DISCUSSION

The WHO consistently reports on the severity of health issues caused by smoking, and emphasizes the importance of quitting. The worsening oral health of cigarette users, represented by increases in various diseases, is especially concerning. The American Academy of Periodontology has stated that smoking is one of the risk factors that may affect treatment and therapeutic outcomes for periodontal diseases. In the current study, data from the 2013–2015 KNHANES yielded association of conventional cigarette smoking and electronic cigarette vaping with periodontal disease, after adjusting for demographic, socioeconomic, and health‐related characteristics. This association was higher in both electronic cigarette vapers and conventional cigarette smokers, when compared to non‐users. These results indicate that stopping cigarette use provides a substantial benefit to periodontal health.

Smoking leads to an augmentation in oral Gram‐negative bacteria, which in turn increases dental calculus and gingivitis. As gingivitis is an initial symptom of periodontal disease, this shows a clear path in how smoking amplifies the risk of periodontal disease. This is true not only for conventional cigarettes, but also electronic cigarettes, as the current results indicate. In a previous study resembling ours, the evidence suggested a correlation between vaping electronic cigarette and increased risk of periodontal damage due to high levels of nicotine dosing. Electronic cigarette is a preferred option for people who attempts quitting; however, electronic cigarette also delivers nicotine. Thus, vaping electronic cigarette could be another way to create new nicotine addicts. These results show that both electronic cigarette vaping and conventional cigarette smoking are risk factors of periodontal diseases.

In both men and women, higher age increased the likelihood of periodontal disease, a result supported by previous research that has shown correlations with age. It is notable that in the current study, incidence of periodontal disease increased with age, but lost statistical significance at age 50. This counterintuitive result is likely due to the loss of teeth that occurs with aging. In other words, individuals with fewer teeth are less likely to exhibit periodontal disease.

For the dental related variables, individuals who reported vaping electronic cigarette or smoking conventional cigarettes demonstrated a higher risk for periodontal disease than non‐users. Interestingly, there was little difference in dental caries, toothache, and dental damage between these two groups. This shows that vaping or smoking each cigarettes affects periodontal disease independently of other dental issues.

In the analysis of regional variables, both electronic cigarette vapers and conventional cigarettes smokers demonstrated higher chances of having periodontal disease than non‐users. However, this effect was more pronounced in rural areas. This could be due to differences in healthcare accessibility associated with regional characteristics. A prior study reported that rural residents have fewer chances to visit healthcare services and see fewer medical specialists (i.e., more generalists) for their care than urban residents. This means that citizens living in rural areas have less of a chance to see a specialist, resulting in worsening of oral health.

It should be noted that the current study has several limitations. First, the results of this study are based on self‐reporting. Thus, some survey questions might be subject to recall bias, especially for health‐related characteristics. Responses could also have been affected by social desirability bias. Therefore, caution should be taken when interpreting the results. Second, due to this study's cross‐sectional design, cause, effect, and directionality of the relationships observed cannot be determined. Third, only the CPI was used to assess periodontal disease. Assessments might have been inaccurate because the CPI can overestimate the severity of disease and underestimate it in patients with previous periodontal care. Nevertheless, the WHO promotes use of the CPI, since it is useful when dealing with large numbers of participants. Fourth, the duration of smoking and vaping habits and daily frequency of smoking and vaping were not considered in our study. Fifth, electronic cigarettes are still a relatively new technology. As such, few respondents reported using them. Despite their low numbers, weight variables developed by the KNHANES improved the representativeness of the sample. Moreover, electronic cigarette vaping demonstrated significant associations with disease, an effect that would likely remain significant if numbers were increased.

Despite these limitations, our study also has strengths. The KNHANES is conducted by a national institution and is based on random cluster sampling. This makes the data more statistically reliable and representative when compared to surveys performed by private institutions. Furthermore, the KNHANES combines a health interview with a physical examination and nutrition survey, allowing it to be used as a base for creating health‐related policies or programs. Therefore, results from the current study can be used as a baseline for motivating users to stop using cigarettes and aid in the creation of anti‐smoking policies.

As smoking increases the possibility of periodontal disease and affects the treatment of other oral diseases, smoking cessation is of the utmost importance. Prior research shows that smokers who quit demonstrate a normalization of oral health toward non‐smoker levels after quitting. Smoking is currently the principal public health issue globally, as it causes direct damage to the respiratory system. In addition, smoking is an important direct cause of dental disease and an important environmental factor in the development of other oral diseases. In addition, smoking is an important factor in tooth loss, and an overall obstacle to dental health. Electronic cigarette use is associated with increased rates of smoking conventional cigarettes. Therefore, preventing all forms of tobacco use, including electronic cigarettes, is important.

The current study identified a significant relationship between periodontal disease and electronic/conventional cigarette use. Our findings suggest that people who vaping or smoking cigarettes demonstrated a higher probability of periodontal disease when compared to both non‐users and ex‐users. As smoking is detrimental to health, many countries have developed smoking policies that ban or restrict smoking. This can provide protection for non‐smokers from the harmful health effects of exposure to secondhand smoke and provide a supportive environment for smokers who want to quit smoking. Many anti‐smoking laws are also being implemented in South Korea. Nevertheless, a 2016 national survey showed that about 40% of men still smoked. Even worse, there is a lack of studies about health risks of electronic cigarettes, and most existing laws only cover conventional cigarettes. Understanding the country‐specific factors that affect smoking behavior and selecting appropriate anti‐smoking measures could greatly reduce smoking. Policymakers should carefully make regulations including electronic cigarettes. Taken together, the results of the current study could motivate both electronic cigarette vapers and conventional cigarette smokers to quit by highlighting the association of conventional cigarette smoking and electronic cigarette vaping with periodontal disease. Furthermore, these results can be used to help create new anti‐smoking policies.