Polytetrafluoroethylene membrane for oriented regeneration of periodontal tissues

FIELD: stomatologic techniques and materials.

SUBSTANCE: proposed membrane comprises at least two porous polytetrafluoroethylene layers: one adjusting parodentium tissues and the other being outside layer, the two having different porous structure. Layer adjusting parodentium tissues is characterized by volume portion of hollow space equal to 78-94%, specific surface of hollow space 0.5-0.9 mcm2/mcm3, average distance between hollows 20.0-50.0 mcm, and average volumetric chord 20.0-30.0 mcm. Outside layer is characterized by volume portion of hollow space equal to 30-60%, specific surface of hollow space 0.1-0.5 mcm2/mcm3, average distance between hollows 1.8-15.0 mcm, and average volumetric chord 1.0-15.0 mcm.

EFFECT: increased regenerative activity and simplified use.

7 cl, 7 dwg, 1 tbl, 6 ex

 

The invention relates to medicine, in particular to dentistry, and in particular to materials used in the treatment of periodontal disease. It may find application in the reconstruction of periodontal tissues destroyed by a destructive inflammatory processes.

Restoration of damaged tissues (guided tissue regeneration) began with the work P.J.Boyne [J.Dent. Res, 1964, 43, p.827] and C.A.LBasset ["Environmental and cellular factors regulating osteogenesis", H.Frost "Bone biodinamics", Boston, Little Brown, 1966, p.233-244], which in the experiment on animals used microporous cellulose filter for healing of cortical defects of long bones and fascial reconstruction of bone defects. Function microporous cellulose filter was to prevent connective tissue cells inside of the regenerated bone defect. As a result of this osteogenic cells healthy (parent) bones “inhabit” the space under the filter form primary osteomy matrix, which is subsequently mineralized. Method of guided tissue regeneration using different materials then got development in several areas of surgery.

Known membrane (plate)made of kalapana containing the antibiotic gentamicin used to cranioplastic with subsequent regeneration of bone tissue [RF patent is 2199287, MCI 7 A 61 B 17/56 published 27.02.2002]. Callahan - bioactive osteoplastic material, which is homogeneous composition especially pure hydroxyapatite, specially treated collagen and antibiotic. He has osteoprosthesis and matrix properties for the newly formed bone tissue. However, the use of kalapana for the regeneration of periodontal tissues is undesirable for the following reasons.

According to our data [Perov PPM “New in dentistry”. M., 1999, No. 4(74), p.36-43] when implantation hydroxypatite in periodontal tissues it is subjected to encapsulation, does not allow the growth of new structures of periodontal attachment, the result is not a qualitative change in the clinical condition of the periodontium; regenerative effect is not confirmed histologically. When using kalapana in periodontal surgery also noted the pyrogenic effect of degradation products of biodegradable material.

Also known implant, the support matrix is made of collagen used for the treatment of cartilage defect [application for patent of the RF No. 2001107063, MKI 7 A 61 B 17/56 published 27.01.2003].

The specified implant includes a matrix of equine, porcine, bovine, sheep or chicken collagen and Mature cells of the cartilage tissue, fixed in the matrix. He is able to support the growth of cartilage cells defective the area of cartilage tissue with the to create the physical integrity of the implant.

However, when using collagen implants and implant-based collagen) in dentistry is their rapid destruction even with short-term exposure in the oral cavity. Often the outcome of periodontal treatment in these cases is the formation of residual pockets, that is, the formation of inner epithelial lining of the gingival pocket. This outcome leads to the formation of scar [Mdirea. New in dentistry”. M., 1999, No. 4(74), p.36-43].

The products of decomposition of biodegradable materials, such as calapan and collagen, form a cell and/or system response of the body. In the process of hydrolytic degradation decomposition into fragments, with the inevitable impact on the local tissue in the form of bone resorption.

Most similar in essential characteristics to declare the membrane is a PTFE membrane for directed regeneration of periodontal tissues [prospect W.L.Gore (Associates Inc. "Gore-Tex Regenerative Material"], comprising at least two layers of stretched porous polytetrafluoroethylene (PTFE), and adjacent to the periodontal tissues layer has a porous structure with open pores, and the outer layer has a porous structure with closed pores.

