Effects of vaping on the tactile sensitivity of the oral mucosa

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BACKGROUND

Vaping commonly refers to the use of electronic cigarettes (e-cigarettes), vaporizers, and similar devices [1]. The global fight against smoking has led to a decrease in tobacco consumption. However, this has been replaced by increased vaping. The most recent statistics show that the number of e-cigarette users increased from approximately 7 million in 2011 to 35 million in 2016 and 55 million in 2021 [2]. In the United States, 10.5% of middle school students and 27.5% of high school students vaped in 2019 [3]. The rapid increase in e-cigarette use, particularly by young adults and adolescents, is due to the casual attitude toward electronic vaping devices and the perception that these devices are fashionable. Moreover, electronic media promotes the idea that this type of smoking is relatively safe [1].

Sales professionals and opinion leaders present e-cigarettes as a safe system with pleasant organoleptic properties [4]. However, e-cigarette liquids contain components such as propylene glycol, glycerin, flavorings, colorings, and additives, including nicotine. Furthermore, the aerosols produced during vaping contain many toxic components, including metal nanoparticles, formaldehyde, diacetyl, acrolein, acetaldehyde, and acetone [5, 6].

Today, most studies evaluating the effects of e-cigarettes on the body focus on respiratory diseases in vapers. The most common combination of symptoms associated with vape-related lung injury is EVALI (e-cigarette and vaping-use associated lung injury) syndrome. Other lung damage in e-cigarette users is possible, including acute respiratory distress syndrome [1]. Previous studies have provided data on functional disorders of the upper and lower gastrointestinal tract in vapers as determined by peripheral electrogastroenterography and pH-impedancemetry [7, 8]. These disorders are manifested by lower quality of life as measured by the specific Gastrointestinal Symptom Rating Scale and the non-specific Short Form-36 questionnaires [9].

Several studies have investigated the influence of e-cigarettes on dental health [10]. In particular, characteristic mucous membrane changes, such as bleeding and structural changes of the gingiva, were observed in the oral cavities of e-cigarette users. Additionally, lower interalveolar septal height and a high incidence of xerostomia were found [4]. There is evidence that e-cigarettes promote periodontitis [11]. A microbiological evaluation of the oral mucosa of vapers has shown that e-cigarette aerosols lead to oral dysbiosis manifested by the inhibition of commensal reproduction and the increased formation of opportunistic microbe biofilms (e.g., S. mutans). These conditions allow for the rapid colonization of the mucosa by Candida albicans, which may lead to acute candidiasis [12, 13]. Analysis of the oral fluids of e-cigarette users showed a significant increase in rhodanide levels associated with the regular inhalation of hydrocyanic acid metabolites from the inhaled aerosol [14]. This inhalation is accompanied by a decrease in the protective and antibacterial functions of saliva [15].

A detailed understanding of the normal physiology of the oral mucosa and its sensory function requires studying the differences in pain sensitivity to various mechanical influences. This study could be used to solve dental disorders, especially in orthopedic treatment [16]. Previous studies of the tactile sensitivity of the oral mucosa determined the quantitative threshold at various points on both jaws of individuals of different sexes. It was found that there are no sex differences in healthy populations. No significant differences in sensitivity thresholds between the jaws were revealed. Thus, the authors considered this type of sensitivity to be a single type [17]. The evaluation of the pain sensitivity threshold of the oral mucosa in patients with chronic somatic diseases (chronic kidney disease, inflammatory bowel disease, and type 2 diabetes mellitus) showed an increase that persists even when the disease is under control [18]. The data on changes in tactile sensitivity thresholds of the oral mucosa in internal and endocrinological diseases is important for both dental disease treatment and management of underlying chronic diseases. Given the rapid increase in vaping and its direct influence on the oral mucosa, assessing oral tactile sensitivity in e-cigarette users is relevant.

The study aimed to specify the of tactile sensitivity in the oral mucosa of e-cigarette users.

MATERIALS AND METHODS

Study Design

A cross-sectional single-center observational study was conducted.

