Influence of interleukin-1 gene polymorphism on the outcome of supportive periodontal therapy explored by a multi-factorial periodontal risk assessment model (PRA).

Abstract

BACKGROUND: Multi-factorial risk models have been proposed to enhance the ability to predict risk for the progression of treated chronic periodontitis. AIMS: to study if the outcomes of supportive periodontal therapy (SPT) based on a multi-factorial periodontal risk assessment are influenced by IL-1 gene polymorphism (IP) status. MATERIAL AND METHODS: Information about the IP and smoking status, clinical periodontal conditions and age related bone level measurements were used to calculate a peridontal risk assessment model (PRA). The surface area of this diagram was calculated for 224 subjects who had participated in an SPT program over four years. Baseline and 4-year follow-up data were studied in relation to the IP status. RESULTS: Positive IP tests were obtained for 80/224 (35.7%) of the subjects. At baseline the mean PRA for the IP positive group was 79.9 units, which at year four had increased to 81.3 units (mean diff: 1.4 units, S.D.+/-16.5, p<0.45, 95% CI: 2.3 to 5.1). At baseline and year four the mean PRA for the IP negative group was 44.2 and 38.6 units, respectively. This difference was statistically significant (mean diff: 5.6, S.D.+/-16.1, p<0.001, 95% CI: 3.0 to 8.3). Independent t-tests confirmed that the IP status was significantly associated with a less favorable change in PRA over the four-year period (PRA difference: 7.04, t=3.01, p<0.003, 95% CI: 2.4 to 11.65). Bleeding on probing, and probing depth values alone did not differ between positive and negative IP status. Regression analysis demonstrated that the best-fit model for change in PRA included bleeding on probing at baseline, IP status, proportional alveolar bone loss in relation to the age, and gender. CONCLUSION: The PRA allowed the assessment of the outcomes of SPT therapy. Subjects with positive IP did not respond to individualized SPT as favorably as did IP negative subjects.