Prior to the 1980s, periodontal tissue regeneration obtained through periodontal treatment was very limited. in the late 1970s and early 1980s, a series of studies, represented by Nyman, Lindhe, Karrin9 and Gottlow, demonstrated that only periodontal membrane cells had the potential for periodontal tissue regeneration during periodontal tissue healing. However, during the postoperative healing process, the gingival epithelium grew fastest, crawling from the trabecular margin to the tooth surface and growing along the root surface towards the root within a few days, forming a long bonded epithelium that prevented the formation of new attachments. Subsequently, the authors proposed a series of surgical methods to promote the coronal growth of periodontal cells to form new attachments, and for more than 20 years, research in this area has been flourishing, bringing periodontal treatment into a new era. Liang Zhaozhong, Department of Special Oral Surgery, Urumqi Stomatological Hospital
Guided tissue regeneration (GTR) is a periodontal procedure that uses membranous material as a barrier to block the growth of gingival epithelium along the root surface during the healing process, to block the contact between gingival connective tissue and the root surface, and to provide a certain space to guide periodontal membrane cells with the ability to form new attachments to preferentially occupy the root surface, thus forming a new attachment on the root surface that was already exposed to the This leads to the formation of new bone on the root surface, which was already exposed in the periodontal pocket, and the burial of periodontal membrane fibers to form a new attach-ment healing.
The membrane material used for GTR after the GTFl procedure A. Placement B healing is divided into two categories: non-resorbable and absorbable membranes.
Non-absorbable membranes do not degrade or absorb in the body and require a second surgery to remove the membrane 4-6 weeks after surgery. The main component of the product is polytetrafluoroethylene (PTFE), known as Gote-Tex, which has a stable molecular structure and does not cause any tissue reaction, and is the first and most clinically used membrane material with positive clinical results. Absorbable membranes can degrade and be absorbed during the surgical healing process and do not require a second surgery to remove. These membranes include collagen membranes, polylactic acid membranes, polyglycolic acid and polylactic acid and trimethylene carbonate copolymer membranes, etc. Foreign commercialized products of collagen membranes include BioGuide, BioMend, etc. Polylactic acid products include Atrisorb, etc. Collagen membranes extracted from cow tendons are also used in China.
Recently, the use of artificial skin or autologous periosteal grafts has also been studied, but the clinical effect needs to be confirmed by more long-term f clinical control studies.
(A) Indications
1・Narrow and deep intraosseous pockets are indications for GTR, while wide pockets are less effective. Three walls of bone pocket because of the rich source of periodontal membrane cells, and easy to provide space for the growth of periodontal membrane cells, so the best results, narrow and deep two-walled bone pocket is also a better indication.
2・Root bifurcation lesion of degree II is an indication, but there must be enough gingival height to cover the area completely. In particular, II degree root bifurcation lesions of the mandibular teeth have good results. Some people have reported some efficacy in the early stages of Ⅲ degree root bifurcation lesions, but the results are uncertain.
3. Gingival recession involving only the labial surface, with no alveolar bone resorption on the adjacent surface and an intact gingival papilla.
If the above indications are met, GTR can be performed only after the periodontal infection is controlled through basic periodontal treatment including oral hygiene instruction, scaling, root planing, and regulating Qian. If the patient is a smoker, it will affect the postoperative healing and the surgical result will be poor.
(B) Surgical method
1・Anesthesia, disinfection, local anesthesia, pay attention to the gingival margin and interdental papillae do not over-infiltrate anesthesia, in order to reduce the local ischemia of marginal tissue. Before surgery, the patient should rinse with 0.12% chlorhexidine for 1 minute. The perioral area was routinely disinfected.
2. The design of the incision should be designed to preserve as much gingival tissue as possible, and the location of the internal oblique incision should be at the gingival margin, with a preserved gingival papilla incision if necessary. In addition, the horizontal incision should be extended 1 to 2 teeth in the proximal and distal mesial direction of the affected tooth to fully expose the bone lesion. When increased flap mobility is required, a vertical relaxing incision can be made on the buccal side, beyond the membranogingival coalition.
3. Flap up the full-thickness flap to fully expose the bone defect and adjacent bone by 3 to 4 mm.
4. debridement and root surface leveling Removal of all granulation tissue from the pocket, thorough scraping of root surface tartar and other irritants, leveling of the root surface, and removal of endotoxin from the bone are essential for the formation of new attachments.
