E-Cigarettes Increase Candida albicans Growth and Modulate its Interaction with Gingival Epithelial Cells

Candida species in periodontitis: a new villain or a new target?

OBJECTIVES

Recent research indicated that fungi might have a role in periodontitis alongside traditional periodontal pathogens. This state-of-the-art narrative review explores current concepts on the involvement of Candida species in periodontitis, and suggests the potential for ecological management of this disease.

DATA, SOURCES AND STUDY SELECTION

A literature search was conducted for a narrative review on Web of Science, PubMed, Medline and Scopus about periodontitis associated with Candida species. Published articles, including case reports, case series, observational and interventional clinical trials, and critical appraisals of the literature were retrieved and reviewed.

CONCLUSIONS

Several factors predispose individuals to periodontitis associated with Candida species. These include systemic diseases that lead to immunosuppression and oral environment changes such as cigarette smoking. While a consistent significant increase in the detection rate of Candida species in patients with periodontitis has not been universally observed, there is evidence linking Candida species to the severity of periodontitis and their potential to worsen the condition. Candida species may participate in the development of periodontitis in various ways, including cross-kingdom interactions with periodontal pathogens, changes in the local or systemic environment favoring the virulence of Candida species, and interactions between Candida-bacteria and host immunity.

CLINICAL SIGNIFICANCE

Mechanical plaque control is the most common treatment for periodontitis, but its effectiveness may be limited, particularly when dealing with systemic risk factors. Understanding the specific role of Candida in periodontitis illuminates innovative approaches for managing the ecological balance in periodontal health.

The potential health effects associated with electronic-cigarette

A good old gateway theory that electronic-cigarettes (e-cigarettes) are widely recognized as safer tobacco substitutes. In actuality, demographics also show that vaping cannibalizes smoking, the best explanation of the data is the "common liability". However, the utilization of e-cigarette products remains a controversial topic at present. Currently, there has been a widespread and substantial growth in e-cigarette use worldwide owing to their endless new flavors and customizable characteristics. Furthermore, e-cigarette has grown widespread among smokers as well as non-smokers, including adolescents and young adults. And some studies have shown that e-cigarette users are at greater risk to start using combustible cigarettes while e-cigarettes use was also observed the potential benefits to people who want to quit smoking or not. Although it is true that e-cigarettes generally contain fewer toxic substances than combustible cigarettes, this does not mean that the chemical composition in e-cigarettes aerosols poses absolutely no risks. While concerns about toxic substances in e-cigarettes and their widespread use in the population are reasonable, it is also crucial to consider that e-cigarettes have been associated with the potential for promoting smoking cessation and the clinically relevant improvements in users with smoking-related pathologies. Meanwhile, there is still short of understanding of the health impacts associated with e-cigarette use. Therefore, in this review, we discussed the health impacts of e-cigarette exposure on oral, nasal, pulmonary, cardiovascular systems and brain. We aspire for this review to change people's previous perceptions of e-cigarettes and provide them with a more balanced perspective. Additionally, we suggest appropriate adjustments on regulation and policy for e-cigarette to gain greater public health benefits.

Social determinants of health as drivers of fungal disease

Disparities in social determinants of health (SDOH) play a significant role in causing health inequities globally. The physical environment, including housing and workplace environment, can increase the prevalence and spread of fungal infections. A number of professions are associated with increased fungal infection risk and are associated with low pay, which may be linked to crowded and sub-optimal living conditions, exposure to fungal organisms, lack of access to quality health care, and risk for fungal infection. Those involved and displaced from areas of armed conflict have an increased risk of invasive fungal infections. Lastly, a number of fungal plant pathogens already threaten food security, which will become more problematic with global climate change. Taken together, disparities in SDOH are associated with increased risk for contracting fungal infections. More emphasis needs to be placed on systematic approaches to better understand the impact and reducing the health inequities associated with these disparities.

