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A recent increase in reported adverse events associated with the use of tobacco products consumed via electronic nicotine delivery systems (ENDS)1 has intensified scrutiny of the effects of such products on both oral and overall health. ENDS are noncombustible nicotine delivery devices that heat "e-liquids," which may contain nicotine, varying compositions of flavorings, propylene glycol, vegetable glycerin, and/or other ingredients, to create an aerosol that the user inhales.2 These ENDS may resemble conventional cigarettes, cigars, or pipes as well as universal serial bus (USB) drives, pens, or larger tank systems (Figure 1).2,3 In 2019, the American Dental Association (ADA) adopted an interim policy on vaping, which echoed an earlier policy from the American Medical Association (AMA).4,5 The policy called for a total ban on all vaping products that are not approved by the US Food & Drug Administration (FDA) for tobacco cessation purposes and made available by prescription only as well as advocated for an increase in funding to study the safety and efficacy of e-cigarettes and vaping products for tobacco cessation purposes and their effects on oral health.4 The focus in the healthcare community and the lay media is on the use of ENDS; however, it is imperative for dental healthcare providers to be aware of the current tobacco use trends and understand the potential impact that all forms of nicotine consumption can have on oral health.
Overall, tobacco use is one of the leading causes of preventable illness in the United States, accounting for approximately 20% of the country's deaths.6 The prevalence of cigarette smoking among US adults declined from 20.9% in 2004 to 13.7% in 2018; however, this rate is still higher than the federal government's Healthy People 2020 smoking prevalence goal of 12% or less.7 Currently, more than 34.2 million US adults smoke cigarettes, disparities in smoking prevalence persist (eg, sex, age, race/ethnicity, socioeconomic status, etc), and 16 million US adults are living with a smoking-related illness.8 In addition to the systemic diseases that are associated with tobacco use, cigarette smoking has been shown to increase the risk of tooth loss and periodontitis.
ENDS represent the most recent mechanism for nicotine delivery, and they are growing in popularity. Since the introduction of ENDS in 2006, the market has ballooned to include nearly 500 brands and over 7,000 flavors.9 Given the large commercial market and the widespread prevalence of ENDS products, it is imperative that dental professionals understand the potential impact of all nicotine consumption on oral and periodontal health and are able to discuss effective strategies for cessation with their patients.
The Epidemiology of Tobacco Use
Tobacco use remains the largest preventable cause of death and disease in the United States and is responsible for the deaths of approximately 480,000 individuals annually.6 The overall societal costs of tobacco use are estimated to total about $300 billion per year, including approximately $170 billion in direct medical costs and approximately $156 billion in lost productivity and other indirect costs.10,11 In 2018, an estimated 13.7% of US adults reported that they smoked tobacco, and 74.6% of these individuals reported daily use.7 With the widespread impact of tobacco use on morbidity and mortality, understanding the trends in tobacco consumption can help dental healthcare professionals address its impact on oral and overall health.
US Tobacco Trends
Historically, cigarette use has decreased in both adults and high school students. Since 1965, the rate of cigarette smoking among those aged 18 and older has dropped nearly 43%, and from 1991 to 2018, the rate of cigarette smoking among youths dropped approximately 68%.12 Furthermore, since 2002, more than half of the individuals who were ever smokers have quit, and the average number of cigarettes smoked per day continues to decline among current smokers.12 Although these decreases are encouraging, alternative forms of tobacco consumption are increasing among certain demographics.12 For example, between 2002 and 2015, the use of smokeless tobacco increased 133% among women aged 18 to 25 years, the use of cigars increased 50% among women aged 26 or older, and the use of pipe tobacco increased 46% among all individuals aged 18 to 25 years.12 This increase in tobacco use was the most marked among young people, with the use of any tobacco product increasing 11% among high school students; however, the majority of the increase can be attributed to the use of ENDS.12
US ENDS Trends
The use of ENDS in the United States has increased significantly since their introduction. Evidence suggests that approximately 2.8% of adults use e-cigarettes,13 but the rates of use are significantly higher among younger individuals with 10.5% of middle school students and 27.5% of high school students reporting that they used an e-cigarette within the last month.14,15 From 2017 to 2018, the rate of e-cigarette use increased 48% among middle school students and 78% among high school students.16 Much of this increase has been attributed to the expanding numbers of e-cigarette flavors on the market because an increasing percentage of younger ENDS users are reporting the use of flavored products.16 In one survey, more than half of the teenagers reported that they only "vaped" flavored e-cigarettes; however, just 11% of these participants understood that they were consuming significant levels of nicotine.17
These trends regarding the consumption of ENDS by adolescents are particularly concerning given the effects of nicotine on the developing brain, the propensity for nicotine use to lead to other substance abuse disorders, and the normalization of cigarette-like behaviors in these groups.18-20 Adolescent e-cigarette users are also 4 times more likely to become conventional cigarette smokers as they age.21 These use patterns among young people pose unique challenges to dental healthcare professionals who are working to address the impact of ENDS on oral and overall health and to counsel users regarding cessation.
