Guided bone and tissue regeneration | |
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MeSH | D048091 |
Guided bone regeneration (GBR) and guided tissue regeneration (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. Guided bone regeneration typically refers to ridge augmentation or bone regenerative procedures; guided tissue regeneration typically refers to regeneration of periodontal attachment. [1]
Guided bone regeneration is similar to guided tissue regeneration, 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. When bone grafting is used in conjunction with sound surgical technique, guided bone regeneration is a reliable and validated procedure.
Use of barrier membranes to direct bone regeneration was first described in the context of orthopaedic research 1959. [2] 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. [3] 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. The GBR principle was first examined by Dahlin et al. in 1988 on rats. The selective ingrowth of bone-forming cells into a bone defect region could be improved if the adjacent tissue is kept away with a membrane; this was confirmed in a study by Kostopoulos and Karring in 1994. GBR can be used for bone regeneration on exposed implant coils . [4]
Four stages are used to successfully regenerate bone and other tissues, abbreviated with the acronym PASS: [5]
After tooth removal, it takes 40 days for the normal healing process to take place (clot formation to socket filled with bone, connective tissue and epithelium). [6]
The first application of barrier membranes in the mouth occurred in 1982 [7] [8] [9] in the context of regeneration of periodontal tissues via GTR, as an alternative to resective surgical procedures to reduce pocket depths. [5] [10] A barrier membrane is utilized in the GBR technique to cover the bone defect and create a secluded space, which prevents the connective tissue from growing into the space and facilitates the growth priority of bone tissue. An added benefit of the membrane is that it provides protection of the wound from mechanical disruption and salivary contamination. [6]
Barrier membrane criteria should be as follows:
Several surgical techniques via GBR 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 which is then packed into the bony defect and covered by resorbable membranes. In cases where augmentation materials used are autografts (tissue transfer from same person [12] ) or allografts (tissue from genetically dissimilar members of same species [12] ) the bone density is quite low and resorption of the grafted site in these cases can reach up to 30% of original volume. Other materials available xenografts (tissue donor from another species [12] ) and autogenous bone. [6] 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. [13] Current treatments for destructive periodontal disease are not able to restore damaged bone and connective tissue support for teeth (infra-bony defects).[ citation needed ]
Currently there are two types of barrier membranes available: resorbable and non-resorbable. [6]
Non-resorbable membranes:
The main types of non-resorbable barrier membranes are expanded polytetrafluoroethylene (e-PTFE), high-density polytetrafluoroethylene (d-PTFE), titanium mesh and titanium-reinforced PTFE. [6]
Expanded polytetrafluoroethylene (e-PTFE) became the most common non-resorbable membrane used for bone regeneration in the 1990s. Gore-Tex was the most popular type of e-PTFE. [14] The e-PTFE membrane is sintered with pores of 5 - 20 μm within the framework of the material. The e-PTFE membrane behaves as a barrier to prevent fibroblasts and various connective-tissue cells from entering the bone defect in order to allow the slower moving cells that are osteogenic to repopulate the defect. [15] A study used e-PTFE membranes to cover surgically constructed average size bone defects in the mandibular angles of rats. Consequently, the e-PTFE membrane acted as a barrier to soft tissue and sped up bone healing, which took place between 3–6 weeks while no healing occurred in the non-membrane control group during a 22 week period. [16]
The biological method of osteopromotion by exclusion is good for predicting ridge growth or defect regeneration. [17]
Resorbable membranes:
There are many different types of resorbable membranes out there but the main ones are synthetic polymers and natural biomaterials. Synthetic polymers are such that it is a polylactic acid bilayer, or the collagen-derived membranes. These membranes can be obtained from bovine or porcine or dermis. E.g. Emdogain which has been shown to significantly improve probing attachment levels (1.1mm) and periodontal pocket depth reduction (0.9mm) when compared to a placebo or control materials. [18] Resorption rates ranging from six to 24 weeks depending on its different chemical structures. With the resorbable membrane used, the membrane will bio-degrade. There is no need for a second surgery to remove the membrane, this will prevent any disruption to the healing process of the regenerated tissues. [11] A synthetic resorbable membrane (eg: Powerbone Barrier Membrane) is an ideal alternative to the resorbable collagen material. Randomised clinical trials compared the stability of augmented bone between a synthetic resorbable membrane and a collagen membrane with guided bone regeneration simultaneous to dental implant placement in the aesthetic zone in terms of facial bone thickness. [19]
Success depends on several factors: osteoblasts being present at the site, a sufficient blood supply, stabilisation of the graft during healing, and soft tissue not being under tension. [12]
There are several uses of bone regeneration:
Contraindications include: [20]
Potential complications include: [20]
A dental implant is a prosthesis that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, or facial prosthesis or to act as an orthodontic anchor. The basis for modern dental implants is a biological process called osseointegration, in which materials such as titanium or zirconia form an intimate bond to the bone. The implant fixture is first placed so that it is likely to osseointegrate, then a dental prosthetic is added. A variable amount of healing time is required for osseointegration before either the dental prosthetic is attached to the implant or an abutment is placed which will hold a dental prosthetic/crown.
Osseointegration is the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant. A more recent definition defines osseointegration as "functional ankylosis ", where new bone is laid down directly on the implant surface and the implant exhibits mechanical stability. Osseointegration has enhanced the science of medical bone and joint replacement techniques as well as dental implants and improving prosthetics for amputees.