Electronic cigarette exposure disrupts airway epithelial barrier function and exacerbates viral infection

The use of electronic cigarettes (e-cigs), especially among teenagers, has reached alarming and epidemic levels, posing a significant threat to public health. However, the short- and long-term effects of vaping on the airway epithelial barrier are unclear. Airway epithelial cells are the forefront protectors from viruses and pathogens. They contain apical junctional complexes (AJCs), which include tight junctions (TJs) and adherens junctions (AJs) formed between adjacent cells. Previously, we reported respiratory syncytial virus (RSV) infection, the leading cause of acute lower respiratory infection-related hospitalization in children and high-risk adults, induces a "leaky airway" by disrupting the epithelial AJC structure and function. We hypothesized chemical components of e-cigs disrupt airway epithelial barrier and exacerbate RSV-induced airway barrier dysfunction. Using confluent human bronchial epithelial (16HBE) cells and well-differentiated normal human bronchial epithelial (NHBE) cells, we found that exposure to extract and aerosol e-cig nicotine caused a significant decrease in transepithelial electrical resistance (TEER) and the structure of the AJC even at noncytotoxic concentrations. Western blot analysis of 16HBE cells exposed to e-cig nicotine extract did not reveal significant changes in AJC proteins. Exposure to aerosolized e-cig cinnamon or menthol flavors also induced barrier disruption and aggravated nicotine-induced airway barrier dysfunction. Moreover, preexposure to nicotine aerosol increased RSV infection and the severity of RSV-induced airway barrier disruption. Our findings demonstrate that e-cig exposure disrupts the airway epithelial barrier and exacerbates RSV-induced damage. Knowledge gained from this study will provide awareness of adverse e-cig respiratory effects and positively impact the mitigation of e-cig epidemic.NEW & NOTEWORTHY Electronic cigarette (e-cig) use, especially in teens, is alarming and at epidemic proportions, threatening public health. Our study shows that e-cig nicotine exposure disrupts airway epithelial tight junctions and increases RSV-induced barrier dysfunction. Furthermore, exposure to aerosolized flavors exaggerates e-cig nicotine-induced airway barrier dysfunction. Our study confirms that individual and combined components of e-cigs deleteriously impact the airway barrier and that e-cig exposure increases susceptibility to viral infection.

Oral microbiome of electronic cigarette users: A cross-sectional exploration

OBJECTIVE

Electronic cigarettes have increased in popularity globally. Vaping may be associated with oral symptoms and pathologies including dental and periodontal damage, both of which have an underlying microbial etiology. The primary aim of this pilot study, therefore, was to compare the oral microbiome of vapers and non-vapers.

SUBJECTS AND METHODS

This secondary data analysis had a cross-sectional comparative descriptive design and included data for 36 adults. Bacterial 16S rRNA genes were extracted and amplified from soft tissue oral swab specimens and taxonomically classified using the Human Oral Microbiome Database.

RESULTS

Data for 18 vapers and 18 non-vapers were included in this study. Almost 56% of the vapers also smoked conventional cigarettes. Beta diversity differences were identified between vapers and non-vapers. Vapers had a significantly higher relative abundance of an unclassified species of Veillonella compared with non-vapers. Dual users had higher alpha diversity compared with exclusive vapers. Beta diversity was also associated with dual use. Multiple OTUs were identified to be associated with dual use of e-cigarettes and conventional cigarettes.

CONCLUSIONS

Vapers exhibit an altered oral microbiome. Dual use of electronic cigarettes and conventional cigarettes is associated with the presence of several known pathogenic microbes.

IMPACT OF E-CIGARETTES ON THE ORAL HEALTH - LITERATURE REVIEW

E-cigarettes are electronic devices used to inhale aerosols generated from the vaporization of flavored liquids. Nowadays, the use of e-cigarettes has become one of the most popular alternatives to traditional smoking. The wide variety of devices and liquids makes it challenging to assess the health effects of using e-cigarettes. During the vaporization of e-liquids, toxins, carcinogens, and various other chemicals can be released and inhaled by the user. Limited data exist regarding the potential health impact of exposure to e-vapors, primarily derived from animal studies and in vitro research. The oral tissues are the first site of direct interaction with the components of the inhaled vapor. While e-cigarettes are commonly portrayed as safer alternatives to tobacco cigarettes, little is known about the short- or long-term health effects of their use. The aim of this review is to briefly present the available data regarding the impact of chemical ingredients and toxins present in e-cigarette vapors on oral cavity cells.

