Modulation of clinical expression of plaque-induced gingivitis: interleukin-1 gene cluster polymorphisms

The purpose of the present study was to determine the association of interleukin-1 (IL-1) gene polymorphisms with clinical parameters of gingivitis in a large experimental gingivitis trial and with each of two subgroups, high responders (HR) and low responders (LR), with distinct susceptibility to gingivitis.

Ninety-six systemically and periodontally healthy non-smokers, 46 males (mean age: 23.9+/-1.7) and 50 females (mean age: 23.3+/-1.6) were included in a randomized, split-mouth, localized 21-day experimental gingivitis trial. Plaque index (PI), gingival index (GI), gingival crevicular fluid volume (GCF), and angulated bleeding score (AngBS) were recorded. Two subgroups were defined from the total study population (HR, LR) characterized by substantially different severity of gingival inflammation despite similar plaque accumulation rate. The study population was typed for interleukin-1 alpha (IL-1A+4845), interleukin-1 beta (IL-1B+3953, IL-1B-511), and IL-1 receptor antagonist (IL-1RN, intron 2 variable number tandem repeats) gene polymorphisms. Gene variants were analyzed by amplifying the polymorphic region using polymerase chain reaction, followed by restriction-enzyme digestion and agarose gel electrophoresis.

Neither IL-1A+4845, IL-1B+3953, or the combined (IL-1A+4845 x 2 - IL-1B+3953 x 2) genotype was associated with clinical parameters in the overall population. IL-1RN was significantly associated with test quadrant PI (P= 0.046), GCF (P= 0.05), and GI (P= 0.018). The genotype distribution in HR and LR subjects was significantly different for IL-1RN (P= 0.045) and for IL-1B-511 (P= 0.023).

The results of the present study suggest an association between IL-1RN polymorphism and subject-based clinical behavior of the gingiva in response to de novo plaque accumulation, as well as a possible association between IL-1B-511 polymorphism and gingivitis susceptibility.