Despite growing knowledge of the adverse effects of cigarette smoking on general health, smoking is one of the most widely prevalent addictions around the world. Globally, about 1.1 billion smokers and over 8 million people die each year because of cigarette smoking. Smoking acts as a source for a variety of oral and systemic diseases. Various periodontal issues such as increased pocket depth, loss of alveolar bone, tooth mobility, oral lesions, ulcerations, halitosis, and stained teeth are more common among smokers. This systematic review was conducted according to the guidelines from PRISMA, and research articles were retrieved from the Web database sources on 31 May 2021. The quality of research articles was ensured by the type of evidence from combined schema incorporating as schema-13 evidence type description, Cochrane health promotion and public health field (CHPPHF), and the health gains notation framework-14 screening question for quality assessment of qualitative and quantitative studies. Smokers have been found to have bleeding on probing, periodontal pockets, and clinical attachment loss compared to nonsmokers. Oral and respiratory cancers are among the most lethal known diseases caused by cigarette smoking and other commonly occurring sequelae such as stained teeth, periodontal diseases, etc.
1. Introduction
Oral diseases appear to be a global problem that should be addressed as a matter of global health concern. Oral health issues include various behavioral and social features such as habits, oral health knowledge, practices, availability, modifiable risk factors, and accessibility to oral health treatments [1]. Health is considered as a significant factor in making life valuable [2]. In general, lifestyles and behavioral patterns are continuously changing, making people more susceptible to oral disorders. Common preventable risk factors for oral diseases include consuming great amounts of sugary food and alcohol and smoking excessively [3]. Back in 2015, untreated oral disorders crippled over half of the world’s population (age-standardized prevalence: 48.0 percent), affecting 3.5 million individuals worldwide [4,5].
Oral and orofacial problems can affect children and adolescents, affecting physical functioning and psychosocial well-being [6]. One of the scientific theories used to influence human health-related behaviors is the knowledge, attitude, and practices (KAP) theory. According to the KAP theory, healthy knowledge is the foundation for developing an optimistic and healthy lifestyle, attitudes are the motivating factor behind changing behavior, and the goal is to promote oral health [7]. This is why oral health professionals play a critical role in disease prevention and diagnosis through screening and raising awareness [8]. Recently, a shift of focus in health care has been noticed, signaling a transition from biological to a more complete and broader biopsychosocial concept of health [9].
Rationale: The most critical risk factor associated with the onset of various gingival and periodontal diseases is tobacco smoking. It reduces the quality of life of patients and poses a risk to oral health. It has been demonstrated that oral health among smokers is compromised in comparison to nonsmokers. Thus, this study is aimed at reviewing the literature to evaluate the effect of smoking on oral health.
Objectives: In this systematic review, we aim to examine the effects of cigarette smoking on oral health, present the major oral diseases caused by cigarette smoking, and determine if there is any possibility of bacterial or fungal infections among smokers.
2. Analysis on Study Results
2.1. Study Selection Results
A total of 3696 studies were retrieved from the PubMed, Scopus (2271), WOS (1822), and MDPI (711) according to the inclusion/exclusion criteria as listed in Table 2. Data were extracted from 19 studies that purely met the eligibility criteria. Figure 2 and Figure 3 shows the results of the total studies evaluated. Initially, a total of 3696 articles were screened from PubMed, 711 from MDPI and 4093 form other databases (Scopus and WOS) as per the search criteria described in Table 1. After identifying duplicate articles, 972 were excluded from PubMed, 657 from Scopus, 507 from WOS, and 120 from MDPI. After removal of duplicates, the remaining 3315 articles were screened by reading the title and abstracts, after which 2929 articles were excluded. The remaining 47 articles were then fully read and assessed for the inclusion/exclusion criteria and quality assessment. After reading the full text, 28 studies were excluded due to reasons including cigarette cessation studies with no oral effects, prevalence of cigarette smoking among different population reporting no oral effects, questionnaire-based studies, and studies with chewable tobacco or other oral tobacco products. The finally selected articles were finalized to proceed further for data extraction. Based on the quality assessment of the research studies, these 19 articles were screened for the present study. A meta-analysis of the studies included in this study was not performed due to the methodological heterogeneity of the findings.
