Repeatability of a Spectrophotometer and Mobile Applications for Measuring the Colour of Gingival Tissue

(1) To evaluate the repeatability of a spectrophotometer and seven mobile applications for measuring colour in different gingival regions; (2) to compare repeatability between instruments within each region; and (3) to compare, for each instrument, repeatability across gingival regions.

A SpectroShade Micro spectrophotometer and seven mobile applications (four iOS and three Android) were evaluated. Gingival colour was recorded in 250 participants with healthy gingiva at five regions: mesial papilla, distal papilla, free gingival margin, middle attached gingiva, and mucogingival line. CIELAB coordinates were obtained in triplicate. Repeatability was assessed using the MCDM₀₀ metric and interpreted according to the 50:50% gingival perceptibility (ΔE₀₀ = 1.1) and acceptability (ΔE₀₀ = 2.8) thresholds. Data were analysed using one-way randomised-blocks ANOVA and eta squared (η²).

All instruments showed MCDM₀₀ values below the acceptability threshold. The spectrophotometer, all iOS applications, and the Android Colorimeter remained below the perceptibility threshold, whereas Android Color Meter exceeded it. Repeatability differed significantly between instruments, with the spectrophotometer and iOS OptiShade showing the highest repeatability and Android Color Meter the lowest. Repeatability was generally consistent across gingival regions; only the spectrophotometer and iOS ColorMeter (RGB) showed significant regional differences, with negligible effect sizes. These results describe repeatability under the study conditions and should not be interpreted as evidence of trueness or absolute accuracy.

All instruments demonstrated clinically acceptable repeatability. The spectrophotometer and iOS OptiShade provided the most consistent measurements, while Android Color Meter showed the lowest repeatability. Gingival region had minimal influence on repeatability.

The spectrophotometer and iOS OptiShade are the most reliable options for gingival colour assessment. Mobile applications are clinically promising, although performance remains device- and environment-dependent. This conclusion refers specifically to repeatability; the study did not establish trueness or absolute accuracy.