IL1A and periodontitis: However, a number of previous studies did report a strong association between the unphased composite genotype (simultaneous carriage of the T allele at the IL-1A C[−889]T and IL-1B C[3954]T loci) and chronic periodontitis [9, 38–40], which is somewhat is in line with the current findings although haplotyping data cannot be directly compared with raw composite genotyping data.