Electro-conductive and anti-bacterial composite material, for endodontic use

Abstract

A gutta-percha-silver composite with determined weight percentage and particle size, is provided. The composite exhibits electro-conductivity greater than the standard gutta-percha composites. The new material simplifies root canal treatments, shortens the times both for clinician and patients, and reduces the exposure to patients from X-rays. The material is not only electro-conductive; it is anti-bacterial, which improves the outcomes of the procedures. Also, it has improved thermal conductivity, and mechanical properties.

Claims

1. An endodontic filling material for root canal treatment, comprising: a gutta-percha-based material; and a metallic powder having particles greater than 10 μm, wherein at least 70% by weight of the metallic powder is mixed with the gutta-percha-based material so as to form a mixture exhibiting electro-conductivity that is detectable with an electronic apex-locator.

2. The endodontic filling material of claim 1, wherein the metallic powder is a powder of at least one of silver, titanium, stainless steel, graphite, aluminium, copper, and gold, or mixtures thereof.

3. The endodontic filling material of claim 2, wherein the metallic powder is a silver powder.

4. The endodontic filling material of claim 1, wherein the amount of the metallic powder in the mixture is 70-80% by weight.

5. The endodontic filling material of claim 1, wherein the metallic powder particles have an elongated shape.

6. The endodontic filling material of claim 1, wherein the gutta-percha-based material includes one paste and one powder material comprising more than 20% gutta-percha.

7. An endodontic filling material for root canal treatment comprising: a gutta-percha-based material; and a metallic powder, wherein the metallic powder is mixed with the gutta-percha-based material in sufficient quantity to form a mixture exhibiting electro-conductivity that is detectable with an electronic apex-locator, and wherein the gutta-percha-based material includes one paste and one powder material comprising 20% gutta-percha, 66% zinc oxide and 11% heavy metals powder.

8. The endodontic filling material of claim 1, wherein the gutta-percha-based material includes an anti-bacterial powder component.

9. The endodontic filling material of claim 8, wherein the anti-bacterial powder is selected from the group consisting of silver, titanium, iron, gold, copper, platinum, aluminum, molybdenum, zinc, tungsten, brass, carbon, nickel, palladium, tin, carbon steel, stainless steel, mercury, and their alloys, and mixtures thereof.

10. The endodontic filling material of claim 1, wherein the endodontic filling material has antibacterial properties and assists in infection control after an endodontic procedure.

11. The endodontic filling material of claim 1, wherein the endodontic filling material has X-ray radiopacity.

12. An endodontic point for root canal treatment, comprising: the endodontic filling material of claim 1, wherein the mixture formed from the gutta-percha-based material and the metallic powder is formed into a point.

13. A method for performing root canal treatment, the method comprising the steps of: forming an opening in a crown of a tooth; removing tissue in a root canal system of the tooth; shaping the root canal; placing the endodontic point of claim 12 into the root canal; determining when the endodontic point is at the root canal apex with an electronic apex-locator; stabilizing the endodontic point in place in the root canal; and filling the opening.

14. The method of claim 13, wherein the method further includes the step of taking an X-ray of the tooth after the point is placed in the root canal so as to view the location of the point due to its radiopacity.

15. The method of claim 13, wherein the method further includes the step of adding an anti-bacterial powder component to the gutta-percha-metal powder material of the endodontic point.

16. The method of claim 15, wherein the anti-bacterial powder is selected from the group consisting of silver, titanium, iron, gold, copper, platinum, aluminum, molybdenum, zinc, tungsten, brass, carbon, nickel, palladium, tin, carbon steel, stainless steel, mercury, and their alloys, and mixtures thereof.

17. The method of claim 13, wherein the metallic powder of the endodontic point is a silver powder, and the composition of silver powder in the mixture of the endodontic filling material is greater than 50% by weight.