Electronic Cigarettes: A Pro-Con Review of the Current Literature

Electronic cigarettes (e-cigarettes, e-cigs, or electronic nicotine delivery systems) are battery-operated devices typically containing glycerol and/or propylene glycol-based solutions with varying nicotine content, known as e-liquids. Although e-cigarettes were originally developed as a potentially less harmful alternative to traditional combustible tobacco cigarette smokers, several factors have driven their popularity among smokers and nonsmokers alike, including their sleek product designs, innumerable appealing flavors, lack of combustible smoke and odor, and high potential nicotine concentrations. Furthermore, many advocates have promoted the idea that e-cigarettes are safe to use, or at least safer than conventional tobacco, despite limited longitudinal data to support these claims. Here, we examine what is known about the impacts of e-cigarette use on traditional cigarette smoking cessation, lung health, and youth and young adult tobacco product exposure. Upon review of the currently available literature, the negative effects of e-cigarette use seem to outweigh any potential benefit, because the available evidence does not confirm the use of e-cigarettes as an effective strategy for supporting traditional combustible tobacco cigarette smoking cessation, particularly given the emerging adverse effects on lung health and the potential future public health effects of e-cigarette adoption among a burgeoning new generation of tobacco product users.

Targeting Virulence Factors of Candida albicans with Natural Products

Natural products derived from natural resources, including nutritional functional food, play an important role in human health. In recent years, the study of anti-fungal and other properties of agri-foods and derived functional compounds has been a hot research topic. Candida albicans is a parasitic fungus that thrives on human mucosal surfaces, which are colonized through opportunistic infection. It is the most prevalent cause of invasive fungal infection in immunocompromised individuals, resulting in a wide variety of clinical symptoms. Moreover, the efficacy of classical therapeutic medications such as fluconazole is often limited by the development of resistance. There is an ongoing need for the development of novel and effective antifungal therapy and medications. Infection of C. albicans is influenced by a great quantity of virulence factors, like adhesion, invasion-promoting enzymes, mycelial growth, and phenotypic change, and among others. Furthermore, various natural products especially from food sources that target C. albicans virulence factors have been researched, providing promising prospects for C. albicans prevention and treatment. In this review, we discuss the virulence factors of C. albicans and how functional foods and derived functional compounds affect them. Our hope is that this review will stimulate additional thoughts and suggestions regarding nutritional functional food and therapeutic development for patients afflicted with C. albicans.

Effect of Cigarette and E-Cigarette Smoke Condensates on Candida albicans Biofilm Formation and Gene Expression

Smoking triggers environmental changes in the oral cavity and increases the risk of mucosal infections caused by Candida albicans such as oral candidiasis. While cigarette smoke has a significant impact on C. albicans, how e-cigarettes affect this oral pathogen is less clear. Here, we investigated the effect of cigarette and e-cigarette smoke condensates (CSC and ECSC) on C. albicans growth, biofilm formation, and gene expression. Whereas pure nicotine (N) at the minimum inhibitory concentration (MIC, 4 mg/mL) prevented C. albicans growth, enhanced biofilm formation was observed at 0.1 mg/mL. In contrast, at this nicotine sub-MIC (0.1 mg/mL) concentration, CSC and ECSC had no significant effect on C. albicans biofilm formation. Additionally, N, CSC, and ECSC increased the expression of HWP1 and SAP2 genes. The ECSC group exhibited elevated expression levels of the EAP1 and ALS3 genes, compared to the nicotine-free ECSC (-) control. Moreover, our in vitro study illustrated that the antifungal drugs, fluconazole and amphotericin B, alleviated the effect of nicotine on C. albicans gene expression. Overall, the results of the study indicated nicotine from different sources may affect the pathogenic characteristics of C. albicans, including hyphal growth, biofilm formation, and particularly the expression of virulence-related genes.

Efficacy of antimicrobial photodynamic therapy in reducing oral yeasts carriage among individuals using electronic nicotine delivery systems

OBJECTIVE

The aim was to assess the efficacy of antimicrobial photodynamic therapy (aPDT) in reducing oral yeasts carriage among individuals using electronic nicotine delivery systems (ENDS).

