Guided bone regeneration (GBR) is a procedure that uses barrier membranes to harness the regenerative capacity of the patient’s own bone to rebuild lost alveolar bone (jawbone), thereby enabling the placement of an implant (an artificial tooth root). Bone defects occur after tooth extractions (removal of a tooth without further surgical measures) and due to alveolar ridge atrophy (regression of the alveolar ridge bone) in the case of prolonged edentulism. When a tooth is removed, the bone in the area of the extraction wound recedes due to lack of functional loading. The alveolar ridge atrophies in both height and width by up to 50 percent. Since an implant (an artificial tooth root) must be completely surrounded by bone, the build-up of new bone may be required for implant placement. With this in mind, GBR has become an integral part of implant dentistry. The goal of any regenerative therapy is not only to repair lost structures, but to regenerate them. This means that lost alveolar bone should be rebuilt in a differentiated manner. Under the protection of a membrane as a mechanical barrier, the body’s own bone is able to develop its regenerative capacity and form new bone. If the shape and localization of the bone defect are favorable, membrane technology alone can be used. However, if the defect morphology (nature of the defect) is unfavorable, the membrane must be protected from collapsing by filler material. In this case, it serves not only as a barrier but also to stabilize the grafted bone or bone substitute. Without the membrane barrier, the bony defect would be filled with rapidly proliferating (growing) connective tissue instead of the slower-growing bone.
Indications (areas of application)
- For bone augmentation to allow implant placement (placement of an artificial tooth root).
- To prevent connective tissue growth instead of bony regeneration.
- For local stabilization of inserted bone or bone substitute material by a membrane.
- For augmentation in immediate implantation (bone augmentation when placing an implant immediately after tooth extraction).
Contraindications
- Lack of plaque control by the patient.
- Heavy nicotine use
- Poorly controlled diabetes (diabetes)
- Severe general diseases that adversely affect the ability to treat.
- Condition after radiatio (radiotherapy).
- Periodontitis (inflammation of the tooth bed) with residual pockets after therapy of more than 5.5 mm
Before surgery
A prerequisite for the success of regenerative therapy is that the patient adopts adequate oral hygiene prior to treatment. Only then is there a chance of long-term retention of the implant made possible by bone regeneration. For diagnostic purposes, X-rays are taken during the planning phase, and in special cases digital volume tomography is also used. Mucosal thickness measurements and analysis of jaw models help to find the optimal implant position, estimate the extent of the bone defect and decide on a suitable procedure. If the membrane technique is combined with the insertion of autogenous (body’s own) bone, this must be harvested and prepared from a suitable site – e.g. the chin region or the retromolar space (behind the last molars) – prior to grafting. As a rule, the surgical procedure is shielded by administration of an antibiotic (two hours of preoperative amoxicillin). Allogenic (foreign) bone material can also be used. It comes from the long tubular bones of multiorgan donors. The risk of pathogen transmission and immunological reaction is reduced by the DFDBA (Demineralized freeze dried bone allograft) procedure, which combines demineralization of the implant with freeze drying. However, it cannot be completely excluded. Xenogenic (from animal tissue) bone is derived from cattle (Bio-Oss). Deproteinization (removal of protein) removes the organic component and thus reduces the risk of transfer and allergization, but it cannot be completely ruled out here either.The remaining inorganic portion is incorporated into newly forming bone. The immature bone tissue is protected from connective tissue ingrowth by the membrane technique (Bio-Guide). Alloplastic bone substitutes (AACs) are synthetically (artificially) produced materials made of calcium carbonate, tricalcium phosphate, hydroxyapatite, bioglass, or calcium-coated polymers (methacrylates: plastics) that are biocompatible (biologically well tolerated). Osteoblasts (bone-forming cells) can colonize the synthetic surfaces. Membrane technology prevents ingrowth of connective tissue cells.
The procedures
GBR must be combined with the formation of a mucoperiosteal flap (mucosa-bone flap): Surgical detachment of the flap from the bony support allows insertion of the membrane and, if necessary, the bone or bone graft substitute material to be grafted and, after extension of the flap, complete coverage by periosteal slitting (to stretch the periosteum). Simultaneous implant placement (placing an implant at the same time) is possible. If primary stability of the implant cannot be achieved, a two-phase procedure is required: implant placement is performed after three to four months in a second procedure after bone regeneration. I. Non-resorbable barrier membrane
Filter membranes or polytetrafluoroethylene films (e-PTFE, GoreTex; n-PTFE, TefGen) or titanium (Frios Boneshield) delineate a cavity facing the bone and are positioned to completely cover it, with some overlap of the membrane at the bone edges. The membrane is secured from slipping by pins, fine nails or screws (made of titanium) or by suturing. The detached mucoperiosteal flap (flap of mucosa and periosteum) must be reduced (brought back to an approximate normal position) and sutured so that the membrane is completely covered. This requires extension of the mucoperiosteal flap through a periosteal slit. The disadvantage of the technique with non-absorbable membranes is the fact that the membrane must be removed again in a second surgical procedure after approximately four to six weeks. II. Resorbable barrier membrane
Resorbable membranes made of polylactides or of compomers (polylactides/polyglycolides) or uncrosslinked collagen are used in the same way as the materials mentioned under I., but have the advantage that they are gradually degraded by the organism and thus do not require a second surgical procedure for removal. III. Liquid barrier membrane
A liquid polyethylene glycol-based hydrogel (MembraGel) is applied to the bone graft or bone graft substitute overlapping to the bone edges of the defect and solidifies 20 to 50 seconds after application. Wound closure is performed as in I. and II. above the stabilized material.
After surgery
- Immediately after surgery, the patient is given instructions on how to care for the surgical wound. Chlorhexidine-based disinfectant rinses are usually prescribed to reduce the postoperative (“after surgery”) risk of infection, and mechanical cleaning is temporarily prohibited.
- After seven to ten days, the sutures are removed, that is, the stitches are removed.
- The healing phase of the implant is six to nine months, depending on the augmentation material used (material for bone augmentation). Exposure of the implant is followed by the provision of the superstructure (denture on the implant).
