Guided tissue regeneration (synonyms: guided tissue regeneration, GTR, regenerative therapy) is used to describe procedures that aim to restore periodontal (tooth-supporting) structures lost in intrabony (“inside the bone”) defects that have been degraded by inflammatory processes (chronic inflammation) that have occurred previously. In the course of periodontitis (inflammation of the periodontium), it is not only the gingiva that recedes. The underlying alveolar bone (bony compartments in which the teeth are anchored) and the desmodont (connective tissue apparatus that forms the connection between the tooth and the bone) are also degraded. As this bony and connective tissue supporting tissue is lost, tooth loosening occurs, eventually leading to the loss of the affected tooth. Periodontal treatment therefore aims first of all to halt further degradation of alveolar bone and desmodont and, in addition, ideally to generate (produce) new formation of the lost tissues. In principle, after surgical periodontal treatment without controlled tissue regeneration, only reparative wound healing takes place – which means that the newly formed tissue does not correspond to the structure of the lost tissue. The main cause of reparation is the high rate at which the marginal epithelium covering the gingival pocket towards the tooth is newly formed. This epithelial growth competes with and precedes the new formation of alveolar bone and desmodont. The result is a long, deep fringing epithelium that separates the bone from the root surface and a periodontal pocket that is free of inflammation but only slightly less deep than before surgery. Periodontal treatment with guided tissue regeneration attempts to use barriers to prevent the rapidly proliferating (growing) marginal epithelium from growing deep, thus providing the periodontal tissues with the time necessary for new desmodontal fibers to form connections with the root surface and for new alveolar bone to fill the defect.
Indications (areas of application)
Thus, the goal of any regenerative therapy is not only to repair lost structures of the periodontium, but to regenerate them, i.e., to restore the lost tissue structures – alveolar bone and desmodont – in a differentiated manner. The newly formed bone substance is clinically measurable. The indications are limited to:
- Bone loss in mandibular furcations (root bifurcations of the lower molars) with furcation grade II (more than 3 mm deep in the horizontal direction).
- Mandibular furcation infestation grade III (from the cheek side to the tongue side continuous bone loss in the mandible), provided that the furcation is exposed a maximum of 3 mm in the vertical direction
- Bone loss in buccal maxillary furcations (to the cheek pointing root bifurcations of the upper molars) with furcation infestation grade II.
- Three-walled bone pockets
- Two-walled bone pockets
- Single-walled bone pockets
Contraindications
- Horizontal bone loss (without bone pockets).
- Lack of plaque control by the patient
- Market red teeth with inadequate endodontic (root canal) treatment.
- Teeth with severe loosening without stabilization
- Smoking
- Poorly controlled diabetes mellitus (diabetes).
- Other diseases that have an unfavorable effect on the ability to treat.
- Intraoperative damage to the mucoperiosteal flapBefore the procedure.
Before the procedure
An indispensable prerequisite for the planning and success of regenerative therapies is that the patient has adopted techniques for optimal oral hygiene prior to treatment. This includes not only the appropriate toothbrushing technique with the toothbrush alone, but also consistent care of the interdental spaces (spaces between the teeth) with aids for daily oral hygiene such as interdental brushes. Only in this way is there a chance of maintaining the treatment result achieved by regenerative therapy in the long term.GTR will be preceded by professional dental cleaning (PZR) and conventional (non-surgical) periodontal treatment in terms of closed curettage to remove biofilm (plaque, bacterial plaque), calculus and calculus (tartar below the gingival margin) to a large extent, thus achieving a reduction of periodontopathogenic microorganisms (germs causing gingivitis) and a relative absence of inflammation of the gingiva in advance.
The procedures
GTR is a periodontal surgery procedure that must be combined with flap surgery (open surgical periodontal treatment). This is because only by surgically detaching the gingiva can all subgingival (below the gingival margin) root surfaces be exposed and subjected to scaling and root planning (cleaned and smoothed) under visual control. In the course of the flap operation, e.g. following the cleaning of the root surfaces, selected areas are further treated with the aim of preventing the proliferation of the marginal epithelium into the depth of the gingival pocket and thus giving the actual structures of the periodontium (periodontium) time to form again. I. Non-absorbable barrier membranes
Filter membranes or polytetrafluoroethylene (Teflon) films are positioned over the periodontal bone intrusion so that they are flush with the tooth neck, completely covering the defect and overlapping the bone edge by approximately 3 mm. The detached mucoperiosteal flap (flap of mucosa and underlying periosteum) must be repositioned (brought into the correct position) and sutured so that the membrane is completely covered. This may require 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 about four to six weeks. II. Resorbable barrier membranes
Resorbable membranes made of polylactides or of compomers (polylactides / polyglycolides) 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 a second surgical procedure for removal is not necessary. III. enamel matrix proteins (Straumann Emdogain)
In the course of natural tooth development, acellular root cementum (in which the desmodontal fibers are inserted) is formed when cells of the tooth sac come into contact with enamel matrix. Following this principle, enamel matrix proteins (synonym: amelogenins) applied intraoperatively (introduced during surgery) trigger the regeneration of periodontal tissues by initiating (triggering) the formation of new root cementum. They form an insoluble matrix that remains on the root surface for up to four weeks and enables its colonization with cementum formers during this period. Filling of the bone defect takes place in the following months. Emdogain is applied in gel form to the root surface, which has been cleaned and conditioned (pre-treated) with 24% EDTA (ethylenediaminetetraacetic acid). The mucoperiosteal flap, which may have been extended by periosteal slitting, is then sutured as closely as possible to the tooth necks. Enamel matrix proteins are taken from tooth germs of animal origin, but do not elicit an immune response in humans and are considered pharmacologically safe. The low immunogenic potential of enamel matrix protein is due to its amino acid sequence, which has not undergone any changes during its evolutionary history. IV. Bone
IV.1 Autogenous bone grafting
The patient’s own bone material is harvested to fill the periodontal bone defects. Intraoral donor sites (in the mouth) may be edentulous jaw sections or the tuber maxillae (bone region behind the last upper molars). IV.2 Allogenic bone implant
Allogeneic bone implants are derived 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. The additional use of a membrane leads to a small, non-significant improvement in regeneration.An alternative to the membrane is the stabilization of the bone implant material with a gel made of polyethylene glycol (MembraGel), which is applied in liquid form and solidifies quickly. IV.3 Xenogenic bone implant
Xenogenic bone implant is derived from bovine bone (Bio-Oss). Deproteinization (removal of protein) removes the organic component and thus reduces the risk of transfer and allergization, but neither can be completely ruled out. The remaining inorganic component is incorporated into the newly forming bone. The immature bone tissue is protected from connective tissue ingrowth by a resorbable collagen membrane (Bio-Guide). V. Alloplastic bone substitutes
Alloplastic bone substitutes (AOBs) are synthetically 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 can prevent ingrowth of connective tissue cells.
After surgery
Immediately after surgery, the patient receives instructions on how to care for the surgical wound. Chlorhexidine-based disinfectant rinses are usually prescribed to reduce the risk of postoperative infection, and mechanical cleaning is temporarily prohibited. Sutures are removed after seven to ten days. Close recalls (follow-up appointments), combined with professional dental cleaning (PZR) and refresher training on oral hygiene techniques, contribute significantly to stabilizing the achieved treatment result. In contrast, the risk of disease recurrence (recurrence of the disease) is very high if the patient lacks motivation for consistent oral hygiene and adherence to recalls.
Potential complications
- Postoperative membrane infection
- Intraoperative damage to the mucoperiosteal flap.