The membrane material should fit closely with the bone around the defect to avoid folding, and attention should be paid to prevent the membrane from collapsing into the bone lesion, and a certain gap should be kept under the membrane to give the tissue with the ability to form new attachments The membrane should be left with a gap underneath to provide space for growth of tissue with the ability to form new attachments. The PTFE membrane should be fixed to the tooth by suspension sutures to ensure the stability of the membrane under the gingival flap.
The flap should be repositioned and sutured so that the membrane is completely covered, not exposed, and to avoid excessive tension on the flap, which can be repositioned in the coronal direction if necessary. The suture should be made first at the gingival papilla with a longitudinal mattress suture to ensure closure of the adjacent buccal and lingual flaps.
7. Use periodontal plugging agent and remove stitches 10 days after surgery.
8. If a non-absorbable membrane is used, a second surgery should be performed 4 to 6 weeks after surgery to remove the membrane. During the surgical removal of the membrane, the incision is made to cover only the treated tooth, the soft tissue is gently turned up, and the membrane is separated by sharp excision, and if a pocket is formed on the exterior of the membrane, the epithelium of the pocket must be removed. It is important not to damage the neoplastic tissue during the secondary procedure, and the gingival flap should be completely covered by the trauma when it is reset.
(C) Postoperative care
1. Use systemic antibiotics to prevent infection within 1 to 2 weeks after surgery. Rinse with 0.12% chlorhexidine for 4 to 6 weeks to control plaque and prevent infection. After the second film removal surgery, rinse with 0.12% chlorhexidine for 2 to 3 weeks.
2. Review every 1 to 2 weeks within 8 weeks after the operation, and simply cleanse and remove the plaque.
3. Patients are taught to brush their teeth with a soft-bristled toothbrush before surgery and can resume brushing and interdental cleaning measures (flossing, gap brushing, etc.) after 2 to 3 weeks postoperatively. And regular follow-up visits for routine periodontal maintenance.
(D) Factors affecting the efficacy Poor plaque control, poor compliance in the periodontal maintenance phase, failure to review and remove plaque on a regular basis after surgery, and smoking will all affect the efficacy of GTR after surgery. The design of the flap during surgery cannot cover the membrane completely, the bone pocket is wide and shallow, the membrane material used degrades prematurely, and whether a certain gap can be maintained between the membrane and the root surface will also affect the efficacy. If the membrane is exposed after surgery, it will easily cause infection, and once infection will prevent the formation of new attachment. Therefore, attention should be paid to the above aspects before, during and after GTR to avoid unfavorable factors in order to obtain ideal treatment results.
The combined application of guided tissue regeneration and bone grafting can further improve the results of regenerative surgery by utilizing the joint advantages of bone grafting and guided tissue regeneration.
The biocompatibility of the root surface is also an important factor in neoadhesive healing, and thus, it has been proposed that root surface conditioning (root surface conditioning) can be performed to promote neoadhesion in order to improve the biocompatibility of the root surface. It can be used alone in flap surgery, in combination with guided tissue regeneration or with bone grafting. Citric acid, tetracycline, fibronectin, and various growth factors such as platelet-derived growth factor, insulin-like growth factor, bone formation protein, and transforming growth factor are used for root surface conditioning.
In vitro studies have shown that citric acid treatment of root surfaces can remove the smear layer formed when the root surface is flattened, degrade the endotoxin in the diseased root surface, cause mild demineralization of the root surface, expose Sharpey fibers, facilitate the attachment of endogenous fibronectin to the root surface, and promote the formation of new bone. formation of new dental bone. In animal experiments, there is a good effect of promoting new attachment, but in clinical application studies in humans, there is no more new attachment formation when treating root surfaces with citric acid compared with the control group without it, and, in recent years, it has been found that due to its low pH (pH I 1), it can cause necrosis of surrounding healthy tissues, delay early tissue healing, affect alveolar bone formation, and predispose to root and bone cementation. Therefore, it is rarely used in clinical practice.
Tetracycline is the most recently studied and clinically used root surface treatment agent. In vitro studies have shown that its aqueous solution has the same effects of removing the staining layer, degrading endotoxin, demineralizing the root surface, and exposing collagen fibers. In addition, it also has antibacterial effect and collagenase inhibition, and can be adsorbed on the root surface and released slowly. Minocycline hydrochloride, a drug of the tetracycline family, is used to treat the root surface and has the same effect as tetracycline. In vitro studies have shown that it promotes the attachment and proliferation of periodontal cells on the root surface and facilitates the formation of new attachments. In vivo studies have shown that treatment of root surfaces with drugs of the tetracycline family has a tendency to increase connective tissue attachment. Therefore, they are currently used clinically in free gingival flaps and connective tissue flap grafts to improve the attachment of connective tissue to the root surface and promote the formation of new attachments.
