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dental caries. By influencing these factors directly or through some intermediates, it is possible to change the route of caries process. From this perspective, it can be stated that dental caries, is a result of complex chains of events which can be proximal or distal. Proximal factors acts directly or almost directly in the causal chain of caries process, while distal factors act indirectly and via several intermediary causes (Petersen 2005a). Dentists and Preventive Oral Health Care 209 Determinants of dental caries can be seen from three different perspectives: tooth level, individual level, and population level. At each of these levels there are some factors which may influence the equilibrium between demineralisation and remineralisation constantly taking place at tooth surface. At tooth level, factors which affect pH fluctuations, such as thickness of microbial deposits, amount and composition of saliva, the diet, and the concentration of fluoride ion in oral fluids will determine the likelihood of mineral loss and rate at which caries occurs. At the individual level, oral health behaviour like frequency of removing dental plaque by tooth brushing or dental floss, frequency of sugar use and fluoride usage will influence factors mentioned in tooth level. At the population level accordingly factors such as socio-economic status, access to oral heath care, and level of education may have controlling effect on the factors in individual level (Baelum and Fejerscov 2003). A considerable amount of studies over the past decades have shown the linkage between oral health and socio-behavioural factors (Locker 2000, Petersen 2005a, Antunes et al. 2006). Accordingly major oral diseases are primarily considered as behavioural diseases (Petersen 2005a). Dental caries has been found to be more prevalent among children of families in lower social class than those in higher social class (Gratrix and Holloway 1994, Watt and Sheiham 1999), in deprived than affluent families (Prendergast et al. 1997, Antunes et al. 2002, Willems et al. 2005) and also in children with low level of parent’s education and family income (Petersen 1992). Miura et al. (1997), analyzing data on oral health and socioeconomic factors of 44 developing countries, found a statistically significant correlation between dental caries of 12-year-olds and socioeconomic factors such as population employed in the service sector, urban population, life expectancy, and school attendance rate. Different dental caries risk has been shown across cultures and ethnic groups even inside a same population (Sundby and Petersen 2003). Tooth loss as an outcome of oral diseases has been shown to have psychosocial causes (Burt et al. 1990). Negative health behaviour such as smoking and infrequent toothbrushing, low income and low level of education (Gilbert et al. 1993, Eklund and Burt 1994) and heavy drinking (Slade et al. 1997, Kressin et al. 2003, Klein et al. 2004, Kida et al. 2006) have been reported to associate with tooth loss. Therefore, to control oral diseases adopting healthy habits including oral self-care (Löe 2000, Axelsson et al. 2002) and regular dental check-ups (Ismail et al. 1994, Richards and Ameen, 2002) are essential. Furthermore, good oral health behaviour will contribute to general health promotion since oral diseases have common risk factors with some other chronic diseases (Sheiham and Watt 2000, Petersen 2003a). Smoking, as one of the greatest threats to global health, has been considered as a major cause of many oral diseases and unfavourable oral conditions (Reibel 2003) contributing significantly to the global burden of oral disease (Petersen 2003b). The adverse effects of tobacco on oral health range from some harmless to life-threatening conditions such as staining and discoloration of teeth, mouth odor, bad taste and smell, negative effect on wound healing, periodontal disease, and success of dental implants, potentially malignant lesions and oral cancer, and possibly caries and