Three direct composite resins currently indicated for esthetic anterior and/or posterior
restorations were used in the present study. Information regarding composite type,
composition, curing time and manufacturer is given inTable 1 .
Fifteen specimens (15 mm diameter x 2 mm thick) of each composite were fabricated using
a stainless steel matrix. each material was inserted into the matrix in 1.0-mm-thick
increments photoactivated with a halogen light-curing unit (Ultralux, Dabi Atlante,
Ribeirão Preto, SP, Brazil), according to the manufacturer’s information (Table 1 ). The specimens were polished with aluminum
oxide discs (Sof-Lex, 3M eSPe, St. Paul, MN, USA) in a sequence of decreasing
abrasiveness with intermittent movements, and the specimen surface was kept moist at
each disc change. The polished specimens had their thickness measured with an electronic
digital caliper accurate to 0.1 mm (Digimess, São Paulo, SP, Brazil). The
polished specimens were stored in the dark at 100% of humidity for 24 h.
Color was measured according to the CIe (Commission Internationale de l´eclairage)
L*a*b* system relative to CIe standard illuminant D65, against a white background
(Standard for 45/0 degrees; Gardner Laboratory, Inc, Bethesda, MD, USA) in a reflection
spectrophotometer (PCB 6807 BYK Gardner, Geretsried, Germany). This equipment is
specific for color measurement and has 30 LED lamps with 10 different colors arranged in
a circle, which directs a light bundle at 45º with the material surface. This
light bundle is reflected 0º back to the equipment, which captures and records
the L*, a* and b* values of each specimen. The axis L* refers to the lightness
coordinate and its value ranges from zero (black) to 100 (white). The axes a* and b* are
chromaticity coordinates in the red-green axis and the yellow-blue axis, respectively.
Positive a* values indicate a shift to red and negative values indicate a shift to
green. Similarly, positive b* values indicate the yellow color range and negative values
indicate the blue color range.
After baseline color measurement, the specimens were assigned to three groups (n=5),
each one immersed in a different solution, and subjected to a new color measurement.
Group 1 (control) was immersed in distilled water; Group 2 was immersed in coffee
prepared by dissolving 1.5 g of soluble coffee (Nescafé Classic; Nestlé
SA, Vevey, Switzerland) in 50 mL of boiling distilled water, and Group 3 was immersed in
a cola soft drink (Coca-Cola®, Refrescos Ipiranga, Ribeirão
Preto, SP, Brazil). The solutions were replaced every day.
After 15 days immersed in the solutions, the specimens were rinsed with distilled water
for 5 min and blotted dry with absorbent paper before the second color measurement.
Color of the specimens was measured after immersion in the different solutions by the
spectrophotometer, as previously described. Using the values of L*, a*, b*, color
variation (De1) between 15-day immersion and baseline measurements was determined using
the following equation:
ΔE1 = [ (ΔL*) 2 + (Δa*) 2 +
(Δb*)2]½
The values of ∆ > 1 are considered as visually perceptible and values of DE
≥ 3.3 are considered as clinically unacceptable18 (link). After determination of color variation (De1), the
specimens were repolished with Sof-Lex discs (3M ESPE) as previously described in the
first polishing procedure. The repolished specimens were submitted to a new color
measurement (CIe L*a*b*) and these values were compared to those of the baseline color
measurements, so a second value of color variation (∆2) was obtained.
The means and standard deviations of color change (∆1 and ∆2) were
calculated and submitted to statistical analysis by 3-way repeated measure ANOVA
(variation factors: composite, treatment and evaluation period) and Tukey’s test at 5%
significance level.
restorations were used in the present study. Information regarding composite type,
composition, curing time and manufacturer is given in
Fifteen specimens (15 mm diameter x 2 mm thick) of each composite were fabricated using
a stainless steel matrix. each material was inserted into the matrix in 1.0-mm-thick
increments photoactivated with a halogen light-curing unit (Ultralux, Dabi Atlante,
Ribeirão Preto, SP, Brazil), according to the manufacturer’s information (
oxide discs (Sof-Lex, 3M eSPe, St. Paul, MN, USA) in a sequence of decreasing
abrasiveness with intermittent movements, and the specimen surface was kept moist at
each disc change. The polished specimens had their thickness measured with an electronic
digital caliper accurate to 0.1 mm (Digimess, São Paulo, SP, Brazil). The
polished specimens were stored in the dark at 100% of humidity for 24 h.
Color was measured according to the CIe (Commission Internationale de l´eclairage)
L*a*b* system relative to CIe standard illuminant D65, against a white background
(Standard for 45/0 degrees; Gardner Laboratory, Inc, Bethesda, MD, USA) in a reflection
spectrophotometer (PCB 6807 BYK Gardner, Geretsried, Germany). This equipment is
specific for color measurement and has 30 LED lamps with 10 different colors arranged in
a circle, which directs a light bundle at 45º with the material surface. This
light bundle is reflected 0º back to the equipment, which captures and records
the L*, a* and b* values of each specimen. The axis L* refers to the lightness
coordinate and its value ranges from zero (black) to 100 (white). The axes a* and b* are
chromaticity coordinates in the red-green axis and the yellow-blue axis, respectively.
Positive a* values indicate a shift to red and negative values indicate a shift to
green. Similarly, positive b* values indicate the yellow color range and negative values
indicate the blue color range.
After baseline color measurement, the specimens were assigned to three groups (n=5),
each one immersed in a different solution, and subjected to a new color measurement.
Group 1 (control) was immersed in distilled water; Group 2 was immersed in coffee
prepared by dissolving 1.5 g of soluble coffee (Nescafé Classic; Nestlé
SA, Vevey, Switzerland) in 50 mL of boiling distilled water, and Group 3 was immersed in
a cola soft drink (Coca-Cola®, Refrescos Ipiranga, Ribeirão
Preto, SP, Brazil). The solutions were replaced every day.
After 15 days immersed in the solutions, the specimens were rinsed with distilled water
for 5 min and blotted dry with absorbent paper before the second color measurement.
Color of the specimens was measured after immersion in the different solutions by the
spectrophotometer, as previously described. Using the values of L*, a*, b*, color
variation (De1) between 15-day immersion and baseline measurements was determined using
the following equation:
ΔE1 = [ (ΔL*) 2 + (Δa*) 2 +
(Δb*)2]½
The values of ∆ > 1 are considered as visually perceptible and values of DE
≥ 3.3 are considered as clinically unacceptable18 (link). After determination of color variation (De1), the
specimens were repolished with Sof-Lex discs (3M ESPE) as previously described in the
first polishing procedure. The repolished specimens were submitted to a new color
measurement (CIe L*a*b*) and these values were compared to those of the baseline color
measurements, so a second value of color variation (∆2) was obtained.
The means and standard deviations of color change (∆1 and ∆2) were
calculated and submitted to statistical analysis by 3-way repeated measure ANOVA
(variation factors: composite, treatment and evaluation period) and Tukey’s test at 5%
significance level.
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