METHODS

Self-reported ENDS users and non-users (individuals that reported to have never used any nicotinic product) were included. Demographic data was collected using a questionnaire. Patients were divided into 2 subgroups: (a) aPDT group; and (b) sham aPDT group. aPDT was performed using a curcumin-based photosensitizer that was exposed to a central wavelength of 660 nm and an estimated average fluency of 200 J/cm2. The system delivered light by uniform diffusion for 5 minutes. Sham aPDT was performed using a non-activated laser tip. Oral yeasts colony forming units were determined using standard techniques. Oral yeasts were assessed at baseline and at 3-months of follow-up. Level of significance was set at P<0.05.

RESULTS

Twenty-three ENDS-users (19 males and 4 females) and 23 controls (17 males and 6 females) were included. ENDS-users were vaping for 8.3 ± 0.6 years and were using their ENDS devices 13.6 ± 2.7 times daily. Toothbrushing twice daily was reported by 8.7% and 21.7% of ENDS-users and controls, respectively. Tongue brushing was reported by none of the individuals. At baseline, oral yeasts CFU/ml were significantly higher among ENDS-users in the PDT (P<0.05) and sham PDT (P<0.05) groups compared with controls (Table 2; Figure 1). At 3-months of follow-up, CFU/ml were significantly higher among ENDS-users in the PDT (P<0.05) and sham PDT (P<0.05) groups compared with controls CONCLUSION: : A single session of aPDT is ineffective in reducing the oral yeasts CFU/ml in ENDS-users. Further studies are needed to assess the impact of multiple sessions of aPDT in reducing the oral yeasts CFU/ml in ENDS-users.

Fabrication and Validation of an Economical, Programmable, Dual-Channel, Electronic Cigarette Aerosol Generator

Vaping (inhalation of electronic cigarette-generated aerosol) is a public health concern. Due to recent spikes in adolescent use of electronic cigarettes (ECIGs) and vaping-induced illnesses, demand for scientific inquiry into the physiological effects of electronic cigarette (ECIG) aerosol has increased. For such studies, standardized and consistent aerosol production is required. Many labs generate aerosol by manually activating peristaltic pumps and ECIG devices simultaneously in a predefined manner. The tedium involved with this process (large puff number over time) and risk of error in keeping with puff topography (puff number, duration, interval) are less than optimal. Furthermore, excess puffing on an ECIG device results in battery depletion, reducing aerosol production, and ultimately, its chemical and physical nature. While commercial vaping machines are available, the cost of these machines is prohibitive to many labs. For these reasons, an economical and programmable ECIG aerosol generator, capable of generating aerosol from two atomizers simultaneously, was fabricated, and subsequently validated. Validation determinants include measurements of atomizer temperatures (inside and outside), electrical parameters (current, resistance and power) of the circuitry, aerosol particle distribution (particle counts and mass concentrations) and aerosol delivery (indexed by nicotine recovery), all during stressed conditions of four puffs/minute for 75 min (i.e., 300 puffs). Validation results indicate that the ECIG aerosol generator is better suited for experiments involving ≤100 puffs. Over 100 puffs, the amount of variation in the parameters measured tends to increase. Variations between channels are generally higher than variations within a channel. Despite significant variations in temperatures, electrical parameters, and aerosol particle distributions, both within and between channels, aerosol delivery remains remarkably stable for up to 300 puffs, yielding over 25% nicotine recovery for both channels. In conclusion, this programmable, dual-channel ECIG aerosol generator is not only affordable, but also allows the user to control puff topography and eliminate battery drain of ECIG devices. Consequently, this aerosol generator is valid, reliable, economical, capable of using a variety of E-liquids and amenable for use in a vast number of studies investigating the effects of ECIG-generated aerosol while utilizing a multitude of puffing regimens in a standardized manner.

Pulmonary actinomycosis and marijuana vaping

A 33-year-old man without significant medical history presented to the emergency department with a 6-month history of fatigue and 30 pounds of unintentional weight loss, with a recent cough and fever over the past week. He recalled two similar illnesses during college that did not require medical care. He denied tobacco use but reported inhaling marijuana 1-2 times daily over the past year with a vaping device. Physical exam was notable for a temperature of 100.0°F and an elevated blood pressure at 161/77 mm Hg. He was diaphoretic with clear breath sounds bilaterally. Chest imaging revealed diffuse ground glass opacities with subpleural sparing and mildly enlarged hilar lymph nodes. Bronchoscopy with transbronchial lung biopsies and needle aspirate of lymph nodes revealed organising pneumonia, and subsequent cultures grew Actinomyces odontolyticus He was treated with amoxicillin and corticosteroids with subsequent resolution on repeat chest imaging.

