RU2605814C1 - Method of processing of fine and hybrid composite filling materials - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention relates to medicine, namely to dentistry. Method of processing of fine and hybrid composite filling materials is disclosed, consisting in that filling material is subjected to ultrasound vibrations, intensity of which varies from 3 to 50 W/cm². Exposure is preferably carried out for period of time from 15 to 30 minutes, immediately before installation filling material in tooth cavity or no more than 2 months before its application.

EFFECT: use of method enables to destroy formed agglomerates and make uniform distribution of ultrafine particles in volume of filling material, thus improving aesthetic and mechanical properties of fine-grained and hybrid composite filling materials.

4 cl, 8 dwg

Description

The claimed invention relates to dentistry and can be used for the processing of fine-grained and hybrid composite filling materials.

The microfill composites widely used in modern dentistry contain particles ranging in size from 0.007 microns to 0.04 microns. [Composite materials. [Electronic resource]. - Electron, given. - Access mode: http://www.medterapevt.ru/85.html]. The introduction of nanosized non-agglomerated particles leads to an improvement in the aesthetic properties of fillings, as well as to a decrease in their polymerization shrinkage [Suvorova I.V. The study of composite dental materials by x-ray phase analysis // Polzunovsky bulletin. - 2008.-№3. - S. 242-244]. However, a number of drawbacks are inherent in these materials (for example, the formation of cracks on the boundary surfaces of fragmentation prepolymerizates and matrices during polymerization and under the influence of chewing loads [Composite materials. [Electronic resource]. - Electron, data. - Access mode: http: // www. medterapevt.ru/85.html]. This is responsible for the increasing use of nanohybrid materials (materials in which about 85-90% by weight of the filler are particles of the order of microns and 10-15% of the particles of no more than tens of nanometers in size) materials. tnye microfill materials, and hybrid composites containing fillers with a particle size of less than 20 nm, enabling them to call nanonapolnennymi composites.

The use of such materials faces certain difficulties. It is well known that nanoscale objects, under the action of van der Wals forces, tend to unite (agglomerate). The speed of this process is slowed down by placing nanosized particles in surfactants and a decrease in the temperature of the medium (storage in a refrigerator). However, it is impossible to completely stop the agglomeration process in non-solid media [A. Novik Investigation of the process of ultrasonic dispersion of ceramic materials in liquid media; dis. for a job. student Art. Ph.D. - St. Petersburg, 2013. - 131 p.]. As a result, a few months after manufacture, nanofilled composites have an inhomogeneous structure with large (of the order of a few microns) agglomerates that contain millions of ultrafine particles. This combination also leads to significant unevenness in the distribution of particles over the volume of the material. As a result, the filler particles can no longer fully fulfill the functions assigned to them.

This is claimed by manufacturers of similar materials [Filtek. Technical product profile. [Electronic resource]. - The electron. Dan. - Access mode: http://multimedia.3m.com/mws/media/629066O/filtektm-supreme-ultra-universal restorative.pdf]. Such a structure, on the one hand, worsens the volumetric mechanical properties of future fillings, and on the other hand, during medical treatment of the surface of fillings, due to the difference in the mechanical properties of the agglomerates and the surrounding polymer materials, inhomogeneities remain on the surface of these fillings, in which, in the future, pathogenic bacteria can accumulate and which significantly affect the aesthetic properties of fillings.

The presence of these problems requires the creation of conditions under which the filling materials will have a uniform structure immediately before their installation in the dental cavity.

To solve the problem of mixing heterogeneous materials, various kinds of mechanical mixers are usually used. In particular, in [Dental composition, method of producing and use thereof. United States patent. No. 2013303653655] homogenization of the filling material is achieved through the use of a special design mixer.

In the case of nanofilled composites, first of all, it is necessary to destroy the formed agglomerates. That is, to solve the problem fundamentally different from the one that the mixers solve. To solve the problem of agglomerate destruction, a powerful effect localized in sizes comparable with the sizes of agglomerates is needed, which is realized in the volume of filling material. Creating such an impact with traditional mixing methods is impossible. Therefore, these methods do not allow to solve the main task of the invention is to improve the aesthetic and mechanical properties of fine-grained and hybrid composite filling materials.

