This systematic literature search detected 256 potentially relevant studies on the prevalence of oral pain symptom amongst the ST users during or after cessation of the habit, and psychological distress, social capital and socio-economic factors.
A standardised check list was used to identify and assess the methodological quality of each study before an attempt was made to summarise the results. In the final study only four studies were found relevant. These were included in this review to investigate the findings regarding association between demographic, socio-economic, psychological distress, and behavioural factors, namely smokeless tobacco use and cessation, and oral health problems relevant to oral pain symptoms. The reported evidence demonstrating the association of oral pain symptoms with the causality of oral pain symptoms such as ST chewing, behavioural factors are discussed below.
2.3.1. Literature search, identification and selection of studies
The most important feature of this literature search was the effort to locate all relevant primary studies. An electronic literature search using one database, four websites, and citation tracking were used to gather the papers of interest. Other electronic databases namely Embase was used but the outcome of the search was the same as the PubMed (Medline) search. The PubMed database showed
the highest sensitivity (76 percent) compared to combined collection of studies through websites and citation tracking (24 percent).
The most common problem for this systematic literature search was to obtain studies with more positive selection criteria based on the check list presented in Appendix 2.2. Most of the studies identified as potentially relevant to the current study objectives were found to be irrelevant according to the selection criteria set for the identification of the relevant studies (Appendix 2.2). Only four studies were found meeting the selection criteria in this literature search and study identification.
Secondly, PubMed retrieved the highest proportion of irrelevant studies, and this could be due to publication bias or prejudice of the relevant studies. The references obtained from a computerised search and references by citation tracking were also used in this literature search. Data extraction for quality and methodological design assessment was done by one reviewer but was confirmed by an independent academic coordinator.
2.3.2. Literature review
2.3.2.1. Description of the studies
This review included three cohorts and one cross-sectional study. One of the three cohort studies (Riley et al., 2004) used a large sample size (n=873) and the other two (Croucher et al., 2003a; Croucher et al., 2003b) used relatively smaller sample size (n=52 and n=130). The larger study used both male and female volunteers in groups of smokers and ST users whereas the two smaller studies used female volunteers only. One of the two latter studies segregated ST users and ST and smoking tobacco users. The participants in the study conducted by Riley et al.
(2004) was followed up for 48 months to assess the impact of smoking and ST use
on the onset of oral pain without any specific advice such as cessation of tobacco use. The participants were followed up at 1-month, 6-month, and 48-month intervals. The participants in the other two cohort studies were followed up weekly for four weeks. The sample size of the cross-sectional study was small (n=58) and limited to female participants only, and they were followed up once only by telephone after completion of a paan tobacco cessation programme conducted by Bangladeshi Stop Tobacco Project (BSTP). The actual time of onset of oral pain symptoms was not identified. This study identified presence of oral pain symptoms after paan tobacco cessation or a cessation attempt.
None of the studies in this review described appropriate sample size using statistical power or addressed the respective target population although one study used a large sample size (Riley et al., 2004). It was very difficult to estimate the association of oral pain symptoms with the tobacco exposure. This was because tobacco cessation was poorly classified in all four studies. It is essential to have classification of both oral pain symptom and nature and type of tobacco exposure, even at a modest level such as two-fold increase in risk (Macfarlane et al., 2002).
None of the studies mentioned the risk ratio of this clinical symptom to estimate the level of exposure. Two longitudinal studies reported outcome of the study at the completion of a four-week follow up study (Croucher et al., 2003a; Croucher et al., 2003b), and Riley et al. (2004) presented the outcome (oral pain) without adjusting for confounders of ST use (Table 2.10).
The results of these studies (Croucher et al., 2003a; Croucher et al., 2003b; Riley et al., 2004) were not logical to conclude an association of oral pain with paan tobacco chewing and its cessation. The cross-sectional study (Pau et al., 2003)
was carried out following a paan tobacco cessation programme conducted by Croucher et al. (2003b) and the findings on the incidence of oral pain symptoms following paan tobacco cessation or cessation attempt without comparing the incidence of oral pain symptoms at study baseline before entry into the cessation programme. It clearly showed that the level of oral pain symptoms increased compared to the baseline data of Croucher et al. (2003b). However, the incidence of oral pain symptoms was higher in Croucher et al. (2003b) study (71.3%) compared to the study conducted by Pau et al. (2003) 69%. It can be described that there was not enough reported evidence that demonstrates the association between the onset and/or continuation of oral pain symptoms and causality of oral pain. Therefore, there is a clear need for prospective studies to determine the association of oral pain symptoms during use and following paan tobacco cessation or cessation attempt, and factors/ predictors associated with onset and/or continuation of oral pain (Table 2.7–Table 2.10 in Section 2.2.1).
2.3.2.2. Quality assessment
The quality assessment of the studies identified for the review demonstrated a lack of addressing target population and statistical power in data analyses. However other information on methodology and results satisfied the quality criteria (Section 2.1.4.2).
2.3.2.3. Methodological problems defining oral pain
The varied levels of incidence, nature and site/ source of oral pain symptoms amongst the ST users, most importantly paan tobacco chewers, were reported in a different way by the studies included in this review. These variation included site of pain: tooth, gum, oral mucosa, and nature of pain: pounding, crushing, and simply
oral pain. Such variations in the presentation of oral pain in such a small number of studies make the comparison between the studies as well as in the assessment of the association of oral pain with exposure extremely difficult.
2.3.2.4. Statistical analyses
It is essential to identify the confounding factors in the association of oral pain symptoms and exposure to tobacco cessation. None of the studies in this review attempted to control the effect of relevant confounding variables such as demographic, socioeconomic, psychological, and social capital in the onset of oral pain after paan tobacco cessation or effect of oral health problems in the onset of oral pain after paan tobacco cessation. One study adjusted for age sex, race, oral hygiene, dental care and level of education with a number of oral pain complaints during follow ups but not after stopping ST use (Riley et al., 2004). The adjustment for the confounding factors did not suggest an association between onset of oral pain and ST cessation. The remaining three studies did not show the effect of modifying the properties of relevant variables (Croucher et al., 2003a; Croucher et al., 2003b; Pau et al., 2003). Detailed, accurate information needs to be collected about potential confounding factors which then should be adjusted to estimate the concerted effect of the causative factors.
2.3.2.5. Summary of literature review
The summary findings of this review suggest that the aetiology, association of oral pain symptoms before and onset or continuation following paan tobacco cessation as well as the impact of confounding factors/ predictors are still not well understood by pain researchers. It would be helpful if this current research covered a broad range of factors including demographics, economic,
socio-cultural, psychological distress and social capital for data collection and analyses.
The association or correlation of these possible predictors can be achieved through a prospective longitudinal cohort study with regular uniform intervals of follow up.