When it comes to cosmetic dentistry, one of the most popular forms of treatment is professional tooth whitening.  It’s little wonder. Tooth whitening treatments are non-invasive, simple to perform and who doesn’t want a brighter, healthier-looking smile? (It’s estimated that 14 percent of the US population – 45 million Americans – have had at least one professional whitening procedure).  Of course, the colour of our teeth changes naturally with age. Teeth also stain as a natural side-effect to what we eat…