The technical result of the invention should be to improve the uniformity of the filling material, and hence its aesthetic and mechanical properties.

To obtain the technical result, a fine-grained or hybrid composite filling material is exposed to ultrasonic vibrations (US), the intensity of which is in the range from 3 to 50 W / cm ² , and it is advisable to carry out the exposure for a period of time from 15 s to 10 minutes immediately before installation of filling material in the dental cavity. Under the influence of ultrasonic vibrations, starting from a certain intensity, cavitation cavities can be obtained in the bulk of the material under which the conditions necessary to “break up” agglomerates of nanoparticles are realized [Promtov M. A. Cavitation. [Electronic resource]. Electron - Access mode: http://www.tstu.ru/structure/kafedra/doc/maxp/eito14.doc]. In this case, depending on the properties of the particular processed materials, ultrasonic vibrations should be of a certain intensity and the time of their impact on the material should be strictly regulated. At the same time, nanomaterials tend to agglomerate over time. And already 2 months after ultrasonic treatment, the nanoparticles form agglomerates of a significant volume, which must be “broken up” again.

Ultrasonic treatment of a certain intensity allows you to: “break” the majority of agglomerates and evenly distribute particles of nanomaterials in the volume, thereby significantly improving the uniformity of the filling material, and therefore, to solve the main objective of the invention is to improve the aesthetic and mechanical properties of fine-grained and hybrid composite filling materials.

The essence of the invention is illustrated by the following graphic materials:

- in FIG. 1 shows the spatial distribution ("height") of the profile of the particles that make up the surface of Charisma Opal filling material at a resolution of 15 by 15 microns,

- in FIG. 2 shows the results of studies of the surface of seals for samples of filling materials Charisma Opal, Filtek Ultimate, TE Econom,

- in FIG. 3 shows the results of AFM studies on the phase of the filling material Filtek Ultimate, mixed with ultrasound after 9 months of storage in the refrigerator at a resolution of 5 by 5 microns,

- in FIG. 4 shows the results of AFM studies of the surface profile of the filling material Filtek Ultimate,

- in FIG. 5 shows the results of studies on the phase of filling materials Charisma Opal, Filtek Ultimate, TE Econom, which were carried out after ultrasonic mixing of these materials for 15 s at an intensity of 40 W / cm ² ,

- in FIG. 6 shows the results of studies on the phase of the filling material Filtek Ultimate, mixed using ultrasound, which were carried out 1 hour after ultrasonic mixing of this material for 5 min at an intensity of 30 W / cm ²

- in FIG. 7 shows the results of studies on the phase of the filling material Filtek Ultimate, mixed with ultrasound, after 2 months of storage in the refrigerator,

- in FIG. Figure 8 shows the results of studies on the phase of the filling material Filtek Ultimate, mixed with ultrasound after 9 months of storage in the refrigerator.

The results of all studies were obtained using an atomic force microscope (AFM)

The technical implementation of this method has been tested experimentally.

The I100-6 / 1-1 unit [Laboratory ultrasonic unit was used as a source of intense ultrasonic vibrations. [Electronic resource]. - Electron, given. - Access mode: http://utinlab.ru/articles/laboratornaya-ultrazvukovaya-ustanovka-ultrazvukovoj-dispergator-ultrazvukovoj-emulgator].

The studies were subjected to light-curing, radiopaque fine-grained hybrid composite materials:

1. Charisma opal. Heraeus Kulzer. Shelf life until 2016-02.

Composition: BIS-GMA acrylic monomer and 58 weight percent fillers (barium aluminum fluoride glass with a particle size of 0.02-2 microns; highly dispersed silicon dioxide with a particle size of 0.02-0.07 microns).

2. Te-Econom (Vivadent). Shelf life until 2016-07.

Composition: a mixture of UDMA, Bis-GMA and TEGDMA. The total inorganic filler content is 62% by volume or 82% by weight. 58 weight percent fillers (barium aluminum fluoride glass with a particle size of 0.04-3 microns; highly dispersed silicon dioxide with a particle size of 0.02-0.07 microns).

