Elastic-plastic element for filling root canals and a preparation method

The invention relates to an elastic-plastic element comprising an isoprene-based matrix and at least one filler, the element being suitable for filling root canals of humans or animals and being characterised by calcium hydroxide, incorporated into the matrix, as filler. The invention relates also to a method of preparing the element according to the invention.

The present invention relates to an elastic-plastic element comprising an 
isoprene-based matrix and at least one filler, the element being suitable 
for filling root canals of humans or animals. The invention relates also 
to a method of preparing the elastic-plastic element. 
In the treatment of the disorder known as pulpitis, the diseased pulpa is 
removed mechanically from the root canal and the root canal is cleaned and 
drilled out, filled with an elastic-plastic element or with a different 
filling material and then sealed. For the prior art, see, for example, 
Friedman et al. in J. Dent. Res., 54 (1975) 921-925, Briseno in Philipp J. 
2.98 (1990) and U.S. Pat. No. 4,632,977. As root canal filling materials, 
Briseno describes, inter alia, semi-rigid cements based on synthetic 
resin, zinc oxide eugenol or on calcium hydroxide. U.S. Pat. No. 4,632,977 
proposes filling materials based on trans-polyisoprene, for example based 
on gutta-percha or balata. Gutta-percha points are commercially available, 
the standard composition thereof being 20% by weight of gutta-percha as 
matrix, from 60 to 75% by weight of zinc oxide as filler, from 1 to 17% by 
weight of heavy metal sulphates as X-ray contrast agent and from 3 to 4% 
by weight of waxes and resins as plasticizer. That known filling material 
is inert in the root canal and accordingly does not react with body 
tissue. 
During the filling of a root canal with a known inert filling material, it 
cannot, however, be ruled out that, for example as a result of germs 
remaining in the canal, after the filling operation an inflammatory 
process may slowly develop which renders further treatment necessary, 
often resulting in complete loss of the tooth. 
In view of the prior art, the problem underlying the present invention is 
to provide an elastic-plastic element for filling root canals of humans or 
animals that can be prepared and processed readily and simply and is not 
subject to the adverse effects mentioned. The problem underlying the 
present invention is also to provide a method of preparing such an 
element. 
That problem is solved according to an embodiment of the invention by an 
elastic-plastic element comprising an isoprene-based matrix and at least 
one filler, the element being suitable for filling root canals of humans 
or animals and being characterised by calcium hydroxide, incorporated into 
the matrix, as filler. 
Calcium hydroxide can be processed readily with an isoprene-based matrix, 
such as gutta-percha, it being advantageous to roll in the calcium 
hydroxide in the form of a powder, which simplifies the preparation 
process substantially. 
Since calcium hydroxide has an alkaline action, it is able to buffer the 
acids that form in inflammatory processes and is able to limit a rise in 
the pH value. As a result, the healing process is advantageously 
accelerated and assisted. The insert can remain in the root canal 
temporarily or for a prolonged period of time. 
According to the invention, a matrix based on trans-polyisoprene, 
gutta-percha and/or on balata may be provided. The matrix may be 
characterised by at least 80% by weight of trans-polyisoprene. 
The elastic-plastic element according to the invention may be in the form 
of a gutta-percha point. 
The calcium hydroxide used as filler according to the invention may be 
provided in the form of a mixture with a customary, different filler, such 
as zinc oxide, or may be provided as sole filler. The filler is preferably 
more of calcium silicate. 
Of course, the elastic-plastic element according to the invention may 
comprise additionally a pharmaceutical active ingredient, especially an 
active ingredient that is soluble or dispersible in an aqueous medium, for 
example an antibiotic and/or glucocorticoid, and also a customary X-ray 
contrast agent and customary waxes, resins or other excipients. An 
elastic-plastic element according to the invention may be characterised 
preferably by: 
(a) from 43.5 to 65.0% by weight of matrix, 
(b) from 35.0 to 56.5% by weight of filler, 
(c) optionally additionally up to 8% by weight of X-ray contrast agent, 
based on (a) and (b), and 