Figure 2. Flowchart of articles retrieved from different Web sources.
Figure 3. Articles included in the current study (MDPI and PubMed).
From the total retrieved articles (MDPI, PubMed, Scopus, and Web of Sciences), only MDPI and PubMed articles were further included in this study.
2.2. Study Features
A total of 19 studies were included in this systematic review. The studies were conducted in different countries; many researchers cited different time durations. The number of citations for each of the study was observed from Google Scholar. Each of the included studies was published in reputed and indexed journals. Table 3 summarizes the sample type, total sample size, adopted methodology, results, and the conclusion of each study. Different types of samples were collected from the patients to observe the effects of smoking on oral health, including biopsies, blood, buckle cells, teeth, saliva, etc. In the included studies, a total of 26,236 samples were observed.
Table 3. Methodology, outcomes, and conclusion of articles included in the current study.
2.3. Quality Assessment of Research Articles
All of the articles were shortlisted and screened based on the inclusion and exclusion criteria, titles, and abstract. Full texts were read one by one after the screening process and assessed for the quality of material using the CHPPHF recommendations. CHPPHF assessed articles for internal and external validity and rated the criteria for allocation biases, selection biases, intervention integrity, blinding, withdrawals and dropouts, confounding, data collection methods, and statistical analysis. No statistical assessment of publishing bias was carried out for the included studies as there were limited experimental techniques. A total of eight RCTs were included in the present systematic review.
Bias assessment was conducted according to the Cochrane tool of bias risk assessment. Overall, four included RCTs were at higher risk of bias, four were at lower risk of bias, and many items according to Cochrane tool of bias risk assessment were unclear in eight included RCTs. Selection bias was observed in two of the eight included RCTs, as was performance bias in two studies, detection bias in one study, attrition bias in one study, reporting bias in two studies, and other concerns in one study (Figure 4).
Figure 4. Risk of bias summary: review authors judgment about each risk of bias item for each included RCT.
3. Current Insights
Cigarette smoking has been linked to a variety of health problems. When comparing current smokers to nonsmokers, the rate of mortality from any cause was two to three times higher [
42,
43]. In many smoking-related studies, the duration of smoking, a quantity of cigarettes smoked per day, brand of cigarettes smoked, cigarette type, and topographical factors related to smoking all are linked to the severity of tobacco consumption [
19]. Because of tobacco use, other lifestyle risk factors, and poor dental care usage, smokers are at a higher risk for many oral diseases. As many oral health problems go unrecognized and untreated, the lack of regular dental care becomes particularly problematic [
8,
44].
Oral diseases are one of the most frequent chronic diseases, and they are significant public health issues due to their prevalence, effect on people and society, and treatment costs [
33,
45]. Oral disease determinants are well understood. Oral hygiene, smoking, drinking, hazardous behaviors, and stress are all risk factors for various chronic diseases, and efficient public health interventions to prevent oral diseases [
7]. Smoking is one of the most common risk factors for oral diseases [
3].
Dental caries and periodontal disease and the probable consequences of both (tooth loss) are serious dental public health issues that affect people all over the world [
6,
21,
46]. Individuals’ quality of life and general health are negatively impacted by poor oral health and untreated oral illnesses [
9]. A significant positive association between tobacco smoking and higher risk for periodontitis has been found in prospective longitudinal studies.
The elevations in interleukin (IL)-1 and IL-6 associated with smoking levels upregulate bone resorption through the increase in the ratio between the receptor activator of nuclear factor-κβ ligand (RANKL) and its inhibitor osteoprotegerin (OPG). In addition, higher concentrations of elastase and matrix metalloproteinase (MMP)-8 and MMP-9 with proteolytic activity and decreased levels of protease inhibitors, such as alpha-2-macroglobulin and α-1-antitrypsin, may compromise periodontal healing.
