiation Through Zirconia on the Degree of Conversion of Composite Cements
Inokoshi, Masanao / Pongprueksa, Pong / De Munck, Jan / Zhang, Fei / Vanmeensel, Kim / Minakuchi, Shunsuke / Vleugels, Jozef / Naert, Ignace / Van Meerbeek, Bart
Purpose: To assess the light irradiance (LI) delivered by two light-curing units and to measure the degree of conversion (DC) of three composite cements and one flowable composite when cured through zirconia or ceramic-veneered zirconia plates with different thicknesses.
Materials and Methods: Three dual-curing composite cements (Clearfil Esthetic Cement, Panavia F2.0, G-CEM LinkAce) and one light-curing flowable composite (G-aenial Universal Flo) were investigated. Nine different kinds of zirconia plates were prepared from three zirconia grades (YSZ: Aadva and KATANA; Ce-TZP/Al2O3: NANOZR) in three different thicknesses (0.5- and 1.5-mm-thick zirconia, and 0.5-mm-thick zirconia veneered with a 1.0-mm-thick veneering ceramic). Portions of the mixed composite cements and the flowable composite were placed on a light spectrometer to measure LI while being light cured through the zirconia plates for 40 s using two light-curing units (n = 5). After light curing, micro-Raman spectra of the composite films were acquired to determine DC at 5 and 10 min, 1 and 24 h, and at 1 week.
Results: The zirconia grade and the thickness of the zirconia/veneered zirconia plates significantly decreased LI. Increased LI did not increase DC. Only the Ce-TZP/Al2O3 (NANOZR) zirconia was too opaque to allow sufficient light transmission and resulted in significantly lower DC.
Conclusion: Although zirconia-based restorations attenuate the LI of light-curing units, the composite cements and the flowable composite could be light cured through the YSZ zirconia. LI is too low through Ce-TZP/Al2O3 zirconia, necessitating the use of self-/dual-curing composite cements.
Keywords: zirconia, degree of conversion, micro-Raman, light spectrometer, light-curing unit, composite cement