Interleukin-1 composite polymorphism as a risk factor for chronic periodontitis: a review

The aetiology of chronic periodontitis is multi-factorial. Bacterial challenge can initiate the disease but the degree of extension and severity of disease are related to certain host factors, and are mediated mainly by inflammatory cytokines. The objective is to review current knowledge of the association between interleukin-1 polymorphisms and chronic periodontitis. The review focuses on the prevalence of and risk factors for the chronic form of periodontitis in order better to understand the backgrounds which led to the recognition of the genetic influences on the periodontal disease process. The commonly studied IL-1 composite polymorphism is discussed in relation to some clinical aspects of chronic periodontal disease.

"Medline" and "Pubmed" databases were searched electronically up to November 2008, with keywords: periodontitis, chronic periodontitis, Interleukin-1, composite genotype, polymorphisms. Articles in English that studied the effects of Interleukin-1a, Interleukin-1b or the composite genotype on periodontitis were selected by a single reviewer.

The prevalence of chronic periodontitis, studies of natural history of periodontitis, family studies and twin studies implied a genetic risk factor for chronic periodontitis. Linkage and association studies combined with cytokine genetics analyses further strengthened the evidence for a genetic risk. The most well studied cytokine polymorphism is for Interleukin-1, a potent inflammatory mediator which apparently can precipitate periodontal destruction, but results of the studies to assess the association of IL-1 gene polymorphisms with chronic periodontitis are conflicting.