Coffee is one of the most widely consumed beverages worldwide and a major cause of extrinsic staining in resin-based dental materials. This study evaluated the effects of different coffee types, along with their chlorogenic acid (CGA) and total phenolic content (TPC) levels, on the color stability, surface roughness, and microhardness of resin composites. The TPC and CGA levels of Turkish, filter, and instant coffee were quantified spectrophotometrically. A total of 120 disc-shaped specimens (8 × 2 mm) were fabricated from three resin composites: G-ænial A’Chord (GA, nanohybrid), Estelite Sigma Quick (ESQ, suprananohybrid), and Filtek Universal (FU, nanofilled). Baseline color, roughness, and microhardness values were recorded. Specimens were immersed in coffee solutions or distilled water for 7 and 30 days, after which measurements were repeated. Data were analyzed using IBM SPSS v25; normality was tested with the Kolmogorov–Smirnov test, and homogeneity of variance with Levene’s test. A mixed-design three-way ANOVA with Tukey post hoc tests was used (α = 0.05). Color, surface roughness, and microhardness were significantly influenced by time, solution, and material. Discoloration was mainly solution-dependent, with instant coffee causing the greatest color change and GA showing better color stability than FU and ESQ. Surface roughness increased in all groups and microhardness decreased, most notably in filter and instant coffee; overall, FU showed the highest hardness and GA the lowest, while instant coffee had the highest phenolic/chlorogenic acid content. All coffee types produced clinically unacceptable discoloration (ΔE00 > 1.8), most pronounced with instant coffee, whereas GA showed superior color stability to FU and ESQ. Surface roughness increased but remained below the 0.2 μm plaque-retentive threshold, and microhardness losses were greatest in filter and instant coffee and smallest in Turkish coffee. These findings indicate that coffee composition and composite resin matrix/filler characteristics jointly influence staining and degradation. Considering phenolic content (TPC, CGA) and particulate load, coffee type and composition should guide material selection in heavy coffee drinkers, with more hydrophobic composites potentially improving long-term color stability. Different coffee types/brewing methods can variably effect staining, underscoring the need to counsel patients on diet-related discoloration.
Ersoz et al. (Thu,) studied this question.