Facial Remodelling and Biomaterial - Biomaterials: Physics and Chemistry - page 453

features and the pathologic process of implanted biomaterials. It represents a low-cost and
low-radiation dose technique for a careful follow-up of patients affected by facial deficit
disease after biomaterial implantation. The US technique shows a high radiologic sensibility
in evaluating the features of the biomaterials. For its use, the limited cost and lack of
investigation on harmful US is the key for studying of the biomaterials. (18)
4. Discussion
A biomaterial is defined as a several composed structure, able to interface with the
biological systems in order to increase the volume, to give support or to replace a tissue. The
performances of the installed materials are evaluated on the basis of bio-functionality and
bio-availability therefore bio-compatibility ( 1) .
The bio-functionality is the property of a bio-material to produce a determinate function
from the physical and mechanical point of view while the bio-availability is the capacity of a
bio-material to develop a determinate function during all the useful life of the plant ( 2) . The
final properties of a material depend both on the intrinsic molecular structure of the
polymer and on the chemical and physiques processes to which it is exposed and can be
widely manipulated intervening on the 10 operating conditions of such processes and on the
polimerizzation's reaction. The immediate answers of the human body to the action of a bio-
material is divided in two phases: an inflammation is initially developed because of the first
defensive reaction of the organism to an foreign body; subsequently there is a restorative
process of the damage. In general if the installed material is toxic, this causes the necrosys of
the surrounding tissues; if it is not toxic and inert under the biological point of view a
fibrous capsule around to the plant is formed (this answer is quite rare because the
biomaterial is usually not completely inert); if, at last, the material is bioactive, it stimulates
a precise biological answer and it is progressively supplemented with the surrounding
tissue .
In most cases the material undergone some degradation form and the products of such
process are released in the tissues. Such products, if they are not biologically active and they
are not toxic, are removed with the normal metabolic processes, if however their
concentration reaches high values they can locally accumulate and give an acute or chronic
pathologies .In case, instead, of toxic products, a persistent inflammation developed; the
products of the degradation processes, can stay in the releasing zone, with only local effects,
or they can spread in the vascolare system and have so effects also on organs and tissues far
from the releasing zone. The progress of the medical research has allowed the perfectioning
and the development of new biomaterial in the reconstructive surgery, that has aesthetic
licence to obtain excellent results by no much invasive surgical techniques and immediate
results. An ideal bio-material presents these characteristics: absence of toxicities, anti-allergic
properties, bio-compatibility ( 2) , biofunctionality, easy to use and easy to remove. In our
study the porous polyethylene and the bio bone have been analysed as substitutive of the
hard tissues and the polyacrylamide and polialkylimide for the soft tissues (3) . The bony
reintegration is a complex and multi-factory process studied end analyzes in the time ( 4) . At
present several substitutive alternatives of the bone by autologus and eterologus bone,
biomaterial are possible. Since the past what better choice was considered the allograft bone
( 5-6) which was useful for replacement of big bony deficits even if with difficult 11
vascularization (16-50% of fractures)( 7) . The bone-conductive, mechanical and