PTFE has a high chemical biologicheskii inertia, does not dissolve in the oral cavity and does not interact with the adjacent tissues. Porous stretched PTFE has a spatial structure in the form of microscopic nodes, interconnected fibers (fibrils). Elements of nodes connected by fibrils, and the elements of the voids between the nodes are connected in a three-dimensional network. To obtain the open pores on the membrane surface part of the fibrils are removed from the surface so that the surface remains free groups of nodes that are not connected by fibers, between which are formed the free grooves. The production of a material with open pores is described in U.S. patent No. 5462781, MKI 6 A 61 F 2/01, 1995, owned firm W.L.Gore and Associates Inc. Surface treatment was carried out by the action of gas-discharge plasma of high frequency for 10-120 minutes. The material of this structure can be used in various fields of reconstructive surgery, and in particular in dentistry for directed tissue regeneration (page 5, lines 54-55 said patent).

The Gore-Tex membrane is superimposed on the area of periodontal defect, dressed under the periosteum, overlapping the defect around the perimeter of 1.5-2 mm, and the wound is sutured in each mizuna space. The membrane covers the defect within 3-6 weeks, then removed and held decapitalization and mobilization mucoperiostal flaps with full ukry the receiving young tissue profile and suturing wounds.

Gore-Tex allows you to regenerate destroyed periodontal tissues. However, the explantation of her at the end of the term in citu complex; according to our data, the membrane is not completely resistant to sedimentation of microbial colonies on the exposed surface of the biomaterial, which makes removing the membrane before the time required for regeneration. In addition, the Gore-Tex does not have the necessary combination of hardness and ductility, making it difficult for her modeling in the form of periodontal defect. In the regenerative therapy of the damaged periodontium with Gore-Those are not effective enough.

Technical result achieved in the present invention is to simplify use and increase the regenerative activity of the inventive membrane.

This technical result is achieved by a PTFE membrane for directed regeneration of periodontal tissues, including at least two layers of a porous stretched PTFE, having a structure made in the form of the nodes connected by fibrils, and elements of space voids with connection elements in a three-dimensional network, the layer adjacent to the periodontal tissues, and the outer layer have different porous structure as a layer adjacent to the periodontal tissues, includes a layer of PTFE having a vol the stake space voids 78-94%, the specific surface space voids of 0.5-0.9 µm2/μm3the average distance between voids in the volume of 20.0-50,0 μm and an average chord volume 20,0-30,0 μm, and as the outer layer includes a layer of PTFE having a volume fraction of the space of voids 30-60%, specific surface space void of 0.1-0.5 μm2/μm3the average distance between voids in the amount of 1.8 to 15.0 μm and an average chord volume from 1.0 to 15 μm.

The inventive membrane can have 2-20 layers of porous PTFE film, of which 1-16 layers, aimed to periodontal made of a more porous film, and 1-4 of the outer layer is made of a less porous film. On the surface of the membrane adjacent to the periodontal can be performed corrugation in the form of a dotted line, grid or randomly distributed dents. The inventive membrane can include reinforcing elements placed inside between the layers of film. The reinforcing elements may be made of wire, rolled or foil made of metal, with biological inertness.

For manufacturing membranes according to the present invention are biaxially oriented PTFE film obtained from crude calendered film, such as film SCR (HOST-05-405-80). Raw calendered film is subjected to longitudinal orientation at a temperature of 50-300°and the linear speed of extrusion to 20 m/min Film for the outer layer of the membrane is pulled to the point of drawing 50-200% (orientation ratio from 1:1.5 to 1:3); film layer membrane directed to the periodontium, pull up to a degree of extrusion of 200-900% (orientation ratio from 1:3 to 1:10). Longitudinally oriented film after heat treatment at 320-340°C for 3-10 minutes is subjected to a transverse orientation at a temperature of 50-200°and linear speeds of up to 23 m/min Film for outer layer extend to the point of drawing 100-200% (orientation ratio from 1:2 to 1:3); film layer directed to the periodontium, pull to the point of drawing 200-800% (orientation ratio from 1:3 to 1:9). After transverse orientation are heat setting of the obtained biaxially oriented film in a heating Cabinet at 320-340°C for 15-20 minutes. Get a film thickness of from 45 to 125 μm labeled longitudinal direction of the hood.

Stereological volume settings of the films is determined by well-known methods [Panteleev VG, Ramm, K.S. “Inorganic materials”, 1986, vol. 22, No. 12, s-1951; Autogrow, and other System stereometry in the study of the pathological process”, M, “Medicine”, 1981; Cherniavsky HP “Stereology in metallography”, M, “metallurgy”, 1977].

