M.D. Perova State Center of Periodontology & Dental Implants, Ministry of Health of the Russian Federation, Krasnodar V.E. Dyakov, L.M. Fedotova, Yu.V. Kortunov JSC SPC "Ecoflon", Saint Petersburg Efficiency evaluation of a new resorbable membrane of PTFE in case of guided parodentium tissue regeneration. Controlled clinicopathologic study.

Comprehensive studies of foreign scientists based on fundamental conception of prominent histologist A.A Maksimov about blood system and connective tissue unity" offered new solutions expected by clinicians for a long time to reparative regeneration of biological structures. The matter concerns restoration of destroyed tissues in their original histoarchitectonics, as well as function of stem stromal cells in ontogenesis.
In 1960s Bassett & Boyne Company used microporous laboratory cellulose filter for cortical defect repair of long bones and for facial bony skeleton reconstruction in experiments on animals. The idea of physical barrier or filter usage lies in elimination of connective tissue cells ingress from surrounding soft tissue structures into regenerable bone defect. As a result osteogenous cells from a healthy (maternal) bone occupy sub-membrane space; initial osteoid matrix is created which then is mineralized. This method was called Guided Bone Regeneration.
The continuation of this study made the basis for progressive medical approach in parodontics - reconstruction of periodontal tissues destroyed during inflammatory and destructive processes. By the present time due to the usage of various bio-adsorbable and irresorbable m embranes the m ethod called Guided Tissue Regeneration has been documented with a high level of authenticity (Buser et al., 1994; Bartold & Narayanan, 1998; M.D. Perova, 1999(a); M.D. Perova, 1999(b); M.D. Perova, 2001(a); M.D. Perova, 2001(b); Machtei, 2001; Zucchelli et al., 2002 and others).
Routine application of membrane technique in treatment of parodentium diseases and their consequences held in Krasnodar parodontics and dental implantation centre allowed to formulate the following conclusions:
1.  Porous barrier materials functioning on semipermeable membrane properties  and promoting repopulation of "necessary" cells in parodontal defect zone not only help to stop the process of tissue destruction but also lead to dentogingival attachment growth, namely help to get fundamentally new quality of treatment.
2. Bio-adsorbable membranes demonstrate less predictable results for Guided Tissue Regeneration. Their usage is severely limited by absence of mechanical properties and by low resistance to oral cavity microbial flora.
3. Foreign irresorbable membranes used in modern parodontics need improvement to achieve more predictable results in reparative therapy.
The aim of the present сontrolled research is the efficacy study of the new membrane barrier for the reconstruction of structures destroyed during inflammatory and destructive processes in parodentium.
In the course of the study we tried to answer the questions concerning the following:
1) nature and dynamics of tissue structures formed in parodontal defects protected by membranes,
2) time for cell proliferation control while forming clinical attachment,
3) prognosis possibilities of qualitative and quantitative characteristics of regenerated dentogingival attachment.

