The Effect of Positioning Guide Color on Shade Measurements Using a Clinical Spectrophotometer

Area of Science:

• Dental Materials Science
• Color Science in Dentistry
• Spectrophotometry

Background:

• Accurate shade selection is critical in restorative dentistry for achieving aesthetic outcomes.
• Clinical spectrophotometers are widely used for objective color measurements.
• The influence of ancillary devices, such as positioning guides, on measurement accuracy requires investigation.

Purpose of the Study:

• To evaluate how different colors of positioning guides affect CIEL*a*b* color coordinates of dental materials and natural tooth surfaces.
• To determine if positioning guide color influences the accuracy of spectrophotometric shade measurements.

Main Methods:

• Ten positioning guides in various colors (translucent, purple, yellow, green, blue) were fabricated for ceramic, resin composite, and bovine tooth surfaces.
• CIEL*a*b* color coordinates were measured with and without positioning guides using a clinical spectrophotometer.
• Color differences (ΔL*, Δa*, Δb*, ΔE*ab, ΔE00) were calculated and analyzed using ANOVA and Tukey's post-hoc test.

Main Results:

• Positioning guide color significantly altered color coordinates across all tested surfaces (ceramic, resin composite, bovine tooth).
• Mean color difference values (ΔE*ab, ΔE00) generally exceeded visual acceptability thresholds for all guide colors and surfaces.
• An exception was noted for the bovine tooth surface with the green positioning guide, where differences were within acceptable limits.

Conclusions:

• The color of positioning guides demonstrably affects spectrophotometric shade measurements.
• Careful selection of positioning guide color is necessary to minimize measurement bias and ensure shade accuracy in clinical dental applications.
• Current positioning guide colors, except for green on bovine teeth, introduce unacceptable color variations.