Interventions to prevent periodontal disease in tobacco-, alcohol-, and drug-dependent individuals

Substance abuse affects more than one sixth of the world's population. More importantly, the nature of the abuse and the type of addictive substances available to individuals is increasing exponentially. All substances with abusive potential impact both the human immuno-inflammatory system and oral microbial communities, and therefore play a critical role in the etiopathogenesis of periodontal diseases. Evidence strongly supports the efficacy of professionally delivered cessation counseling. Dentists, dental therapists, and hygienists are ideally placed to deliver this therapy, and to spearhead efforts to provide behavioral and pharmacologic support for cessation. The purpose of this review is to examine the biologic mechanisms underlying their role in disease causation, to understand the pharmacologic and behavioral basis for their habituation, and to investigate the efficacy of population-based and personalized interventions in prevention of periodontal disease.

Electronic cigarette vapor increases Streptococcus mutans growth, adhesion, biofilm formation, and expression of the biofilm-associated genes

OBJECTIVE

It still not known whether electronic cigarettes (e-cigarettes) contribute to dental caries. This study aimed to evaluate the effect of e-cigarettes on the growth of Streptococcus mutans, the formation of biofilm, and the expression of certain virulence genes.

MATERIALS AND METHODS

Streptococcus mutans cells were exposed or not to e-cigarettes with and without nicotine or to cigarette smoke twice a day for 15 min each exposure period. The bacterial growth and the expression of glucosyltranferase, competence, and glucan-binding genes were evaluated after 24 hr. Biofilm formation was assessed after 1, 2, and 3 days. S. mutans adhesion and growth to e-cigarette exposed human teeth were assessed.

RESULTS

We observed an increase in S. mutans growth with e-cigarettes, mainly at the early culture period. This was confirmed by an increase of biofilm mass ranging from 8 ± 0.5 mg with the control to 47 ± 5 mg after six exposures to nicotine-rich e-cigarettes. S. mutans cells adhered better to e-cigarette exposed teeth. E-cigarettes increased the expression of glucosyltranferase, competence, and glucan-binding genes.

CONCLUSIONS

E-cigarettes increased the growth of S. mutans and the expression of virulent genes. E-cigarettes promoted the adhesion to, and formation of biofilms on teeth surfaces.

Oral mycobiome identification in atopic dermatitis, leukemia, and HIV patients - a systematic review

INTRODUCTION

Oral mycobiome profiling is important to understand host-pathogen interactions that occur in various diseases. Invasive fungal infections are particularly relevant for patients who have received chemotherapy and for those who have HIV infection. In addition, changes in fungal microbiota are associated with the worsening of chronic conditions like atopic dermatitis (AD). This work aims, through a systematic review, to analyze the methods used in previous studies to identify oral fungi and their most frequent species in patients with the following conditions: HIV infection, leukemia, and atopic dermatitis.

METHODS

A literature search was performed on several different databases. Inclusion criteria were: written in English or Portuguese; published between September 2009 and September 2019; analyzed oral fungi of HIV-infected, leukemia, or AD patients.

RESULTS

21 studies were included and the most identified species was Candida. The predominant methods of identification were morphological (13/21) and sugar fermentation and assimilation tests (11/21). Polymerase chain reaction (PCR) was the most used molecular method (8/21) followed by sequencing techniques (3/21).

CONCLUSIONS

Although morphological and biochemical tests are still used, they are associated with high-throughput sequencing techniques, due to their accuracy and time saving for profiling the predominant species in oral mycobiome.

