Can dentists tell if you vape?

Yes, dentists can usually determine through an oral examination whether you are using e-cigarettes.
The aerosol produced by e-cigarettes (not "steam") contains chemical components such as nicotine, propylene glycol, and flavoring agents. These substances can cause a series of characteristic changes in the mouth. Dentists, who have undergone professional training, are able to identify these subtle signs.
Typical signs that dentists will notice
Persistent dry mouth: The propylene glycol (PG) and glycerol (VG) in e-cigarettes absorb moisture from the mouth, and nicotine also inhibits saliva production. Reduced saliva leads directly to a decrease in the mouth's self-cleaning ability. Dentists will notice dry, sticky oral tissues, along with bad breath and a higher risk of tooth decay.
Gum inflammation or atrophy: Nicotine is a vasoconstrictor, which reduces the blood supply to the gums. This can lead to swollen and bleeding gums, or a discolored appearance that is unhealthy and pale; the gums may also recede and separate from the teeth, making the teeth appear longer. People who use e-cigarettes for a long time have a faster rate of gum atrophy than smokers.
Abnormal teeth:
Tooth staining: The nicotine in e-cigarettes can cause yellow or brown stains to form on the surface of the teeth.
Enamel erosion: The flavoring agents in fruit-flavored electronic cigarettes are highly acidic, with a pH value as low as 3.5. They will directly erode the enamel. In the early stages, horizontal "vaporization lines" may appear at the tooth neck.
Increased tooth decay: The combined effect of dry mouth and an acidic environment significantly increases the risk of tooth decay, especially in atypical locations such as near the gum line.
Oral mucosal lesions: The high-temperature aerosol from e-cigarettes may irritate the oral mucosa, causing problems such as oral ulcers, red patches on the palate (known as "vaporized palate"), or peeling of the inner lining of the mouth. Studies have also found that e-cigarette users are more prone to nicotine stomatitis, hairy tongue, and angular cheilitis.
"E-cigarette Tongue" (Vaper's Tongue): Prolonged use may lead to dulled taste buds or even loss of taste, which is also one of the symptoms that dentists might inquire about.
⚠️ Regarding the claim of "safer than smoking"
Although some studies suggest that the harm to periodontal tissues from e-cigarettes may be slightly lower than that from traditional cigarettes, this does not mean that it is "safe". E-cigarettes can cause a series of unique oral health problems, and their long-term effects are still unclear.
In conclusion, whether containing nicotine or not, e-cigarettes have a significant negative impact on oral health. Dentists can identify these signs. The purpose is not to judge, but to help you detect problems early and prevent more serious consequences. If you have the habit of vaping, informing your dentist voluntarily will help them provide you with more targeted care advice.