Discoloration of flowable and universal resin composites immersed in black tea for 30 days

Ayaka Hori-Ishikawa, Yuka Ogawa, Ayako Okada, Nana Sakaeda, Daichi Aizawa, Masao Hanabusa, Kaoru Ohmori, Takatsugu Yamamoto

Department of Operative Dentistry, Tsurumi University School of Dental Medicine, Yokohama, Japan

Purpose: This study evaluated the discoloration of current flowable and universal resin composites by immersing in black tea over 30 days.

Materials and Methods: Three flowable resin composites and three universal resin composites were evaluated. The composites were inserted into a disk-shaped stainless steel mold and properly cured. The surfaces of the composite disks were wet-ground and ultrasonically cleaned. Colors – L*, a*, and b* were measured at the center of disks on a gray background using a spectrophotometer. The disks were immersed in black tea at 37˚C for 30 days, and the colors were repeatedly measured at 1, 3, 5, and 30 days of immersion. Color differences ΔE*ab were calculated from the L*, a*, and b* values. Water sorption and solubility of the composites were also measured as per ISO 4049. The results were statistically analyzed, and regression analyses were done between ΔE*ab and ΔL*, Δa*, Δb* or sorption/solubility.

Results: All the composites showed observable increases of ΔE*ab within the first 5 days of immersion. Values of ΔE*ab ranged from 0.64 to 4.97, and three composites exhibited values above the clinically acceptable value, 3.3. ΔL* and Δb* revealed strong correlations with ΔE*ab. Both water sorption and solubility had positive correlations with ΔE*ab at 30 days.

Conclusion: Tea immersion induced discoloration of the current resin composites. This discoloration was affected most by the change in brightness and difference in its blue-yellow chromaticity, and the level of discoloration was material dependent.
(Asian Pac J Dent 2020; 20: 9-15.)
Key Words: discoloration, flowable composite, solubility, tea, universal composite, water sorption