[Guided bone tissue regeneration--a clinical and histological pilot study].

The aim of the present investigation was to study whether a technique based on the principle of guided tissue regeneration is able to generate new osseous tissue around osseointegrated implants in humans. 14 titanium implants (IMZ) were inserted in 4 patients. The fixtures were modified by hydroxyapatite (HA) or titanium discs measuring 3 mm in height, which were screwed onto the implants. The modified implants were inserted in such way, that the discs were above the level of the alveolar bone. 3 modalities of treatment were performed. In group I HA granules were placed on the bone around the disc-implant-constructions and completely covered by an ePTFE membrane in order to create a space for ingrowth of bone-derived cells. In group II the membrane alone was placed and in the control group HA granules alone were used. After complete closure of the flap and 2-4 months of healing, the membranes including the generated tissue and the discs were removed and processed for histological examination. Clinical results demonstrated that in group I hard tissue had formed underneath the membrane, which strongly adhered to alveolar bone. Histological examination revealed new formation of trabecular bone. When the membrane alone was used, the created space was almost completely reduced during healing and no significant tissue formation had occurred. The greatest clinical problem was flap dehiscence over the membrane. In the control group the HA granules and discs were encapsulated in connective tissue. Limited by the small number of sites, the study indicates that a membrane technique according to the principle of guided tissue regeneration promotes new bone formation around osseointegrated implants in humans.