The film used for the manufacture of a layer of the inventive membrane adjacent to the periodontal tissues, have the volume up to the th space voids 78-94%, the specific surface space voids of 0.5-0.9 µm2/μm3the average distance between voids in the volume of 20.0-to 50.0 μm, the average chord volume 20,0-30,0 mm.

The film used for making the outer layer of the inventive membranes have the volume fraction of the space of voids 30-60%, specific surface space void of 0.1-0.5 μm2/μm3the average distance between voids in the amount of 1.8 to 15.0 μm, the average chord volume of 1.0 to 15.0 μm.

The inventive membrane and its elements are presented in figure 1-7.

Figure 1 shows the micrograph of the PTFE film used for the layer of the inventive membrane adjacent to the periodontal tissues. Figure 2 presents the micrograph PTFE film used for the outer layer of the membrane. Clearly visible three-dimensional network formed by the space void, and the nodes of the polymer matrix; however, the structure of the films 1 and 2 are noticeably different.

3 shows the micrograph of the cross-section of the membrane, comprising 8 layers. Clearly shows the difference of structures more porous layers adjacent to the periodontal tissues, and less porous outer layers. The inventive membrane made as described in the patent of Russian Federation №2203685, M CL A 61 L 27/14, published 10.05.2003.

Figure 4-6 shows micrographs of the surfaces of the membranes with different corrugation pattern. For n of the order of riffling use aluminum plate coated with the surface of the convex pattern. The specified plate press stop films, arranged in a specific order, before sintering.

In the case when the membrane contains reinforcing elements, they are placed between the outer and inner layers of the membrane. The reinforcing elements are made of metal wire with a diameter 0,010-0.250 mm or a metal foil having a thickness of 0,010-0,250 mm Form reinforcing elements presented on figa) Reinforcing elements may be made of tantalum, titanium, nitinol, stainless steel or cobaltreciprocating alloy “plastocrete-08”.

The following examples illustrate the present invention.

Example 1.

To obtain membranes take three samples of size 100×100 mm PTFE film thickness of 60 μm, with the degree of stretching in the longitudinal direction 100% and in the transverse direction 200%, as well as four sample PTFE film thickness of 60 μm with a degree of stretching in the longitudinal and transverse direction 300%.

On an aluminum plate placed the sample film with a degree of hood 100% in the longitudinal direction and 200% in the transverse direction; then the second and third samples of the same film stack so that the longitudinal axis of orientation of the fibers in adjacent layers are perpendicular to each other.

Then also in mutually perpendicular directions to the preceding adjacent layer stack four the Loya PTFE film with a degree of stretching in the longitudinal and transverse direction 300%. The assembled package is served another aluminum plate and placed in a heat chamber, where the lamination at a temperature of 360°under load, 24 g/cm3within 1 hour.

The resulting membrane is examined by the following methods:

1. The tensile strength and elongation according to GOST 11262-80.

2. The strength stitching on the method developed by us, which measured the force required to rupture the membrane at the site of the puncture.

Composition, stereological parameters used films and physico-mechanical properties of the membrane are given in the table.

Examples 2-6.

The membranes are made as in example 1, but used different film thickness and the degree of extraction with different stereological parameters and other combinations.

Composition, stereological parameters used films and physico-mechanical properties of the resulting membranes are shown in table.

The membrane of example 1 was tested in 154 sites of damaged periodontium in groups of 15 people, 80 plots in the lower jaw, 74 plot in the upper jaw.

After the event, prior to the surgical treatment of periodontal destruction (reorganization), blood clot in the deep periodontal defects introduced osteoconduction biocidal. Form defects of the membrane was cut out flaps. The edges of the gloss is s refueled under the periosteum with the overlap of the defect along the perimeter of 1.5-2 mm. Wounds were usualis monofilament thread horizontal mattress and normal joints (in addition to mattress), imposed in each mizuna space.

