Biomedical Engineering Reference
In-Depth Information
The barrier membranes used in GTR process should meet several prerequisites. A general require-
ment is biocompatible, nonimmunogenic, and nontoxic, and the membranes are supposed to have
suitable mechanical stability and optimal porosity. Other properties such as tissue integration, cell
occlusivity, nutrient transfer, space-making ability, and ease of use in the clinic are also of interest
[12]
. Mechanical stability is believed closely relating to membrane barrier function for selective cell
growth during implantation period.
A variety of synthetic and naturally derived GTR barriers have been used to facilitate periodontal
tissue regeneration. Clinical data and numerous reports indicated that the use of membranes with dif-
ferent compositions and structures, including both nonresorbable and resorbable barrier membranes,
allowed the regenerative potential cells (such as PDL cells, bone cells, and cementoblasts) to prolifer-
ate and migrate into the protected wound area. It has been shown that GTR treatment of periodontal
lesions resulted in significantly greater clinical improvements than only surgical debridement
[13]
.
10.2.1
Studies Using Nonresorbable Membranes
Nonresorbable membranes, including Millipore
®
filters and expanded polytetrafluoroethylene
(ePTFE) membranes (GORE-TEX
®
), were initially used for GTR treatment
[14]
. The purpose-
designed ePTFE membranes had been proven biocompatibility by numerous animal and human tests
and were predominantly used in reconstruction of periodontal defects. Defects treated with this mem-
brane have healed faster and with greater quality and quantity of regenerative bone than defects with-
out this treatment
[12,15]
. Experimentally, a porous ePTFE membrane was inserted over exposed
tooth surface and sutured with the soft tissues. As the newly formed tissues filled the space, the nonre-
sorbable ePTFE membrane should be removed by a second surgical procedure. This additional surgi-
cal trauma is obviously inconvenient to the patient and the clinician. More importantly, it may increase
the risk of patient infection and other undesirable effects like disruption of the newly regenerated
tissues
[16-18]
.
On the other hand, some authors had argued that rat PDL-derived cells could not proliferate on
ePTFE membrane. Their study showed that periodontal ligament cells (PDLCs) attached and prolifer-
ated well on collagen or copolymer of polylactic acid (PLA) and polyglycolic acid membranes
[19]
.
To avoid the removal of the membrane after healing and to achieve more efficient periodontal
regeneration, thus many researchers have assessed the value of biodegradable membranes, which
received high interest for clinical trials in recent years
[20]
.
10.2.2
Studies Using Bioresorbable Membranes
The development and manufacture of bioresorbable GTR devices had been spurred by the concerns
stated above, by using natural derivatives and synthetic organic polymer technologies. A variety of
biomaterials have been suggested and used, most commonly type I collagen, PLA, and poly(lactide-
co
-glycolide) (PLGA)
[21-25]
. Collagen membrane has excellent cell affinity and biocompatibility to
regenerate tissues, nevertheless, there might exhibit disadvantages in use of collagen membranes. The
mechanical strength of collagen membrane is normally weak and it is therefore difficult to manipu-
late; moreover, it might cause localized chronic inflammatory response and rapid degradation behav-
ior
[25,26]
. Membranes of polylactide and its copolymer with glycolide have provided an alternative
