PERIODONTAL REGENERATION IN CLASS-III FURCATION DEFECTS OF BEAGLE DOGS USING GUIDED TISSUE REGENERATIVE THERAPY WITH PLATELET-DERIVED GROWTH-FACTOR

WE DEVELOPED AN EFFECTIVE REGENERATIVE THERAPY, referred to as platele t-derived growth factor-BB (PDGF-BB)-modulated guided tissue regenerat ive (GTR) therapy (P-GTR), capable of achieving periodontal regenerati on of horizontal (Class III) furcation defects in the beagle dog. To d etermine its efficacy, repair and regeneration of horizontal furcation defects by P-GTR therapy and GTR therapy were compared. Chronically i nflamed horizontal furcation defects were created around the second (P 2) and fourth mandibular premolars (P4). After demineralization of the root surfaces with citric acid, the surfaces of left P2 and P4 were t reated with PDGF-BB (P-GTR therapy) and those of contralateral teeth w ere treated with vehicle only (GTR therapy). Periodontal membranes wer e placed and retained 0.5 mm above the cemento-enamel junction for bot h groups. The mucoperiosteal flap was sutured in a coronal position an d plaque control was achieved by daily irrigation with 2% chlorhexidin e gluconate. At 5, 8, and 11 weeks, two animals each were sacrificed b y perfusion with 2.5% glutaraldehyde through the carotid arteries, and the lesions were sliced mesio-distally, demineralized, dehydrated, an d embedded. Periodontal healing and regeneration after GTR and P-GTR t herapy were compared by histomorphometric as well as morphological ana lysis. Morphometric analysis for each time period was performed on the pooled samples of P2 and P4. Five weeks after both therapies, the les ions were filled primarily by tissue-free area, epithelium, inflamed t issue, and a small amount of newly formed fibrous connective tissue. A t 8 and 11 weeks after P-GTR therapy, there was a statistically greate r amount of bone and periodontal ligament formed in the lesions. The n ewly formed bone filled 80% of the lesion at 8 weeks and 87% at 11 wee ks with P-GTR therapy, compared to 14% of the lesion at 8 weeks and 60 % at 11 weeks with GTR therapy. Also, with P-GTR therapy there was les s epithelium and tissue-free area, less inflamed tissue, and less conn ective tissue. Morphological analysis indicated that the defects aroun d P2 revealed faster periodontal repair and regeneration than those ar ound P4. While the lesions around P2 were effectively regenerated by 1 1 weeks even after GTR therapy, those around P4 failed to regenerate. On the other hand, P-GTR therapy further promoted periodontal repair a nd regeneration so that at 8 weeks the lesions around P2 and P4 demons trated complete and nearly complete regeneration, respectively. Intere stingly P-GTR therapy stimulated formation of fibrous connective tissu e compared to GTR therapy in the early stages of repair, thereby filli ng the wound space with the tissue and stabilizing the wound. Later, t he fibrous connective tissue was found to be mineralized into bone or cementum depending on locations during remodeling. Consequently, P-GTR therapy effectively promoted periodontal regeneration with reproducib ility.