Biomedical Engineering Reference
In-Depth Information
Calcium hydroxide, originally designed as a channel disinfectant and filler material by Hermann
in 1920, remains a topical antiseptic widely used. The suspension of calcium hydroxide releases Ca
ions that results in alkalinization of the environment. Similarly, the antibacterial properties of bio-
active glasses are based on the potential of increasing the pH in aqueous suspensions
[51]
resulting
from the exchange of sodium ions and protons of the glass matrix in an aqueous environment
[52]
.
The broad-spectrum antimicrobial effect of bioactive glass in different oral microorganisms has
been reported, which justifies its use as an intracanal medication endodontic therapy
[42]
. The
increase in specific surface area of bioactive glass nanoparticles improves the area of active release
of ions, resulting in the improvement of antibacterial properties of the material. E. faecalis is one
of the more resistant microorganisms in endodontic therapy and is often associated with treatment
failure. However, research has shown that particles of 20
50 nm bioactive glass increased antibac-
terial properties against E. faecalis in direct contact model
[43]
.
Bioactive glasses are known for osteoconductivity and bonding to bone through the release of
ions and formation of a layer of apatite
[53]
. Because of these characteristics, bioactive glasses are
widely used for bone reconstruction and tissue engineering, but are also interesting candidates for
the mineralization in dentistry. In the past decades, bioactive glass nanoparticles have been used on
studies about the specific effects of remineralization of dentin, due to their excellent regenerative
properties in mineralized tissues.
Dentin is a permeable tubular structure representing most of the dental tissue composed of the
organic matrix embedded in a crystalline matrix of apatite, having about 70% of apatite, 20% of
collagen, and 10% of water. Although there is a physiological balance between demineralization
and remineralization of dental hard tissues in the oral cavity, some factors such as an acidic diet or
the presence of plaque can cause disequilibrium, which results in tooth demineralization.
Several studies suggest that bioactive glass has potential as an agent of dentin mineralization and
restorative filling
[54,55]
. As explained above, bioactive glass when in contact with body fluids inter-
acts with the environment, releasing ions and subsequently forming a layer of apatite. Saliva is also a
body fluid that will stimulate the interaction of bioactive glass with the environment and release of
ions and the formation of apatite. However, the mineralization process is long, which impedes the
use of bioactive glass in dental practices. A possible acceleration of this process is the use of bio-
active glass nanoparticles, since the high specific surface area of the nanoparticles may facilitate the
dissolution of ions from the glass and thus accelerate the dentin mineralization
[10]
. Vollenweider
et al. (2007) showed that after treatment with bioactive glass nanoparticles for 30 days, there was a
pronounced increase in the mineral content of the dentin samples
[53]
. In addition, bioactive glass
nanoparticles can be used in minimally invasive cavity preparation teeth. However, it is still neces-
sary to create alternatives that allow effective use of bioactive glass nanoparticles in this procedure.
Another application of the ability of remineralization of bioactive glass is related to the dentin
sensitivity. Dentin hypersensitivity is characterized by sharp, localized, non-spontaneous pain
occurring in response to some stimulus. This pain is caused by loss of the tooth structure, resulting
in exposure of dentinal tubules to the oral environment. The currently accepted theory for hypersen-
sitive dentin is the hydrodynamic theory, which proposes that external stimuli such as cold, hot,
pressure, or tactile when applied to exposed dentin causes movement within the dentinal tubules
[56]
. This movement of fluid stimulates mechanoreceptors near the dentinal tubule and can trigger
a pain response. This theory is based on the understanding that open tubules allow fluid flow
through the tubules, which results in pressure changes that excite the nerve endings in the tooth
