safety of bone allografts used in dentistry (2)
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The desire to repair or replace injured ordiseased parts by transplantation of healthytissues has been described in ancient medicalrecords and depicted in works of art many
centuries old.Ollier originally discussed the concept of bone
preservation in 1867.
First concerted effort to store bone for
elective use and description of clinicalefficacy provided by Inclan-1942.
Past decade brought forth significant advancesin bone grafting options.
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Autogenous bone still remains goldstandard of the bone graft materials.
ADVANTAGES:
Use of autografts diminishes risk ofinfectious disease transmission
Osteoconductive, osteoinductive andosteogenic properties of the graft are
optimal.No immune response after implantation,
enhancing its ability to incorporate intoits new site
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DISADVANTAGES:
Harvest of autografts associated with severe donorsite pain and morbidity.
In procedures requiring large amount of graft, there
may not be adequate quantities of autogenous bone
available.
Risk of wound infection
Additional post operative discomfort.
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FDBA DFDBA
FDBA provides an osteoconductive
scaffold and elicits resorption when
implanted in mesenchymal tissues.
DFDBA also provides osteoconductive
surface and in addition, it provides a
source of osteoinductive factors.So, itelicits mesenchymal cell migration,
attachment and osteogenesis when
implanted in well vascularized bone.
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Bone banks exist for the purpose ofsupplying the surgeon with safe andeffective bone tissue that is suitable for
intended clinical application and areavailable whenever the need arises.
Use of substitute for autogenous tissuerequires consideration of its biological
and biomechanical potential as a graftmaterial and of the possibility of transferof disease from ,donor to recipient aswell as the presence and significance ofimmune responses to foreign antigens.
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FDA: FDA Centre for Biologics Evaluation and
Research (CBER) regulates human
cells,tissues and cellular based products
under federal law,title 21 of U.S. Code ofFederal Regulations (cfr),parts 1270 and
1271.
CFR Title 21 part 1271 requires HCT/p
manufactureres to register their companiesand products with FDA cber and comply with
applicable FDA regulations.
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AATB
American Association of Tissue Banks is an
independent nonprofit organization
dedicated to ensuring and maintaining the
safety, consistency and availability ofallografts in the United States.
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Prior to processing, the donors medical/socialhistory is screened for medical conditions or
disease processes that would contraindicate thedonation of tissues in accordance with currentpolicies and procedures approved by BONEBANKALLOGRAFTS.
All BONE BANKALLOGRAFTS policies andprocedures for donor screening, serologic andmicrobiologic testing should meet current
Standards established by the AmericanAssociation of Tissue Banks.
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Donor from high risk groups, as determined
by medical testing and/or behavioral risk
assessments.
Donors testing positive for HIV antibody byELISA
Autopsy of donor reveals occult disease.
Donor bone tests positive for bacterial
contamination.
Donor and bone test positive for Hepatitis B
surface antigen (HBsAg) or Hepatitis C virus
(HCV).
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Donors testing positive for syphilis.
Testing of donor blood and tissue samples
began at the site of recovery and continued
throughout processing.
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NOTIFICATION OFPROSPECTIVE DONORS DEATH
DETERMINATION OF INITIAL DONOR ELIGIBILITY
CONSENT FROM DONOR
DISPATCH OF RECOVERY TEAM
ASSIGNMENT OF TRACKING NUMBER TO
PROSPECTIVE DONOR
DETERMINATION OF ADDITIONAL DONOR
ELIGIBILITY TISSUE PROCUREMENT
AUTOPSY
TRANSPORT
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SOFT TISSUE STRIPPING
INITIAL SIZE REDUCTION
INITIAL CLEANSING AND DECONTAMINATION
MICROBIOLOGICAL TREATMENT
FREEZING
DEHYDRATION
SECONDARY SIZE REDUCTION PACKAGING
TERMINAL STERILIZATION
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SOFT TISSUE STRIPPING
INITIAL SIZE REDUCTION
INITIAL CLEANSING AND DECONTAMINATION
MICROBIOLOGICAL TREATMENT
FREEZING
DEHYDRATION
SECONDARY SIZE REDUCTION
DEMINERALIZATION
BUFFERING FINAL RINSE
PACKAGING
TERMINAL STERILIZATION
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VISUAL INSPECTION TEST
REIDUAL MOISTURE TEST
RESIDUAL CALCIUM TEST
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Exponential reduction in the potential for
graft contamination, disease transfer or
both.
With proper processing, allografts for dentalpurposes routinely achieve SAL of 10-6.
SAL is probability that an item will not be
sterile after it has been subjected to a
validated sterilization process. With a SAL of 106, the odds of an organisms
surviving allograft processing are less than
one in 1 million.
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Most frequently used methods of assuringgraft sterility is irradiation because of the
belief that irradiation will prevent HIV
transmission, thus making it worthwhile to
trade safety for the loss of osteoinductionand alteration of biomechanical properties of
the bone.
However, a study performed by Smith et
al.*shows that, even at doses at which tissuequality begins to be compromised (1.5-2.5
Mrads), irradiation failed to be virucidal for
HIV type 1
* Smith RA, Ingels J, Lochemes JJ, et al: Gamma irradiation of HIV-l. JOrthop Res 19:5, 2001
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Although 4 cases of HIV have been reported
following procedures using frozen bone
allografts, it should be emphasized that
frozen & fresh allografts typically are notused in periodontal therapy.
The delay required to process DFDBA and
FDBA ensures that there is adequate time for
testing for potential pathogens, helping toassure the safety of these materials.
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Mechanical properties of tissues may be
adversely affected by irradiation.
Irradiation of DFDBA reduced bone induction
ability by 40%. Ethylene oxide may produce inflammation
and impair healing, unless it or its by-
products are removed from the graft.
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FDA regulations require human bone
allografts must be tracked so that tissue
banks and clinicians can notify recipients in
the event of a product recall.CFR Title 21 part 1271.290 addresses tracking
protocols for human bone allografts to
facilitate the investigation of actual or
suspected transmission of communicablediseases.
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According to this regulation, HCT/P
processing facilities must label each
manufactured HCT/P
with a uniquealphanumeric identification code that does
not contain the donors name or Social
Security number.
This code allows each manufacturer to record
and track the donor graft to its recipient and
vice versa.
Most tissue banks supply a self-addressed
prepaid postage tracking form with each
human bone allograft
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Ever-increasing use of human bone allografts
reflects positively on the usefulness and
safety of these products.
Progressive FDA policies and industry self-regulation through agencies such as the AATB
have allowed reputable tissue-processing
facilities to uphold their fiduciary
responsibility to the public.
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As is recommended for medical surgeons,
when using human bone allografts in thepractice of dentistry, practitioners should
investigate carefully and be familiar with the
institutions that they are patronizing.
Purchasing products from HCT/Pmanufacturers such as those accredited by
the AATB may provide practitioners with
peace of mind, knowing that these
institutions accept and adhere to strict andreliable safety measures in the creation of
their products.