Color stability of maxillofacial prosthetic silicone functionalized with oxide nanocoating

Statement of problem: Maxillofacial prostheses made of silicone elastomers undergo undesirable color degradation over time. How this color change can be prevented is unclear. Purpose: The purpose of this in vitro study was to evaluate the ability of an oxide nanocoating to prevent color degradation of maxillofacial silicone elastomers after artificial accelerated aging. Material and methods: A silicone elastomer with functional intrinsic pigment was tested. Specimens (N=20) were fabricated, and half of them were coated with a nanolayer of titanium dioxide (TiO ₂ ) using atomic layer deposition. Both coated and noncoated specimens (control) were exposed to artificial aging at 450 kJ/m ² of total energy. Changes in the color of all the specimens with and without TiO ₂ nanocoating were measured before and after the atomic layer deposition coating and before and after aging. The obtained color data were analyzed by using independent t tests and the 1-sample t test (α=.05). Results: Color change (ΔE1=3.4 ±1.4) was observed for the silicone elastomers after the specimens were surface coated with TiO ₂ nanofilm, although this change was not statistically significant (P=.369) compared with the acceptability threshold (ΔE=3.0). Upon exposure to artificial aging, the noncoated control specimens underwent color change (ΔE2=2.5 ±0.7, P=.083 compared with the acceptability threshold). The specimens with TiO ₂ nanocoated surface experienced the least color change (ΔE3=1.4 ±0.6) when subjected to artificial aging, and this change was significantly lower (P<.001) than the established acceptability threshold of ΔE=3.0. In addition, the chemical analyses confirmed that the TiO ₂ nanocoating remained on the surface after exposure to artificial aging. Conclusions: TiO ₂ nanocoating was shown to be effective in reducing color degradation of the silicone elastomer exposed to artificial aging for 120 hours with 450 kJ/m ² of total energy.