Smokers get 'stains', turning teeth from a healthy-looking white to an unhealthy-looking yellow/brown color. Although this staining is commonly referred to as nicotine staining, it is not caused by nicotine, but by tar in smoke.
As part of a wider study on oral health, scientists at British American Tobacco studied discoloration in teeth
. A prototype Vype e-cigarette and a tobacco heating product, glo, were assessed for tooth discoloration and the impact on teeth compared to that of cigarette smoke.
A puffing robot was used to puff on the products to produce smoke and vapor. In each case, the smoke or vapor was collected onto a filter pad and then a solvent was used to extract the solid material from the filter pad. The impact of the extracted material (extract) on tooth discoloration was then tested using cows' teeth.
Cows' teeth are routinely used in laboratory experiments in lieu of human teeth. They are used for example to test oral hygiene products like toothpaste and mouthwash.
The teeth were prepared by polishing them using fine sandpaper to create a surface more like that of human teeth. The teeth were then incubated at body temperature in human saliva to create an environment mimicking that in the human mouth. This incubation results in the creation of the so-called pellicle layer on the teeth, which is the smooth film you can feel on your teeth when you rub your tongue over them. It is the normal protein layer that forms on teeth when certain molecules in saliva bond to the tooth enamel.
The teeth were incubated in an oven at body temperature and exposed to the various extracts from the cigarette smoke or e-cigarette
or THP vapor. Some teeth were also incubated in solvent with no extract at all to act as a control/blank.
After the first day, the teeth exposed to the smoke extract started to change color and over the course of 14 days, these teeth got darker and darker in color. Even with the naked eye, the color changes with the cigarette extract could be easily seen after 1 day. The exact color change was also measured in the laboratory using a special camera that can detect tiny changes in hue. In contrast to teeth exposed to smoke those exposed to e-cigarette or THP vapor exhibited minimal change in color, similar to untreated teeth.