E-cigarettes: A lot of hot air

Many thanks to the ADAVB for permission to use this article, and particularly to ADA member Dr Sophia Do, for preparing this summary and quiz, based on the original material sourced from Aus Dent J 66:224-233, 2021. Briggs K, Bell C, Breik O.

This article was published as the cover story in the ADA's News Bulletin, October 2022.

e-cigarettes are rechargeable battery-powered devices that heat liquid to produce an aerosol inhaled by users (called ‘vaping’). Vaping is thought to produce less toxins than conventional smoking because there is no tobacco combustion involved. The main ingredients are propylene glycol, glycerol, flavouring and often nicotine. e-cigarettes have also been found to contain diacetyl, ultrafine particulate matter, volatile organic compounds (e.g. benzene), and heavy metals (e.g. nickel, tin, lead); aerosols can contain nicotine, tobacco-specific nitrosamines, acetaldehyde, acrolein, and toluene.
 

Demographics

In Australia, e-cigarette use among smokers and ‘never smokers’ has increased since 2001. In 2013 Australia, 20% of smokers had tried e-cigarettes, with 7% reporting current use. The 2019 National Drug Strategy Household (NDSH) Survey reported 11% of the population over 14 years of age have used e-cigarettes. Vaping was the most common in the 18-24 age group, with 26% having vaping experience. 64% of the current smokers in this age bracket had used e-cigarettes, increasing from 49% in 2016.

In the UK, adult e-cigarette use increased from 1.7% to 7.1% between 2012-2019; 54.1% were former smokers and 39.8% were dual users. Most users were over 25 years of age. The primary motivation for use was smoking cessation. There was a perception that e-cigarettes were less harmful than conventional smoking, but this belief has declined from 45% to 34% between 2014-2019. In the USA, in 2015, 98% of e-cigarette users aged 45 years and above were current or former smokers and 40% of users aged between 18-24 years were “never smokers”. The 2016 International Tobacco Control (ITC) Survey found a tendency for dual usage, especially if associated with alcohol problems, high psychological distress, and mental health conditions. 

Internationally, prevalence of vaping is increasing in younger demographics, while remaining steady in older populations. The World Health Organization (WHO) has expressed concerns of e-cigarettes becoming an ‘entry portal’ into long-term cigarette use. The Australian 2019 NDSH Survey reported 65% of 14 to 17-year-olds and 39% of 18 to 24-year- olds were a ‘never smoker’ before trying an e-cigarette. Some data from the USA and UK suggest e-cigarette users are more likely to progress to conventional smoking, dual use and subsequently develop nicotine dependence. More research is needed about this causal relationship. In the USA in 2019, 81% of young users cited flavourings as their reason for uptake. Consequently, the Food and Drug Administration (FDA) recommended a ban on flavoured e-cigarettes. This can be diffcult to regulate because users may add flavouring themselves.
 

e-cigarettes and smoking cessation

e-cigarettes have been considered a ‘harm reduction tool’ in smokers who are unwilling or unable to completely quit tobacco products. The Smoking Toolkit Study (STS) infers that e-cigarettes have become England’s most popular cessation tool since 2013. UK sources estimate that 6.1 million smokers have quit following e-cigarette use; however, there are many factors that can influence cessation success.

e-cigarette (or any other nicotine medication) use is more effective with concurrent behavioural support and counselling. One study suggests regular or daily use is more conducive than infrequent use. A Cochrane review found that e-cigarettes containing nicotine had greater efficacy as a cessation tool. Currently, the long-term health impact of e-cigarettes is uncertain and its marketing risks making smoking socially acceptable again.
 

Passive vaping

The device alone does not produce smoke, but the aerosols exhaled by users may affect bystanders. Aerosols may contain potentially carcinogenic chemicals such as glycerine, metals, propylene glycol, and carbonyls (formaldehyde and acetaldehyde). Second-hand air nicotine concentration has been recorded at 125μg/m3. Volatile organic compounds have also been found in aerosols. Toxin levels may be 9-450 times lower compared with conventional smoking. There is limited evidence examining the effects of passive vaping, but the WHO has advised that exposure to secondhand vapours can potentially be harmful.
 

Oral health effects

e-cigarette users have reported a variety of oral symptoms including dryness, burning, irritation, bad taste, bad breath, pain, oral mucosal lesions, black tongue, and burns. Any mucosal changes seemed to be minor and temporary. Some symptoms were linked to specific flavours. Menthol and cinnamon were linked to increased mouth irritation. Citrus, sour, cola and custard flavours were linked to increased throat symptoms, such as tonsillitis, tonsilloliths, uvulitis, para-tracheal oedema, laryngitis, throbbing, itching, numbness, choking sensation, diffculty swallowing, burning, and hoarseness. Compared with conventional smoking, symptoms are fewer and less severe. Some former smokers report improvements to taste and halitosis after switching to e-cigarettes, hence marketing e-cigarettes as healthier alternatives to ‘improve oral health’.
 