(d) optionally additional customary components. 
For example, the elastic-plastic element according to the invention may be 
characterised, for example, by 
(a) approximately 43.5% by weight of gutta-percha, 
(b) approximately 56.5% by weight of calcium hydroxide as sole inorganic 
filler, 
(c) optionally additionally up to 8% by weight of X-ray contrast agent, 
based on (a) and (b), and 
(d) optionally additional customary components. 
The elastic-plastic element according to the invention has, accordingly, 
essentially three components which will be explained in greater detail 
hereinafter. 
Component 1 
The mechanical properties of an elastic-plastic element according to the 
invention are determined primarily by the properties of the matrix, which 
makes up, for example, from 43.5 to 65.0% by weight together with from 
35.0 to 56.5% by weight of filler (component 2). The matrix must, on the 
one hand, be elastic so that it can be processed easily and introduced 
readily into the root canal. On the other hand, it should have plastic 
properties so that the root canal can be completely filled permanently 
without a gap being left at the wall. Moreover, the matrix must be able to 
take up other components, especially the filler, readily. For those 
purposes, a matrix having at least 80% by weight of trans-polyisoprene has 
proved advantageous. Gutta-percha may be mentioned by way of example, 
which is a naturally-based matrix, the main component of which is 
trans-polyisoprene. Of course, other trans-polyisoprenes can also be used, 
such as balata, isoprene-based synthetic materials or derivatives of the 
mentioned materials. 
Component 2 
The elastic-plastic element according to the invention is characterised by 
calcium hydroxide as filler. The filler is present, for example, in an 
amount of from 35.0 to 56.5% by weight together with from 43.5 to 65.0% by 
weight of matrix. Calcium hydroxide is a substance that is tolerated by 
tissue and by the body and can be mixed with the matrix and compounded 
additionally with pharmaceutical active ingredients and customary 
excipients. 
Calcium hydroxide can be rolled in powder form into gutta-percha, which 
renders the preparation process very simple. 
As already stated, calcium hydroxide is able to buffer the pH rise that 
usually occurs in inflammatory processes. It is therefore desirable to 
introduce as much calcium hydroxide as possible into the root canal. The 
amount of calcium hydroxide in the elastic-plastic element according to 
the invention is accordingly guided by that desire, on the one hand, and 
by the capacity of the matrix to take up the inorganic filler, on the 
other. An example of an elastic-plastic element having a very high filler 
content is a gutta-percha point having a content of approximately 56.5% by 
weight of calcium hydroxide together with approximately 43.5% by weight of 
gutta-percha. 
Component 3 
A further, optional (although customary) component that may be provided is 
an X-ray contrast agent, for example a heavy metal sulphate, such as 
barium sulphate, or a bismuth/strontium compound. The component may be 
provided in an amount of up to 8% by weight, based on matrix and filler. 
Finally, according to a further embodiment of the invention, there is 
provided a method of preparing an elastic-plastic element according to the 
invention, characterised by: 
(a) forming a film of an isoprene-based matrix; 
(b) rolling into the matrix film at least one filler and optionally also an 
X-ray contrast agent and further optional customary excipients, preferably 
in powder form or in a form that is not too highly viscous; 
(c) comminuting and extruding the compounded film; and 
(d) cutting up the extruded material and rolling the cut piece to form 
elastic-plastic elements that are suitable for filling root canals of 
humans or animals.

The invention will be illustrated hereinafter by an Example. 
EXAMPLE 
To prepare gutta-percha points, first, gutta-percha as matrix is rolled 
between a support roller and a pressure roller so that the gutta-percha 
lies around the support roller in the form of a thin film or in the manner 
of a skin. Calcium hydroxide in powder form in a weight ratio of 56.5% 
Ca(OH).sub.2 : 43.5% gutta-percha is subsequently rolled into the film 
that has been formed, the film is peeled away from the support roller, and 
the peeled-off film is comminuted and extruded to form a thin wire-like 
strand. The strand is then cut up and rolled. 
The resulting elastic-plastic elements can be introduced readily into root 
canals and are positioned without canalization.