Material and methods
During the study a new barrier irresorbable membrane of polytetrafluoroethylene was tested (a joint development of Krasnodar parodontics and dental implantation centre of Ministry of Public Health of RF and Scientific Production Complex "Ecoflon", Saint Petersburg). This membrane has fundamentally new structure, porosity volume and is processed using a unique nuclear chemical method on a specially constructed device at SPC "Ecoflon".
The testing group I consisted of 15 people (6 males, 9 females at the age of 28 - 57). The membrane developed by us was used on 154 sections of defective parodentium (80 sections - on lower jaw: 9 of them are furcation injuries of I degree, 4 - of II degree; 74 sections on upper jaw: 9 of them are furcation injuries of I degree, 3 - of II degree). Furcation parodontal defects are classified according to Ramfijord & Ash (1970). The clinical index of dentogingival attachment in case of furcation injuries takes into account vertical and horizontal components.
The control group I included 14 patients (5 males, 9 females at the age of 32 - 60). Irresorbable membrane GoreTex (including reinforced) and TefGen (USA) were used in 136 sections of defective parodentium with the same test indications (64 sections - on lower jaw: 6 of them are furcation injuries of I degree and 3 - of II degree; 72 sections - on upper jaw: 7 of them are furcation injuries of I degree and 2 - of II degree).
The testing group II consisted of 19 people (7 males, 12 females at the age of 25-55), who were made flap operations implanting osteoplastic materials (biositall or hydroxyapatite) without membrane barriers. Clinical parameters were evaluated on 145 sections of defective parodentium with similar medical indications (77 sections - on lower jaw: 10 of them are furcation injuries of I degree and 4 - of II degree; 68 sections - on upper jaw: 7 of them are furcation injuries of I degree and 3 - of II degree).
Of all patients who took part in that study 21 people (12 males, 9 females) were practically h ealthy; 27 people (6 males, 21 females) had сardio-vascular diseases (4 males, 6 females), diseases of gastrointestinal tract (1 male, 11 females), pathology of thyroid gland (1 male, 4 females, 3 of whom were on hormonal substituting treatment), controlled pancreatic diabetes (1 male, 1 female). Combined diseases - pathology of cardio-vascular system and thyroid gland had 1 male, pathology of gastrointestinal tract and pancreatic diabetes had 1 female, pathology of thyroid gland and gynecological disorders had 4 females.
All the necessary measures described earlier in detail (Perova M.D., 1998) were executed prior to surgical treatment of parodontal destruction. Initial measurements were made after initial therapy; the level of dentogingival attachment lost was measured directly during surgical treatment. The clinical procedure of Guided Tissue Regeneration (GTR) is based on limitation with the help of access membrane of competitive tissues to the roots of teeth and isolation parodontal defect till muco-periosteal flap placing over biomaterial. Resorbable material- osteoconductor biositall (Biosit-Elcor, St.Petersburg) was injected into a blood clot in case of deep parodontal defects for submembrane space support. The edges of membranes cut off to the defect shape were put under periosteum covering the defect along the perimeter for 1.5 -2 mm. The wound was being closed with horizontal mattress and ordinary sutures (additional to mattress ones), put in every interdental space with monofilament thread.
Along usual hygienic care for gums and teeth the patients were recommended to make frequent oral rinsing (up to 8 times a day) with 0.05% - 0.1% solution of chlorhexidine. The sutures were removed in 14 - 16 days.
Before the membrane barriers were removed medical examination was held once a week to control the membrane surface denudation and bacterial contamination as well as to control stability in regeneration focus. Antibiotic therapy was not used. The time of membrane being in tissues varied from 3 up to 6 weeks. After membrane explantation of the testing group soft flaps were not additionally deepithelized and closed. During 8-10 days they joined to the tissue profile arisen under membrane independently. After barrier removing the members of the control group I (using GoreTex membranes) were made deepithelization and muco-periosteal flap mobilization with the full cover of new tissue profile and wound closure as the developers suggest.
Treatment results of parodontal destruction were valuated in 6 - 8 months from the treatment beginning with the help of standardized clinical indications:
1. The depth of probation (ID) - from gum edge to the bottom of dentogingival sulcus (in
mm).
2. Gum recession - from enamel-cement tooth border to the gum edge (in mm).
3. Clinical (dentogingival) attachment lost - from enamel-cement tooth border to the most
apical point of the conserved osseous structures (in mm).
Hygiene index (Green &Vermillion) and gum index was calculated in all test groups before and after treatment (in units).
Measurements were held by 5 parodontists from Krasnodar parodontics and dental implantation centre of RF Ministry of Public Health after a special instruction. Graduated parodontal probe and Gerdex (Dentsply) computer digital diagnostic complex.
A morphological study of biopsy material was conducted in order to verify tissue structures received after parodontal defects treatment. The cuts-off of the soft attachment zone of 10 testing group patients, 6 patients of control group I and 8 patients of control group II were studied in 6-8 months after operation. The gum bits were fixed in 10% solution of neutral formalin and according to conventional rules were poured by paraffin. The thickness of multiple cuts-off that were painted with hematoxylin and eosin was 7 mcm. Correlations of microstructures of soft attachment were determined with the help of calibrated net in ocular of 10 power light microscope. After treatment mediodistal cuts-off of testing group and control group II were studied additionally to learn the behavior of osteoplastic materials in parodentium tissues.
Microphotograms have been made by the digital photographic camera Nicon COOLPIX 800 (Japan) using light microscope with x7 and x10 ocular magnification and x40, x60 and x90 objective magnification.
Digital data processing was conducted with the help of the methods of variational statistics using Student's pairwise test and casual stratified selection method (U. Kokren, 1976) with the help of software for ЮМ (Software, SAS version 6.12). Differences of parameter before and after treatment as well as in comparison with control groups were considered as reliable in case of p<=0.05.

