The influence of membrane exposure on the outcomes of guided tissue regeneration: clinical and microbiological aspects.

The aim of the present study was to evaluate the influence of membrane exposure on guided tissue regeneration (GTR). Thirty patients with 2-wall or 3-wall intraosseous defects were treated with GTR. Periodontal index, gingival index, bleeding on probing, probing depth, clinical attachment level and recession were assessed at the baseline examination, as well as immediately prior to and six months after GTR. The numbers of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans on the retrieved expanded polytetrafluoroethylene (e-PTFE) membranes were assessed using polymerase chain reaction. The results showed that 26.3% of the membrane exposure sites had zero attachment gain. The membrane exposure sites tended to achieve a smaller clinical attachment gain and had significantly greater marginal tissue recession ( p = 0.006). In addition, the exposed membranes harbored significantly more A. actinomycetemcomitans than the non-exposed membranes (p = 0.029). In conclusion, membrane exposure resulted in a poor GTR outcome. The amount of A. actinomycetemcomitans on the exposed membrane may be a major contributing factor to the outcome of GTR.