Association between passive smoking and dental caries among 3-8 years children in Bangalore city

Introduction

Oral cavity is a large microbial complex ecosystem consisting of oral fluids, immunoglobulin, agglutinins, microflora, carbohydrates, proteins and certain anti-microbial enzymes. The abundance of oral microbes results in the formation of dental biofilm which on contact with the host may result in disturbances in tissue homeostasis and subsequent disease like dental caries.1

Global Burden of Disease 2010 Study reported that the global prevalence of untreated caries was the highest and its global burden is ranked 80^th.2 Carious lesion constitutes a progressive infectious process with multifactorial aetiology. Besides dietary habits, oral microorganisms, and host susceptibility, some risk factors, such as sex, age, dietary habits, socioeconomic, exposure to environmental tobacco smoke and oral hygiene status, are also associated with increased prevalence and incidence of dental caries in paediatric population.3

The association between second-hand smoking and dental caries have been revealed by epidemiological survey by various authors4, 5, 6, 7 and several studies have also shown dose-response relationship between the extent of smoking by parents and unfavorable effects on children.8, 9 Thus, it is not surprising that SHS would be an independent risk factor for dental caries development.

Passive smoking(PS), refers to the smoke discharged from the lit end of a burned tobacco product as well as the smoke exhaled during active smoking.10 The World Health Organization (WHO) has estimated that almost one-half of the world’s children (nearly 700 million) are exposed to tobacco smoke from the 1.2 billion adults who smoke.11 Furthermore, infants and children are generally not capable to manage their environment & consequently unable to perform action to escape from second hand exposure (SHS) because of low-socioeconomic status, under educated parents and small house which constrains parents to smoke inside the house.12

Exposure to PS can be assessed Quantitatively by determining the concentration of the most important metabolite of cotinine (by product of nicotine). It is found in blood, saliva and urine after exposure to nicotine and the levels are elevated in passive smokers. Measurement of cotinine in body fluids are sensitive technique to assess passive smoking exposure.13 In saliva, values between 1 ng/mL and 30 ng/mL may be associated with light smoking or passive exposure, and levels in active smokers typically reach 100 ng/mL or more.14

Children are comparatively more vulnerable to systemic ill effects of second-hand smoke effects because of higher breathing rates per body weight, immature lungs and more lung surface area compared with adults.15 SHS not only affects their general health, also few studies16, 17, 18 have proposed a positive association between SHS exposure and oral health. The risk of developing dental caries by exposure to secondhand smoke may be explained by three major mechanisms: (1) direct exposure of the developing teeth buds to chemicals of smoke, leading to delay in the formation and impair of mineralization:19 (2) damage to salivary glands by chemicals of smoke, resulting in a decreased salivary flow, which affects buffering capacity and cleansing mechanism:20 and (3) Secondhand smoking also impairs the salivary immune system by reducing the salivary Antimicrobial Peptides (AMP) and flow rate in children and simultaneously increases the colonization of Streptococcus mutans, which have been attributed to the formation of dental caries.21, 22

It is biologically plausible that passive smoking could cause caries, particularly at childhood and there is lack of literature regarding the same. Hence, this study was designed to assess the correlation between passive smoking and dental caries in exposed and unexposed children and possible correlation to age, gender, salivary flow rate, salivary AMP dental caries experience was determined

Materials and Methods

Results

A total of 120 Participants, participated in the present case-control study after filling the given questionnaire and thorough clinical examination. Among them, the subjects were divided into PE and UE groups.

Discussion

Since decades, smoking is known as a potential risk factor and a major preventable cause of morbidity and mortality. Thousands of chemicals are present in complex aerosol of cigarette which contains volatile gases with suspension of particulate matter.23

Several hypotheses support the biological plausibility of the association and explains the causal mechanism of caries due to passive tobacco exposure. Our study demonstrated that the mean DMF score was significantly higher in PE group children than those in UE group children. Similarly, Chowdhury and Bromage24 and Heikkinen et al.25 have also stated that exposure to tobacco use directly affects both the mineralisation of the developing tooth and the microorganisms, while cross-sectional study by Mattheus et al.26 revealed that caries prevalence was 1.59 times more in children who were exposed to smoke inside the house in comparison to smoke outside. Another study conducted by Tanaka et al.27 also stated that exposure to tobacco smoke at 4 months of age was associated with an approximately two fold increased risk of caries.