If smoking were eliminated in this population, the risk of periodontitis would be reduced by approximately 14% as calculated using the population attributable risk fraction. In underdeveloped countries, the burden of oral diseases is significantly higher [
4,
47,
48]. Among smokers and nonsmokers, in the treatment of chronic periodontitis (CP), Al-Ahmari et al. (2019) checked the effectiveness of scaling & root planning (SRP) with and without the adjunct antimicrobial photodynamic therapy (aPDT). Bleeding on probing (BOP), plaque index (PI), clinical attachment loss (CAL), and probing pocket depth (PD) 4 mm were all assessed at baseline, one month, and three months of follow-up. Smokers and nonsmokers had similar BOP, PI, PD, and clinical AL at the start of the study. PD, PI, and clinical AL were shown to be greater in smokers than nonsmokers after a one-month and three-month follow-up. At the one-month and three-month follow-ups, all nonsmokers’ BOP, PI, clinical AL, and PD were equivalent [
34]. In similar research, Al-Bayaty et al. (2013) conducted a study to observe the effects of cigarette smoking on gingival bleeding, to measure the serum haptoglobin, cotinine, and alpha 1-antitrypsin concentrations in Malaysian smokers. BOP levels were determined to be low, whereas PI values were high. Smokers had considerably more significant levels of serum haptoglobin, cotinine, and alpha 1-antitrypsin than nonsmokers. There was a strong connection between PI and smoking duration (years) and blood cotinine levels [
24].
Even though tobacco use has decreased in many high-income countries such as the United States and the United Kingdom, it is growing in many low- and middle-income countries [
11,
35]. According to the World Health Organization (WHO), there are more than 1.1 billion smokers throughout the world, with more than 80% of them residing in low- and middle-income countries [
49]. After nonsurgical periodontal treatment, Varghese et al. (2020) studied the salivary 8-hydroxyguanosine (8-OHdG) levels in smokers and nonsmokers with CP. Clinical periodontal markers (PI, GI, PD, and CLI) were assessed at the start of the study. SRP was performed on patients with CPs (CP smokers) and CPns (CP nonsmokers) [
40]. In a three-month follow-up period, all of the clinical measures and salivary collections were repeated. At the baseline period, the PI, GI, PD, and CAL values in the CPs and CPns groups were significantly higher as compared to the CHns and CHs groups. At baseline, salivary levels of 8-OHdG were found significantly higher in the CPs group than the other groups. All of the clinical measures in the CP group improved by the follow-up interval at the third month. However, the salivary levels of 8-OHdG in the CP smoker category were still higher values than the CPns [
40]. Haswell et al. (2014) analyzed the biomarkers of biological effect (BOBE) and demonstrated the difference between smokers, nonsmokers, and ex-smokers. The levels of biomarkers were compared, and it was seen that there were 27 possible biomarkers evaluated in all, 14 of which were substantially different between smokers and nonsmokers, and 12 of which were able to discriminate between smokers and former smokers, indicating the possibility of reversibility [
26].
The maxillary antrum, submandibular region, salivary glands, and tongue are commonly affected by cervicofacial actinomycosis [
35]. The mandible is affected in about half of the cases, with the chin (15%), cheek (15%), and submaxillary ramus and angle (15%). The paranasal sinuses, tongue, larynx, middle ear, thyroid gland, and lachrymal pathways are all nonodontogenic orofacial regions that may also be get affected by cervicofacial actinomycosis [
22]. Abduljabbar et al. (2017) worked on a project and wanted to see how effective aPDT was at preventing oral fungus colonization in smokers and nonsmokers suffering from denture stomatitis (DS). Among smokers, a statistically significant decrease in the mean fungal CFU/mL was seen at the 3-month follow-up compared to their respective baseline values of CFU/mL. When compared to their individual baseline values, nonsmokers’ mean levels were lower. After a 3-month follow-up, smokers’ fungal CFU/mL levels were statistically substantially higher than nonsmokers [
30].
This entry is adapted from the peer-reviewed paper 10.3390/ijerph182111003
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