Effect of layering strategy and prolonged water aging on masking ability of composite resins.

STATEMENT OF PROBLEM: Layered composite resins may adequately mask discolored substrates. However, whether color changes that occur over time affect masking ability is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of layering and water aging on the masking ability of 2 composite resins. MATERIAL AND METHODS: Disk specimens (1.5 mm-thick and shade A1) from Charisma Diamond (CD) and Filtek Z350XT (Z350) were made according to the composite resin shade combination used in the layering strategies: bilayer for CD (enamel/dentin) and for Z350 (enamel/body and enamel/dentin) and trilayer for Z350 (enamel/body/dentin) (n=5). Color measurements were obtained with a spectrophotometer over an A3.5 ceramic substrate, and the whiteness index for dentistry (WID) was calculated. The specimens were aged in water at 37 °C and evaluated at different times: 24 hours, 1 week, 1 month, 2 months, 6 months, 12 months, 18 months, and 24 months. CIEDE2000 color differences (ΔE00) and WID differences (ΔWID) were calculated and interpreted by 50:50% color and whiteness perceptibility and acceptability thresholds. Changes among strategies and aging times were analyzed using the Kruskal-Wallis test (α=.05). Contrasts were made using the Mann-Whitney U test with Bonferroni correction (α=.001). RESULTS: ΔE00 decreased from 24 hours to 2 months of aging. From 2 months onwards, ΔE00 increased for all layering strategies and times, without significant changes in lightness for CD (P>.004). Overall, for the CD restorative system, an increase in ΔWID was observed after 1 month of aging (P<.001), while for the Z350 restorative system, ΔWID decreased after aging (P<.001), except for the Z350 bilayer strategy (enamel + dentin) at 1 week and 2 months (P>.004). For all layering strategies and aging times, color differences were higher than the 50:50% perceptibility threshold for ΔE00 and, after 6 months, higher than the 50:50% acceptability threshold for ΔE00 and the 50:50% whiteness acceptability threshold. CONCLUSIONS: The ability of the tested composite resins to mask a discolored substrate was affected by the layering approach applied and by prolonged water aging.

Masking ability of resin composites: A scoping review.

OBJECTIVE: To map the existing evidence regarding the masking ability of resin composites. OVERVIEW: The literature search was conducted electronically, based on the PRISMA Extension for Scoping Reviews-online protocol at https://osf.io/m2h67/ with no language or time restrictions. Two independent reviewers conducted the screening, and a third reviewer was consulted in case of disagreement. Studies that evaluated resin composite masking ability regardless of background, application technique, thickness, or number of layers were selected. The search found 2995 potentially eligible studies. After removal of duplicates (657), irrelevant articles (2323), 15 citations met the eligibility criteria based on title and abstract, and eight studies were included based on full text analysis (seven in vitro, and one case report). Acceptable masking ability is obtained by one layer of opaque shade resin composite or by the layering technique. A black background is masked with 1.0- to 2.0 mm-thick layers of opaque shade resin composites. Masking of the C4 background is achieved with one layer of 0.5- to 1.5 mm-thick opaque shade resin composite or by the layering technique using different combinations of enamel body and dentin shades with a final thickness of 1.5 mm. CONCLUSIONS: Acceptable masking of C4 shade background is achieved with one layer of opaque shade composite at least 0.5 mm-thick or by different combinations of the layering technique, with a final thickness of 1.5 mm. Acceptable masking of the black background of the oral cavity is achieved with a resin composite of at least 1.0 mm opaque shade. CLINICAL SIGNIFICANCE: The thickness of the resin composite layer required to achieve adequate masking is variable and depends on the translucency/opacity of the tested resin composites and the background shade.

Masking ability of resin composites: Effect of the layering strategy and substrate color.

OBJECTIVE: To evaluate the effect of layering strategy and substrate color on the masking ability of resin composites. MATERIALS AND METHODS: A1-shaded specimens from Charisma Diamond and Filtek Z350XT were produced using different layering strategies. Color measurements were made by a reflectance spectrophotometer over A2, C2, A3.5, C3, C4 substrates. Color differences were calculated and interpreted by the 50%:50% perceptibility and acceptability visual thresholds. Data was analyzed by Kruskal-Wallis and Dunn post hoc test. Chi-square test was used to determine the association between masking ability, and independent variables. RESULTS: Color differences were significantly lower on A2 and C2 in comparison with C4 for the majority of the layering strategies. Acceptable matches were observed on most of the combinations over A2. Moderately unacceptable mismatches were observed in most of the combinations over C2 and A3.5. Clearly unacceptable mismatches were observed on the C3 and C4. The ΔE00 color shifts were predominantly influenced by ΔL00 for all layering strategies and substrate colors. CONCLUSION: Masking ability was affected by the layering strategy and substrate color. Acceptable masking was associated with A2 and C2, and with layering strategy composed of 0.5 mm enamel opacity and 1.0 mm dentin opacity thicknesses, using the Filtek Z350XT. CLINICAL SIGNIFICANCE: Resin composites-shade A1-applied by different layering strategies with a final thickness of 1.5 mm were able to mask mild and moderately discolored substrates. Severely discolored substrates were not masked effectively.

Masking Ability of the Combined Application of Opaquers and Resin Composite on Discolored Backgrounds.

