The periodontal disease– systemic health–infectious disease axis in developing countries C YRIL O. E NWONWU &N ATHANAEL S ALAKO Periodontal disorders ⁄ diseases may have an inflammatory, genetic, developmental or metabolic origin (37, 72, 93). Periodontitis, resulting in destruction of the periodontal ligament and alveolar bone, is an outcome of the hostÕs exaggerated inflammatory immune response to infectious agents in periodontal biofilm ⁄ dental plaque (68, 93). Perio- dontitis is classified into subgroups based on clinical disease features such as the time of onset, the rate and the degree of periodontal tissue loss and the pattern of alveolar bone loss (112). The present report focuses on chronic periodontitis and aggressive periodontitis (78). The latter affects mainly young individuals and progresses at a faster rate than chronic periodontitis. Inflammation and alveolar bone loss are hallmarks of periodontitis (14, 17, 19, 41). Using the Community Periodontal Index (CPI) introduced by the World Health Organization (129), the prevalence and the severity of periodontal diseases have been evaluated in several population surveys (89, 90) (Fig. 1). The most prevalent disease score worldwide is CPI 2, which reflects poor oral hygiene status (5, 89, 90). The most severe disease score or sign of periodontitis (CPI 4) in adult populations varies globally from 10 to 20% (89). There are reports that periodontal diseases are more prevalent and of greater severity in re- source-poor countries than in developed countries (26, 30, 37, 93), but some researchers (5) caution against such generalizations. Racial differences in the inflammatory response to dental plaque may exist, with neutrophil activity in black people being more prominent than in white people (125). Aggressive periodontitis displays a familial pattern of occurrence and is much less pre- valent in Caucasian populations than in adolescents residing in or originating from Mediterranean and West African countries, including Arabs, Berbers and Africans (105). Similar findings have been reported for various ethnic groups within the same country (2, 105). In the Republic of Sudan, the prevalence rate of aggressive periodontitis in people of African ethnicity is 6% compared with 2.3% in Afro-Arabs in the same country (24). This report examines the complex relationships between periodontal diseases and sys- temic health within the context of key periodontal risk factors in developing countries. Risk factors for inflammatory periodontal diseases The risk factors for periodontal diseases are fairly well documented in several publications (73, 78, 93). They include genetics, tobacco and alcohol use, poor oral hygiene, age, sex, nutritional dysfunction (both undernutrition and overweight ⁄ obesity), infections (including HIV ⁄ AIDS, herpesviruses, or parasitic diseases such as malaria), poorly controlled diabetes mellitus 1 and 2, osteoporosis, physical inactivity and emotional stress, among others (33, 104, 105). Hypertension is considered a putative risk factor for periodontitis (37). Patients with mutations in the NALP3 gene, which controls the activity of the intracellular cysteine protease (caspase-1), suffer from systemic inflammatory diseases. Genetic vari- ants of interleukin-1 have important associations with the clinical presentation of several diseases, 64 Periodontology 2000, Vol. 60, 2012, 64–77 Printed in Singapore. All rights reserved Ó 2012 John Wiley & Sons A/S PERIODONTOLOGY 2000