In Vitro Efficacy of Single-Shade Composite on Masking Discolored Tooth Structure

Introduction: Intrinsic tooth discoloration is often challenging to mask using conventional composites due to difficulties in shade matching. Single-shade composites, however, can blend with multiple shades. The objective of this in vitro study was to evaluate the efficacy of single-shade composite materials in masking discolored tooth structures.

Methods: Ten extracted bovine teeth were prepared by removing the lingual enamel and polishing the labial surface with 1000-1500-grit silicon carbide paper to create a 7×7 mm testing area. Intrinsic discoloration was induced by immersing the specimens in a tea solution at 37°C for 7 days. Five single-shade resin composites, Omnichroma, A-UNO, Zenchroma, Transcend, and Vitra were evaluated. For each material, ten 0.5-mm and ten 1.0-mm-thick composite disks were prepared. Masking performance was evaluated using a 0.5-mm composite disk, a 0.5-mm composite disk combined with a 0.5-mm blocking layer, and a 1.0-mm composite disk. Color differences (ΔE) were determined using CIELAB color coordinates.

Results: Two-way ANOVA demonstrated that both composite material and thickness significantly influenced the masking of discolored tooth substrates (p<0.05). Masking performance generally improves with increasing composite thickness. The addition of a 0.5-mm blocking layer did not produce significant improvement for most materials, except Omnichroma (p<0.05). The 1.0-mm composite condition demonstrated the greatest overall masking effect. Significant differences were also observed among the tested materials (p<0.05). Vittra demonstrated the highest ΔE value (43.40), followed by Transcend (40.17), Omnichroma (37.74), Zenchroma (35.88), and A-UNO (32.73). Vittra exhibited significantly greater masking performance than the other tested materials.

Conclusion: The masking ability of single-shade resin composites over discolored tooth substrates is material and thickness-dependent. Increasing composite thickness improved masking performance. Under the conditions of this in vitro study, Vittra demonstrated the greatest masking effect among the evaluated single-shade composites.