Effect of interleukin-1 gene polymorphisms on gingival inflammation assessed by bleeding on probing in a periodontal maintenance population

Bleeding on probing (BOP) is the most significant clinical parameter for th e assessment of periodontal inflammation. The aim of this prospective longi tudinal trial was to study the association between allelic variants of the IL-1 gene complex and gingival inflammation. Three hundred and twenty-three randomly selected periodontal maintenance patients (64.4% females) receive d a periodontal examination that included probing depth measurements and BO P at each of 4 supportive periodontal therapy (SPT) appointments. A brood s ample taken from each subject was analysed for the presence of specific all otypes of the IL-1 gene complex. Two polymorphisms located at +4845 bp in t he IL-1 alpha region and at +3954 bp in the IL-1 beta region were evaluated by a polymerase chain reaction method; 35.3% of the examined subjects were positive for specific combinations of allotypes of the IL-1 gene complex p reviously associated with an increased risk for severe periodontitis. The p opulation consisted of 90 current smokers and 94 former smokers. An analysi s of the association between the IL-1 genotype and BOP in the whole populat ion (including smokers) did not reach statistical significance because of t he overriding effect of smoking. A subset analysis of the 139 never smokers indicated that genotype positive patients had a significantly elevated cha nce of presenting an increase in the BOP% over a 4-appointment recall perio d (p=0.03) after correcting for oral hygiene. In fact, patients who were ge notype-negative had a 50% smaller chance of showing increases in BOP% durin g SPT. A further analysis explored the relationship between the genotype an d the level of BOP% at the most recent recall visit. A generalized linear m odel showed a statistically significant effect of the genotype status after correcting for plaque accumulation and prevalence of residual pockets(grea ter than or equal to 5 mm). Genotype-negative subjects had significantly lo wer BOP% (p=0.0097). It is concluded that the increased BOP prevalence and incidence observed in IL-1 genotype-positive subjects indicates that some i ndividuals have a genetically determined hyper-inflammatory response that i s expressed in the clinical response of the periodontal tissues.