Glass Ionomer Cements (GIC) are widely used dental materials. They
adhere to hard dental tissues, release fluoride ions and are
bio-compatible. GIC are obtained from the reaction during the hardening
process between a polymeric acid and acid-degradable glass.
Water plays a crucial role in this reaction; its absence retards or
even prevents the reaction while high concentrations results in
improper glass matrix formation. In either case, the resulting
cement has poor mechanical properties. A potential problem that may
manifest itself in clinical applications is the migration of water from
the oral cavity into the still hardening cement. To prevent this
process, special surface coatings (varnishes) were proposed. Magnetic
resonance microscopy is a convenient tool for studying water migration
into dental cements and other porous materials because of its good
spatial resolution and high sensitivity. The aim of our MR microimaging
study was to evaluate the effect of surface coating on the reduction of
water contamination in glass GIC restorations [1].
Water concentration in glass ionomer dental cement 36 hours (a, b) and
192 hours (c, d) after immersion in water measured by MR microscopy (a,
c) and computer simulated (b, d).
Precise assessment of anatomical
features of a human tooth pulp chamber is essential for a successful
endodontical treatment. The shape of dental pulp anatomy is often
difficult to predict correctly. In many cases dental pulps of first,
second, third molars, premolars or even incisors or canines have
different number of root channels, which may be irregularly shaped and
may have pulpo-periodontal communications. A standard X-ray radiograph
of human tooth is obtained by absorption of X rays in hard dental
tissues, such as dentine or enamel. Therefore, it yields
an image of pulp’s projection in 2D in one orientation only. The X-ray
image is also an inverse image of the pulp and the pulp’s shape can be
judged just from its outline. X-ray radiographs therefore do not
provide sufficient information on pulp’s anatomy, which makes the
outcome of the endodontical treatment unpredictable. An efficient 3D
imaging technique could minimize these problems as it would enable
precise assessment of pulp anatomy in 3D and enable visualization of
all root channels and fine anatomical details. Therefore MR microscopy
has great potentials to become future standards for dental pulp imaging
[2].
Images above show a first molar imaged by the conventional X-ray
radiography
(left) and by the volume rendered 3D MR microscopy (right). In MR
microscopy signal comes from the pulp directly and the pulp can be
therefore much better visualized than by X-ray radiography.
Unfortunately, due to limitations of the present hardware,
high-resolution MR imaging of human teeth can be done
in
vitro only as the scanning time is too long and there is no
dedicated hardware for
in-vivo tooth MR microscopy.
In spite of that, MR microscopy is very promising tool for studying the
pulp anatomy. It enables precise determination of a number and a shape
of root channels; it can visualize communications between
the channels and can even reveal fine anatomical details such as
pulpo-periodontal communications.
