Biomedical Engineering Reference
In-Depth Information
Evidence suggests that orthodontic tooth movement can be enhanced by supplementing the
mechanical forces with electricity
[44,45]
. Animal experiments indicated that when 15
20 micro-
amperes of low direct current (dc) was applied to the alveolar bone by modifying the bioelectric
potential, osteoblasts and periodontal ligament cells demonstrated increased concentrations of the
second messengers cAMP (adenosine-3
0
,5
0
-cyclic monophosphate) and cGMP (cyclic guanosine
monophosphate). These findings suggest that electric stimulation enhanced cellular enzymatic phos-
phorylation activities, leading to synthetic and secretory processes associated with accelerated bone
remodeling. However,
the intraoral source of electricity is a major problem that has to be
addressed.
It has been recently proposed that microfabricated biocatalytic fuel cells (enzyme batteries) can
be used to generate electricity to aid orthodontic tooth movement
[46]
. An enzymatic microbattery,
when placed on the gingiva near the alveolar bone, might be a possible electrical power source for
accelerating orthodontic tooth movement. It is proposed that this device uses organic compound
(glucose) as the fuel and is noninvasive, and non-osseointegrated. The enzyme battery can be fabri-
cated with the combination of two enzyme electrodes and biocatalysts such as glucose oxidase or
formate dehydrogenase to generate electricity (
Figure 11.6
)
[46]
. However, there are several issues
like soft tissue biocompatibility, effect of food with different temperature and pH range on the out-
put of such microfabricated enzyme battery that need to be addressed. The use of microenzyme bat-
teries has issues like enzyme stability, electron transfer rate, and enzyme loading which result in
shorter lifetime and poor power density.
Glucose
O
2
Gluconolactone
H
2
O
FIGURE 11.6
A schematic diagram of an oral biocatalytic fuel cell. In this system, the following reaction generating electricity
for enhancing orthodontic tooth movement occurs: Glucose
O
2
-
gluconolactone
H
2
O/H
2
O
2
[46]
.
1
1
