Effectiveness of bleach and opaquer shades to mask discolored teeth

Aim: The objective of the present study was to compare the masking ability of bleach and opaquer shades applied on discolored substrates using a spectrophotometer.
Materials and methods: A total of 90 samples (6 groups, n = 15) of composite resin disks were prepared with different thicknesses of bleach, opaquer, and shades C3 and A2, as follows: Group I: 2-mm C3, 0.5-mm bleach, 1.5-mm A2; Group II: 2-mm C3, 1-mm bleach, 1-mm A2; Group III: 2-mm C3, 0.5-mm opaquer, 1.5-mm A2; Group IV: 2-mm C3, 1-mm opaquer, 1-mm A2; Group V (positive control): two layers of 2-mm A2; Group VI (negative control): 2-mm C3, 2-mm A2. Three measurements were taken using a Vita Easyshade spectrophotometer. The color differences were measured using the CILAB color system, with the A2 shade as a reference point.
Results: The univariate three-way analysis of variance (ANOVA) with post hoc Bonferroni tests were used to analyze the data. The results showed that the masking ability of the C3 shade composite resin disks was as follows: for opaquer of 1-mm thickness: ∆E = 3.51, P = 1, and for opaquer of 0.5-mm thickness: ∆E = 3.44 P = 1, with acceptable masking ability according to the acceptability threshold (∆E ≤ 3.7). However, the bleach group with 1 mm (∆E = 7.34) and 0.5 mm (∆E = 4.17) thicknesses had lower masking ability.
Conclusions: Within the limitations of this laboratory-based study, the opaquer (0.5 to 1 mm) was shown to mask the discolored substrate more effectively compared with the bleach shade of the same thickness. Keywords: bleach, composite resin, discolored substrate, masking ability, opaquer