A method of manufacturing a base of a dental prosthesis


A61C13/15 - for curing by the action of light

 

(57) Abstract:

The invention relates to prosthetic dentistry. A method of manufacturing a base of a dental prosthesis provides for the formation and thermal polymerization of acrylic plastic. Plastic consists of a powdered acrylic material and acrylate monomers, taken in the ratio of 2.5: 1. The polymerization is carried out under the influence of electromagnetic radiation of far-field radio-frequency range. The power source of electromagnetic radiation is 1 to 10 watts. The frequency range of the radiation is determined on the basis of the minimum content of monomers in the test samples of the target product. The proposed method allows to reduce the residual content of toxic monomers in the target product while simplifying the formulation of the material. 5 C.p. f-crystals, 3 tab., 3 Il.

The invention relates to medicine and can be used in orthopedics, mainly in prosthetic dentistry in the manufacture of prostheses and devices to restore lost teeth, mastication, articulation of speech and other oral and maxillofacial surgery. It can also be used for isotopologues prosthesis by molding and thermal polymerization of acrylic plastic (Makarov, K. A., Steinhart M. H. Copolymers in dentistry.- M.: Medicine, 1982; materials Science in dentistry / edited by A. I. Rybakov. - M.: Medicine, 1984; SU 169183, A 61 C 13/08, 1965; SU 1061817, A 61 K 6/02, 1983).

Emitted from the target products residual monomer provides local and General effects on the body, causing inflammatory changes in the mucous membrane of biological tissues and various allergic reactions of the body, as it is stated in numerous sources. The content of residual monomer in acrylic denture bases affects both the technology of polymer, and the technology of forming the prosthesis. Thus, the monomers are introduced to enable the carrying out of the process. However, they do not take fully into the polymerization reaction in the modes permitted for use in the technology of medical prostheses, and are present in the resulting product (see, for example: Boatman A. Ya. and other Sanitary-chemical properties of the base plastic used in prosthetic dentistry / Dentistry. - 1977. - N 5. - S. 55-57). Therefore, the main technical problem of the manufacturing bases of the dental prosthesis is to minimize the toxic content of residual monomers, while keeping the other technicality solution to this problem is to optimize the composition of the raw materials used. However, this approach provides only a partial solution, allowing you to obtain the target product with a content of residual monomers of 0.8 to 1.4%, as reported, in particular, in (Makarov, K. A., Steinhart M. Z. this work, S. 86).

Closest to the claimed is a method of manufacturing a base of a dental prosthesis, providing for the formation and thermal polymerization of acrylic plastic, which is to reduce the content of residual monomer in the feedstock further added sclareol in the following ratio of ingredients, wt. including:

Polymethylmethacrylate - 8 - 10

The methyl methacrylate - 2,5 - 4

Sclareol - 0,9 - 1,1

(EN 2001602 C1, A 61 C 13/00, 1993).

This way, as one of the representatives of the above directions of development of a given field of technology also reduces the content of monomers in the target product only in part.

The technical objective of the proposed method is to reduce the residual content of toxic monomers in the target product.

The solution of the stated problem is that in the method of manufacturing a base of a dental prosthesis, providing for the formation and thermal polymerization of acrylic plastic surgery polymerization ASU electromagnetic radiation (EMR) from 1 to 10 watts.

The operation of polymerization in the electromagnetic field in the manufacture of the base of the dental prosthesis is known from JP 5-11984, A 61 C 13/14, 13/01, 1993). However, in the specified similar use electromagnetic field of the microwave range, whereas the proposed technical solution, using an electromagnetic field far field radio frequency range. In this similar polymerization in a microwave electromagnetic field is conducted to ensure minimum content of residual monomers, and for rapid and uniform heating of the polymerized material. In the proposed way electromagnetic effect to the heating of the material is not relevant, because AMY is not in the microwave range. In addition, the source of the EMP has little power (1 - 10 W).

