Guided Bone Regeneration
GUIDED BONE REGENERATION stands for a set of procedures which enable reconstruction of the bone structure and functional restoration of the lost paradontium tissue and the alveolar process bone. In this way we eliminate whatever anatomical limitations are diagnosed to create e.g. the proper base environment for implants and further reconstructive denture.
In the event the volume of the bone is insufficient to root the implant, we reconstruct it with transplants of the Patient’s own bone or bone building preparations.
The bone regeneration techniques will vary depending on the degree of bone atrophy on the implant site. If the bone deficit is minor and the attainment of primary implant stabilisation is unlikely, the implantation is performed in combination with a simultaneous GBR procedure. If the atrophy is more advanced, bone regeneration comes first and the implantation is deferred for 6-9 months. The natural conditions for implantation are particularly challenging in the distal section of the jaw. Here, tooth loss triggers bone resorption and advancing pneumatisation of the maxillary sinus. Moreover, low bone density in the area does not guerantee sufficient stabilisation of the implant.
The surgical procedures employed in the area of the mandible include horizontal bone augmentation combined with a sinus lift performed through the proximal sinus wall, or the so-called open sinus lift.
The original bone size and the possibility of attaining primary stabilisation determine the decision whether to place the implant simultaneously or defer it in time. The less traumatic method, though used only in cases of minor bone atrophy, consists in performing the so-called closed sinus lift from the alveolar process, combined with implant insertion.
Search for new methods of regenerating the maxilla and mandible bone continues. The procedure gradually gaining in popularity consists in stretching the bone /distraction osteogenesis/ where new bone tissue is formed at the incision point /corticotomy/ in effect of controlled relocation of the resulting bone fragments under the impact of external forces or the so-called distractors.
Since proper osseointegration of the implant is primarily dependent on sufficient volume of the bone tissue, the dynamic development of the regenerative techniques has vastly broadened the range of indications for implantoprosthetic treatment, giving the patients much more physical and mental comfort than the previously used conventional prosthetic treatment methods.
In the past, before methods of surgical preparation of the oral cavity to prosthetic treatment were developed and dental implantology evolved, the doctors had been limited to using the existing prosthetic base, irrespective of the degree of bone atrophy. Frequently, the treatment results remained unsatisfactory for both the doctor and the patient. The progress in stomatology made in recent years has borne fruit of the developed surgical methods which improve the condition of the bone base before the planned implantoprosthetic treatment is undertaken. The breakthrough in the area came with the development of the production technologies and clinical application of barrier membranes. This particular treatment method has been called guided tissue regeneration or GTR. The barrier membrane takes over the function of the periodontium separating the creeping connective tissue of the mucous membrane from the regenerating bone tissue. At the early stage in the healing process the membrane protects the clot by proper distribution of the mechanical forces affecting the soft tissue flap. Today, when repairing bone defects, barrier membranes (resorbable and non-resorbable) are complemented with various reconstructive materials or the so-called biomaterials. The process of planned and directed bone formation on the atrophy site is called guided bone regeneration - GBR.
Biomaterials are grouped into: autogenic /bone harvested from the patient’s own body/, allogeneic /dried and frozen decalcified bone – DFDB, frozen dried bone – FDB/, heterogenic /e.g. lyophylised bovine bone – Bio-Oss/, and alloplastic /natural and synthetic ceramics, bioglass, corundum-based preparations, polymers/. All share the feature of bioactivity expressed in bone formation – osteogenesis, induction of bone formation – osteoinduction, or creation of the environment conducive to bone regeneration – osteoconduction. The osteogenetic properties can only be found in the autogenic bone, which thus continues to be the best reconstructive material causing no biological problems. Unfortunately, oral bone harvesting frequently does not provide the material in sufficient volume, whereas harvesting bone graft from more distant locations burdens the patient far more than the operation proper. Therefore, indications to take up this treatment are limited to extreme cases of the mandible and maxilla atrophy. For this reason, the modern implantology is searching for bone substitutes that will meet the prerequisites of biocompatibility, prove osteoconductive and resorptive in such areas where resorption of the substitute and its replacement by own bone is necessary because of tissue transformation.