18. The method of claim 17, wherein the silver powder is comprised of particles that are elongated in shape and have a size greater than 0.1 micrometers.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

(1) The foregoing and other objects and advantages of the present invention will become more apparent when considered in connection with the following detailed description and appended drawings in which like designations denote like elements in the various views, and wherein:

(2) FIGS. 1a-1e illustrate a sequences of standard root canal treatment procedures:

(3) FIG. 2a illustrates positive control in which the metal probe (file) is located outside the tooth and the apex-locator shows no activity, FIG. 2b illustrates the file inside the tooth with the apex-locator showing the location of the root canal apex, and FIG. 2c illustrates a view of the tip of the file located exactly at the root canal apex;

(4) FIG. 3a illustrates negative control in which a standard gutta-percha point is located outside the tooth and the apex-locator showing no activity, FIG. 3b illustrates the standard gutta-percha point inside the tooth and the apex-locator showing no activity, and FIG. 3c illustrates a view of the tip of the standard gutta-percha point protruding out from the root canal apex; and

(5) FIG. 4a illustrates a test of the electro-conductive gutta-percha point located outside the tooth and the apex-locator showing no activity; FIG. 4b illustrates the electro-conductive gutta-percha point inside the tooth with apex-locator showing its location at the root canal apex, and FIG. 4c shows a view of the tip of the electro-conductive gutta-percha point located exactly at the root canal apex.

(6) FIGS. 5a-g illustrate an example of the process for preparing the electro-conductive gutta-percha point illustrated in the FIG. 4 of the present invention.

(7) FIGS. 6a-i show the pictures of the filler material used in the examples of the present description.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

(8) In the following examples, one gutta-percha composite material available from the market (20% gutta-percha, 66% zinc oxide, and 11% barium sulphate) is mixed with silver particles. Also, other components such as titanium, stainless steel, graphite and silver of different particle sizes may be used. Preferably the silver particles have an elongated shape. The formulation preferably requires a minimum of 50% silver by weight to achieve some electro-conductivity. With higher percentages of silver the electro-conductivity is improved. Also, with different gutta-percha materials (pastes), including pure gutta-percha, a smaller amount of metal powder may be needed. It is easily within the capability of one of reasonable skill in the art to try different percentages of silver or other metal powders with different gutta-percha materials to determine a minimum percentage of metal powder at which there is electro-conductivity.

(9) While the present invention may use single metal components, it is also possible to use mixtures, e.g., mixtures of two or more of titanium, stainless steel, graphite and silver powders, as well as alloys thereof.

(10) Particles of size <0.1 μm have worse electrical properties and, although they achieve some electro-conductivity at 50% silver by weight, they are in a saturated state compromising the mechanical properties of the material. In particular, the material may become less formable and may lose powder. On the contrary, particles >0.1 μm show some electro-conductivity at 50% silver by weight without the above-mentioned limitations. Therefore, preferably silver with particle size >10 μm and with >50% silver by weight can show conductivity comparable to the metallic probe (file) commonly mounted on the apex-locator.

(11) Some examples showing the potential range of the present invention are as follows: An example with a typical composition: Paste (20% gutta-percha, 66% zinc oxide, 11% barium sulphate) plus Powder (100% silver), with powder/paste ratio of 70% in weight, and Particle size ≈2500 micro meters, with elongated shape. An example with less gutta-percha and less weight percentage: Paste (>20% gutta-percha) plus Powder (100% silver), with powder/paste ratio of >50% in weight, and Particle size >10 micro meters, with elongated shape. As extreme example, very low gutta-percha and weight percentage: Paste (>1% gutta-percha) plus Powder (100% metal), with powder/paste ratio of >1% in weight, and Particle size >0.1 micro meters.

(12) The new developed electro-conductive endodontic gutta-percha composite possesses anti-bacterial properties (e.g., against the dental microbe Porphyromonas gingivalis). In particular, the following materials provide both electro-conductive and anti-bacterial powder components (e.g., silver, titanium, iron, gold, copper, platinum, aluminum, molybdenum, zinc, tungsten, brass, carbon, nickel, palladium, tin, carbon steel, stainless steel, mercury, or their alloys, or compositions, or various particle sizes of different powders).