Tobacco Use and the Periodontium
Tobacco smoking is the most potent modifiable risk factor for periodontitis and may be responsible for more than half of the periodontitis cases among adults in the United States.22 A meta-analysis of six studies concluded that current smokers are almost 3 times as likely to have severe periodontitis when compared with nonsmokers after adjusting for other risk factors, such as plaque accumulation and dental care.23-25 A direct causal relationship between smoking exposure and the prevalence and severity of periodontal disease in a dose-dependent fashion has been defined in the literature.22-25 Several biological mechanisms may be involved in the pathogenesis or progression of periodontitis that contribute to these negative effects among cigarette smokers.22 These proposed mechanisms, which are generally related to nicotine consumption, include vasoconstriction, changes in oxygen gradients, altered innate and adapted immune responses, increased number and virulence of periodontal pathogens, altered fibroblast attachment and function, collagen degradation, upregulation of local and systemic proinflammatory markers, and decreased efficacy of mechanical and surgical therapies in reducing bacterial burden and resolving inflammation.23-25
According to Kumar, on a microscopic level, nicotine exerts adverse effects on gingival fibroblast attachment, extracellular matrix formation, and integrin production.25 In addition, it increases proinflammatory responses to bacterial antigens and negatively impacts neutrophil and mast cell activity. Nicotine can also increase the invasion potential of Porphyromonas gingivalis and Streptococcus mutans.26,27 When compared with nonsmokers, current smokers have been found to exhibit more supragingival calculus deposits and demonstrate deeper probing depths, greater attachment loss, and fewer teeth.24 Smokers also present with poorer outcomes following periodontal therapy.24 Several studies have shown that smokers demonstrate a diminished response to nonsurgical and surgical periodontal therapy, which results in approximately half as much improvement in probing depth and/or attachment level gain as well as overall wound healing when compared with non-smokers.23-25 This response appears to be mediated by the proinflammatory effects of nicotine exposure because it can be ameliorated with systemic host modulation therapy.28
The Contents andEffects of ENDS
Similar to conventional cigarettes, ENDS involve the inhalation of nicotine materials, and therefore, the initial point of contact is the oral cavity. Although we currently lack robust scientific data about the direct effects of ENDS on the oral cavity, largely due to the relatively recent onset of their increased usage and the chronicity of many oral diseases (eg, oral cancer, caries, periodontal disease), the biologic mechanisms that underlie the effects of nicotine on oral tissues are well established. Early research indicated that e-cigarettes may deliver fewer tobacco-related toxicants than conventional cigarettes29; however, more recent investigations have raised the concern that the risks from the nicotine and other components contained in e-cigarettes may be as high or even higher than those of conventional cigarettes. The reasons for this are manifold and include the following:
• The quantity of nicotine within ENDS varies considerably, but the quantity in one ENDS e-liquid pod may be equivalent to a pack of cigarettes.30-32
• Although more than half of the nicotine in conventional cigarettes is not consumed while the cigarette burns, ENDS users can consume up to 85% of the nicotine in the liquid.32
• Regardless of how deeply or frequently one inhales, 45% of the nicotine released from ENDS is deposited in the oral cavity.33
• The nicotine within ENDS is usually suspended in propylene glycol or vegetable glycerin, which release known carcinogens (eg, acetaldehyde, formaldehyde, acrolein) when heated using ENDS partial-combustion chemistry (ie, high-heat, high-pressure conditions).34-36
• Many e-liquids contain flavoring, and preliminary data suggest that some of the sweet flavors may have cariogenic properties.35,37
Clinical reports indicate that e-cigarette use is associated with dry mouth, an increased inflammatory response relevant to periodontal disease, and effects on the composition of the oral microbiome.38-40 The results of these studies, taken together, suggest mechanisms by which e-cigarette use might potentiate periodontal diseases and caries. Considering the dose-dependent nature of the relationship between conventional cigarette use and periodontal disease (ie, pack-years as an increasing risk factor),38 the high rate of adoption of ENDS among adolescents is particularly worrisome.