Eligibility Criteria

The study included volunteers who complied with the study design (e-cigarette users and non-smokers). None of the participants had systemic or severe dental diseases. The exclusion criteria of the study included acute infectious diseases, significant dysfunction of internal organs due to somatic diseases, diabetes mellitus, mental illness, and gestation or lactation.

Study Setting

The study was conducted at the Izhevsk State Medical Academy of the Ministry of Health of the Russian Federation.

Study Duration

All study participants underwent a single dental assessment of status and tactile discrimination sensitivity (TDS) assessment of the oral mucosa.

Intervention

Dental parameters, including the dental formula, the decayed, missing, and filled teeth (DMFT) index, and the GreenVermillion hygiene index (OHI-S) were evaluated in all participants and appropriate oral care recommendations were provided. Oral mucosa sensitivity was assessed using the TDS threshold at preset points on the alveolar zone of the premolars on both sides.

Main Study Outcome

The TDS threshold was determined on the upper jaw on the side of the hard palate and on the lower jaw on the anterior surface of the alveolar gingiva in the premolar area as these zones have identical oral mucosa structures and pliability [17].

Subgroup Analysis

A total of 80 people (40 males and 40 females) aged 18 to 30 years (mean age: 23.5 ± 0.2 years) participated in the study. The participants were divided into two groups. The observation group included 40 participants (20 males and 20 females) who were regular e-cigarette users. The control group included 40 non-smokers who never smoked (20 males and 20 females).

Outcomes registration

Weber’s compass was used to determine the TDS threshold. The compass’s legs were placed on the oral mucosa. The minimum distance (mm) at which two touches were distinguished was set when the legs were moved further apart.

Ethics Approval

The study was approved by the local Ethics Committee of the Izhevsk State Medical Academy of the Ministry of Health of the Russian Federation (protocol No. 761 dated September 26, 2023).

Statistical Analysis

Univariate statistical methods were used for statistical analysis in Statistica 6.0 and Microsoft Excel . Parametric methods were used as the data distribution corresponded to a normal distribution (normality was verified using the asymmetry coefficient). The results were presented as the mean ± standard error of the mean (M ± m). Student’s t-test was used to determine the reliability of quantitative variable differences. Results were considered significant at p ≤ 0.05.

RESULTS

Participants

Seventy-five percent of study participants in the observation group had two to four years of experience with e-cigarettes; whereas the remaining 25% participants had more than four years of experience. Eighty percent of vapers used smoking liquid with a nicotine content of 20 mg/ml; whereas the rest used liquid with a nicotine content of 50 mg/ml or higher. Additionally, 70% of e-cigarette users took 150–500 puffs per day; 20% took less than 150 puffs; and 10% took more than 500 puffs.

An analysis showed that 40% of participants had concerns about gingival bleeding, including 15% of non-smokers and 25% of e-cigarette users. Seventy-five percent of study participants indicated a desire to change the color of their teeth for aesthetic reasons, including 35% of non-smokers and 40% of e-cigarette users.

Primary Results

An objective examination of the oral cavity showed significant differences between groups in terms of oral mucosal condition, degree of caries, and hygiene (see Table 1).

Table 1. Objective examination of the oral cavity (M ± m)

E-cigarette users had a 6-fold higher frequency of gingivitis and a 7.5-fold higher frequency of dental calculus compared to the control group. Smokers had worse DMFT and OHI-S values than non-smokers.

The study of the TDS threshold of the oral mucosa using Weber’s compass show demonstratively a significantly lower sensitivity in the observation group (see Table 2).

Table 2. Threshold of tactile discrimination sensitivity of the oral mucos (M±m). mm

The study found that the TDS threshold of the oral mucosa on the upper jaw (both right and left) was 1.5-fold higher in e-cigarette users compared to the control group. In the observation group, the value on the lower jaw was 2.3-fold higher on the left and 2.5-fold higher on the right compared to non-smokers.

