Effects of delayed post-polymerization on physical, chemical, and biological properties of a 3D printing interim...

This study evaluated the effects of delayed post-polymerization on color, degree of conversion (DC), flexural strength (FS), and cellular response of a 3D-printed dental interim resin.

Specimens were divided into six groups based on delays of 0 h, 2 h, 4 h, 6 h, 8 h, and 10 h before post-polymerization. Color was characterized using a spectrophotometer (n = 10), DC (n = 10) with FTIR-ATR, and FS (n = 10) with a universal testing machine. Cellular response (n = 30) was assessed through cell viability and pro-inflammatory gene expression of the gingival fibroblast cell line (L929) and human monocytic cell line (THP-1).

Delayed post-polymerization significantly affected color (L* and b*; both P < 0.001,) and color difference (P = 0.016). L* values at 6 h, 8 h, and 10 h significantly decreased compared to 0 h (P < 0.001), while b* values showed a significant decrease in all groups. (P < 0.001). No significant difference was found in a* (P = 0.417) or translucency (P = 0.394). DC significantly decreased at 8 h and 10 h (P < 0.05). There was no significant difference in FS. Cytotoxicity and pro-inflammatory gene expression (IL-6 and TNF-α) were not significantly affected by time delays.

Within the limitations of this study, a delay of up to 6 h before post-polymerization did not compromise FS, FM, cell viability, or pro-inflammatory gene expression. However, notable changes in DC and color suggest that the appearance and polymerization characteristics may be adversely affected, while mechanical and biological properties remained stable.