Guided bone and tissue regeneration
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|Guided bone and tissue regeneration|
Guided bone regeneration or GBR, and guided tissue regeneration or GTR are dental surgical procedures that use barrier membranes to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics or prosthetic restoration.
GBR is similar to guided tissue regeneration (GTR) but is focused on development of hard tissues in addition to the soft tissues of the periodontal attachment. At present, guided bone regeneration is predominantly applied in the oral cavity to support new hard tissue growth on an alveolar ridge to allow stable placement of dental implants. Bone grafting used in conjunction with sound surgical technique, GBR is a reliable and validated procedure.
Use of barrier membranes to direct bone regeneration was first described in the context of orthopaedic research 1959. The theoretical principles basic to guided tissue regeneration were developed by Melcher in 1976, who outlined the necessity of excluding unwanted cell lines from healing sites to allow growth of desired tissues. Based on positive clinical results of regeneration in periodontology research in the 1980s, research began to focus on the potential for re-building alveolar bone defects using guided bone regeneration. The theory of Guided tissue regeneration has been challenged in dentistry. Most frequently by Hessam Nowzari and Jorgen Slots.
Four stages are used to successfully regenerate bone and other tissues, abbreviated with the acronym PASS:
- Primary closure of the wound to promote undisturbed and uninterrupted healing
- Angiogenesis to provide necessary blood supply and undifferentiated mesenchymal cells
- Space creation and maintenance to facilitate space for bone in-growth
- Stability of the wound to induce blood clot formation and allow uneventful healing
The first application of barrier membranes in the mouth occurred in 1982 in the context of regeneration of periodontal tissues via GTR, as an alternative to resective surgical procedures to reduce pocket depths.
Several surgical techniques have been proposed regarding the tri-dimensional bone reconstruction of the severely resorbed maxilla, using different types of bone substitutes that have regenerative, osseoinductive or osseoconductive properties. In cases where augmentation materials used are autografts or allografts the bone density is quite low and resorption of the grafted site in these cases can reach up to 30% of original volume. For higher predictability, nonresorbable titanium-reinforced d-polytetrafluoroethylene (d-PTFE) membranes—as a barrier against the migration of epithelial cells within the grafted site—are recommended. In patients with systemic problems interdisciplinary collaboration is indicated to adjust therapy background so that it does not adversely affect implanto-prosthetic treatment.
There are several uses of bone regeneration:
- building up bone around implants placed in tooth sockets after tooth extraction
- socket preservation for future implantation of false teeth or prosthetics
- filling of bone defects after removing the root of a tooth, cystectomy or the removal of impacted teeth
- repairing bone defects after the reopening of a wound
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