Development of a model shade guide for primary teeth.

AIM: Large disparities in colour ranges and distribution between primary and permanent teeth make shade guides for permanent teeth unsuitable for primary teeth applications. The aim of the study was to develop a model shade guide for primary teeth. STUDY DESIGN: The Vita Easyshade intraoral spectrophotometer was used to determine colour at the middle labial/buccal third surface of 612 primary teeth of 102 patients. METHODS: Model shade guides, containing 1-16 tabs, were designed in CIELAB (DeltaE*) and CIEDE2000 (DeltaE') colour difference formulae using nonlinear optimization. The coverage error (DeltaECOV) was calculated as the mean of minimal colour differences between each of primary teeth and the "closest" shade tab. Results were analyzed using descriptive and analytical statistics. RESULTS: The coverage error of Vitapan Classical shade guide applied to the primary teeth evaluated was 4.2 (SD +/- 1.8). DeltaE*COV and DeltaE'COV values for model shade guides with 16 tabs were 1.8 and 1.3, respectively. The CIELAB coverage error of the model shade guide containing two tabs outperformed DeltaE*COV of Vitapan Classical. CONCLUSIONS: As compared with Vitapan Classical shade guide, significantly smaller coverage error was obtained in the model shade guide with the same number of tabs, designed via constrained nonlinear optimization.