DISCUSSION

The significant difference in objective assessments of oral cavity condition between smokers and non-smokers is clearly related to the less careful hygiene by e-cigarette users and the influence of inhaled aerosol components on the oral mucosa and dentoalveolar apparatus. The combination of nicotine and glycerol creates favorable conditions for the deposition of nicotine plaque on teeth and oral mucosa. This plaque is covered by a glycerol film that promotes the multiplication of pathogenic microorganisms, causing rapid progression of dental carious lesions and exacerbating existing inflammatory periodontal diseases [4]. According to previous studies, xerostomia is the most common side effect of e-cigarette use, affecting 2.5% of participants in the observation group [10].

A significant increase in the TDS threshold of the oral mucosa, along with poor oral hygiene and a higher frequency of inflammatory lesions and carious processes, creates a false sense of well-being in e-cigarette users. This contributes to the progression of inflammatory and dystrophic diseases without obvious clinical manifestations, allowing users to postpone dental visits for oral cavity sanitation.

A lower sensitivity of the oral mucosa in chronic kidney, intestinal, and endocrine diseases found by other authors is usually associated with dystrophic and degenerative processes in the nerves that innervate the oral mucosa. These include disorganized myelin and the complete demyelination of some axons, as well as axoplasmic vacuolization. They develop due to metabolic disorders in patients with severe internal diseases [18]. However, no significant differences were found in the degree of decrease in mucosal sensitivity of the upper and lower jaws in cases of somatic diseases. The significant difference in TDS thresholds of the mucosa of the upper and lower jaws in the e-cigarette study group (1.7-fold on both sides) indicates the profound local damaging effect of the inhaled aerosol and systemic effects caused by inhalation. The TDS threshold of the oral mucosa in non-smokers was close to other studies with similar data on the absence of significant differences in tactile sensitivity in the alveolar zone of the upper and lower jaws in the premolar area on both sides [17].

Study Limitations

The study was limited by the young age of the participants and their short history of e-cigarette use. In addition, only the TDS of the oral mucosa was assessed.

CONCLUSION

The study indicated a significant adverse effect of inhaled aerosol on the oral mucosa when using e-cigarettes. E-cigarette users showed a significant increase in TDS threshold in all evaluated zones of the lower and upper jaws compared to non-smokers. E-cigarette users showed a 1.7-fold higher increase in lower jaw TDS compared to upper jaw TDS. The deterioration of oral mucosa sensitivity is accompanied by oligosymptomatic progression of inflammatory and dystrophic diseases of the oral mucosa and dentoalveolar apparatus. This progression is more common in e-cigarette users due to poor oral hygiene and the direct damaging effect of inhaled aerosol components.

Further study of the TDS of the oral mucosa could lead to a better understanding of its sensory function and the influence of various local and general damaging factors that dentists encounter daily.

ADDITIONAL INFORMATION

Author contributions. A.E. Shklyaev — concept and design of the study, writing the text, compiling the list of references, statistical data processing; I.G. Malakhova — writing the text, statistical data processing, editing; V.A. Khamidullina — collection and processing of material. All authors confirm that their authorship meets the international ICMJE criteria (all authors have made a significant contribution to the development of the concept, research and preparation of the article, read and approved the final version before publication).

Ethics approval. The study was approved by the local Ethics Committee of the Izhevsk State Medical Academy of the Ministry of Health of the Russian Federation (Protocol No. 761 dated 09/26/2023).

Patients’ consent. Written consent was obtained from all the study participants before the study screening in according to the study protocol approved by the local ethic committee.

Funding sources. This study was not supported by any external sources of funding.

Disclosure of interests. The authors confirm the absence of obvious and potential conflicts of interest related to the publication of this article.

About the authors

Aleksey E. Shklyaev

Author for correspondence.
Email: shklyaevaleksey@gmail.com
ORCID iD: 0000-0003-2281-1333
SPIN-code: 3537-8929

MD, Dr. Sci. (Medicine), Professor

Inessa G. Malakhova

Email: inessa78@inbox.ru
ORCID iD: 0009-0001-1588-1862
SPIN-code: 3592-1773

MD, Cand. Sci. (Medicine)

Venera A. Khamidullina

Email: venerochka200@mail.ru
ORCID iD: 0009-0006-9076-4486
Russian Federation, Izhevsk

References

Supplementary files