ENDS and Smoking Cessation
Data regarding the use of ENDS as a tobacco cessation tool are limited and show inconsistencies.41-46 In a recent study evaluating adult cigarette smokers aged 33 to 52 years, the 1-year quit rate was higher for participants in the e-cigarette cohort than those in the nicotine replacement therapy cohort43; however, a 2019 investigation of adolescents aged 16 to 20 years found that e-cigarette use was prospectively associated with progression toward increased cigarette smoking and potentially toward more frequent use of both products over time.44 In addition, in other studies performed with adults, the results indicated that the odds of quitting smoking were lower and, in many instances, delayed for those using e-cigarettes.45,46
The Dental Professional's Role in Cessation
Dental healthcare professionals play a critical role in tobacco cessation. According to the US Centers for Disease Control and Prevention (CDC), during 2015, 68% of adult smokers wanted to stop smoking, 55.4% had made an attempt to quit during the past year, 7.4% had recently quit smoking, 57.2% had been advised by a health professional to quit, and 31.2% had used cessation counseling and/or medication when trying to quit.47 In addition, although both counseling and medication are independently effective when used to treat tobacco dependence, a combination of counseling plus medication has been found to be more effective than using either method alone and should therefore be considered the gold standard.48
Smoking cessation interventions, including counseling, that are offered during dental visits have been shown to be successful in helping patients quit using tobacco.49 In one generally accepted model of intervention recommended by the Agency for Healthcare Research and Quality, often referred to as the "5 A's" of intervention, users are identified and appropriate interventions are initiated based upon a patient's willingness to quit. The 5 A's include50:
• Ask. Identify and document nicotine use status, including cigarettes, ENDS, and other forms, for every patient at every visit.
• Advise. Discuss the negative outcomes of nicotine use and in a clear, strong, and personalized manner, urge every nicotine user to quit.
• Assess.Is the nicotine user willing and motivated to make an attempt at quitting at this time?
• Assist. For the patient willing to make an attempt at quitting, discuss counseling and pharmacotherapy to help him or her quit, including referral for specialized care.
• Arrange. Schedule follow-up contact, in person or by telephone, preferably within the first week after the quit date.
Furthermore, although 94% of dentists report assessing patients' current smoking status,51in practice, tobacco cessation counseling by dentists has generally been limited and restricted to lower-level interventions, such as "ask" and "advise." 52 Participation in an interdisciplinary team to allow for referral, follow-up, and pharmacotherapeutics, as needed, is critical to providing optimal care and maximizing the likelihood of tobacco cessation.
For patients who are using ENDS, dentists can and should play a similar role; however, there appears to be a gap in dental professionals' engagement in conversations about noncigarette nicotine product use.53 It is imperative that dentists understand the risks of ENDS for nicotine-naïve users, as well as for patients attempting to quit conventional cigarettes; that they are able to recommend FDA-approved and scientifically based tobacco cessation strategies, including nicotine replacement approaches such as patches and gum; and that they follow-up with their patients' primary healthcare providers about medication and/or behavioral counseling.54 For individuals who have moved from conventional cigarette smoking to e-cigarette use, CDC's guidelines indicate that reverting to conventional cigarettes is not recommended and that efforts to reduce or quit e-cigarette use should be suggested.55
Tobacco consumption, including the use of cigarettes and vaping, is widely prevalent; therefore, understanding the user demographics as well as the oral and overall risks associated with nicotine consumption, particularly the novel risks associated with ENDS, will allow dental healthcare professionals to better serve their patients and communities. Both the AMA5,54 and the ADA4,56 have issued calls to action regarding vaping and the concerns about its effects on oral and overall health. Dentists can play a critical role in reducing rates of cigarette use and vaping and addressing the impact of ENDS on patients in their practices. As a part of taking a thorough medical history, dentists should gather information regarding both tobacco and ENDS use, evaluate the impact that nicotine and other toxicants may have on their patients' risks of developing oral disease, and consider the role that they can play in aiding patients to stop using such products. Dentists are also encouraged to report any ENDS-related injuries to the FDA via its website.57
Queries regarding this course may be submitted to firstname.lastname@example.org
About the Author
Maria L. Geisinger, DDS, MS
American Board of Periodontology
Professor and Director
Advanced Education Program in Periodontology
University of Alabama at Birmingham
School of Dentistry
Jennifer H. Doobrow, DMD
American Board of Periodontology
1. Layden JE, Ghinai I, Pray I, et al. Pulmonary illness related to e-cigarette use in Illinois and Wisconsin - final report. N Engl J Med. 2020;382(10):903-916.