(13) Standard root canal treatment is shown in FIG. 1. In particular, FIG. 1a shows an infected tooth with decay penetrating to the dentin that leads to pulp necrosis and an abscess at the apex of the root. In the procedure, after local anaesthesia (if required by clinical evaluation), an opening is drilled into the crown to create an access point. In FIG. 1c there is illustrated a file being used through the opening to reach the root canal system and to remove most of the nerve tissue. Next the root canal system is shaped and irrigated with antibacterial agents (such as sodium hypochlorite), which help to flush out debris and bacterial remnants as well. Then the root canal system and pulp chamber are dried.

(14) Subsequently, as shown in FIG. 1d, a plugger extends into the opening and is used to pack and fill the root canal system with heat-softened gutta-percha composite. The gutta-percha composite should be used to fill the root canal system exactly to the root canal apex. In some cases (e.g., in the lateral cold condensation technique) the gutta-percha composite is neither melted nor heat-softened, but is simply placed in the root canal and stabilized with endodontic cement. The newly developed electro-conductive gutta-percha composite is thus suitable for cold techniques as well.

(15) Finally in FIG. 1e the opening is sealed with a filling material. Failure to completely seal the root canal system may lead to micro-leakage and will lead to future bacterial colonization inside the root canal system, and possibly re-infection leading even to the loss of the tooth.

(16) In order to achieve a complete filling of the root canal system to the root canal apex, it is necessary to know the length of the root canal. Measuring the length of the root canal can be achieved either by taking one or more X-rays with a metallic probe (file) of a known length inserted in the root canal and then measure it. As an alternative an apex-locator can be used to determine the location of the metallic probe (file), and then measure it. This method is the gold standard in the endodontic treatment, and the apex-locator (measuring the root canal length using electrical resistivity principles) is considered the best practice, and most dentists use this method.

(17) The gutta-percha composite material that fills the root canal system is provided in cone-shaped points. These points have to be inserted into the tooth with their tip precisely reaching the root canal apex. Thanks to the previous length measurements, the dentist knows the length of the root canal, and can insert the gutta-percha point the right amount to reach the root canal apex. However, since a high precision is required and because the gutta-percha point may bend and the metallic probe previously used (file) is different from a gutta-percha point, after inserting the real gutta-percha point in the supposed correct position, an X-ray is necessary to check that the tip of the gutta-percha point is really at the root canal apex.

(18) FIG. 2a illustrates a positive control test in which the outside of the tooth 10 is surrounded by a plastic holder. The extracted tooth alone has no detectable differences in the electrical conductivity between the root canal system and the surrounding air. Therefore, to simulate the clinical situation the holder firmly stabilizes the tooth and an electro conductive gel is placed around the root. In this way, the endodontic procedures can be performed in vitro simulating the clinical environment. A metal probe or file 14 is outside the tooth and the meter 16 of the apex-locator shows no activity FIG. 2b illustrates the file inside the tooth with the apex-locator showing the location of the root canal apex on the meter. FIG. 2c illustrates a view of the tip of the file located exactly at the root canal apex.

(19) FIG. 3a illustrates a negative control test in which a standard gutta-percha point 18 is located outside the tooth and the meter of the apex-locator shows no activity. The source of said standard gutta-percha point 18 is a manufacturer from the market, the composition is 20% gutta-percha, 66% ZnO, 11% BaSO.sub.4, 3% wax. In FIG. 3b the standard gutta-percha point is inside the tooth and the apex-locator still shows no activity because it has no electro-conductive properties. FIG. 3c shows the tip of the standard gutta-percha point protruding out from the root canal apex.

