The effect of surface treatments on the color stability of CAD-CAM interim fixed dental prostheses

J Prosthet Dent. 2021 Aug;126(2):248-253. doi: 10.1016/j.prosdent.2020.05.017. Epub 2020 Aug 21.


Statement of problem: Additive manufacturing or 3D printing is gaining popularity in dentistry, including for interim fixed dental prostheses (IFDPs). However, evidence regarding the color stability of 3D-printed IFDPs is lacking.

Purpose: The purpose of this in vitro study was to investigate whether different surface treatments could affect the color stability of milled and 3D-printed IFDPs after simulated physiological aging.

Material and methods: Forty milled IFDPs were fabricated with a 5-axis dental mill (DWX-51D; Roland DGA Corp) from polymethyl methacrylate disks (Temp Esthetic 98, A3.5, 98.5×16 mm; Harvest Dental Products, LLC). Forty 3D-printed IFDPs were fabricated with an in-office digital light processing 3D printer (MAX; Asiga) and light-polymerizing resin (NextDent Crown & Bridge A3.5; NextDent B.V). All milled and 3D-printed IFDPs were allocated into 4 different groups (n=10), according to different surface treatments: Control, Polish, Optiglaze, and Skinglaze. In the Control group, no surface treatment was applied to the IFDPs. For the Polish group, IFDPs were finished and polished with aluminum oxide finishers/polishers (Enhance PoGo Complete Kit; Dentsply Sirona). For the Optiglaze and Skinglaze groups, specimens were first finished and polished and prepared with additional light-polymerizing protective coatings (Optiglaze; GC America Inc, or New Outline Skin Glaze; anaxdent North America). Shade measurements were recorded with a digital spectrophotometer (Vita Easyshade V; VITA North America) before and after the thermocycling for the color stability comparisons. The effects of interim prosthesis type and surface treatments on ΔE∗, ΔL∗, Δa∗, and Δb∗ were examined using 2-way analysis of variance (ANOVA), and ΔE∗ was considered as the primary outcome variable. Post hoc pairwise comparisons were performed by using the Tukey honestly significant difference (HSD) method (α=.05 for all tests).

Results: Milled IFDPs had significantly smaller ΔE∗ than 3D-printed prostheses for the Control group only (P<.001). Within the milled IFDPs, Optiglaze group (mean ±standard deviation, 1.01 ±0.38) had significantly lower ΔE∗ than all the other surface treatments groups (Control group: 2.38 ±0.44, P<.001; Polish group: 1.83 ±0.51, P=.025; and Skinglaze group: 1.85 ±0.78, P=.021). Within the 3D-printed IFDPs, the Control group (3.83 ±0.71) had significantly larger ΔE∗ than all other surface treatments (Polish group: 2.66 ±0.89, P=.018; Skinglaze group: 1.40 ±0.73, P<.001; and Optiglaze group: 1.37 ±0.67, P<.001). The Polish group had significantly higher ΔE∗ than Skinglaze group (P=.009) and Optiglaze group (P=.007), while Skinglaze and Optiglaze groups were not significantly different from each other (P=1.000).

Conclusions: For the milled IFDPs, only the nano-filled, light-polymerizing protective coating significantly lowered color changes after thermocycling simulating 6 months of intraoral physiological aging. For the 3D-printed IFDPs, surface polishing and both light-polymerizing protective coating agents all significantly reduced color changes of the prostheses after thermocycling. The protective effect of light-polymerizing coating agents was more substantial.

MeSH terms

  • Color
  • Computer-Aided Design*
  • Denture, Partial, Temporary
  • Esthetics, Dental*
  • Humans
  • Materials Testing
  • Printing, Three-Dimensional
  • Surface Properties