Effects of post-curing light intensity on the trueness, compressive strength, and resin polymerization...

To investigate the effect of different post-curing light intensities on the trueness, compressive strength, and resin polymerization of 3D-printed 3-unit fixed dental prostheses (FPD).

A total of 60 specimens were prepared to support a 3-unit FDP with a deep chamfer marginal design, utilizing computer-aided design and computer-aided manufacturing (CAD-CAM) technology. Light-polymerizing FDP resin with varying light intensities (105, 210, 420, and 840 mW/cm²) was employed for 10 min. Subsequently, trueness assessment, fracture load testing, scanning electron microscopy (SEM) surface examination, and Fourier-Transform Infrared (FTIR) analysis were conducted. A one-way analysis of variance (ANOVA) was performed to ascertain the differences between the experimental groups (p < 0.05).

The group exposed to 210 mW/cm² showed the highest trueness (57.6 ± 2.1 µm), while the 840 mW/cm² group had the highest deviation (79.3 ± 2.7 µm) (p < 0.001). Significant differences in fracture resistance were found between groups (p < 0.001), with mean fracture strengths of 1149.77 ± 67.81 N, 1264.92 ± 39.06 N, 1331.34 ± 53.62 N, and 1439.93 ± 34.58 N for light intensities of 105, 210, 420, and 840 mW/cm², respectively (p < 0.001). The resin polymerization analysis shows a peak intensity surge at 3579 cm^-1 for O-H and C-H stretching vibrations, except in samples exposed to 105 mw/cm² light, with the lowest peak at 2890 cm^-1. The performance of resin polymerization is most significant under the condition of 840 mW/cm².

The light intensity of 210 mW/cm² exhibited the highest trueness, while the 840 mW/cm² group showed the highest deviation. However, the light intensity of 840 mW/cm² demonstrated the highest compressive strength. Furthermore, polymerization occurred at all post-treatment light intensities except 105 mW/cm². These findings indicate that while low-intensity usage offers greater trueness, high-intensity usage provides better compressive strength and polymerization. Therefore, 210 mW/cm² could be the recommended solution for post-curing.