2. U.S. Food & Drug Administration. Vaporizers, e-cigarettes, and other electronic nicotine delivery systems (ENDS). U.S. Food & Drug Administration website. https://www.fda.gov/tobacco-products/products-ingredients-components/vaporizers-e-cigarettes-and-other-electronic-nicotine-delivery-systems-ends. Updated April 13, 2020. Accessed May 18, 2020.
3. Centers for Disease Control and Prevention. E-cigarettes fact sheet. Centers for Disease Control and Prevention Smoking & Tobacco Use website. https://www.cdc.gov/tobacco/basic_information/e-cigarettes/pdfs/Electronic-Cigarettes-Infographic-508.pdf. Reviewed February 24, 2020. Accessed May 19, 2020.
4. American Dental Association. ADA announces interim policy on vaping. American Dental Association website. https://www.ada.org/en/publications/ada-news/2019-archive/december/ada-announces-interim-policy-on-vaping. Published December 16, 2019. Accessed May 18, 2020.
5. American Medical Association. E-cigarettes and vaping: a public health epidemic. American Medical Association website. https://www.ama-assn.org/delivering-care/public-health/e-cigarettes-and-vaping-public-health-epidemic. Accessed May 18, 2020.
6. Levy JM, Abramowicz S. Medications to assist in tobacco cessation for dental patients. Dent Clin North Am. 2016;60(2):533-540.
7. Creamer MR, Wang TW, Babb S, et al. Tobacco product use and cessation indicators among adults - United States, 2018. MMWR Morb Mortal Wkly Rep. 2019;68(45):1013-1019.
8. U.S. Department of Health and Human Services. The health consequences of smoking-50 years of progress. U.S. Department of Health and Human Services website. https://www.ncbi.nlm.nih.gov/books/NBK179276/pdf/Bookshelf_NBK179276.pdf. Published January 2014. Accessed May 18, 2020.
9. National Institute on Drug Abuse. Vaping Devices (Electronic Cigarettes) DrugFacts. National Institute on Drug Abuse website. https://www.drugabuse.gov/publications/drugfacts/vaping-devices-electronic-cigarettes#ref. Updated January 2020. Accessed July 29, 2020.
10. U.S. Department of Health and Human Services. The health consequences of smoking-50 years of progress. U.S. Department of Health and Human Services website. https://www.ncbi.nlm.nih.gov/books/NBK179276/pdf/Bookshelf_NBK179276.pdf. Published January 2014. Accessed May 18, 2020.
11. Xu X, Bishop EE, Kennedy SM, et al. Annual healthcare spending attributable to cigarette smoking: an update. Am J Prev Med. 2015;48(3):326-333.
12. American Lung Association. Overall tobacco trends. American Lung Association website. https://www.lung.org/our-initiatives/research/monitoring-trends-in-lung-disease/tobacco-trend-brief/overall-tobacco-trends.html. Updated March 19, 2020. Accessed May 18, 2020.
13. Wang TW, Asman K, Gentzke AS, et al. Tobacco product use among adults - United States, 2017. MMWR Morb Mortal Wkly Rep. 2018;67(44):1225-1232.
14. Cullen KA, Gentzke AS, Sawdey MD, et al. E-cigarette use among youth in the United States, 2019. JAMA. 2019. doi: 10.1001/jama.2019.18387.
15. Marynak K, Gentzke A, Wang TW, et al. Exposure to electronic cigarette advertising among middle and high school students - United States, 2014-2016. MMWR Morb Mortal Wkly Rep. 2018;67(10):294-299.
16. U.S. Food & Drug Administration. 2018 NYTS data: a startling rise in youth e-cigarette use. U.S. Food & Drug Administration website. https://www.fda.gov/tobacco-products/youth-and-tobacco/2018-nyts-data-startling-rise-youth-e-cigarette-use. Updated May 4, 2020. Accessed May 18, 2020.
