Biomedical Engineering Reference
In-Depth Information
However, the advent of nanotechnology in recent years has made it possible to structurally
change many dental materials including impression materials, composites, and glass ionomers. This
in some cases has resulted in the overcoming of physical limitations previously thought to be insur-
mountable. Not only have the limited hardness and resistance to stress of GIC been overcome but it
has also been possible to give GICs an appearance of translucency and coloration that are a good
solution in many areas of the oral cavity. Although composite materials are now the reference
material for reconstructions, a glass ionomer system based on nanotechnology can represent a
good, or in certain conditions even better, alternative if the chemical properties, the protection of
the ablation of caries, and the constant release of fluoride are taken into consideration case by case.
5.6
Resin-modified nano-glass ionomer composites
In addition to conventional and resin-modified GIC, a nanofilled resin-modified GIC or “nanoiono-
mer” was developed recently by 3M ESPE
N100 (KN). KN light curing nanoionomer
restorative is the first paste/paste, resin-modified glass ionomer material developed with nanotech-
nology. Because it adds benefits not usually associated with glass ionomers, it has resulted in a new
category of glass ionomer restorative: the nanoionomer. The technology of KN restorative represents
a blend of FAS technology and nanotechnology. Nanoparticle-filled RMGIC is developed by the
addition of nanoparticles (100 nm compared to 30
Ketac
t
m in traditional GIC, which is equivalent to
30,000 nm) to RMGIC materials. This combination offers unique characteristics of wear and polish,
and filler particle size can influence strength, optical properties, and abrasion resistance. The addition
of nanoparticles to KN would be expected to provide an improved finish and a smoother, more
esthetic restoration without adversely affecting other advantageous properties, including fluoride
release, adhesion to enamel and dentin, high early bond strength, and less susceptibility to moisture
and dehydration
[42]
. In vitro study demonstrates that the addition of nanofillers provides enhanced
surface wear and polish relative to some other commercially available dental materials
[43]
.
According to 3M ESPE, by using nanosized fillers and nanoclusters, along with FAS glass, KN
restorative provides enhanced esthetics as well as the benefits of glass ionomer chemistry, such as
fluoride release. The nanoionomer is based on the acrylic and itaconic acid copolymers necessary for
the glass ionomer reaction with alumino-silicate glass and water. The nanoionomer also contains a
blend of resin monomers, bisphenol A-glycidyl methacrylate (BisGMA), triethylene glycol dimetha-
crylate (TEGDMA), and hydroxy ethylmethacrylate (HEMA), which polymerize via the free radical
addition upon curing primary curing mechanism is by light activation. The originality of this GIC is
the inclusion of nanofillers which constitute up to two-thirds of the filler content (circa 69 wt%). In a
study, the fluoride release pattern of KN was investigated and it was found that KN presented
a similar cumulative F
2
release pattern compared to resin-modified glass ionomer; however, the fluo-
ride release was lesser than conventional GIC. Based on this, it might be speculated that the nanopar-
ticles presented in the tested GIC (KN) do not have influence on the cumulative F release profile.
This phenomenon could be due to low solubility of nanoparticles, and the material does not exhibit
any voids, cracks, and microporosities after immersion in saline, as found with all other GICs tested
[44]
. However, it is claimed by the manufacturer that KN has the tendency for high fluoride release
that is rechargeable after being exposed to a topical fluoride source. Additionally, in vitro tests
showed that KN has the ability to create a caries inhibition zone after acid exposure
[45]
.
μ
