Biomedical Engineering Reference
In-Depth Information
Elution
0.5
PMM+NC
PMM+CHX
PMM+NC+CHX
PMM
0.4
0.3
0.2
0.1
0
FIGURE 21.5
Histogram with plotted optical density values for CHX release over a 2-week time period. The nanocomposite
group with CHX (PMM
CHX) showed a consistently higher release with time compared to
nanocomposite without CHX (PMM
NC
1
1
1
NC), regular composite (PMM), and composite with CHX
(PMM
CHX).
1
One significant property of nanocomposites is the ability for drug elution. Initial reports with
dental composite materials such as 50/50 hydroxyethylmethacrylate, and urethane dimethacrylate
have demonstrated antimicrobial release of chlorhexidine (CHX) despite polymerization shrinkage
[71]
. Unpublished pilot data of PNC containing CHX diacetate salt hydrate 2% indicated, based on
optical density readings (
Figure 21.5
), that the PNC showed initiation of CHX elution at 3 h that
peaked at 4 days and remained constant till the length of experiment (2 weeks) [Chogle et al., unpub-
lished data]. The authors claim from ongoing experiments that the elution of CHX can also be con-
trolled by certain factors. Although very nascent, the ability to create, place, and control a “smart”
root-end filling material may be vital to counter primary, secondary, and refractory apical infections.
The cytotoxicity of such PNCs has been investigated as well. Modareszadeh et al.
[72]
evaluated
polymer PNC resins with C-18 organoclay dispersed within the resin matrix and containing CHX
diacetate salt hydrate 2% and compared it to that of two widely accepted commercially available
materials, ProRoot
. Elutes of materials extracted after 24 h and 1, 2, and 3
weeks were interacted with the mouse fibroblasts L-929 using a colorimetric cell viability assay
Mitochondria-Targeting Sequence (MTS) which is based on mitochondrial dehydrogenases activity
and differences in the mean bioactivity values were assessed. The results showed no statistically
significant difference in cytotoxicity between ProRoot
MTA and Geristore
s
s
, and PNC resin C-18 at
all-time intervals. Further investigations would be needed to confirm these in vitro findings.
MTA, Geristore
s
s
21.3
Applications for repair and pulp regeneration
Repair and regeneration in endodontics deal with systems and mechanisms that maintain or restores
original structures and functions of tissue by reproducing embryonic development. In the tooth, the
main concern of researchers and ultimately clinicians is the maintenance or regeneration of the
