Young Bui
 |
 TA,
mineral trioxide aggregate, is a new material developed for endodontics
use. MTA appears to be a significant improvement over other materials
for procedures in bone. Unlike ZOE cement, amalgam, and resin composite,
which resulted in the formation of fibrous connective tissue adjacent to
the bone, MTA allows osteoblasts to attach and spread on it with little
or no tissue inflammation. It is the first restorative material that
consistently allows for the overgrowth of cementum. Schwartz et al
(July 1999) showed that root ends filled with MTA had a complete layer
of cementum over the filling. Comparing gap sizes between the root-end
filling materials and their surrounding dentin shows that MTA had better
adaptation compared with amalgam, Super-EBA, and IRM. This improved
adaptation allows MTA to provide a better seal when used as retrograde
filling.
Keiser et al (May 2000) compare the cytotoxicity
of MTA to other commonly used retrofilling materials, Super-EBA and amalgam.
In the freshly mixed state, the sequence of toxicity was amalgam > Super-EBA
> MTA. In the twenty-four-hour set state, the sequence of toxicity
at a low extract concentration was Super-EBA > MTA, amalgam, and Super-EBA
> amalgam > MTA at a higher extract concentration. Torabinejad et
al (July 1998) showed the tissue reaction to implanted MTA, amalgam, IRM,
and Super-EBA in the tibias and mandibles of guinea pigs. The tissue
reaction to MTA implantation was the most favorable observed at both sites.
In the tibia, MTA was the material most often observed with direct bone
apposition.
There are many uses for MTA in addition to its use
as a root-end filling. MTA can be used to seal perforations; it acts
as a pulp capping material; it produces apical hard tissue formation in
immature teeth; and it acts as an apical barrier in open apex cases.
Sealing off the perforation site immediately during
the initial visit will give the best prognosis for the tooth. The
trick for sealing mid-root strip perforation is to first clean out the
canal completely and then fill it with gutta percha and sealer. Next,
remove the gutta percha to about 2 mm below the perforation and irrigate
out the debris. Next, mix the MTA to a putty consistency and pack
it down the canal with either a plugger or a medium-size gutta percha.
The trick to mixing the MTA is not to have it too dry. If it is too
dry, it will fall apart on you as you try to pick it up. Use enough
water to make it into a putty so that you can pick it up easily.
MTA can be used as a pulp capping material in vital
mechanical exposure or in primary tooth pulpotomy. Ford et al (October
1996) found that pulps capped with MTA had no pulpal inflammation after
five months in five of six samples and all six pulps in this group had
a complete dentin bridge formation. In contrast, all the pulps capped
with Ca(OH)2 showed pulpal inflammation, and bridge formation occurred
in only two samples. Eidelman, Holan, and Fuks (January 2001) did
a study to compare the effect of MTA with that of formocresol as pulp-dressing
agents in pulpotomized primary molars with carious pulp exposure.
They found that none of the MTA-treated teeth showed any clinical or radiographic
pathology at a 17-month recall.
Ca(OH)2 has been the material of choice for apexification
in vital teeth. Shabahang et al (January 1999) showed that MTA produced
apical hard tissue formation with significantly greater consistency than
Ca(OH)2 or osteogenic protein-1. For non-vital open apex cases, MTA
can be packed down to the apex and the canal can be filled in on the same
visit. The MTA will act as an apical barrier and allow for bone to
grow around it. The radiograph in Figure 1 shows the before and after
of a non-vital open apex sealed with MTA and gutta percha in a one-visit
treatment.
I’m sure that you are probably saying, “Wow, great
stuff! But how much will it cost me?” MTA is being sold in
six one-gram packages for $249, manufactured by Tulsa Dentsply. Holland
(2001) compared the healing property of MTA and Portland cement as a pulp-capping
material and found no difference between the two. MTA has the same
chemical properties as Portland cement except that MTA also has bismuth
to give it a more opaque look in a radiograph.
January-February 2002
|
FIGURE 1: Radiograph
showing a non-vital open apex before sealing.
FIGURE 2: Radiograph showing
a non-vital open apex after sealing with MTA and gutta percha in a one-visit
treatment.
|
