Discoloration of coating resins exposed to staining solutions in vitro.

The purpose of this in vitro investigation was to study the effects of coffee and tea immersion on surface discoloration of one commercial temporary resin coating material, White Coat (WHC; Kuraray Medical Inc., Tokyo, Japan), and an experimental one, SI-R20209 (SIR; Shofu Inc., Kyoto, Japan). Disk-shaped specimens were prepared, their colors were determined at baseline, and after immersion in water (control), tea and coffee solutions for 24, 48, and 72 hours. Very little discoloration was found with the water-stored specimens. Staining response was most pronounced after coffee immersion for White Coat and after tea immersion for the experimental material, exceeding the clinically acceptable discoloration threshold value of deltaE=3.3. However, most of the resin shades tested are likely to be sufficiently safe against heavy discoloration when used for short-term restoration only.