Knowledge and attitudes of adolescents to e-cigarettes: an international prospective study

Purpose The aim of the study was to assess the familiarity of adolescents with e-cigarettes. We performed a survey to investigate the frequency of their contact with e-cigarettes, beliefs about this sort of smoking (vaping), and their real knowledge of its effects. Methods The survey was carried out among 1600 high school students in the USA, Israel, Ukraine and Australia. The questionnaire comprised three parts, each with five questions. The first part was designed to assess the frequency of contact with the phenomenon. The second part assessed misconceptions and opinions concerning vaping. The third part questioned the participants' real knowledge of the subject. Results Out of a maximum score of 5, the average score of 4.25 for Part 1 indicated that the participants had frequent contact with e-cigarettes. The score of 3.65 for Part 2 showed that adolescents have both right and wrong beliefs on the subject. Part 3 was completed by 1224 participants (76.5%) while 376 (23.5%) reported a lack of any specific knowledge about vaping. The average score of 3.33 demonstrated that adolescents who completed Part 3 of the survey have incomplete knowledge about e-cigarettes. For the whole cohort of 1600 participants, the average score was 2.80. No significant sex differences were detected. The Ukranian participants had poor knowledge about the dangers of vaping in comparison with the participants in the USA and Australia (p = 0.03). Conclusion While the contact of adolescents with e-cigarettes users is extensive, their actual knowledge remains inadequate. Various school-based smoking risk campaigns face a necessity for further adjustments and improvements.

Harmful chemicals emitted from electronic cigarettes and potential deleterious effects in the oral cavity

Use of electronic nicotine delivery systems (ENDS), such as electronic cigarettes (e-cigs), is increasing across the US population and is particularly troubling due to their adoption by adolescents, teens, and young adults. The industry’s marketing approach for these instruments of addiction has been to promote them as a safer alternative to tobacco, a behavioral choice supporting smoking cessation, and as the ‘cool’ appearance of vaping with flavored products (e.g. tutti frutti, bubble gum, and buttered popcorn etc.). Thus, there is a clear need to better document the health outcomes of e-cig use in the oral cavity of the addicted chronic user. There appears to be an array of environmental toxins in the vapors, including reactive aldehydes and carbonyls resulting from the heating elements action on fluid components, as well as from the composition of chemical flavoring agents. The chemistry of these systems shows that the released vapors from the e-cigs frequently contain levels of environmental toxins that considerably exceed federal occupational exposure limits. Additionally, the toxicants in the vapors appear to be retained in the host fluids/tissues at levels often approximating 90% of the levels in the e-cig vapors. These water-soluble reactive toxins can challenge the oral cavity constituents, potentially contributing to alterations in the autochthonous microbiome and host cells critical for maintaining oral homeostasis. This review updates the existing chemistry/environmental aspects of e-cigs, as well as providing an overview of the somewhat limited data on potential oral health effects that could occur across the lifetime of daily e-cig users.

The oral health impact of electronic cigarette use: a systematic review

Introduction: Electronic cigarette (e-cigarette) use is becoming more prevalent and is particularly popular among adolescents and conventional smokers. While the oral health sequelae of conventional smoking are well-established, the impact of e-cigarettes on oral health is still unknown. This study aims to systematically review the available research evidence on the oral health impact of e-cigarette use.Methods: This systematic review was conducted according to PRISMA guidelines and used the Effective Public Health Practice Project Quality Assessment Tool to evaluate the evidence. Three electronic databases (PubMed, Web of Science, and Embase) were systematically searched for studies including case reports. Two independent reviewers extracted data and synthesized the findings.Results: Ninety-nine articles were included in this systematic review. Analyses of the articles yielded seven categories based on symptom similarity and/or focus: mouth effects, throat effects, periodontal effects, dental effects, cytotoxic/genotoxic/oncologic effects, oral microbiome effects, and traumatic/accidental injury. The majority of mouth and throat symptoms experienced by e-cigarette users were relatively minor and temporary, with some evidence that conventional smokers who switched to e-cigarettes experienced mitigation of these symptoms. E-cigarette exposure increased the risk for deteriorating periodontal, dental and gingival health as well as changes to the oral microbiome. Extensive dental damage as a result of e-cigarette explosions were described in case reports. Components of e-cigarette vapor have known cytotoxic, genotoxic, and carcinogenic properties.Conclusions: Although switching to e-cigarettes may mitigate oral symptomatology for conventional smokers, findings from this review suggest that a wide range of oral health sequelae may be associated with e-cigarette use. Well-designed studies to investigate oral health outcomes of e-cigarette use are needed.

