Biomedical Engineering Reference
In-Depth Information
significantly lower SBS for KN compared to a conventional light-cure orthodontic bonding adhesive
(Transbond XT). However, it has been suggested that this nanoionomer may be used for bonding ortho-
dontic brackets since the obtained SBS is within clinically acceptable range. The results in that study
demonstrated that Transbond XT (12.60
4.48 MPa) had higher SBS values than nanocomposite
6
(8.33
2.12 MPa). No statistically significant differences were
found between nanocomposite and nanoionomer (P
5.16 MPa) and nanoionomer (6.14
6
6
0.05). The nanoionomer did not have the disad-
vantage of the nanocomposite wherein the consistency of the adhesive paste is thick, and the nanoiono-
mer easily flowed into the retention pad of the bracket base. The flowability of the nanoionomer may
make it superior to composite resins for penetrating the bracket retention features and possibly coating
the enamel during the bonding procedure. Such an attribute might reduce the possibility of caries form-
ing under brackets during treatment. Fluoride release and recharge might also reduce the possibility of
caries formation near the bonding material excess interface between the bonding material/enamel/oral
environment lines. From this perspective, KN nanoionomer should be considered a potentially useful
adhesive for bonding orthodontic brackets. Reynolds
[51]
suggested that minimum bond strength of
5.9
.
7.8 MPa is adequate for most orthodontic needs during routine clinical use. A microleakage
around Class V cavities was analyzed and results showed that Er:YAG preparation exhibited greater
microleakage than a conventional cavity preparation with a bur when a nanoionomer (KN) and a nano-
composite (Filtek Supreme XT) were used as restorative materials
[52]
.
Recently, another nanofilled resin-modified glass ionomer composite (Equia system) has been
developed which contains inorganic nanofiller (represents 15% by weight and 80% by volume), adhe-
sive monomer, functional methacrylate, methyl methacrylate, and photochemical initiator. The fillers
are composed of silica powder with an average size of 40 nm and, being uniformly dispersed within
the solution, give the restoration a high degree of wear resistance. The nanofiller particles tend to
agglutinate in the resin matrix, which is used to form a layer with an average thickness of 35
m
that seals and protects both the surfaces of the restoration and the adhesive interface between the res-
toration and the dental structure. The estimated setting time is only 3 min of which 1 min and 15 s is
for mixing and manipulation and 2 min for the hardening of the cement. It has a decisive advantage
over traditional GIC, whose hardening requires more than 5 min. The infiltration and dispersion of
the nanofilled particles protect the restoration and margins, and increase the hardness and resistance
to both flexion and wear. Furthermore, the nanofilled resin also maintains the polished surface of the
restoration for a long time because it hinders the dissolution and disintegration of the outermost layer
of the material. In contrast, traditional finishing using abrasive polishing pastes is always accompa-
nied by a certain amount of wear on the restoration, which becomes clinically evident after a while
because of the loss of translucency. The esthetic appearance has also been improved with nanofilled
resins that give the filling the same brilliance as that of a natural tooth
[53]
. The clinical trials showed
(
Figure 5.2
) that after the removal of the metallic reconstructions, teeth were reconstructed, first using
Vita shade A3 Equia. Then its surface was modeled and the G-Coat coating resin positioned. It was
therefore possible to create effective contact points. The GIC of the Equia system called Fuji IX GP
has a maturation period of 7
40
μ
10 days from placement of the reconstruction.
Rehman and group
[54]
synthesized N-vinyl-pyrrolidone (NVP) containing polymers and altered
monomeric sequences (AA-NVP-IA) and incorporated into glass ionomer liquid formulations. It was
envisaged that NVP molecules interspersed between the itaconic and acrylic acid and would act as a
spacer to decrease the degree of steric hindrance of carboxylic acid groups. Subsequently, the probabil-
ity of ionic bond formation and polysalt bridge formation within the final set cement would be
