Shade Selection Timing — ORE Part 1 MCQ
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Correct answer: B — Before isolation and tooth preparation begin
The shade should be selected before isolation and tooth preparation begin. Dehydration, including that associated with rubber dam isolation and prolonged treatment, makes enamel appear lighter and can produce a clinically perceptible colour change. Selecting the shade early therefore records the natural hydrated appearance of the tooth. Option E is incorrect because the tooth may already have dehydrated. Option A is inadequate: illumination affects colour assessment, but changing the operating light does not prevent dehydration-related error. A photograph may assist communication with the laboratory but does not replace direct shade assessment of a hydrated tooth. A fixed A2 choice ignores normal individual variation in tooth colour.
Reference: Burki Z, Watkins S, Wilson R, Fenlon M. A randomised controlled trial to investigate the effects of dehydration on tooth colour. Journal of Dentistry. 2013. https://pubmed.ncbi.nlm.nih.gov/23160038/