The influence of a continuous increase in thickness of opaque-shade composite resin on masking ability and translucency

Abstract

Objectives. This study was conducted to determine the minimum thickness of opaque-shade composite resin required to mask discolored tooth structures or darkness of the oral cavity and to determine the effect of the brand and shade of composite resins on masking ability and translucency. Materials and methods. Discs and beveled specimens were manufactured using six opaque-shade light-curing composite resins (Charisma, Heraeus Kulzer; Estelite Sigma Quick, Tokuyama; Gradia Direct Anterior, GC). The discolored tooth structures and darkness of the oral cavity were reproduced using background tiles. The disc specimen colors were measured using a spectroradiometer by increasing the thickness of the beveled specimens on the backing by 0.05 mm in series, and color difference (ΔE*_ab) and translucency parameter (TP) were calculated. Results. The thicknesses of opaque-shade composite resins that masked the C4 shade and black backings were 0.80–1.45 and 1.85–2.00 mm, respectively. Overall, the ΔE*_ab and TP values decreased as the thickness of the opaque-shade composite resins increased. When the shades of the composite resins were identical, the TP decreased in the order of Charisma, Estelite Sigma Quick and Gradia Direct Anterior. When the brand was fixed, the TP was higher in the OA3 shade than in the OA2 shade. A significant correlation was seen between ΔE*_ab and TP (p < 0.05). Conclusions. The brands and shades of the composite resins were shown to have a clear effect on TP, but an inconsistent tendency for ΔE*_ab.