Effect of Different Impression and Fabrication Techniques on the Precision of Custom Metal Posts: Fully Digital,...

This study evaluated the effect of different impression and fabrication techniques-conventional casting and 3D printing-on the precision of metal post-and-core restorations.

A maxillary central incisor was designed in ExoCAD, and STL files of the reference tooth and the "ideal" post were saved; the reference tooth was additively manufactured in metal. Four workflows were compared (n = 10/group): (1) conventional impression with a direct resin pattern and casting (CO); (2) semi-digital impression with an intra-canal Duralay pattern plus Silicone pick-up, laboratory scan, and direct metal printing (DS); (3) semi-digital Full Silicone (putty/wash) impression, laboratory scan, and direct metal printing (FS); and (4) fully digital intraoral scanning with Medit i700 and direct metal printing (FD). For each specimen, the fabricated post STL was compared to the "ideal post" STL in Geomagic Control X to assess precision. Normality was tested with Shapiro-Wilk, and between-group comparisons used one-way analysis of variance in SPSS (α = 0.05).

In forty specimens (FD, DS, FS, CO; n = 10/group), three outcomes were analyzed: In-Tol, Over-Tol, and Under-Tol. In-Tol differed significantly among groups (p < 0.001); Tamhane's T2 indicated FD > DS, FS, CO (p = 0.006, < 0.001, < 0.001). Over-Tol differed significantly (p < 0.001); FD < FS (p < 0.001), FD < CO (p = 0.021), and DS < FS (p < 0.001). Under-Tol also differed significantly (p < 0.001); DS > FD (p = 0.027), DS > FS (p = 0.011), and CO > FS (p = 0.016).

Fully digital, directly printed Co-Cr posts exhibited superior precision compared with conventional and semi-digital workflows. While conventional casting remains reliable, direct metal printing appears to be a practical and potentially easier alternative.