17. National Institute on Drug Abuse. NIDA live: the science of vaping. National Institute on Drug Abuse website. https://www.drugabuse.gov/videos/nida-live-science-vaping. Updated September 2019. Accessed May 18, 2020.
18. Abreu-Villaça Y, Seidler FJ, Tate CA, Slotkin TA. Nicotine is a neurotoxin in the adolescent brain: critical periods, patterns of exposure, regional selectivity, and dose thresholds for macromolecular alterations. Brain Res. 2003;979(1-2):114-128.
19. Levine A, Huang Y, Drisaldi B, et al. Molecular mechanism for a gateway drug: epigenetic changes initiated by nicotine prime gene expression by cocaine. Sci Transl Med. 2011;3(107):107ra109.
20. Chapman S, Wakefield MA. Large-scale unassisted smoking cessation over 50 years: lessons from history for endgame planning in tobacco control. Tob Control. 2013;22(Suppl 1):i33-i35.
21. National Academies of Sciences, Engineering, and Medicine. Public health consequences of e-cigarettes. National Academies of Sciences, Engineering, and Medicine website. https://www.nap.edu/catalog/24952/public-health-consequences-of-e-cigarettes. Published 2018. Accessed May 18, 2020.
22. Tomar SL, Asma S. Smoking-attributable periodontitis in the United States: findings from NHANES III. J Periodontol. 2000;71(5):743-751.
23. Nociti FH Jr, Casati MZ, Duarte PM. Current perspective of the impact of smoking on the progression and treatment of periodontitis. Periodontol 2000. 2015;67(1):187-210.
24. Johnson GK, Hill M. Cigarette smoking and the periodontal patient. J Periodontol. 2004;75(2):196-209.
25. Tonetti MS. Cigarette smoking and periodontal diseases: etiology and management of disease. Ann Periodontol. 1998;3(1):88-101.
26. Kumar PS. Smoking and the subgingival ecosystem: a pathogen-enriched community. Future Microbiol. 2012;7(8):917-919.
27. Joshi V, Matthews C, Aspiras M, et al. Smoking decreases structural and functional resilience in the subgingival ecosystem. J Clin Periodontol. 2014;41(11):1037-1047.
28. Geisinger ML, Geurs NC, Ogdon D, Reddy MS. Commentary: targeting underlying biologic mechanisms in selecting adjunctive therapies to improve periodontal treatment in smokers: a commentary. J Periodontol. 2017;88(8):703-710.
29. Hecht SS, Carmella SG, Kotandeniya D, et al. Evaluation of toxicant and carcinogen metabolites in the urine of e-cigarette users versus cigarette smokers. Nicotine Tob Res. 2015;17(6):704-709.
30. Schroeder MJ, Hoffman AC. Electronic cigarettes and nicotine clinical pharmacology. Tob Control. 2014;23(Suppl 2):ii30-ii35.
31. Willett JG, Bennett M, Hair EC, et al. Recognition, use and perceptions of JUUL among youth and young adults. Tob Control. 2019;28(1):115-116.
32. Goniewicz ML, Kuma T, Gawron M, et al. Nicotine levels in electronic cigarettes. Nicotine Tob Res. 2013;15(1):158-166.
33. Bergström M, Nordberg A, Lunell E, et al. Regional deposition of inhaled 11C-nicotine vapor in the human airway as visualized by positron emission tomography. Clin Pharmacol Ther. 1995;57(3):309-317.
34. Cheng T. Chemical evaluation of electronic cigarettes. Tob Control. 2014;23(Suppl 2):ii11-ii17.
35. Hutzler C, Paschke M, Kruschinski S, et al. Chemical hazards present in liquids and vapors of electronic cigarettes. Arch Toxicol. 2014;88(7):1295-1308.
36. Jensen RP, Luo W, Pankow JF, et al. Hidden formaldehyde in e-cigarette aerosols. N Engl J Med. 2015;372(4):392-394.
37. Tierney PA, Karpinski CD, Brown JE, et al. Flavour chemicals in electronic cigarette fluids. Tob Control. 2016;25(e1):e10-e15.
38. Tomar SL, Hecht SS, Jaspers I, et al. Oral health effects of combusted and smokeless tobacco products. Adv Dent Res. 2019;30(1):4-10.
