When somebody picks up smoking, one of the first things that happens is their teeth begin to change colour.
It's a common misconception that this is only seen in long-term smokers, but the truth is cigarette smoke (more specifically, tar) leaves noticeable staining after just one day.
In 2016, a study from Italy found that switching from smoking to vaping lead to vast improvements in oral health.
In that particular study, 61% and 65% in each group experienced gum bleeding when tested with a probe. Once the study had finished, upon re-examination, those numbers had dropped to just 8% and 2%.
Let's skip forward to this month.
BAT have funded a study that featured a set of cow teeth soaked in human saliva - to mimic as close to real world environment as possible. After two weeks of one set being used with an e-cigarette and the other set used with combustible cigarettes, they found some promising data.
The vapor from the e-cigarette did not stain the teeth. Even after two weeks of continuous use.
The combustible cigarettes, however, left stains and indications of smoking from the first day!
Over the course of the 14-days, researchers stated that the teeth "...became darker and darker"
Here's an amateur experiment that shows the staining effect from tar with just a single cigarette...