Colourfast pigments in silicone hand and maxillofacial prostheses

Area of Science:

• Materials Science
• Biomaterials Engineering
• Color Science

Background:

• Silicone prostheses are crucial for restoring appearance in hand and maxillofacial reconstruction.
• Long-term discoloration of these prostheses is a significant clinical challenge.
• Achieving accurate and stable tissue color matching is essential for patient satisfaction.

Purpose of the Study:

• To evaluate the colorfastness of essential pigment hues used in silicone prostheses.
• To compare the stability of pigments across different formulations and physical forms (suspensions, pastes, dry).
• To identify pigments most vulnerable to environmental factors like UV light, temperature, and salinity.

Main Methods:

• Twenty-one pigments (seven hues across three formulations) were tested for colorfastness.
• Pigments were exposed to ultraviolet light, elevated temperatures (35°C and 50°C), and saline solutions (0.15 M and 5.0 M) for nine months.
• Color change was quantified using Commission Internationale de l'Eclairage (CIE) L*a*b* units (ΔE).

Main Results:

• Ultraviolet light exposure was the primary cause of pigment discoloration, leading to yellowing (+Δb*) and darkening (-ΔL*).
• Elevated temperature (50°C) caused minor color changes (ΔE 0.77–3.63), except for one blue pigment (ΔE 6.26). Moderate temperatures (35°C) showed good color stability.
• Most pigments were colorfast to saline solutions (ΔE<6), but a red pigment (PD-3) showed significant change in normal saline, indicating vulnerability to sweat.

Conclusions:

• Pigment discoloration in silicone prostheses is significantly influenced by UV light exposure.
• Pigment suspensions demonstrated superior colorfastness compared to pigment pastes.
• Understanding pigment stability is crucial for selecting materials that ensure long-term aesthetic outcomes for prostheses.