Study results
Clinical results of the study
Initial level of hygienic care for oral cavity and the size of parodontal defects (of patients under study) are shown in the table 1.

Table 1.       Initial clinical parameters and characteristics of parodontal defects.

Notes:
* - average value (standard deviation);
NS - non-significant differences;
S - significant differences;

The absence of significant differences in clinical parameters in test and control groups stresses the adequacy of randomization process in the present study. The size of dentogingival attachment destruction corresponds to chronic periodontitis with lost of supporting tissues. Postoperative period proceeded mainly without peculiarities; only 6 patients from control group II (when hydroxyapatite was used as an osteo-substituent) in 2-3 days had a generalized pyrogenic reaction which disappeared spontaneously.
After suture removing and before the moment of membrane barriers removing out of parodentium regeneration focus the control group I (using TefGen barriers) was often marked by biomaterial surface exposure, cyanoticity, slightly dropsical edges of repositioned muco- periosteal flaps and recession of peri-implant tissues (Pic. lb). In test group membrane surface exposure didn't caused such effects and didn't disturbed the stable state of above- and submembrane structures: membranes demonstrated a high level of integration with surrounding tissues during all the period in situ (Pic. la).

Picture la.Exposure of testable membrane without signs of microbial pollution; pigmented deposit on barrier
surface and teeth appears because of frequent use of chlorhexidine. One of the signs of stable situation in
regeneration focus is the growth of above-membrane tissues over biomaterial.
Picture 1 b. Exposure of Teflon membrane with significant recession of above-membrane tissues and local
inflammatory reaction. Microbial pollution of biomaterial surface, unstable situation in regeneration focus.

In order to raise finding reliability during randomization process the whole statistical population was selectively "blocked". The changes of the studied indications were determined:
1. in case of advance membrane barriers removing (2-3 weeks) in comparison with
preset time of their in situ position (6 weeks);
2. in case of biomaterial surface exposure if compared when above-membrane soft
tissues covered barrier completely during regenerative process;
3. in case of microbial pollution of exposed membrane surfaces.
Membrane surface exposure was registered in 2 - 3 weeks on 49 sections (26 sections on lower jaw, 23 sections on upper jaw) - test group; 92 sections (41 sections on lower jaw, 51 sections on upper jaw) - control group I. That is 32% and 68% correspondingly. Unstable s ituation i n p arodentium r egeneration focus с aused b у microbial p ollution о f exposed membrane surface and its mobility were the reason of premature membrane removing. Within 2-3 weeks the membranes were explanted in 25 sections of test group and 44 sections of control group I. In other cases the stability of clinical situation assured by optimal position of membrane barriers in tissues remained during the whole stated period - 6 weeks. The results of clinical measurements made after treatment of severe periodontitis in test and control groups I and II are given in table 2.

Table 2.         Clinical parameters in 6 - 8 months after treatment.

Notes:
* - average value (standard deviation);
NS - non-significant differences;
S - significant differences;
**- non-significant differences of parameters in comparison with initial ones in control group II (table 1).

