Discoloration of auto-polymerized resin applied using a brush-on technique

Yohei Sato, DMD, PhD, Hikari Chiba, DMD, PhD, Tomoko Osada, DMD, PhD, Ema Muraishi, DMD, Chikahiro Ohkubo, DMD, PhD, and Toshio Hosoi, DDS, PhD

Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan

Purpose: The discoloration of auto-polymerized resin has frequently been observed after denture repair. This study is an investigation of the discoloration of auto-polymerized resin applied using a brush-on technique.
Materials and Methods: Rectangular resin plates were fabricated so that five auto-polymerized resins (Unifast II, Unifast Trad, Provinice, Metafast, and Miky) could be packed in a mold (15x30x1 mm) using a brush-on technique (resin brush, horsehair) in six increments for each mold. As controls, the five resins were poured in the molds after the polymer and monomer were mixed at 0.5 mL/g for 10 s. After polymerization, half of the resin plates were covered with aluminum foil. All the plates were soaked in distilled water (37°C) and exposed to xenon light for 24 hours according to ISO 7491. They were soaked in water again for 5 days. After removing the aluminum foil, the discoloration was measured using a color difference meter (Shade eye system) three times for each specimen. The color differences (ΔE: n=5) were analyzed by ANOVA/Tukey’s test (α=0.05).
Results: For the brush-on technique, Provinice had the greatest color change of any of the resins tested. There were significant differences between the brush-on technique and the controls for Unifast II and Miky.
Conclusion: The brush-on technique resulted in fewer color changes than the mixing technique on all resins except for Provinice, as shown by the fact that many porosities were found in the control specimens.(Int Chin J Dent 2010; 10: 23-27.)

Key Words: autopolymerized acrylic resin, brush-on technique, color change, discoloration