Objectives: A randomized controlled tooth whitening clinical trial was conducted to evaluate treatment differentiation and measurement variability of two commercial spectrophotometers relative to standard digital images. Methods: Balancing for age and color, 66 adults were randomly assigned equally to one of three groups: a positive control carbamide peroxide tray-based system QD for 2 hours (Opalescence® 10%), a paint-on peroxide gel BID (Signal Xtra White), or an untreated negative control. Subjects received an anticavity dentrifrice and brush, and treatment was unsupervised over a 14 days. CIELAB tooth color was measured on the maxillary anterior tooth surfaces using a standard digital imaging method. In addition, two commercially available contact spectrophotometers, VITA EasyShade® and Shofu® ShadeEye-NCC® measured tooth color from gingival, middle, and incisal regions. Results: Mean (SD) age was 31.0 (10.2) years. Both commercial spectrophotometers had statistical outliers that were removed prior to data analysis. Using digital imaging, adjusted mean (SE) Db* (yellowness) were -1.7 (0.15), -0.5 (0.10), and -0.2 (0.06) for the positive control, intermediate paint-on gel, and untreated groups, respectively. Results were similar for DL*. All 3 methods showed significant (p < 0.05) between-group differences in Db* and DL* for the positive and negative controls. The coefficient of variation was lowest with imaging and highest with VITA. Ratios of variance to squared treatment difference between the paint-on and untreated groups ranged from 1.46 with imaging to 1.99 with VITA for Db*, and 3.27 with imaging to 31.44 with VITA for DL*. Conclusions: In a randomized controlled trial, digital imaging and two commercial spectrophotometers differentiated positive and negative whitening controls. There were appreciable sample size implications associated with use of the commercial spectrophotometers to differentiate intermediate and untreated controls.

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