(20) FIG. 4 illustrates a test of the electro-conductive gutta-percha point of the present invention. The composition of said electro-conductive gutta-percha point is 70% Ag, 6% gutta-percha, 20% ZnO, 3% BaSO.sub.4, 1% wax, which is prepared by the process illustrated in the FIG. 5. FIG. 4a shows the point 20 according to the present invention located outside the tooth and the apex-locator showing no activity. In FIG. 4b the electro-conductive gutta-percha point is shown inside the tooth with apex-locator meter 16 showing its location at the root canal apex. FIG. 4c shows the tip of the electro-conductive gutta-percha point located exactly at the root canal apex.

(21) FIGS. 5a-g illustrate an example of the process for preparing the electro-conductive gutta-percha point illustrated in the FIG. 4 of the present invention, which comprises the following steps: a) Providing gutta-percha composite from the market, c.f. FIG. 5a. b) Providing the metal from the market, c.f. FIG. 5b. c) Preparing a metal powder from by milling the metal, c.f. FIG. 5c. d) Softening the gutta-percha composite on a heating plate, c.f. FIG. 5d. e) Adding the necessary amount of metal powder to the softened gutta-percha composite and mixing the two components with a spatula to form a composite material, c.f. FIG. 5e. f) Rolling the new composite material to give the desired shape, c.f. FIG. 5f. g) Verifying the electro-conductivity of the material, c.f. FIG. 5g.

(22) The same preparing process is used to prepare electro-conductive gutta-percha points with filler material selected from titanium (Ti), stainless steel (SS), graphite (C), and silver (Ag) powders having small (S) and big (B) particle size and different filing percentage (10% to 90%). Moreover, the resistivity and the mechanical properties are tested for the above electro-conductive gutta-percha points.

(23) The electrical resistivity is measured by a known instrument (multimeter/ohmmeter) by contacting two metallic probes (input terminals) of the instrument with the electro-conductive gutta-percha points with a distance (expressed in mm) between the tips of said two metallic probes.

(24) The parameters for the preparation of said electro-conductive gutta-percha points and their test results are shown in the following tables.

(25) TABLE-US-00001 TABLE 1a RESISTIVITY (ohm) FILLER (g/g.sub.tot) 10% 20% Matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), ZnO Ti S I I I I I I I I I I (66%), BaSO.sub.4(11%), wax B I I I I I I I I I I (3%) SS S I I I I I I I I I I B I I I I I I I I I I C S I I I I I I I I I I B I I I I I 2 * 10.sup.4 3 * 10.sup.4 5 * 10.sup.4 1 * 10.sup.5 1 * 10.sup.5 Ag S I I I I I I I I I I M I I I I I I I I I I B I I I I I I I I I I

(26) TABLE-US-00002 TABLE 1b RESISTIVITY (ohm) FILLER (g/g.sub.tot) 30% 40% matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), Ti S I I I I I 10 20 20 50 50 ZnO (66%), B 1 * 10.sup.2 2 * 10.sup.2 3 * 10.sup.2 5 * 10.sup.2 2 * 10.sup.3  8 16 25 40 2 * 10.sup.2 BaSO.sub.4(11%), wax SS S I I I I I I I I I I (3%) B I I I I I I I I I I C S 8 * 10.sup.3 1 * 10.sup.4 2 * 10.sup.4 2 * 10.sup.4 3 * 10.sup.4 R R R R R B 5 * 10.sup.2 8 * 10.sup.2 8 * 10.sup.2 8 * 10.sup.2 1 * 10.sup.3 R R R R R Ag S I I I I I I I I I I M I I I I I I I I I I B I I I I I I I I I I

(27) TABLE-US-00003 TABLE 1c RESISTIVITY (ohm) FILLER (g/g.sub.tot) 50% 60% matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta Ti S 8 8 10 12 15 R R R R R percha B R R R R R R R R R R (21%), SS S I I I I I 10 * 10.sup.3 10 * 10.sup.3 15 * 10.sup.3 20 * 10.sup.3 30 * 10.sup.3 ZnO B 2 * 10.sup.3 5 * 10.sup.3 10 * 10.sup.3 20 * 10.sup.3 I 60 3 * 10.sup.2 4 * 10.sup.2 7 * 10.sup.2 2 * 10.sup.3 (66%), C S R R R R R R R R R R BaSO.sub.4 B R R R R R R R R R R (11%), Ag S I I I I I R R R R R wax (3%) M I I I I I 50 10 * 10.sup.2 10 * 10.sup.3 I I B I I I I I 50 10 * 10.sup.2 10 * 10.sup.3 I I