Cellular effects and cancer risk

Propylene glycol, found in E-liquids, has been deemed carcinogenic by the WHO. Carcinogens, such as N’-nitrosonornicotine and thiocyanate, have also been found in the saliva of e-cigarette users. Exposure to vapours can incite cytotoxic, genotoxic, and inflammatory cellular effects in the oral epithelium. The adverse cellular effects include reduced cell proliferation and viability, altered cell morphology and activity, increased apoptosis and necrosis, DNA damage and increased transcription of pro-inflammatory cytokines. e-cigarette vapour can also induce the metabolism of tobacco carcinogens to genotoxic metabolites, inferring dual users may be at greater risk of cancer; however, one study found oral mucosal scrapings from e-cigarette users were more microscopically similar to non-smokers than conventional smokers.

The use of heat in the device may increase carcinogenic potential. Higher temperatures can cause aldehyde release and oxidative stress, which has been associated with pre-cancerous nicotine stomatitis. Acrolein, an e-cigarette by-product, has also been associated with inducing oxidative stress and inflammation, resulting in the impairment of the endothelial cell barrier in the lungs.
 

Effects on periodontal health

Conventional smoking and e-cigarettes induce periodontal inflammation, cell injury and impaired cellular repair. A 2020 study found both cigarettes and e-cigarettes had similar adverse effects on markers of oxidative stress and inflammatory cytokines. A 2018 study reported e-cigarette users displayed an increase in plaque index, probing depths, bone loss, volume of gingival crevicular fluid, and localised inflammatory markers.

e-cigarette users were found to be twice as likely to have deteriorating periodontal health, compared with non-smokers. The periodontal symptoms in e-cigarette users tends to be less than those experienced by conventional smokers, but more than that of non-smokers. e-cigarette use can also significantly decrease osteoblast attachment and growth, thereby contributing to implant complications.
 

Effects on oral and dental health

Many dental conditions, such as caries and cracked teeth, are multifactorial. Liquid flavourings can increase cariogenic potential and were found to increase biofilm formation. Liquid viscosity can further facilitate adhesion of bacteria to the tooth surface. Metals involved in enamel demineralisation, such as calcium, iron, and copper, have also been identified in e-cigarette vapours. Studies have found e-cigarettes do not alter the commensal oral microbiome as much as conventional smoking, but users still had an increasing caries rate over a six-month period. There is currently no research examining e-cigarette use and risk of alveolar osteitis.
 

Effects secondary to trauma

Intraoral injuries can occur if accidents happen while the device is in use. There are reports of e-cigarette devices over-heating or exploding in the user’s hands, pocket, or mouth. This can result in peri-oral and peri-orbital burns, lacerations, fractured teeth, alveolar fractures, avulsions, and luxation injuries. One case study described long-term effects can include insomnia, flashbacks and depression. Allergic reactions or poisoning have been reported; 41.7% of calls to the USA poison control centre were related to smoking and e-cigarettes, with 51.1% of these calls related to children and e-cigarettes. There is a pending review by the European Union Tobacco Products Directive into the presence and effectiveness of e-cigarette safety features.
 

Other risks

The presence of nicotine increases risk of cardiopulmonary diseases, neurodegenerative disorders, and cancer. Vaping has also been associated with a series of lung injuries and deaths in the USA in 2019; these have been linked to the addition of cannabis derivative tetrahydroncannabinol oil and vitamin E acetate. In the UK, legally available e-cigarette products do not contain these ingredients.
 

Implications for dental professional

In 2019, the American Dental Association released a statement saying vaping is “not a safe alternative to cigarettes or other tobacco products”. The Canadian and Australian Dental Associations acknowledge the lack of evidence regarding the health effects and questions the benefits of e-cigarettes as a cessation tool. In 2015, the British Dental Health Foundation said e-cigarettes were “significantly less harmful than tobacco and have a real potential in helping smokers quit”. A survey of dental professionals found that most had mixed opinions regarding e-cigarettes and were unsure of the current regulatory advice.
 

A guide on answering patient questions regarding e-cigarettes

Is it safer for me to use e-cigarettes than normal cigarettes?
No, there is a lack of evidence to say it is safer. e-cigarettes have more adverse outcomes than non-smoking, and similar or less health risks than conventional cigarettes.

Do you recommend that I use e-cigarettes to help quit smoking?
Not on their own. Effectiveness of any cessation tool (e-cigarettes, nicotine patches) increases in combination with traditional evidence-based behavioural therapies and counselling. Involve your GP and other smoking cessation services.

Is vaping dangerous to my dental and oral health?
Yes. Oral effects include mouth and throat discomfort, oral mucosal lesions, changes in oral microbiome, dental and periodontal damage. Some ingredients of e-liquids are found to produce metabolites which have genotoxic or carcinogenic properties, increasing risk of oral and oropharyngeal cancer. e-cigarettes have also been known to explode or cause traumatic injuries.

Is it better to vape, rather than smoke cigarettes, after having dental/oral surgery?
Please refrain from smoking or vaping for as long as possible. Smoking can impair healing mechanisms and vaping may have similar effects.

e-cigarette users often do not identify themselves as “smokers” and may answer negatively on medical history forms. It may be more appropriate to ask: “do you smoke cigarettes or any other forms such as vaping?”. Follow-up questions include motivations for use, frequency, and dual use habits.
 

Conclusions

More research is required to assess the long-term oral health outcomes of e-cigarette usage and its effectiveness as a cessation tool. With its growing popularity among youth, there are rising concerns about increased nicotine uptake and progression to smoking, violations of the age of sale law and the ethics of using social media for marketing.