3. Filtek ultimate. Shelf life until 2016-03.

3M ESPE Filtek tm Ultimate Universal Restorative is a light curing composite containing BiS-GMA, UDMA, TEGDMA and BIS-EMA resins. To reduce shrinkage, part of the TEGDMA resin of the Filtek tm Supreme XT material was replaced by PEGDMA.

The filler is a combination of 20 nm free silicon nanoparticles, unbound zirconium particles from 4 to 11 nm, and silanized zirconium-silicon clusters (consisting of 20 nm silicon particles and 4-11 nm zirconium particles). In shades of Dentin, Enamel and Body, the cluster size is from 0.6 to 20 microns. By weight, the filler is 72.5% (55.6% by volume) for Transluscent shades and 78.5% by weight (63.3% by volume) for other shades.

The possibility of studying the spatial distribution of nanoparticles in the volume of the resulting fillings in the case of filling materials is complicated by the fact that the polymer particles and microfillings are almost the same size. Particles of nanofillers are significantly (hundreds of times) smaller. As a result, one has to look at the surface, the change in height of which is microns, particles the size of nanometers. A similar problem can be solved using atomic force microscopy. This method allows you to get not only a three-dimensional picture of the surface under study, but also allows you to "feel" the presence of particles whose parameters (size, density, etc.) vary significantly with their identical external shape [Experience in the study of hard tooth tissues using atomic force microscopy (AFM) A.V. Antonova, V.D. Goncharov, A.N. Kipchuk, E.A. Bobrov. "Dentistry", No. 4. - 2014]. Therefore, this method was chosen as the main tool for research.

For studies using AFM, samples were prepared using the following procedure.

The material was applied to a glass slide. The diameter of the experimental sample was about 5 mm; the thickness of the material layer was 1.5–2 mm. The polymerization was carried out immediately after application by means of a Translux polymerization lamp from Heraeus Kulzer for 40-60 seconds (before hardening "by eye"). Finishing and polishing (diamond burs, polishing discs with water supply) were carried out 20 minutes after polymerization. As a result, the material was shot to a depth of 0.2-1 mm. The surface of the materials was processed using one technology, one hand and one tool.

Immediately before conducting research, samples of polymerized filling materials:

1. dried for 10 min at a temperature of 100 ° C;

2. purged with compressed air.

In a number of experiments, the samples were subjected to ultrasonic treatment in water for 5 minutes before drying (intensity 20 W / cm ² , frequency 20 kHz). In this case, no significant changes in the surface topography were observed.

During the AFM studies, a number of sample parameters were measured, the main of which are height and phase. "Height" allows you to explore the 3-dimensional picture of the distribution of particles on the surface of the material. "Phase" has increased sensitivity to the physical properties of the individual particles that make up the material.

All experiments were carried out for the above materials. For each of them were prepared:

1) experimental samples of material that has not undergone any processing (3 pcs.);

2) experimental samples of material mixed for 2 min mechanically (3 pcs.);

3) experimental samples of material mixed using ultrasonic vibrations (3 pcs. For each mode).

The intensity of ultrasonic vibrations was determined according to the method described in [Agranat B. A. Ultrasonic technology. - Moscow, 1974. - 501 p.].

All of these samples were tested in three randomly selected areas.

Below are the results typical of the research.

In FIG. Figure 1 shows the spatial distribution ("height") of the profile of particles that make up the surface of Charisma Opal filling material at a resolution of 15 by 15 microns. Obviously, the surface consists of particles with sizes ranging from 2 to 1 μm (1), which are collected in agglomerates of 2-7 μm in size (2). It is also obvious that a similar picture does not allow to separate the particles of the polymer and other fillers from highly dispersed silicon dioxide (the particle sizes declared by the manufacturer of which are 0.02-0.07 microns).

