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GBR Membranes and the Barrier Effect

Melcher, in 1976, described the theoretical principles of GTR (guided tissue regeneration around teeth) and these were later applied to GBR (guided bone regeneration for placement of dental implants). These principles are based on placing a physical barrier that prevents unwanted tissues' invasion od the isolated site, allowing selective cell population of the defect. 

Today it is commonly accepted that GBR with bone grafts and barrier membranes is highly predictable, minimally invasive and the most cost effective procedure in everyday clinical practice. The barrier function should last 4-6 months to allow bone regeneration of an average defect.

Over the last 15-20 years there was a shift from non-resorbable synthetic barrier membranes to resorbable, predominantly collagen membranes. This was driven by two main drawbacks of synthetic non-resorbable materials:
1. Poor handling 
2. High complication rate mostly from premature exposures
Although collagen has many good qualities that support GBR in the oral cavity, it poses a major drawback: it is rapidly degraded by tissue collagenases when submerged and by bacterial collagenases when exposed. The latter are so potent that a non cross linked collagen device exposed to the oral cavity is completely degraded within several days. But even a fully submerged non cross linked collagen device will be degraded and loose its barrier function in 2-4 weeks.

This is the reason why many materials and techniques have been tested over the last 15 years to cross link collagen and extend its bio-durability and hence the barrier function. Of these, only sugar based cross linking (GLYMATRIX™ technology) has been proven to be both effective and safe, and commercially available as a barrier membrane (OSSIX® and OSSIX® PLUS). Others who have attempted to develop highly cross linked collagen products have limited success due to ineffective or unsafe devices.  

There are three basic technologies used for production of collagen membranes for GBR:
1. Processed Tissue – Animal or human tissue, chemical extraction, cross linking (with or without) and sterilization.
2. Fiber reconstitution – Mechanical disintegration, chemical extraction, fibrillation, engineering into membranes, cross linking (with or without) and sterilization.
3. Molecular reconstitution - Mechanical disintegration, solubilization, removal of tello-peptides (the immunogenic tails of the collagen molecule) , full purification and filtration, reconstitution of fibers (fibrillation), engineering into membranes, cross linking, and sterilization.

Clinicians should be aware of the following when choosing a collagen barrier membrane for a GBR procedure:
1. Several manufacturers produce membranes that are being distributed under different brand names. One manufacturer produces at least 8 different brands of membranes for implant and catalog companies.
2. Most collagen membranes are made of non cross linked collagen. Most are processed human or animal tissues. Hence their barrier effect is short term and insufficient in most cases.
3. Cross linking of membranes with non natural chemical reagents such as; Formaldehyde, Glutaraldehyde and Ethyldimethylaminopropyl Carbodiimide (EDC) may compromise the biocompatibility of the membrane.
4. Except for two commercial membranes, publications in peer reviewed journals are scarce and are mostly case reports. Very few prospective and comparative studies exist. Long term animal and human histology is scarce.
5. One should distinguish between "resorption time" and effective barrier duration which are not necessarily overlapping. For most membranes, the effective barrier duration is much shorter than the resorption time and if the membrane is completely resorbed within six months the effective barrier duration is only 1-2 months. 

We suggest that clinicians ask the following questions before making a decision on which dental barrier membrane they use on their patients:
1. Is the product made of processed tissue or reconstituted collagen?
2. What is the collagen origin (specious, organ, atelo-collagen)?
3. Is the membrane made of cross linked or native collagen?
4. If cross linked – by which cross linking agent or method?
5. Does the product come with reliable information on resorption time or barrier duration? (Resorption time is insignificant).
6. Have you seen the membrane as a barrier at reentry? If not it was probably not a barrier for enough time.
7. Who is the manufacturer? What is the basis technology? Is the facility certified? 
8. Does the product have all regulatory approvals?
9. Is the product supported by publications in peer-reviewed journals (comparative studies, human histology, etc.)?

What are the benefits for my patients and for myself?
Having a barrier that lasts during the entire healing period (4-6 months) will allow high predictability to achieve true bone regeneration i.e. vital bone to the implants' level.
In addition, in cases with post surgical complications such as flap opening and dehiscence, OSSIX® PLUS will maintain its integrity and barrier function for an additional 3-5 weeks and can actually save the procedure. This will increase implant stability, form favorable bone to implant contact, reduce long term recession of bone and gingiva, and might decrease the probability of peri implantitis over the years.
It will obviously reduce short term failures, increase patients’ satisfaction and decrease long term complications.
OSSIX® PLUS may contribute to the establishment of a successful long term implants practice.

References
1. Friedmann, A., Dehnhardt, J., Kleber, B. M. & Bernimoulin,J. P. (2008); Cytobiocompatibility of collagen and ePTFE membranes on osteoblast-like cells in vitro. Journal of Biomedical Materials Research A 86, 935–941.
2. McAllister, B. S. & Haghighat, K. (2007) Bone augmentation techniques. Journal of Periodontology 78, 377–396.


WHO WE ARE

Datum Dental Ltd is a subsidiary company of Datum Biotech. The Company was created in order to develop, manufacture and market a full line of dental biomaterials for tissue and bone regeneration.

Datum Biotech Ltd is an Israeli based Biomaterials company that specializes in developing, manufacturing and commercializing proprietary technologies, which are based on innovative and unique sugar cross-linked collagen products for tissue engineering and regenerative medicine.
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