Avçar et al.4 observed that children exposed to tobacco use had lower salivary pH, buffer capacity and saliva flow than non-exposed children however our study showed a contrasting result with no significance difference in the SFR between PE and UE groups.

The present study showed (table-7) increased DMF score of 13.1+/-0.71 in parents with low income followed by mean DMF score 7.35+/- 4.07 in parents with medium income and mean DMF score of 3.24+/-3.97 in high income parents, which indicated a negative correlation between DMF score and socioeconomic status of the parents. Jakhete and Gitterman28 have also stated that exposure to tobacco use were associated with higher caries prevalence in children from a low socio-economic level. Delpisheh29 confirmed that passive exposure to tobacco use in children is significantly associated with low socio-economic level. Majorama et al.30 found that children who lived in families from a low socio-economic level and were exposed to tobacco use had a greater likelihood of suffering severe caries.

Our study revealed that high parental education was associated with low prevalence of dental caries, (table-8) where higher DMF score of 7.02+/-4.431 was seen in parents with below matriculation education status & DMF score of 2.22+/-3.18 in parents with above matriculation similarly, Study results by Alfred et al.31 and Tanka et al.27 substantiate our results which showed education status of the parents were responsible for increased awareness.

The dose-response relationship between levels of exposure to tobacco use and dental caries has been studied by several authors32, 22, 33, 34 all of whom have confirmed this relationship. Our study was found to be similar, (table -9) represents the comparison of mean DMF scores based on the smoking related characteristics. DMF score was 9.38+/-4.23 in children who were exposed to two smokers at home than one smoker with DMF score 4.53+/-4.24. Also DMF score was significantly higher (6.93+/-4.48) in children, whose parents smoked inside & outside and (6.62+/-4.64) in families who had no rules regarding smoking habits. There was also positive correlation in DMF score & duration of smoking. Children who had history of exposure to smoke >3 years had mean DMF score of 8.22+/-3.17 than children exposed to smoke <6 months with absence of caries score. Frequency of smoking also have a significant correlation with respect to DMF score, where DMF was 11.91+/-2.55 in children whose parents smoke > 10 cigarettes/day.

Exposure to tobacco smoke, which contains numerous chemical toxins, might predispose children to infection through suppression or modulation of the immune system.35

Numabae et al.36 showed that the phagocytic activity of salivary PMN’s intensifies after exposure to smoking, where as an another invitro study37 demonstrated that nicotine inhibited phagocytic activity. Sakki and Knuuttila38 showed that tobacco smoking was associated with elevated levels of mutans streptococci and lactobacillus. Yet on the other hand, epidemiological studies on the association between passive smoke exposure and dental caries showed inconsistent results because of unknown factors related to passive smoking which may have confounded the observed relationship.

This study also shows long-term impact of smoking in household on their children which serves as an important motivating factor for their parents to quit smoking and the study also highlights PS as health hazard which is not known by many people in study setting and hence, serves as an important enlightening message.

Present study results showed that passive smoking was positively associated with the prevalence of dental caries, due to the suppression of Salivary AMP, which predisposes to dental caries. However, the limitation is small sample size and assessment of SHS exposure was which was obtained by questionnaire reports and was not validated by measurements of biomarkers, such as salivary cotinine levels. Using questionnaires may result in misclassification from recall bias and response bias due to parents' feelings of guilt for smoking in the presence of their children. Although the biological and behavioural plausibility for an etiological relationship between SHS exposure and dental caries is likely to be high, epidemiological evidence is still insufficient. The addition of objective markers of SHS exposure may help to clarify the role of SHS exposure on dental caries in further research. Hence the correlation between the Salivary AMP, Sal. Cotinine concentration and dental caries will be assessed in the phase 2 of the study by quantitative analysis of Salivary cotinine levels and Salivary AMP’s.

Conclusion

Dental caries is a common public health problem among children due to multi factorial aetiological agents. Our results revealed that passive exposure to tobacco smoke had independent relationship with dental caries in Bangalore children. Although the relationship between passive smoking and dental caries is likely to be high, epidemiological evidences are insufficient. The addition of objective markers in regard to passive smoke exposure may help to clarify the role of passive smoking exposure and caries correlation by additional studies.

Source of Funding

None.

Conflict of Interest

None.