Due to the difficulty of finding particles of nanosize at a "height" in the future, special attention was given to the "phase" when presenting the results of experiments. In the course of research for the listed materials, results were obtained that differ insignificantly from each other as well as from region to region. Typical “phase” patterns for samples of the materials studied are shown in FIG. 2. The sequence of these samples of materials in the figure: a - Charisma Opal (resolution 100 μm) and b - Charisma Opal (resolution 1 μm), c - Filtek Ultimate (resolution 100 μm), g - TE Econom (resolution 100 μm). In all the samples studied, the mathematical processing of the results made it possible to identify nanoscale (with a linear size of the order of 10 nm) particles whose material properties differ significantly in composition from the base material (1). In most cases, these particles are combined into agglomerates (2) up to 5 microns in size.

In FIG. Figures 3 and 4 show the results of AFM studies of Filtek Ultimate material mixed with ultrasound after 9 months of storage in a refrigerator. A comparison of the phase of the studied material (Fig. 3) and the profile of the relief of its surface (Fig. 4), taken along line AA, indicates that the observed change in phase is not associated with sharp changes in the relief, but is determined by a change in the parameters of particles its surface.

The results of ultrasonic mixing for 15 s at an intensity of 40 W / cm ² are shown in figure 5. The sequence of images: Charisma Opal (A), Filtek Ultimate (B), TE Econom (C). In all investigated cases, it was possible to partially “break down” the agglomerates. This is especially evident in the results obtained for Charisma Opal. For Filtek Ultimate, TE Econom materials, the processing time was not enough to completely get rid of agglomerates. That is, for each of the materials studied, the operating modes of the ultrasonic installation (intensity and processing time) must be selected experimentally.

With an increase in intensity above a value of 50 W / cm ² , the polymerization time of filling materials increased several times. This value of intensity can be considered maximum.

When the intensity decreases below 3 W / cm ^3, agglomerates cannot be completely broken for any of the investigated materials, even if the processing time increases to 1 hour.

Our experiments showed that the processing time of the material can vary in the range from 5 s to 30 minutes, depending on the properties of the material and the intensity of ultrasonic exposure.

The results of the study of the filling material Filtek ultimate, which was subjected to ultrasonic mixing for 5 min at an intensity of 30 W / cm ² are shown in FIG. 6. In this mode, the distribution pattern of nanoparticles turned out to be similar for all the materials studied. In FIG. Figure 6 shows the absence of agglomerates of nanoparticles, and the particles themselves are almost evenly distributed over the volume of the filling material. In experiments, a part of the material with which the ultrasonic waveguide was in contact was specially removed. The similarity of AFM images obtained in experiments when taking material to different depths allows us to state the uniform distribution of particles over its volume.

An AFM study of a pre-mixed ultrasound filling material that was stored for 2 months in a refrigerator showed that even at relatively low temperatures, the nanoparticles of this material form agglomerates over time. This is evidenced by the results shown in FIG. 7. After 9 months of storage in the refrigerator, quite large agglomerates of nanocomposites are already formed in the volume of filling material (Fig. 8).

The results of the studies indicate that with the help of ultrasonic exposure of a certain intensity it is possible to "break" the agglomerates of nanoparticles in fine-grained and hybrid composite filling materials. The optimal intensity, which is in the range from 3 to 50 W / cm ² , and the exposure time for each filling material must be selected experimentally. Moreover, after two months of storage of the filling material in the refrigerator, the nanoparticles of its filler begin to agglomerate, and after 9 months they form large (up to 10 microns) agglomerates.

Claims (4)

1. The method of processing fine-grained and hybrid composite filling materials, which consists in the fact that the filling material is subjected to ultrasonic vibrations, the intensity of which is in the range from 3 to 50 W / cm ² . 2. The method according to p. 1, characterized in that the filling material is affected by ultrasonic vibrations for a period of time from 15 s to 30 minutes 3. The method according to p. 1, characterized in that the filling material is affected by ultrasonic vibrations immediately before installation in the tooth cavity. 4. The method according to p. 1, characterized in that the filling material is affected by ultrasonic vibrations no more than 2 months before its use.

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