Bacterial colonization of bioabsorbable barrier material and periodontal regeneration

The objective of the study was to evaluate bacterial colonization of the tooth-facing surface of bioabsorbable membranes and to determine its effect on the clinical outcome of membrane supported reconstructive periodontal surgery. Twenty systemically healthy subjects affected by chronic adult periodontitis were enrolled in the study. One non-furcation tooth site per patient, associated with an angular bony defect and a probing attachment loss of > 5 mm, was selected to be treated by means of a guided tissue regeneration procedure using a polyglicolactic membrane. Antibiotics (amoxicillin/clavulanate potassium 1 g per day) for 2 weeks were prescribed, in addition to the use of chlorhexidine for post-surgical plaque control. All patients were recalled once a week for 5 weeks for professional tooth cleaning. At 5 weeks sites with clinically exposed membranes underwent a second surgery to harvest residual barrier material which was analyzed by scanning electronic microscopic (SEM) for bacterial colonization. Sites with no membrane exposure at 5 weeks were allowed to heal without any other surgical intervention. Professional tooth cleaning and reinforcement of self-performed oral hygiene measures were given at 1 month intervals for the duration of the study. For each treated site the difference in probing attachment loss between baseline examination and a follow-up examination made 6 months after the second surgery was calculated. Gain of probing attachment was statistically (P < 0.001) greater in sites with no membrane exposure when compared to sites with partially exposed barrier material (4.2 +/- 0.5 vs. 3.3 +/- 0.6). The results of SEM analysis revealed that bacterial colonization was evident in all the microscopic fields of the exposed areas of the membranes. In the mid-part of the membranes 16 out of 39 microscopic fields (41%) demonstrated microbial colonization, while no bacteria-positive field was observed in the most apical portion of the membranes. Regression analysis indicated that gain in probing attachment level was negatively correlated to microbial colonization of the mid-part of the membranes. It was suggested the midportion of the tooth-facing surface of polyglicolactic membrane is a critical area for the healing process since its bacterial colonization was detrimental to the outcome of the GTR surgery.