How Does the Location of the Restoration on a Polyjet 3DPrinting Platform Influence Biaxial Strength, Color,...

To evaluate the influence of build platform location on the mechanical and optical properties of a PolyJet-printed temporary dental resin material.

Disc-shaped specimens (10 mm diameter, 2 mm thickness) were additively manufactured from a temporary PolyJet resin on a circular build platform at four radial positions (n = 10 per position). Biaxial flexural strength (BFS) was determined using an ISO piston-on-three-ball test. Colour coordinates (L*, a*, b*), colour difference (ΔEpos, ΔErel) and mean transparency (MT) were obtained from reflection and total transmission spectra. Surface gloss was measured at 60°. Data were analysed using Levene tests, analysis of variance (ANOVA) with post-hoc comparisons, and Pearson correlation (α = 0.05).

Mean BFS differed by about 20% across positions, ranging from approximately 215 MPa at the innermost to the highest values at the outermost tray location; a significant difference was identified only between the extreme positions. BFS showed a positive correlation with radial distance (r ≈ 0.43, p = 0.006). L*, a*, b* and ΔEpos exhibited small but statistically significant positional differences (0.3-0.8) in individual positions. Relative colour differences ΔErel (vs. the inner position) ranged between 1.3 and 1.9 and were not significantly affected by location. MT showed minor but significant variations (<5%) between some positions. Gloss values varied numerically, but without statistically significant positional effects.

In a PolyJet system, the location of the printed object on the build platform has a measurable effect on biaxial flexural strength and induces subtle changes in colour and translucency, whereas gloss remains unaffected. Although most optical differences appear clinically negligible, positional effects on strength may be relevant for load-bearing temporary restorations and should be considered when arranging critical cases on the build platform.