Guided tissue regeneration with bioabsorbable and expanded polytetrafluoroethylene barrier membranes in the treatment of naturally occurring periodontal defects in dogs.

The purpose of the present study was to evaluate the healing events and compare the effects of guided tissue regeneration (GTR) using 3 different membranes: a weakly cross-linked bioabsorbable bovine collagen membrane; a strongly cross-linked bioabsorbable bovine collagen membrane; and a non-resorbable ePTFE membrane. Twenty adult female beagle dogs with naturally occurring periodontitis were subjected to periodontal probing and scaling. In both right and left mandibular quadrants, mucoperiosteal flaps were raised, and after debridement, the roots of experimental premolar teeth received apical reference notches. The following treatments were randomly assigned: 1) gingival flap curettage (GFC) + ePTFE membrane, control membrane; 2) GFC + slightly cross-linked collagen membrane, 1st test membrane; and 3) GFC + strongly cross-linked collagen membrane, 2nd test membrane. The flaps were sutured in such a manner that the membranes were completely covered. All dogs received a soft diet for a 2-week period and an oral hygiene program until time of sacrifice. The animals were randomly scheduled for sacrifice at 2, 4, 12, and 24 weeks. The ePTFE membranes still in place were removed at 6 weeks. The jaws were dissected and specimens prepared for descriptive histology and histomorphometry. The early resorption of the 1st test membrane was achieved at 4 weeks, and the 2nd test membrane at 12 weeks, both with normal inflammatory reaction. Measurements of epithelium, connective tissue attachment, new bone, and neocementum were compared within an animal (paired t test). Analyses were performed on data at 4, 12, and 24 weeks post-healing; little differences were found between these periods. Limited connective tissue repair was favored by the placement of all the membranes (about 20%), with no statistically significant difference. These findings indicate that bioabsorbable collagen membranes with different cross-linking and ePTFE barriers promote similar new attachment in GTR procedures on naturally occurring periodontal defects in dogs.

[Histological comparison of the effect of different implanted hydroxyapatites in the animal periodontium]. / Comparaison histologique de l'effet de diverses hydroxyapatites implantées dans le parodonte chez l'animal.

The effect of various types of synthetic hydroxyapatites (HA), coated or not with collagen or human plasmatic fibrin, has been studied after 3 month implantation either in freshly extracted alveoli in miniature pigs or in experimentally induced periodontal lesions in beagle dogs. The best histological results were observed in HA without organic coating. The Bioapatite consisting in crystals with a mean size of 146 nm +/- 47 nm were well integrated in the alveolar bone. Similar results were obtained with micro-sized hydroxyapatite, with a mean crystal size of 38 nm +/- 16 nm. But at 3 months, this HA type was still actively integrated in bone with osteogenesis. When these 2 types of HA were coated with collagen or plasmatic fibrin, they were less well incorporated in alveolar bone and were even able to develop localized and moderate inflammatory reactions. The main purpose of synthetic HA is to promote alveolar bone formation in periodontal lesions. For an improved tissular regeneration, it is recommended to use simultaneously in the future synthetic HA together with resorbable biocompatible synthetic membranes.

[Polynuclear neutrophils and periodontal diseases]. / Les polynucléaires neutrophiles et les maladies parodontales.

Periodontal diseases are bacteria associated diseases. The host response to these bacteria is critical. Non specific defense mechanisms are mainly mediated by the polymorphonuclear neutrophil which out numbers the others crevicular leucocytes. This paper reviews the beneficial and possible detrimental aspect of the neutrophil functions.

[Ultrastructural study of bone formation after bioapatite implantation in man]. / Etude ultrastructurale de l'induction osseuse après implantation de bioapatites chez l'homme.

Synthetic hydroxyapatite crystals (Bioapatite) were implanted in a vestibular longitudinal groove made in the alveolar bone, the periodontal membrane and the superficial root dentine of 2 human canines in the absence of periodontal disease. The healing process was followed in scanning as well as in transmission electron microscopy. At 6 months, the aggregate of synthetic hydroxyapatite crystals was surrounded by a fibrous connective tissue, devoid of inflammatory cells. Small apatite crystals, similar to the neighbouring bone crystals, were deposited between the Bioapatite crystals in the central area of the aggregates. These small crystals filled the intercrystalline spaces from the center to the periphery. The mineralization extended then directly in the collagen matrix (osteoid tissue) surrounding the synthetic apatite aggregates. Bone tissue was thus formed around the apatite implants. At 1 year, the thickness of the bone tissue formed around the synthetic hydroxyapatite aggregates was increased. It consisted of bone with a well-oriented collagen matrix, with osteocyte lacunae, osteocytes and interosteocytic canaliculi, with normal ultrastructure.

[Histological study of the biocompatibility of hydroxyapatite crystals in periodontal surgery]. / Etude histologique de la biocompatibilité des cristaux d'hydroxyapatite en chirurgie parodontale.

The purpose of this investigation was to analyse, after 6 years of clinical trials, the findings obtained from biopsies of infrabony defects in man treated by grafts of hydroxyapatite. Filled extraction sockets in miniature swine treated in a similar manner with apatite were also studied. Light microscope analysis showed bone neoformation around and in the neighbourhood of grafted apatite fragments with the presence of osteocytes, osteoblasts and a normal peripheral connective tissue without inflammatory reaction. These results demonstrate the biocompatibility of the implanted apatites accompanied by a normal fibrogenesis and a seeming osteogenesis.