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

Background: Specific interleukin (IL)-1 gene polymorphisms are associated with an increased susceptibility to severe periodontitis, increased inflammation, and increased likelihood of tooth loss during the maintenance phase after conventional periodontal therapy. The aim of the present study was to evaluate the impact of genotype on the maintenance of gained clinical attachment obtained after guided tissue regeneration (GTR) surgical therapy in deep intrabony defects. Methods: Forty deep (greater than or equal to4 mm) interproximal angular bony defects with presurgical clinical attachment loss of >8 mm were treated by GTR using a non-absorbable expanded polytetrafluoroethylene (ePTFE) membrane. Membranes were surgically removed 4 to 6 weeks after surgery. Afterwards patients were placed on monthly recall for the first year and every 3 months for the following 3 years. At the 4-year re-evaluation, a IL-1 genetic susceptibility test was performed on all patients. Results: Fourteen (35% of the 40 patients) were genotype-positive (+). At baseline no statistically significant differences were found between patients with different genotypes in full mouth plaque score (FMPS), full mouth bleeding score (FMBS), clinical attachment lever (CAL), probing depth (PD), or gingival recession. At year 1 follow up visit, no statistically significant differences were noted between genotype + and genotype - patients in FMPS, FMBS, amount of CAL gain, decrease in PD, or increase in gingival recession. Sixteen patients had membrane exposure after the GTR procedures. In these 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 patients without membrane exposure. At the year 4 follow-up visit, no significant differences were found between genotype negative and positive patients in FMPS 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 gingival recession was noted. Genotype + patients showed significantly more CAL loss (P<0.002) and increase in PD (P<0.001) between the years 1 and 4 when compared 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 IL-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 when compared to oral hygiene matched genotype-negative patients.