The operating principle of the proposed method is based on first established by the authors of the phenomenon of increasing the activity of acrylic monomers under the action of the electromagnetic field far field radio frequency range. Activation of these monomers increases the completeness of the reaction of polymerization and, consequently, a sharp decrease in their residual content in the target product. Vosschemie the initiators of the process - benzoyl peroxide and other components of the polymerized mass.

Range power source EMR is limited to 1 to 10 watts, because when less power is not activated acrylic monomers, and at higher power increases the intensity of the adverse reactions that prevents the full carrying out the polymerization process.

Due to the fact that the dependence of the residual monomers from the frequency of the electromagnetic radiation within the claimed range is extreme in nature and includes, for specific dental plastics sub-region, where the residual content of monomers close to zero, it is advisable (in the absence of deterioration of other technical characteristics) to set a specific frequency value with the minimum content of residual monomers. For this purpose, we first identify the dependence of the content of residual monomers in the test samples from the frequency source AMY.

For detection of residual monomer can be used known methods for simulating the migration of monomers of the prosthetic base in biological tissue. For this purpose prepare the aqueous extract of the monomers of the test sample (Boatman A. J. and D. the tanks A. I. This work, C. 408-409). However, the extraction of monomers with water some of them associated with macromolecules physical forces, the solution does not pass. The other part is due to the long time of aqueous extract (14 days) is oxidized and converted into non-toxic compounds. All of this distorts the results of the analysis. Moreover, in aqueous solution often does not move and therefore are not considered toxic monomers, the allocation of which in biological tissue occurs within 2-3 years. Therefore, more than not it is expedient to prepare the aqueous extract, and the extract of the monomers in an organic solvent is chloroform and consider the result bromine number (BSC). This definition, unlike the aforementioned analogues, is a direct (known technical solutions, the residual monomer content is defined in relative units, as it is unknown what portion of the monomers moved in aqueous solution). In addition, this modification operations control gives the integral value of the residual reactive monomers (known technical solutions take into account the results on the calibration curves recorded for each monomer, in particular, the prototype of all contained in Celje is bromine, entered into interaction with other components of the extract (chloroform, benzoyl peroxide, etc.), further define the value of the BSC background, which is subtracted from the analysis result of the controlled specimen.

As explained above examples, the optimum values of the frequency of electromagnetic radiation in the manufacture of the target products from the most common acrylic plastic form (see tab. A).

In table. 1-3 lists the technical specifications of the target products of examples 1-3, respectively.

In Fig. 1-3 shows graphs of the values warhead test samples from the frequency of the electromagnetic radiation during operation polymerization examples 4-6, respectively.

The method is illustrated by the following examples.

Example 1. The bases of the dental prosthesis is made from acrylic plastic AKP-15 "Ethacryl".

Source components:

1) powder - copolymer of methyl and ethyl esters of acrylic acid derived from methyl methacrylate (89%), ethyl methacrylate (8%), methyl acrylate (2%) and plasticizer is dibutyl phthalate (1%);

2) liquid - methyl methacrylate (74-75%), ethyl methacrylate (25-26%), hydroquinone (0,005%).

remesiana before the formation of a pasty consistency, capable of being extended in the thread that occurs within 10-30 minutes Prepared molding mass shape cakes for the upper denture and a roller for the lower denture, making plaster of the cell and slowly pressed, ensuring complete filling of the molding space.

Next produce heat treatment of semi-finished product in a water bath equipped with a source of electromagnetic radiation frequency 1508 kHz directed to a cuvette containing the polymerized sample. For this purpose, the cell is immersed in a water bath at room temperature and fix the location of the output element of the source of the EMP. Within 1 h the temperature of the water bath is raised to boiling, which is maintained for 45 min, after which the cell is kept in a cooling water bath for 15 min, and then cooled in air to room temperature. The obtained samples of the target product is subjected to appropriate machining. The operation of thermal polymerization is carried out at different values of the power source of ELECTROMAGNETIC radiation in the range from 0.5 to 15 watts, and in the absence of AMY (control). In this and subsequent examples, the modes of polymerization repeat 3-8 samples.