39. King JL, Reboussin BA, Wiseman KD, et al. Adverse symptoms users attribute to e-cigarettes: results from a national survey of US adults. Drug Alcohol Depend. 2019;196:9-13.
40. ArRejaie AS, Al-Aali KA, Alrabiah M, et al. Proinflammatory cytokine levels and peri-implant parameters among cigarette smokers, individuals vaping electronic cigarettes, and non-smokers. J Periodontol. 2019;90(4):367-374.
41. El Dib R, Suzumura EA, Akl EA, et al. Electronic nicotine delivery systems and/or electronic non-nicotine delivery systems for tobacco smoking cessation or reduction: a systematic review and meta-analysis. BMJ Open. 2017;7(2):e012680.
42. Lindson-Hawley N, Hartmann-Boyce J, Fanshawe TR, et al. Interventions to reduce harm from continued tobacco use. Cochrane Database Syst Rev. 2016;10:CD005231.
43. Hajek P, Phillips-Waller A, Przulj D, et al. A randomized trial of e-cigarettes versus nicotine-replacement therapy. N Engl J Med. 2019;380(7):629-637.
44. Dunbar MS, Davis JP, Rodriguez A, et al. Disentangling within- and between-person effects of shared risk factors on e-cigarette and cigarette use trajectories from late adolescence to young adulthood. Nicotine Tob Res. 2019;21(10):1414-1422.
45. Kalkhoran S, Glantz SA. E-cigarettes and smoking cessation in real-world and clinical settings: a systematic review and meta-analysis. Lancet Respir Med. 2016;4(2):116-128.
46. Kulik MC, Lisha NE, Glantz SA. E-cigarettes associated with depressed smoking cessation: a cross-sectional study of 28 European Union countries. Am J Prev Med. 2018;54(4):603-609.
47. Babb S, Malarcher A, Schauer G, et al. Quitting smoking among adults - United States, 2000-2015. MMWR Morb Mortal Wkly Rep. 2017;65(52):1457-1464.
48. Clinical Practice Guideline Treating Tobacco Use and Dependence 2008 Update Panel, Liaisons, and Staff. A clinical practice guideline for treating tobacco use and dependence: 2008 update. A U.S. Public Health Service report. Am J Prev Med. 2008;35(2):158-176.
49. Carr AB, Ebbert J. Interventions for tobacco cessation in the dental setting. Cochrane Database Syst Rev. 2012;(6):CD005084.
50. Agency for Healthcare Research and Quality. Five major steps to intervention (the "5 A's"). Agency for Healthcare Research and Quality website. https://www.ahrq.gov/prevention/guidelines/tobacco/5steps.html. Reviewed December 2012. Accessed May 19, 2020.
51. McCauley JL, Leite RS, Gordan VV, et al. Opioid prescribing and risk mitigation implementation in the management of acute pain: results from the National Dental Practice-Based Research Network. J Am Dent Assoc. 2018;149(5):353-362.
52. Prakash P, Belek MG, Grimes B, et al. Dentists' attitudes, behaviors, and barriers related to tobacco-use cessation in the dental setting. J Public Health Dent. 2013;73(2):94-102.
53. Chaffee BW, Urata J, Couch ET, Silverstein S. Dental professionals' engagement in tobacco, electronic cigarette, and cannabis patient counseling. JDR Clin Trans Res. 2020;5(2):133-145.
54. Baldassarri SR, Fiellin DA, Friedman AS. Vaping-seeking clarity in a time of uncertainty. JAMA. 2019. doi: 10.1001/jama.2019.16493.
55. Centers for Disease Control and Prevention. For healthcare providers. Centers for Disease Control and Prevention Smoking & Tobacco Use website. https://www.cdc.gov/tobacco/basic_information/e-cigarettes/severe-lung-disease/healthcare-providers/index.html. Reviewed March 17, 2020. Accessed
May 19, 2020.
56. Kumar P, Geisinger M, DeLong HR, et al. Living under a cloud: electronic cigarettes and the dental patient. J Am Dent Assoc. 2020;151(3):155-158.
57. U.S. Food & Drug Administration. Request for information on vaping products associated with lung injuries. Federal Register website. https://www.federalregister.gov/documents/2020/02/18/2020- 03160/request-for-information-on-vaping-products-associated-with-lung-injuries. Published February 18, 2020. Accessed May 19, 2020.