How many shades have my teeth whitened?

Before: (a few years ago, before I got braces) http://www.flickr.com/photos/7929154@N05/4748225630/ After: (after using Crest Whitestrips Premium for 3 days) http://www.flickr.com/photos/7929154@N05/4748151078/
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5-6 .
Source