Abstract
This study determined the reduction threshold in thickness of the dentin shade composite necessary to result in perceptible and acceptable color changes on simulated restorations. Three composite systems (Charisma Diamond, IPS Empress Direct, and Filtek Z350 XT) were evaluated using cylinder-shaped specimens built-up with dentin and enamel shades. The opacity of the composites was assessed using 1.0 mm thick specimens over black and white backgrounds. A baseline color was established for each system by combining 1.0 mm thick enamel shade with 3.0 mm of dentin shade cylinders over a dark background (n = 9). Then, the color changes (∆E00) caused by sequential 0.1 mm reductions on dentin shade cylinders were calculated. Opacity changes on dentin shade cylinders and combined enamel-dentin pair cylinders were also assessed after each thickness reduction. Polynomial regression was performed with averages of ∆E00 as a function of thickness of dentin shade cylinders; and acceptability (∆E = 1.77) and perceptibility (∆E = 0.81) thresholds were calculated. Linear regressions were also performed for ∆E00 as function of opacity of dentin shade cylinders and combined enamel-dentin pair of cylinders. Except for Charisma, enamel shades presented the lowest opacity than dentin one. Perceptible and acceptable color changes were observed for dentin shade cylinders thinner than 2.0-2.4 mm and 1.1-1.4 mm, respectively, were used. No difference among the composite systems was observed. In conclusion, reductions on dentin shade composite lower than 0.6-mm did not yield perceptible color changes, and clinically significant color changes only were observed within reductions higher than 1.6-mm.
Highlights
Direct composite restorations in anterior teeth has been demonstrated be an excellent option to solve esthetic concerns involving alteration in color and/or shape of teeth, or to close diastemata [1,2,3]
Despite the reduced cost and adequate clinical behavior, obtaining aesthetic direct restorations with composites remains a challenge for the clinicians since to reproduce the optical features of hard dental tissues can be a difficult task [3,4,5, 9, 17,18,19,20]
Color changes by thin dentin shade composite requiring changes in the restorative approaches according to the material chosen [12,13,14]
Summary
Direct composite restorations in anterior teeth has been demonstrated be an excellent option to solve esthetic concerns involving alteration in color and/or shape of teeth, or to close diastemata [1,2,3]. Further to easy handling characteristics, the composite systems available nowadays present several shades allowing to mimic both enamel and dentinal tissues [4,5]. The ability and knowledge of clinicians regarding esthetic aspects of smile, and optics characteristics of hard tooth tissue and composites are essential to achieve esthetical direct restorations. The higher organic content of dentin increases its opacity and the chromaticity of this tissue strongly affects the tooth color [8]. Composites shades are available in different degrees of translucency seeking out to simulate the optical characteristics of enamel and dentin [3,5]. Using the same thickness of hard tooth tissue only would result in similar optical aspects if the translucency/ opacity of the composite was like those observed from dentin and enamel. An important matter hindering the stratification of composite restoration is that the enamel shade composites of some manufacturer are more translucent than the tooth enamel, while some dentin shade composites are more opaque than tooth dentin [12,13]
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