To determine the effects of acidulated phosphate fluoride (APF) on the color tone of light-cured restorative materials, these materials were immersed in APF solution and color before and after immersion compared using a spectroscopic color difference meter.
The following 5 types of light-cured restorative materials (LRMs) were used: Fuji II LC Improved® (II LC; GC), Vitremer®(VT; 3 M), F 2000® Compomer (F 2000; 3 M), Clearfil® AP-X (AP-X; Kuraray), and Z 100® (Z 100; 3 M). The APF solution was, Floden® A (Sunstar) and 2nd APF solution produced in-house. To determine the effects of each component of APF,2% NaF and 1.73% phosphoric acid were also used. Distilled water was used as the control. Samples were immersed in the solution for 4 minutes at a time, with immersion repeated 4 times. The color tone was determined using a spectroscopic color difference meter SE-2000 (Nihon Denshoku Kogyo) before the first immersion and after each immersion. The color difference (E*ab) was calculated L*a*b* obtained before the first immersion and after each immersion. Statistical analysis was based on Student's t test and ANOVA and Tukey's HSD test. Significance was defined as 5%. The surface of samples after immersion was examined by scanning electron microscopy (SEM). As a result of immersion of Light-cured restorative materials in the APF solution for 4 mins, significantly more marked color differences were observed in LRMs other than Z 100 when compared to the distilled water group (p<0.05). The largest color difference was observed in AP-X (1.51), followed by VT (1.17), LC (1.12), F 2000 (0.48), and Z 100 (0.39). Values observed with F 2000 and Z 100 were significantly lower than those for the other 3 materials. After immersion of LRMs in APF solution, the color difference increased with the number immersions. After the fourth immersion, II LC showed the largest color difference (4.07), followed by AP-X (3.23), VT (2.81), Z 100 (2.32), and F 2000 (0.94), showing statistically significant differences among restorative materials. In changes in L*a*b*, L* increased and b* decreased after immersion of all samples, but no changes were observed in a*. After immersion of LRMs in 2% NaF and 1.73% phosphoric acid solution, no statistically significant differences were observed in color compared to distilled water samples. When samples after immersion were examined with SEM, erosion was observed in all samples after immersion in APF, indicating an association with the color difference. These findings suggest that APF solution application changes the surface of LRMs, there by affecting their color.