The Trueness of Obturator Prosthesis Base Manufactured by Conventional and 3D Printing Techniques

Abstract

Purpose: To compare the intaglio surface trueness of obturator prosthesis bases manufactured by traditional compression molding, injection molding, and 3D printing techniques.

Materials and methods: A complete edentulous master cast with Aramany Class I maxillary defect was selected for this in vitro study. Four study groups (n = 10/group) were included in this study, Group A: Compression Molding, Group B: Injection Molding, and Group C: Cara Print 3D DLP Printer, and Group D: Carbon 3D DLS Printer. All obturator prostheses' intaglio surfaces were scanned with a laboratory scanner (E4; 3Shape Inc, New Providence, NJ) and the dimensional differences between study samples and their corresponding casts were calculated as the root mean square (measured in mm, absolute value) using a surface matching software (Geomagic design X; 3D Systems, Rock Hill, SC). One-way Analysis of variance (ANOVA) and Fisher's least significant difference (LSD) test were used to compare groups differences in RMS (α = 0.05).

Results: There was a significant effect of manufacturing technique on the RMS values for the 4 conditions [F(3,36) = 5.743, p = 0.003]. Injection Molding (0.070 mm) and Compression Molding groups (0.076 mm) had a lower interquartile range, and the Cara Print 3D-Printer group (0.427 mm) and Carbon 3D-Printer (0.149 mm) groups had a higher interquartile range. The Injection Molding group showed the best and uniform surface matching with the most area in green in the color maps. The Injection Molding group (0.139 ± 0.049 mm) had significantly lower RMS than all other groups (p < 0.001 for all comparisons). Compression Molding (0.269 ± 0.057 mm), Cara Print 3D-Printer (0.409 ± 0.270 mm), and Carbon 3D-Printer (0.291 ± 0.082 mm) groups were not significantly different from each other (Compression Molding versus Carbon 3D-Printer, p = 0.59; Compression Molding versus Cara Print 3D-Printer, p = 0.25; Cara Print 3D-Printer versus Carbon 3D-Printer, p = 0.40).

Conclusion: Obturator prosthesis bases manufactured with injection molding technique showed better intaglio surface trueness than ones made by the compression molding technique and 3D printers. Although obturator prosthesis bases manufactured from different 3D printers showed similar trueness, a DLP 3D printer produced less consistent outcome than a DLS 3D printer.

Keywords: 3D printing; CAD/CAM; compression molding; digital light processing; digital light synthesis; fit; injection molding; removable prosthesis; tissue adaptation.