There weren't drawn certain distinctions during comparative assessment of the level of hygienic care and gingival index values in all groups before and after treatment.
Statistically significant changes of probation depth, size of gum recession and clinical attachment lost were determined after comparison of initial indices and indices after treatment in test group and control group I. The probation depth in test group after treatment was 0.6 mm (0.11) while in control group I it was much higher (if compared with test group) - 1.8 mm (0.73); in control group II (where membranes were not applied) was uncertain decrease of probation depth of dentogingival sulcus - 2.6 mm (0.64). The highest level of gum recession and a wide value range of this index were observed in the group where the membrane technique was not applied - 2.5 mm (0.96). Dentogingival attachment lost value decreased greatly after the treatment in test group and control group I; value decrease of this index was also observed (when p>0.05). Dentogingival attachment growth in test group after treatment was 4.2 mm (0.56), in control group I - 2.8 mm (0.67), in group without membranes - 0.8 mm (0.55). With the help of t test we have determined that in the group where our membranes were used the fact that they were exposed didn't influence the value of clinical attachment growth during 6-8 weeks. Visible microbial deposit accumulation over exposed membranes in this group decreased efficacy of the method of guided tissue regeneration.
Thus, in case of premature membrane removing because of ccumulation of bacterial colonies on exposed surfaces of test group (n=25) dentogingival attachment growth amounted 3.6 mm (0.92) with p<0.05 (between a-e and c-e, with p>0.05 between a-c). In control group I other regularities were revealed: when membranes were exposed during regenerative process (n=92) the growth of clinical attachment to the tooth was 2.3 mm (0.09). If membrane was placed under muco-periosteal flap then this index was 3.6 mm (0.47). The growth of dentogingival attachment during membrane exposure in situ and its surface contamination remains almost the same in control group I (p>0.05 between d-f, while p<0.05 between b-f). Gum recession level (in terms of the present study it's the shrinkage of a new tissue profile) depended straight on the time of membrane barrier being in tissues. When the membrane was removed in 2-3 weeks parameter average value exceeded the same one when barrier located in tissues during the whole period (Pic. 4). Uncertain changes in probation depth were registered in test group while in control group I this index decreased significantly (p<0.05 between a-e, c-g, d-h; p>0.05 between b-f).

In test group 25 furcated defects were to be regenerated. Vertical component of the clinical attachment growth in case of furcation involvement of the first degree after the treatment amounted 2.9 mm, of the second degree - 3.7 mm (table 3), horizontal component - 3.0 mm and 3.1 mm correspondingly.

Table 3.  Results of furcated parodentium involvement treatment.

Notes:
S - significant differences;
NS - non-significant differences.

In the sphere of furcation involvement the clinical attachment of the I degree (while using membrane technique) was fully reconstructed on lower and upper jaws (picture 5a, b).
Only in case of bacterial contamination of barrier biomaterial external surface in case of drifting out above-membrane tectorial tissues during regenerative process and premature barrier removing the volume of the formed soft tissue profile decreased mainly due to vertical component (Pic. 6a -c).
In case of furcation involvement of the II degree membrane technique efficacy was a little higher on the upper jaw in comparison with lower one. Furcation involvements of parodentium of the П degree couldn't be liquidated completely; the growth of clinical attachment didn't exceed 3.2 mm (Pic. 5c). There weren't revealed significant differences of dentogingival attachment indices in control group II before and after parodontal defects treatment.

Picture 5a, b. Clinical result of treatment of furcation defects of the I degree in the sphere of molar teeth of lower
and upper jaws in test group. The full reconstruction of dentogingival attachment in interroot zones of molar teeth.
Picture 5c. Clinical result of treatment of furcation defects of the II degree in the sphere of molar teeth of upper
jaw. The involved furcation volume was decreased significantly but incompletely.

