Effect of Caps Warmer and VisCalor Dispenser preheating on the color stability and surface roughness of resin composites after coffee immersion: an in vitro study

Abstract

Background: Prolonged exposure to coffee can lead to pronounced color changes and increased surface roughness in resin composites (RCs), effects that may be worsened by certain preheating methods. Although preheating is used to facilitate handling and enhance polymerization, evidence regarding its long-term impact on color stability and surface properties remains limited. This study investigates how different preheating approaches affect the esthetic performance and surface roughness of RCs, providing insights to guide clinical practice.

Methods: Four RCs (GrandioSO, Admira Fusion, Admira Fusion Xtra, VisCalor Bulk) were tested. Each RC was divided into three subgroups according to the preheating condition: two different devices (Caps Warmer and VisCalor Dispenser) and a non-preheated group. These were then split into two subgroups (distilled water and coffee) for storage (n = 8), resulting in 192 disc-shaped specimens. In the Caps Warmer group, preheating was done at 68 °C for 3 min, whereas in the VisCalor Dispenser group, it was done at 68 °C for 30 s. All RCs were immersed in coffee for 10 and 30 days. Color measurements were conducted at baseline (T1), 10 days (T2) and 30 days (T3) after immersion. Color differences (ΔE₀₀) were calculated using the CIEDE2000 formula and a profilometer assessed surface roughness (Ra). Statistical analyses were performed using Multivariate and Robust ANOVA (p < 0.05).

Results: The highest ΔE₀₀ value was observed in the VisCalor Dispenser×VisCalor Bulk group at T1-T3 (6.18 ± 1.02, p < 0.001). However, there was no difference between Caps Warmer×VisCalor Bulk (5.03 ± 0.9). The Admira Fusion×non-preheated×distilled water group showed the lowest ΔE₀₀ value at T1-T2 (0.57 ± 0.21, p < 0.001). Except for the Admira Fusion and preheating interaction, ΔE₀₀ above the clinically acceptable level (> 1.8) was observed for all composite-preheating combinations after 10 days of coffee exposure. GrandioSO exhibited the lowest Ra values among tested RCs (0.546 ± 0.05, p < 0.001).

Conclusions: Using preheating devices may increase color changes in resin composites, particularly after prolonged immersion in a staining medium like coffee. Selecting an appropriate preheating method for timing and usability may be crucial for maintaining color stability. This study underscores the importance of considering both material choice and preheating technique in clinical applications to minimize discoloration risk.

Keywords: Color stability; Preheating; Resin composites; Staining; Surface roughness.

Fig. 1

Flowchart of the study

Fig. 2

The mean variations of all groups of ΔE₀₀ values (C: Caps Warmer, V: VisCalor Dispenser, N: Non-preheated, AT: acceptability threshold of 1.8 units, PT: perceptibility threshold of 0.8 units)

Fig. 3

The mean variations of all groups of ΔE₀₀ values (C: Caps Warmer, V: VisCalor Dispenser, N: Non-preheated, AT: acceptability threshold of 1.8 units, PT: perceptibility threshold of 0.8 units)