The resulting products op which can be carried within 14 days at a temperature of 37oC. On the relative concentrations of the monomers represented by the results of gas chromatography in aqueous extracts. The content of monomers in the control is taken for 100%. In this and other examples, providing control of the monomers in aqueous extracts, records of results provides comparability with peers because they are not given sufficient information about the value of security control parameters. Additionally determine the following characteristics of the material of the products: the tensile strength of a material in bending, microhardness and fracture toughness. The average values of the results of the tests are given in table. 1. As can be seen from the table, the residual content of monomers in the examples, the polymerization which is carried out under the action of AMY capacity from 1 to 10 watts, is 5.3 12.8 percent of its content in the control. Beyond the modes (0.5 and 15 W) residual content of monomers 85,1 and 50.2%, respectively. The values of the other technical characteristics in the whole range of capacities lie within acceptable boundaries and are as follows: tensile strength Flexural strength - 57 - 65 MPa; the micro - 107 - 122 MPa; toughness to 8.0 to 8.3 kJ/m2.

Example 2. The bases of the dental prosthesis is made from acrylic the OIC acid and fluoro;

2) liquid - stabilized methyl methacrylate with the addition dimethacrylate ether of diphenylolpropane.

Preparation of moulding mixture and carrying out forming operations, polymerization and control produced as in example 1.

Technical characteristics of the target products are given in table. 2. As can be seen from the table, the residual content of monomers in the examples, the polymerization which is carried out under the action of AMY capacity from 1 to 10 watts, is 3.2 - 7.8% of its content in the control. Beyond the modes (0.5 and 15 W) residual content of monomers 78,5 and 32.6%, respectively. The values of the other technical characteristics in the whole range of capacities lie within acceptable boundaries and are as follows: tensile strength Flexural - 53 - 58 MPa; the micro - 98 - 105 MPa; toughness - 8,6-8,9 kJ/m2.

Example 3. The bases of the dental prosthesis is made from acrylic plastic "Ftoraks", as in the example 2, when the power source of the EMP 5 watts and the following values of the frequency source EMR: 0 (control), 100, 200, 400, 600 and 1000 kHz. To exclude methodological errors determine the content of residual monomers samples of the target product is poured chloroform (1:150 wt. o'clock) and incubated in the number of bromine, entered into interaction with other components of the extract (chloroform etc ), make the results of the analysis of the background according to known methods (Toropova A. M., Belgorod K. C., Bondarenko C. M. Laboratory of chemistry and technology of macromolecular compounds.- L.: Chemistry, 1972. - S. 75).The warhead is calculated by the formula

BF=B1-B0, (1)

where B1- the experimental value of the bromine number in the chloroform extract of the test sample; B0- the value of the bromine number of the used solvent. The results of parallel tests average. For example, for samples obtained from the frequency source of the EMP 400 kHz, the average value of measurements are: B1= 0.22, B0= 0.03. According to the formula (I) BSC=0.190.2.

To control also determine the relative content of residual monomers in aqueous extracts of the target products.

The results are shown in table. 3. As can be seen from the table, the residual content of monomers in the examples, the polymerization which is carried out under the action of ELECTROMAGNETIC radiation in the range from 200 to 600 kHz, BSC is 0.1 to 0.3, that is, by direct measurement, shows almost complete absence of monomers in the target product is still on the value of the warhead, equal to 1.9 and 2.4, respectively, it remains significantly higher than in the optimal mode. At the same time, the definition of the monomers in aqueous extracts distorts the area of optimum modes, expanding it from 100 to 1000 kHz, where the relative content of residual monomers is from 3.2 to 4.4%. This expansion of the region of permissible values of the frequency AMY takes place due to the above methodological errors of determination of the content of the monomers.

In accordance with the results of the test samples in the subsequent target product of plastic "Ftoraks" polimerizuet when the EMP frequency from 200 to 600 kHz.

Example 4. The bases of the dental prosthesis is made from acrylic plastic "Ethacryl", as in example 1, when the power source AMY 3 watts. The content of residual monomers is determined by the BSC, as in example 2. Test samples receive under the influence of AMY frequency 6, 15, 37, 100, 1000, 3000 and 5000 kHz and when the source of the EMP (control).