Table 1.
Composition, stereological parameters of films and physico-mechanical properties of PTFE membranes.
Example No.The number of film layersCharacteristics of the used filmsThe thickness of the membrane mcmThe tensile strength MPaElongation at break %Tensile stitching kg
  The thickness of the initial film mcmThe degree of drawing longitudinally/transversely %Stereological parameters of layers    
    a)b)c)d)    
1360100/200480,4012930015,2 2270,4-1,5
 460300/300800,603726    
21100100/100410,508618015,22170,3-1,2
 1125400/300820,633329    
3445100/200450,351020400a 12.72330,5-1,9
 1645400/300830,674128    
4260100/200440,401010350the 17.32630,3-1,3
 8100500/200 870,704326    
5260100/200480,3812826018,52070,3-1,4
 460300/300810,643726    
61100100/200490,38132322016,22130,3-1,2
 4100300/300830,624026    
a) Volume fraction of the space of voids, %

b) Specific surface space voids, μm2/μm3

(C) the Average distance between voids in size, microns

d) the Average chord volume, mcm

Patients are recommended, in addition to usual care for the teeth and gums, frequent rinsing of the mouth of 0.05-0.1% solution is orexigen. Stitches were removed on 14-16 day. The time spent membranes in tissues 3-6 weeks with weekly medical examination. Antibiotic treatment was not applied.

After removal of the membranes was no need for additional decapitalization and suturing of soft tissues, since they themselves were connected with tissue profile, formed under the membrane.

The results of treatment of periodontal destruction was assessed after 6-8 months for the following standardized clinical indicators:

• - the depth of the sounding from the gingival margin to the bottom of the gingival sulcus (mm);

• - gingival recession from the enamel-cement border of a tooth to the gum margins (mm);

• - loss of clinical periodontal attachment from the enamel-cement border of a tooth to the most apical point of the stored bone structures (mm).

For comparison, similar tests were carried out with membranes Gore-Those Regenerative Material” by W.L.Gore (Associates, Inc. 136 the sites of damaged periodontal (64 plot on the lower jaw and 72 of the plot in the upper jaw) in 14 patients. The tests were carried out as with the inventive membrane, but after removing these membranes were decapitalization and mobilization mucoperiostal flaps with full shelter of the young tissue profile, as this was required by the instructions for use of the membrane Gore-Tex.

Result is you regenerative therapy of damaged periodontal were as follows.

In a period of 6-8 months, the growth of periodontal attachment was 4.2 mm (in the group used the Gore-Tex, 2.8 mm); depth sensing declined by 2.9 mm in the control group was 1.4 mm) and averaged 0.6 mm in the control group and 1.8 mm). There has been a qualitative structural change of periodontal tissues associated with the elimination of periodontal pockets.

Full anatomical microstructure clinical attachment formed from regenerated under the membrane tissue profile, led to the restoration of the natural shape of the periodontal tissues and their functions. There is a more complete regeneration of the periodontal tissues than using membrane Gore-Those Regeneration Material.

1. PTFE membrane for directed regeneration of periodontal tissues, including at least two layers of porous polytetrafluoroethylene having a structure made in the form of the nodes connected by fibrils, and elements of space voids with connection elements in a three-dimensional network, the layer adjacent to the periodontal tissues, and the outer layer have different porous structure, characterized in that the layer adjacent to the periodontal tissues, has a volume fraction of the space of voids 78-94%, specific surface space voids of 0.5-0.9 µm2/μm3average Russ is the right between the voids in the volume of 20.0-50,0 μm and an average chord volume 20,0-30,0 μm, and the outer layer has a volume fraction of the space of voids 30-60%, specific surface space void of 0.1-0.5 μm2/μm3the average distance between voids in the amount of 1.8 to 15.0 μm and an average chord volume of 1.0 to 15.0 μm.

2. PTFE membrane according to claim 1, characterized in that it includes 1-16 layers having a volume fraction of the space of voids 78-94%, specific surface space voids of 0.5-0.9 µm2/μm3the average distance between voids in the volume of 20.0-50,0 μm and an average chord volume 20,0-30,0 mm.

3. PTFE membrane according to claim 1, characterized in that it includes 1-4 layer having a volume fraction of the space of voids 30-60%, specific surface space void of 0.1-0.5 μm2/μm3the average distance between voids in the amount of 1.8 to 15.0 μm and an average chord volume of 1.0 to 15.0 μm.

4. PTFE membrane according to claim 1, characterized in that the surface adjacent to the periodontal tissues, is embossed.

5. PTFE membrane according to claim 4, characterized in that the embossing is made in the form of a dotted line.

6. PTFE membrane according to claim 4, characterized in that the embossing is made in the form of a grid.

7. PTFE membrane according to claim 1, characterized in that it includes separate metallic reinforcing elements placed inside the membrane between the layers.



 

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