Fibronectin is a glycoprotein that is necessary for the attachment of fibroblasts to the root surface. Studies have shown that treatment of the root surface with fibronectin promotes tissue response in early wound healing, prevents flap separation, facilitates hemostasis and connective tissue regeneration, and promotes new attachment. Platelet derived growth factor (PDGF), insulin-like growth factors (IGF), bone morphogenetic proteins (BMP), basic fibroblast IGF, bone morphogenetic proteins (BMP), basic fibroblastie growth factor (bF-GF), transforming growth factor (TGF) and other growth factors can promote cell movement and proliferation in the periodontal membrane and the synthesis of extracellular matrix proteins, so that they can grow along the root to the coronal side and facilitate the formation of bone and bone. formation. The effects of the application of fibronectin and growth factors are still under study and have not been promoted for clinical use.
The use of enamel matrix proteins in periodontal regeneration therapy is also worth mentioning. Enamel matrixprotein, a protein secreted by the epithelial root sheath during tooth development, induces the formation of cell-free dental bone and is thus thought to induce the regeneration of periodontal tissue. Enamel matrix protein has been commercialized abroad (Emdogain), and studies have shown that its injection into subosseous pockets during surgery ee can lead to the formation of new dental bone, alveolar bone and periodontal membrane after surgery, i.e., to periodontal tissue regeneration. Clinical application studies have shown more new bone formation in the group with enamel matrix protein compared to the control group without it. Therefore, enamel matrix protein seems to have a good application prospect in periodontal regeneration treatment.
III. Evaluation of new attachment and alveolar bone regeneration
The evaluation of periodontal neo-attachment and alveolar bone regeneration is performed by the following four methods.
1. histological evaluation Only tissue blocks obtained from the healing area for histological analysis can determine the type of attachment and provide clear evidence of regeneration of periodontal attachment. However, this method requires extraction of the tooth and removal of the surrounding periodontal tissue after healing and is not clinically possible.
2. Periodontal probing explores preoperative and postoperative periodontal pocket depth, attachment level, and bone height. Clinical attachment loss is a commonly used indicator, but the clinical attachment level probed does not accurately reflect the level of the most coronal side of the connective tissue, because the depth obtained by the probing clinic is affected by gingival inflammation and is subject to error due to the probing position, probing angle, and probing force. Using a pressure probe can reduce the error to some extent.
3. Radiographic evaluation of bone regeneration requires standard projection techniques in order to make preoperative and postoperative comparisons, but there is still error and often underestimates the amount of preoperative bone resorption and postoperative bone gain. Digital subtraction analysis can improve the accuracy.
4. Reentry allows direct observation of the postoperative bone repair. The disadvantage is that it is difficult for patients to accept it and it is not suitable as a routine. Even if there is new bone formation by visual observation, it is not possible to determine whether it is a new attachment or a long bonded epithelial healing, because the latter can also have an increase in bone height, but there is no connection between the new bone and the root surface of the tooth with a functionally aligned periodontal membrane.
Of these evaluation methods, only histologic evaluation can most accurately determine the formation of new attachments, but it cannot be used clinically; re-surgical reversal observation can provide evidence of alveolar bone regeneration, yet patients are also often reluctant to undergo re-surgery. Therefore, periodontal probing and radiographic methods are relied upon in clinical work. Doctors should be conscious of the results obtained by these different examination methods.
Regarding the effectiveness of periodontal regeneration treatment, human clinical studies and histological studies have so far shown that GTR can obtain regeneration of periodontal tissues in the treatment of infraosseous pockets and mandibular degree II root bifurcation lesions, and in the treatment of these two lesions, the clinical results obtained by GTR treatment far exceed those of flap surgery alone. In contrast, the results of GTR treatment are not certain for degree III root bifurcation lesions and degree II root bifurcation lesions in the maxilla, with some results being good and others being poor, and the results being unpredictable. the combination of GTR with other regenerative treatment methods such as bone grafting and root surface treatment can improve the results of regenerative treatment. Studies have also shown that the regenerated periodontal tissue obtained through GTR can remain stable for a long time as long as the patient is reviewed at the appropriate time and maintains good oral hygiene. In conclusion, although the types of lesions that can be used for periodontal regeneration therapy are still limited, and the newly attached tissues formed are limited to 2-3 rams, success has been achieved after all. It is believed that with the continuous development and depth of research and the continuous proposal of new methods, the results of periodontal regeneration therapy will be more satisfactory, the predictability of results will be improved, and the scope of application will be more extensive.