Abstract
We aimed to evaluate the color stability of bulk-fill and conventional composite resin with respect to thickness and storage media. Twenty specimens of a conventional composite resin (6 mm diameter and 2 mm thick) and 40 specimens of the bulk-fill Tetric EvoCeram composite resin at two different thicknesses (6 mm diameter and 2 mm thick or 4 mm thick, n = 20) were prepared. The specimens were stored in distilled water during the study period (28 d). Half of the specimens were remained in distilled water and the other half were immersed in coffee solution 20 min/d and kept in distilled water between the cycles. Color changes (ΔE) were measured using the CIE L ⁎ a ⁎ b ⁎ color space and a digital imaging system at 1, 7, 14, and 28 days of storage. Data were analyzed using Two-way ANOVA and Tukey's HSD post hoc test (P < 0.05). Composite resins showed significant increase in color changes by time (bulk-fill > conventional; P < 0.001). Coffee exhibited significantly more staining susceptibility than that of distilled water (P < 0.001). There was greater color changes with increasing the increment thickness, which was significant at 14 (P < 0.001) and 28 d (P < 0.01). Color change of bulk-fill composite resin was greater than that of the conventional one after coffee staining and is also a function of increment thicknesses.
Highlights
Color stability of composite resin is an important property influencing its clinical longevity, which continues as a challenge inherent to material [1]
Color changes can occur due to various etiologic factors; extrinsic discoloration can occur due to staining in the superficial layer of resin composite, water absorption, surface roughness, smoking, and diet [2, 3]
Since color changes are a concern that affects the population and one of the main reasons for replacing resin-based restorations, this study investigated the effects of the increment thickness and the storage media on the discoloration of one of these bulk-fill resin composites
Summary
Color stability of composite resin is an important property influencing its clinical longevity, which continues as a challenge inherent to material [1]. Color changes can occur due to various etiologic factors; extrinsic discoloration can occur due to staining in the superficial layer of resin composite, water absorption, surface roughness, smoking, and diet [2, 3]. Previous investigations reported the influence of coffee on the color stability of composite resins [6,7,8,9,10]. It is recommended that the resins should be placed in 2 mm increments to obtain sufficient light transmittance and complete curing of composite resins [11]. The application of composite resins in an incremental technique and light curing each increment individually is a timeconsuming procedure. There is an increasing possibility of air bubble inclusion or moisture contamination between individual increments of resin composite restorations [13]
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