barrier membrane
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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 A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...
, is desired. Such a method of preventing epithelial migration into a specific area is known as
guided tissue regeneration 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 gingiv ...
(GTR).


Origins

The first membranes developed were nonresorbable and required a second surgery for membrane removal some weeks later. The need for a second surgical procedure hindered the utilization of the original barrier membranes, which led to the development of resorbable membranes; research indicates no statistically significant difference in surgical success between the two types.


Purpose

The purpose of a membrane is to prohibit the penetration of cells, primarily epithelial, through its structure. The bone tissue grows slower than soft tissue. Hence, if a bone defect needs to heal, the membrane separates it from the soft tissue, giving time for the bone cells to fill the defect. In absence of a barrier membrane, the defect would be occupied by soft tissue cells. Greenberg, AM; Prein, Joachim:
Craniomaxillofacial reconstructive and corrective bone surgery
', Springer 2002 page 155-6.


Clinical considerations

When barrier membranes are utilized, the superficial soft tissue flap remains separated from the underlying bone for the primary healing period and must survive on the vascular supply of the flap; it cannot rely on
granulation tissue Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any siz ...
derived from the underlying bone. Two types of bony defects exist that may require the use of a membrane: # Space-making defect # Non-space-making defect Space-making defects, such as extraction sockets with intact bony walls, are not as demanding as non-space-making defects, such as sites of ridge augmentation, where there may be no support for the membrane and the soft tissue cover may cause collapse of the membrane during healing.


Types

Barrier membranes have been derived from a variety of sources, both natural and synthetic, and are marketed under various trade names. Membranes used in guided bone regeneration (GBR) and grafting may be of two principal varieties: # non-resorbable # resorbable.


Non-resorbable

Historically, GBR and grafting techniques began with impractical millipore (paper) filter barriers. Expanded polytetrafluoroethylene (ePTFE) membranes were first used by 1984, being non-resorbable, but compatible with humans and not leading to infection. Although ePTFE is considered the standard for membranes and excellent outcomes have been achieved with this material, they are often contaminated with
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
(which limits the amount of bone regrowth that will occur) and must eventually be removed via at least one extra surgery 4–6 weeks after the tissue has regrown. Resorbable membranes were developed to avoid these limitations. Non-absorbable ePTFE membranes are still used clinically on a regular basis, and long-term studies suggest that bones regrown with ePTFE function as well as non-augmented naive bone.


Resorbable

Resorbable membranes are either animal-derived or synthetic polymers. They are gradually hydrolyzed or enzymatically degraded and therefore do not require a second surgical stage of membrane removal. Their sources are varied, beginning in early years with rat or cow collagen, cargile membrane, polylactic acid,
polyglycolide Polyglycolide or poly(glycolic acid) (PGA), also spelled as polyglycolic acid, is a biodegradable, thermoplastic polymer and the simplest linear, aliphatic polyester. It can be prepared starting from glycolic acid by means of polycondensation or r ...
,
Vicryl Vicryl (polyglactin 910) is an absorbable, synthetic, usually braided suture, manufactured by Ethicon Inc., a subsidiary of Johnson and Johnson. A monofilament version is also made for use in ophthalmic practice. It is indicated for soft tissue ...
,
artificial skin Artificial skin is a collagen scaffold that induces regeneration of skin in mammals such as humans. The term was used in the late 1970s and early 1980s to describe a new treatment for massive burns. It was later discovered that treatment of deep ski ...
and freeze-dried
dura mater In neuroanatomy, dura mater is a thick membrane made of dense irregular connective tissue that surrounds the brain and spinal cord. It is the outermost of the three layers of membrane called the meninges that protect the central nervous system. ...
. Recently developed synthetic membranes often combine different materials.


Collagen resorbable membranes

Collagen membranes are of either type I or II collagen from cows or pigs. They are often cross-linked and take between four and forty weeks to resorb, depending on the type. Collagen absorbable barrier membranes do not require surgical removal, inhibit migration of
epithelial cells Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercell ...
, promote the attachment of new connective tissue, are not strongly
antigen In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respons ...
ic and prevent blood loss by promoting
platelet Platelets, also called thrombocytes (from Greek θρόμβος, "clot" and κύτος, "cell"), are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby i ...
aggregation leading to early clot formation and wound stabilization. Collagen membranes may also facilitate primary wound closure via fibroblast chemotactic properties, even after membrane exposure. Compared to ePTFE membranes, resorbable barriers allow for fewer exposures and therefore reduce the effects of infection on newly formed bone. Use of collagen membranes in particular, with bone mineral as a support and space maintainer, has achieved predictable treatment outcomes.


Synthetic resorbable membranes

Synthetic membranes may be polymers of
lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as nat ...
or
glycolic acid Glycolic acid (or hydroxyacetic acid; chemical formula HOCH2CO2H) is a colorless, odorless and hygroscopic crystalline solid, highly soluble in water. It is used in various skin-care products. Glycolic acid is widespread in nature. A glycolate (s ...
. Their
ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...
bonds are degraded over 30–60 days, leaving free acids that may be inflammatory. The majority of studies consider synthetics comparable to other membranes like ePTFE and collagen, and one author has found synthetics clinically superior to collagen membranes. The integrity of resorbable membranes over the healing period has been questioned relative to the ePTFE membranes, but a 2007 study suggested that collagen membranes do allow for bone regeneration, given the correct patient and conditions. Most studies on resorbable membranes do not use appropriate scientific controls or identify the specific membrane used, making it difficult to compare success and failure rates.


Amniotic membrane and fibrin glue

PETTI Gustavo From Cagliari, Italy has been the first one to have had: "A new attachment: guided tissue regeneration using an amniotic membrane and fibrin glue" Publication: Petti G. (1989) “La rigenerazione parodontale guidata con membrana amniotica e colla di fibrina. (Guided periodontal regeneration with an amniotic membrane and fibrin glue). Il Dentista Moderno, 9, 57-70. Italy Petti G. (1988) “A new attachment:guided tissue regeneration using an amniotic membrane and fibrin glue-preclinical considerations after 2 years” The Journal of the American Dental Association, JADA/FDI. Free Communications, Periodontics, July, USA Petti G. (1988) “ A new attachment:guided tissue regeneration using an amniotic membrane and fibrin glue” Dental Abstract, USA See in The References the others numerous publications


References

{{Periodontology Oral surgery