Color stability of glass-fiber-reinforced polypropylene for non-metal clasp dentures

Purpose

The purpose of this study was to investigate the color stability of a glass-fiber-reinforced thermoplastic (GFRTP), for use in non-metal clasp dentures (NMCDs).

Methods

GFRTPs composed of E-glass fibers and polypropylene with 2 mass% of pigments were fabricated using injection molding. According to our previous study on the optimum fiber content for GFRTPs, we prepared GFRTPs with fiber contents of 0, 10, and 20 mass% (GF0, GF10, and GF20). Commercially available NMCD and PMMA materials were used as controls. The color changes of GFRTPs at 24 h, and at 1, 2, and 4 weeks of coffee immersion at 37 °C were measured by colorimetry, using the Commission Internationale de l’Eclairage (CIE) Lab system. The color stabilities of the GFRTPs were evaluated in two units: the color difference (ΔE¹) and National Bureau of Standards (NBS) units.

Results

After immersion, none of the GFRTPs showed visible color change. From the colorimetry measurement using the CIE Lab system, the ΔE¹ values of the GFRTPs were 0.65–2.45. The NBS values of the GFRTPs were 0.60–2.25, all lower than the threshold level of 3.0, demonstrating clinically acceptable color changes. On the other hand, an available polyamide-based NMCD material exhibited “appreciable” color change, as measured in NBS units.

Conclusions

The results indicate that the GFRTPs showed clinically acceptable color stability and might be satisfactory for clinical use. Therefore, GFRTPs are expected to become attractive materials for esthetic dentures.