Color reproduction trueness of 3D‐printed full‐color dental casts with scans derived from an intraoral scanner
Authors: Alfaraj Amal , Lin Wei‐Shao 
Published: December 2023

Purpose

To investigate the effects of shade tab color variations (tooth‐colored vs. gingiva‐colored) and surface treatment (application of mineral oil) on the trueness of color reproduction from dental shade tabs to 3D‐printed full‐color dental casts, using digital scans obtained from an intraoral scanner.

Materials and Methods

Pristine tooth‐colored (with 16 shade tabs) and gingiva‐colored (with five shade tabs) shade guides were digitally scanned using an intraoral scanner, and subsequently, 3D‐printed replicas were created using a full‐color material jetting 3D printer. Three color measurements using a contact type digital spectrophotometer were recorded, including actual shade tabs (R0), dried 3D‐printed study samples (RP1), and study samples with mineral oil application (RP2), in this study to calculate color differences between the actual shade tabs and 3D‐printed ones. The CIEDE2000 formula was used to calculate the color differences (color reproduction trueness) between reference shade tabs and 3D‐printed full‐color study samples—without and with mineral oil, ∆E00(RP1), and ∆E00(RP2). ∆E00(RP1) and ∆E00(RP2) were compared with a 50:50% accessibility threshold (AT) and a 50:50% perceptibility threshold (PT). A grading system, based on the relative ranges of AT and PT, was employed. The percentage of samples falling into each color‐matching category was then recorded. The data collected were subjected to statistical analysis, utilizing a mixed model ANOVA to evaluate the effects of shade tab color and mineral oil application on color differences, α = 0.05.

Results

The application of mineral oil significantly affected the ∆E00 [F(1, 378) = 19.1, p = < 0.0001]. However, this effect was only significant for the gingiva‐colored study samples; the mineral oil application significantly decreased color difference, showing ∆E00(RP1) of 8.71 ± 3.78 and ∆E00(RP2) of 6.55 ± 2.14 (p < 0.0001). For the tooth‐colored groups, the mineral oil application did not yield any color difference, showing ∆E00(RP1) of 7.05 ± 2.35 and ∆E00(RP2) of 6.94 ± 2.35 (p = 0.497). In the absence of mineral oil, gingiva‐colored samples revealed a significantly larger ∆E00(RP1) of 8.71 ± 3.78 compared to tooth‐colored samples at 7.05 ± 2.35 (p = 0.017). Conversely, mineral oil application rendered comparable ∆E00(RP2) values between gingiva‐colored (6.55 ± 2.14) and tooth‐colored (6.94 ± 2.35) samples (p = 0.558). All 3D‐printed full‐color samples showed Grade 1 (extremely unacceptable mismatch) and Grade 2 (clearly unacceptable mismatch), regardless of the shades or the presence of mineral oil.

Conclusions

Utilizing an intraoral scanner to gather digital color data, along with an MJ 3D printer, offers the potential for producing 3D‐printed full‐color dental casts for prosthesis characterization in the dental laboratory. While mineral oil improves the color reproduction trueness of gingiva‐colored objects, all 3D‐printed full‐color samples exhibited unacceptable mismatches when compared to their target objects. This underscores the need for future improvement in the digital color data acquisition process and color optimization protocols in 3D printing processes.