Interleukin-1 gene polymorphisms and long-term stability following guided tissue regeneration therapy

Background: Specific interleukin (IL)-1 gene polymorphisms are associated w ith an increased susceptibility to severe periodontitis, increased inflamma tion, and increased likelihood of tooth loss during the maintenance phase a fter conventional periodontal therapy. The aim of the present study was to evaluate the impact of genotype on the maintenance of gained clinical attac hment obtained after guided tissue regeneration (GTR) surgical therapy in d eep intrabony defects. Methods: Forty deep (greater than or equal to4 mm) interproximal angular bo ny defects with presurgical clinical attachment loss of >8 mm were treated by GTR using a non-absorbable expanded polytetrafluoroethylene (ePTFE) memb rane. Membranes were surgically removed 4 to 6 weeks after surgery. Afterwa rds patients were placed on monthly recall for the first year and every 3 m onths for the following 3 years. At the 4-year re-evaluation, a IL-1 geneti c susceptibility test was performed on all patients. Results: Fourteen (35% of the 40 patients) were genotype-positive (+). At b aseline no statistically significant differences were found between patient s with different genotypes in full mouth plaque score (FMPS), full mouth bl eeding score (FMBS), clinical attachment lever (CAL), probing depth (PD), o r gingival recession. At year 1 follow up visit, no statistically significa nt differences were noted between genotype + and genotype - patients in FMP S, FMBS, amount of CAL gain, decrease in PD, or increase in gingival recess ion. Sixteen patients had membrane exposure after the GTR procedures. In th ese patients, the amount of CAL gain (P <0.001) and PD reduction (P <0.01) 1 year after surgery was significantly lower than those observed in patient s without membrane exposure. At the year 4 follow-up visit, no significant differences were found between genotype negative and positive patients in F MPS or FMBS and both groups showed a significant loss in CAL (P<0.001) and increase in PD (P<0.001) when compared to year 1 visit. No change in gingiv al recession was noted. Genotype + patients showed significantly more CAL l oss (P<0.002) and increase in PD (P<0.001) between the years 1 and 4 when c ompared to genotype - patients. A significant association between genotype and stability of the regenerated attachment was also demonstrated. Conclusions: The results of this study demonstrate that genotype expression did not effect GTR treatment response at 1 year, but had a great impact on long-term stability (year 4). In a 3-year period, patients with positive I L-1 genotype lost about 50% of the first year gained CAL and were about 10 times more likely of experiencing greater than or equal to2 mm CAL loss whe n compared to oral hygiene matched genotype-negative patients.