A combination of alleles 2 of interleukin (IL)-1A−889 and IL-1B+3954 is associated with lower gingival bleeding tendency in plaque-induced gingivitis in young adults of Arabic heritage

The aim of this study was to investigate the possible association of a distinct combination of polymorphisms in the interleukin (IL)-1 gene cluster on gingival bleeding tendency in young adult Arabs with plaque-induced gingivitis. Fifty otherwise healthy, nonsmoking volunteers, 19–28 years of age, participated. Clinical examinations included periodontal probing depth, bleeding on probing, and plaque index. Probing was done with a pressure-controlled probe at about 1.27 MPa. Examinations were repeated after 2 and 4 weeks. Polymorphisms in the IL-1 gene cluster were assessed using a reverse hybridization assay. A subject carrying alleles 2 at IL-1A−889 and IL-1B+3954 was designated genotype-positive. Twenty-six subjects were genotype-positive (52%). A repeated measures two-level (occasion, subject) model of the proportion of sites bleeding on probing, which was adjusted for gender, average plaque index, probing depth, and calculus, revealed a significantly lower proportion of bleeding sites in genotype-positive subjects (estimate −0.050, standard error 0.025, p < 0.05). Biserial correlations of bleeding proportions were high (0.71–0.78), confirming the steady-state plaque environment. It was concluded that inflammatory responses to dental plaque were considerably dampened in genotype-positive, nonsmoking young adults of Arabic heritage.