In the examples, the polymerization which is carried out under the action of ELECTROMAGNETIC radiation in the range from 15 to 1000 kHz, the value of TT=0,120,04 (Fig. 1), indicating almost complete absence of monomers in the target product by this mode of treatment. In the absence of AMY BCA in control.

In accordance with the results of the test samples in the subsequent target product of plastic "Ethacryl" polimerizuet when the EMP frequency from 15 to 1000 kHz.

Example 5. The bases of the dental prosthesis is made from acrylic plastic "Sinma-M".

Source components:

1) powder - suspension grafted fluorine-containing copolymer;

2) the fluid is a mixture of acrylic monomers and oligomers; stabilized methyl methacrylate with the addition dimethacrylate ether of diphenylolpropane.

Technological operations are performed as in example 3, when the power source of the EMP 2 watts. Test samples receive under the influence of AMY with a frequency of from 100 to 3000 kHz, and when the source of the EMP (control).

BSC in the absence of AMY (control) is 0.45. In the examples, the polymerization which is carried out under the action of ELECTROMAGNETIC radiation in the range from 300 to 1000 kHz, the warhead is close to zero (Fig. 2), indicating almost complete absence of monomers in the target product by this mode of treatment. With increasing frequency AMY from 1000 to 3000 kHz residual content of monomers increases approximately to the level in the control.

In accordance with the results of the test trial is SS="ptx2">

Example 6. The bases of the dental prosthesis is made from acrylic plastic "Colorless".

Source components:

1) powder - suspension polymethylmethacrylate with the addition of antistites - tinuvin;

2) liquid - stabilized methyl methacrylate.

Technological operations are performed as in example 3, when the power source of the EMP 1 watt. Test samples receive under the influence of AMY with a frequency of from 20 to 900 kHz, and when the source of the EMP (control).

BSC in the absence of AMY (control) is 0.42. In the examples, the polymerization which is carried out under the action of ELECTROMAGNETIC radiation in a narrow range from 50 to 150 kHz, the warhead is close to zero (Fig. 3), indicating almost complete absence of monomers in the target product by this mode of treatment. With increasing frequency AMY from 150 to 300 kHz residual content of monomers increases to BSC=2.

In accordance with the results of the test samples in the subsequent target product from the plastic polimerizuet when the EMP frequency from 50 to 150 kHz.

The given examples show that using the proposed method in comparison with the prototype allows to drastically reduce the residual sod which has been created value warhead, close to zero, whereas in the known technical solution, the content of toxic monomer decreases only by 18.1 - 37,8%.

Another technical result compared with the prototype is to simplify the formulation of the material, as it eliminated the necessity of making the composition of the plastic sclareol.

The technical result achieved is to improve the processability of the way, because the optimized values of technological modes of polymerization and control.

1. A method of manufacturing a base of a dental prosthesis, providing for the formation and thermal polymerization of acrylic plastic, wherein the plastic material consisting of a powder of acrylic material and acrylate monomers, taken in the ratio of 2.5 : 1, polymerised by exposure to electromagnetic radiation of far-field radio-frequency range when the power source of electromagnetic radiation 1 - 10 watts and the frequency of the radiation that is installed from the calculation of the minimum content of monomers in the test samples of the target product.

2. The method according to p. 1, characterized in that the content of the monomers is determined by the bromine number of samples, obia plastic "Ftoraks" the frequency of electromagnetic radiation is set in the range of 200 600 kHz.

4. The method according to PP.1 and 2, characterized in that during production of target products from plastics "Ethacryl" frequency electromagnetic radiation set in the range of 15 to 1000 kHz.

5. The method according to PP.1 and 2, characterized in that during production of target products from plastics "Sinma-M frequency of electromagnetic radiation is set in the range of 300 - 1000 kHz.

6. The method according to PP.1 and 2, characterized in that during production of target products from plastics "Colorless" frequency electromagnetic radiation set in the range of 50 to 150 kHz.

 

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