The aim of this study was to evaluate the masking ability of a combined application of opaquers and resin composite over discolored backgrounds: A3, A3.5, C2, C3, and C4. The groups were divided according to the opaquer brand, the number of opaquer coats (one or two), and the thickness of the resin composite layer (0.5 or 1.0 mm). The color measurements were made by a reflectance spectrophotometer (SP60, EX-Rite). The color difference between the opaquer + resin composite + background and a reference background was calculated using the CIEDE2000 formula. ANOVA and Tukey's post hoc test (α=0.05) were used to analyze the ΔE00 mean values. A bivariate analysis was used to determine the association between dependent and independent variables. The masking ability was rated by the ΔE00 visual thresholds of acceptability and perceptibility (Excellent Match: ΔE00 ≤ 0.8; Acceptable Match: 0.8 < ΔE00 ≤1.8; Moderately Unacceptable Mismatch: 1.8 < ΔE00 ≤ 3.6; Clearly Unacceptable Mismatch: 3.6 < ΔE00 ≤ 5.4; Extremely Unacceptable Mismatch: ΔE00 > 5.4). The mean ΔE00 values ranged from 0.5 to 5.52. Masking ability was affected by the opaquer brand, thickness of the resin composite layer, and background shades. Most of the combinations that achieved either excellent or acceptable masking ability were obtained with combinations composed of one or two coats of opaquer and a 1.0-mm-thick resin composite layer for all backgrounds except C4. Acceptable results were also obtained for combinations with 0.5-mm-thick resin composite over C2, A3, and A3.5 backgrounds.

Effectiveness and color stability of bleaching techniques on blood-stained teeth: An in vitro study.

OBJECTIVE: Evaluate the effectiveness and color stability of bleaching techniques on blood-stained teeth. MATERIAL AND METHODS: The teeth were stained by blood and allocated to groups: walking bleach, inside/outside, and in-office bleaching. L*, a*, b*, C*, h° color coordinates were measured using a clinical spectrophotometer at baseline, weekly (T1-T2-T3), and at 1-week (T4), 6-months (T5), and 1-year (T6) follow-up evaluations. ΔEab* , ΔE00 , and ΔWID were calculated between sequential evaluation timepoints and between baseline and each evaluation timepoint. Color coordinates and WID differences in each timepoint and technique were analyzed by Wilcoxon Signed Rank, Kruskal-Wallis and Mann-Whitney U test, respectively. ΔEab* , ΔE00 , and ΔWID were interpreted by color visual thresholds. RESULTS: The techniques presented a significant increase in L* and WID and, a significant decrease in a* and b* until the completion of treatments. Statistical differences between the techniques for a*, b* and WID were observed from T1 until T3. All techniques demonstrated excellent effectiveness for ΔEab* , ΔE00 , and ΔWID between baseline and each evaluation and follow-up timepoints. However, at T6, it was possible to identify a rebound effect for all techniques. CONCLUSIONS: All bleaching techniques presented excellent effectiveness. The stability of the whitening produced was maintained for 6 months. CLINICAL SIGNIFICANCE: Effective whitening of blood-stained teeth was achieved using walking bleach (sodium perborate), inside/outside (hydrogen peroxide - 7.5%) and in-office techniques (hydrogen peroxide - 35%). The bleaching techniques were effective after the completion of the treatments. A slight rebound was observed at 1 year follow-up.

Masking ability of bleach-shade resin composites using the multilayering technique.

OBJECTIVE: Evaluate the masking ability of bleach-shade resin composites applied by multilayering techniques over colored substrates. MATERIALS AND METHODS: Disc-shaped specimens were fabricated from bleach-shade resin composites using different multilayering techniques. Substrates were produced in opaque ceramic discs simulating colored substrates (A2, A3, A3.5, C2, C3, C4) and a bleached tooth (0M1). Color coordinates were obtained using a reflectance spectrophotometer. Color difference was calculated by CIEDE2000 using coordinates of 0 M1 ceramic as standard reference. Data were analyzed by one-way ANOVA and Tukey's post-hoc test (p ≤ 0.05). Masking ability interpretation was based on perceptibility and acceptability thresholds. RESULTS: All combinations presented ΔE00 above the acceptable threshold (ΔE00 >1.8), ranging from 2.49 to 7.42, regardless of the restorative system, multilayering strategy or substrate color. Multilayering combinations placed over A2, A3 and A3.5 were moderately (1.8<ΔE00 ≤3.6) and clearly unacceptable (3.6<ΔE00 ≤5.4), combinations associated with C2, C3 and C4 were clearly unacceptable and, extremely unacceptable (ΔE00 >5.4). Lower ΔE00 was observed for combinations with 0.5 mm extra white enamel layer (2.49), or 1.0 mm white dentin layer (2.69), over A2 and A3.5 substrates. Lightness difference showed the greatest contribution to ΔE00 . CONCLUSIONS: Bleach-shade resin composite systems applied by the multilayering technique were not able to ensure effective masking ability. CLINICAL SIGNIFICANCE: Bleach-shade resin composites applied with different combinations of the multilayering technique were not effective in masking colored substrates. Alternative strategies, techniques and dental materials should be explored to obtain acceptable masking.