Multi-peak Light-emitting Diode Curing Units and Polymerization of 3D-printed Crown and Bridge Resin
This study aimed to evaluate the substitutive and additive efficacy of multi-peak light-emitting diode (LED) curing units for post-curing of a three-dimensional- (3D-) printed crown and bridge resin. A total of 792 disc- and 180 bar-shaped specimens were printed with a crown and bridge resin (NextDent C&B MFH) and post-cured using two LED curing units (VALO Cordless and Bluephase N G4) in fast and standard modes. Conventional post-curing (LC-3D Print Box, Group PC) was compared with LED-only curing (Groups V1, V2, B1, and B2) and LED-combined curing (Groups PV1, PV2, PB1, and PB2) in terms of microhardness, flexural strength, degree of conversion (DC), and CIE L*a*b* color and translucency parameters. Cytotoxicity of the resin eluates was evaluated using the WST-1 assay. Temperature increases on the resin surface were measured with infrared thermography. Data were statistically analyzed using ANOVA and Kruskal-Wallis tests (α=0.05). The microhardness and flexural strength in Groups V1, V2, B1, and DC in all LED-only groups were lower than in other groups (p<0.05). Larger color disparities existed between Group PC and all LED-only groups than between Group PC and the others (p<0.05). There was no significant difference in cytotoxicity among the groups. The temperature increase was lowest in Groups V1 and PV1 during light curing (p<0.05). Post-curing by multi-peak LED curing units was not as effective as the conventional post-curing device. Additional post-curing by LED curing units did not improve the material properties.SUMMARY
Purpose
Methods
Results
Conclusions
Experimental study design.
Schematic illustration of a 2×2×25 mm bar specimen irradiated by the LED curing unit and the load applied in the three-point bending test.
Schematic illustration of thermographic measurement of a specimen irradiated by the LED curing unit.
Means and standard deviations of relative cell viability in each group at 1, 3, and 7 days. Control: DMEM without treatment of resin eluates. Relative cell survivals in Groups V2 and B1 were higher than others on day 1 (p<0.05). All groups exhibited increased cell proliferation at day 3 compared to the control (p<0.05), but not on day 7. No significant differences existed between Group PC and other groups.
Representative thermal images obtained after the first cycle of light-curing on the top surface of the specimen and after the second cycle on the bottom surface of the specimen. The tip sizes of curing light are as follows: VALO Cordless: 9.7 mm, Bluephase N G4: 9.0 mm.
Contributor Notes