The Evolving Landscape of e-Cigarettes: A Systematic Review of Recent Evidence

Smoking continues to be a burden to economies and health-care systems across the world. One proposed solution to the problem has been e-cigarettes; however, because they are a relatively new product in the market, little is known about their potential health impacts. Furthermore, e-cigarettes continue to evolve at a rapid rate, making it necessary to regularly review and summarize available studies. Although e-cigarettes are marketed as a smoking cessation tool by some manufacturers, the reality is that many nonsmokers, including youth, are using them. This review focuses on two major demographic groups (smokers and nonsmokers) and evaluates the most recent data (early 2017 to mid 2019) regarding the potential health effects of e-cigarettes. We assessed peer-reviewed studies on the health impacts of e-cigarettes, with a particular focus on common questions asked by policy makers, clinicians, and scientists: (1) What are the effects of e-cigarettes compared with air/not smoking?; (2) Is there any direct evidence of harm or benefit to humans?; (3) Is there a risk from secondhand exposure?; (4) What are the risks and/or benefits of e-cigarettes compared with tobacco cigarette use?; (5) Are there risks or benefits to specific populations (eg, people with COPD or asthma, pregnant women [and their offspring])?; (6) What are the effects of flavoring chemicals?; (7) What are the effects of including nicotine in e-liquids?; (8) How often is nicotine concentration labeling incorrect?; and (9) What are the risks when e-cigarettes explode?

Oral Candidiasis: A Disease of Opportunity

Oral candidiasis, commonly referred to as “thrush,” is an opportunistic fungal infection that commonly affects the oral mucosa. The main causative agent, Candida albicans, is a highly versatile commensal organism that is well adapted to its human host; however, changes in the host microenvironment can promote the transition from one of commensalism to pathogen. This transition is heavily reliant on an impressive repertoire of virulence factors, most notably cell surface adhesins, proteolytic enzymes, morphologic switching, and the development of drug resistance. In the oral cavity, the co-adhesion of C. albicans with bacteria is crucial for its persistence, and a wide range of synergistic interactions with various oral species were described to enhance colonization in the host. As a frequent colonizer of the oral mucosa, the host immune response in the oral cavity is oriented toward a more tolerogenic state and, therefore, local innate immune defenses play a central role in maintaining Candida in its commensal state. Specifically, in addition to preventing Candida adherence to epithelial cells, saliva is enriched with anti-candidal peptides, considered to be part of the host innate immunity. The T helper 17 (Th17)-type adaptive immune response is mainly involved in mucosal host defenses, controlling initial growth of Candida and inhibiting subsequent tissue invasion. Animal models, most notably the mouse model of oropharyngeal candidiasis and the rat model of denture stomatitis, are instrumental in our understanding of Candida virulence factors and the factors leading to host susceptibility to infections. Given the continuing rise in development of resistance to the limited number of traditional antifungal agents, novel therapeutic strategies are directed toward identifying bioactive compounds that target pathogenic mechanisms to prevent C. albicans transition from harmless commensal to pathogen.

Electronic Nicotine Delivery Systems (ENDS) and Their Relevance in Oral Health

The number and popularity of electronic nicotine delivery systems (ENDS) and especially e-cigarettes (e-cigs) have been increasing in the last decade. Although ENDS owe their popularity to excluding the harmful chemicals that are present in tobacco smoke, there is a debate whether they are safe, regulated, and as harmless as they are assumed to be and have potential unknown long-term effects. Involvement of cigarette smoking to the progression of periodontal diseases, other adverse oral health outcomes, and its detrimental effects to oral health are well-described. ENDS producer companies claim that these products can improve oral health by providing alternatives to smoking. However, the effect of e-cigs on oral health is not fully understood and is still debated among many scientists and clinicians. The number of studies addressing the potential toxic effect of ENDS or e-cig aerosol on oral cells is limited along with the clinical studies which are still preliminary, and their sample size is limited. The long-term effects of inhaled aerosols and the potential synergistic effect of the e-cigs components are not known. It is essential and of utmost importance to determine whether exposure to ENDS aerosol contributes to the progression of periodontal diseases and how it affects periodontal ligament and gingival cells which are believed to be its first targets. This review briefly summarizes the available evidence about the effects of e-cigs on periodontal health including several pathophysiological events, such as oxidative stress, DNA damage, inflammation, cellular senescence, dysregulated repair, and periodontal diseases.