Global InequalIty In PerIodontal HealtH and dIsease

is characterized by bacteria-induced inflammatory destruction of tooth-supporting tissues and alveolar bone, and it remains a major cause of tooth loss in adults in both developed and developing countries (Pihlström et al., 2005). Disease severity is dependent upon a dynamic equilibrium of bacteria-host interactions which are significantly influenced by various genetic, epigenetic, and environmental factors in a susceptible host (Page et al., 1997; Jin, 2008; Kornman, 2008). A great range of risk factors has been studied, including individual determinants, social and behavioral factors, systemic factors, genetic factors, tooth factors, and microbial risk factors (Page et al., 1997; Nunn, 2003; Heitz-Mayfield and Lang, 2010; Shum et al., 2010). The impact of periodontal diseases on an affected individual is increasingly apparent and becomes more significant with progression of the diseases, beginning with gingival recession and associated dentin hypersensitivity at an early stage. The disease then progresses toward tooth mobility, pathological migration, and, eventually, tooth loss, thereby affecting chewing and speech functions, aesthetics, psychological aspects, and quality of life, as well as increasing financial burden (Jin, 2009) (Fig. 1). It should be emphasized that periodontal diseases not only significantly affect oral health, but are also associated with systemic disorders such as cardiovascular diseases, diabetes, pre-term birth, and aspiration pneumonia (Jin et al., 2003; Pihlström et al., 2005; Williams et al., 2008; Armitage and Robertson, 2009; Tonetti, 2009; Lu and Jin, 2010; Li et al., 2011).