Periodontology or periodontics is the specialty of dentistry that studies supporting structures of teeth, as well as diseases and conditions that affect them. The supporting tissues are known as the periodontium, which includes the gingiva (gums), alveolar bone, cementum, and the periodontal ligament. A periodontist is a dentist that specializes in the prevention, diagnosis and treatment of periodontal disease and in the placement of dental implants.
Maxillary sinus floor augmentation is a surgical procedure which aims to increase the amount of bone in the posterior maxilla, in the area of the premolar and molar teeth, by lifting the lower Schneiderian membrane and placing a bone graft.
“Lateral periodontal cysts (LPCs) are defined as non-keratinised and non-inflammatory developmental cysts located adjacent or lateral to the root of a vital tooth.” LPCs are a rare form of jaw cysts, with the same histopathological characteristics as gingival cysts of adults (GCA). Hence LPCs are regarded as the intraosseous form of the extraosseous GCA. They are commonly found along the lateral periodontium or within the bone between the roots of vital teeth, around mandibular canines and premolars. Standish and Shafer reported the first well-documented case of LPCs in 1958, followed by Holder and Kunkel in the same year although it was called a periodontal cyst. Since then, there has been more than 270 well-documented cases of LPCs in literature.
Crown lengthening is a surgical procedure performed by a dentist, or more frequently a periodontist, where more tooth is exposed by removing some of the gingival margin (gum) and supporting bone. Crown lengthening can also be achieved orthodontically by extruding the tooth.
Gingivectomy is a dental procedure in which a dentist or oral surgeon cuts away part of the gums in the mouth.
In dentistry, the subepithelial connective tissue graft is an oral and maxillofacial surgical procedure first described by Alan Edel in 1974. Currently, it is generally used to obtain root coverage following gingival recession, which was a later development by Burt Langer in the early 1980s.
Laser-assisted new attachment procedure (LANAP) is a surgical therapy for the treatment of periodontitis, intended to work through regeneration rather than resection. This therapy and the laser used to perform it have been in use since 1994. It was developed by Robert H. Gregg II and Delwin McCarthy.
Hessam Nowzari is the Director of the University of Southern California Advanced Periodontics program, since 1995, and is a diplomate of the American Board of Periodontology.
A barrier membrane is a device used in oral surgery and periodontal surgery to prevent epithelium, which regenerates relatively quickly, from growing into an area in which another, more slowly growing tissue type, such as bone, is desired. Such a method of preventing epithelial migration into a specific area is known as guided tissue regeneration (GTR).
In dentistry, a furcation defect is bone loss, usually a result of periodontal disease, affecting the base of the root trunk of a tooth where two or more roots meet. The extent and configuration of the defect are factors in both diagnosis and treatment planning.
Socket preservation or alveolar ridge preservation is a procedure to reduce bone loss after tooth extraction. After tooth extraction, the jaw bone has a natural tendency to become narrow, and lose its original shape because the bone quickly resorbs, resulting in 30–60% loss in bone volume in the first six months. Bone loss, can compromise the ability to place a dental implant, or its aesthetics and functional ability.
Chronic periodontitis is one of the seven categories of periodontitis as defined by the American Academy of Periodontology 1999 classification system. Chronic periodontitis is a common disease of the oral cavity consisting of chronic inflammation of the periodontal tissues that is caused by the accumulation of profuse amounts of dental plaque. Periodontitis initially begins as gingivitis and can progress onto chronic and subsequent aggressive periodontitis according to the 1999 classification.
Aggressive periodontitis describes a type of periodontal disease and includes two of the seven classifications of periodontitis as defined by the 1999 classification system:
Peri-implantitis is a destructive inflammatory process affecting the soft and hard tissues surrounding dental implants. The soft tissues become inflamed whereas the alveolar bone, which surrounds the implant for the purposes of retention, is lost over time.
Angularis nigra, Latin for 'black angle', also known as open gingival embrasures, and colloquially known as "black triangle", is the space or gap seen at the cervical embrasure, below the contact point of some teeth. The interdental papilla does not fully enclose the space, leading to an aperture between adjacent teeth. This gap has many causes including gingival recession, and gingival withdrawal post-orthodontic work. Interdental "black triangles" were rated as the third-most-disliked aesthetic problem below caries and crown margins. Treatment of angularis nigra often requires an interdisciplinary approach, involving periodontal, orthodontic and restorative treatment. Possible treatments to correct angularis nigra include addition of composite resin in the space, veneer placement, or gum graft. Angularis nigra is generally only treated based on the aesthetic preference of the patient.
Platelet-rich fibrin (PRF) or leukocyte- and platelet-rich fibrin (L-PRF) is a derivative of PRP where autologous platelets and leukocytes are present in a complex fibrin matrix to accelerate the healing of soft and hard tissue and is used as a tissue-engineering scaffold in oral and maxillofacial surgeries. PRF falls under FDA Product Code KST, labeling it as a blood draw/Hematology product classifying it as 510(k) exempt.
Gingival grafting, also called gum grafting or periodontal plastic surgery, is a generic term for the performance of any of a number of periodontal surgical procedures in which the gum tissue is grafted. The aim may be to cover exposed root surfaces or merely to augment the band of keratinized tissue.
Periodontal surgery is a form of dental surgery that prevents or corrects anatomical, traumatic, developmental, or plaque-induced defects in the bone, gingiva, or alveolar mucosa. The objectives of this surgery include accessibility of instruments to root surface, elimination of inflammation, creation of an oral environment for plaque control, periodontal diseases control, oral hygiene maintenance, maintain proper embrasure space, address gingiva-alveolar mucosa problems, and esthetic improvement. The surgical procedures include crown lengthening, frenectomy, and mucogingival flap surgery.
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