(28) TABLE-US-00004 TABLE 1d RESISTIVITY (ohm) FILLER (g/g.sub.tot) 70% 80% 90% matrix Particle Distance (mm) Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 1 5 10 20 30 Gutta percha Ti S R R R R R R R R R R R R R R R (21%), ZnO B R R R R R R R R R R R R R R R (66%), SS S 5 * 10.sup.3 10 * 10.sup.3 15 * 10.sup.3 20 * 10.sup.3 30 * 10.sup.3 R R R R R R R R R R BaSO.sub.4 B R R R R R R R R R R R R R R R (11%), C S R R R R R R R R R R R R R R R wax (3%) B R R R R R R R R R R R R R R R Ag S R R R R R R R R R R R R R R R M 5 5 5 5 5 5 5 5 5 5 R R R R R B 5 5 5 5 5 5 5 5 5 5 R R R R R Note: I = infinite (means that resistivity is almost infinite, while very small conductivity may be present but might not be detectable with the ohmmeter.) R = saturated (means that with the technique used during the experiment to mix the metallic powder with the guttapercha composite, at that point a limit is reached and no more powder can be added in the mixture, i.e. the composite material is saturated (full). Depending on the material and on the particle size, different percentages of powder are necessary to reach saturation of the mixture. Probably with different mixing techniques/temperatures the saturation percentage can change.)

(29) TABLE-US-00005 TABLE 2a Quality of the mechanical properties FILLER (g/g.sub.tot) 10% 20% Matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), ZnO (66%), Ti S G G G G G G G G G G BaSO.sub.4 (11%), wax (3%) B G G G G G G G G G G SS S G G G G G G G G G G B G G G G G G G G G G C S G G G G G G G G G G B G G G G G G G G G G Ag S G G G G G G G G G G M G G G G G G G G G G B G G G G G G G G G G

(30) TABLE-US-00006 TABLE 2b Quality of the mechanical properties FILLER (g/g.sub.tot) 30% 40% Matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), ZnO (66%), Ti S G G G G G A A A A A BaSO.sub.4 (11%), wax (3%) B G G G G G P P P P P SS S G G G G G G G G G G B G G G G G G G G G G C S P P P P P B P P P P P Ag S G G G G G G G G G G M G G G G G G G G G G B G G G G G G G G G G

(31) TABLE-US-00007 TABLE 2c Quality of the mechanical properties FILLER (g/g.sub.tot) 50% 60% matrix Particle Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), ZnO (66%), Ti S P P P P P BaSO.sub.4 (11%), wax (3%) B SS S G G G G G A A A A A B A A A A A P P P P P C S B Ag S P P P P P M G G G G G G G G G G B G G G G G G G G G G

(32) TABLE-US-00008 TABLE 2d Quality of the mechanical properties FILLER (g/g.sub.tot) 70% 80% 90% matrix Particle Distance (mm) Distance (mm) Distance (mm) Material Material size 1 5 10 20 30 1 5 10 20 30 1 5 10 20 30 Gutta percha (21%), ZnO Ti S (66%), BaSO.sub.4 (11%), wax B (3%) SS S P P P P P B C S B Ag S M A A A A A P P P P P B G G G G G P P P P P Note: P = poor A = acceptable G = good distance (mm) = the distance, expressed in mm, between the tips of the two metallic probes (input terminals) of the instrument to measure the electrical resistivity (multimeter/ohmmeter)

(33) While the present invention has been particularly shown and described with reference to preferred embodiments thereof; it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.