Picture 6a-c. Clinical result of treatment of furcation defect of the I degree during contaminated barrier GoreTex
removing in 2.5 weeks. Horizontal component of dentogingival attachment is more expressed than vertical one -
gum recession value didn't change.

Morphological results of the study.
Histological studies of the gum biopsy materials after the treatment allowed to define the direction of formation and ratio of attachment microstructures in contact with the tooth root substrate.
In those groups where the membrane technique was used the formation of a new attachment of connective tissue was observed in all samples which thickness depended directly on the time of barrier location in tissues (Pic. 8,9).

Picture 8 a, b. A new dentogingival attachment of a test group patient: a short connective epithelium under which is
a new tissue with primary osteoid matrix zones is formed. Collagen fibers functionally oriented to the root surface
present connective tissue attachment structure. Stratified flat keratinizing gum and dentogingival sulcus epithelium
has a normal structure. (oro-facial section, a - x20 magnification; b - x40 magnification. Hematoxylin and eosin
staining).

Patients with chronic and long-lasting pathology of cardio-vascular system as well as hormone-dependent patients had a diminished vascularization of a new tissue; and its composition mainly included fibrous tissue elements. During the assessment of clinical results in
6-8 weeks these patients had a lower level of a new attachment than the healthy ones with a significant gum recession (in comparison with the whole study group), although residual parodontal recesses were liquidated completely. Therefore membrane technique usage for these
patients is justified because it radically removes parodontal recess - a reservoir for parodonto- pathogens.
The main feature of a new formed dentogingival attachment is predominantly perpendicular (or at different angles) arrangement of collagen fibers with respect to the surface of the prepared (polishing, detoxication, conditioning) tooth root (Pic. 10).
In the course of observation it was registered that clinical attachment to the tooth in defects protected by membranes is formed in a certain succession. Blood in submembrane space from surrounding saved marrowy structures is formed into granulation hyper-vascularized tissue
with a high concentration of cellular forms during several days. During the further tissue maturation soft collagen fibers unite into bundles which often functionally fasten to the tooth surface. After barrier removing and joining of repositioned flaps with a new tissue profile it is
epithelized simultaneously with the process of remodeling of clinical attachment and recovery of the normal histo-architectonics of flocculent connective tissue.

Picture 9.
   A new dentogingival attachment of a control group I patient after an 'open' repair in situ:under attachment epithelium is a connective tissue with a full-blown fibroblastic reaction. Connective tissue attachment structure the zone of which is shifted apically is similar to the one in test group. Integumentary gum and sulcus
epithelium has enlarged proportions. (oro-facial section, x40 magnification; Hematoxylin and eosin staining).

In 6-8 months after guided tissue regeneration operation it was difficult to clearly differentiate the border of the connective tissue attachment and primary osteoid matrix in test group and control group I because even in serial sections of one biopsy material different linear ratios of microstructures were determined. The only differentiating sign that characterizes primary osteoid matrix is its more dark staining if compared with other structures of the formed connective tissue under membrane (even in sections stained with hematoxylin and eosin). It is obvious that in test group epithelial and connective tissue component ratios are most close to normal ones (Pic.8). Special attention engages formation of a short (normal) connective epithelium with decrease of cell layers number in apex direction which is between stratified flat keratinizing gum epithelium and new connective tissue that is attached to the root surface. There is a strong case for a high strength of regenerated dentogingival attachment system due to scalloping and uneven borders (Pic.8b) because biopsy sampling was possible only with mechanical injury of the contact part.

Picture 10. Appearance of functionally oriented collagen fibers (of a connective tissue attachment) perpendicular to the  root  surface  sharply  limits  epithelium  growth along  corono-apical  gradient  (oro-facial  section,  x40 magnification; Hematoxylin and eosin staining).
Picture 11. The joining process of epithelial tissue of repositioned muco-periosteal flap with new formed connective tissue structures under membrane. The number of cell layers in basal part of epithelium is increased; there is no papillary layer in connective tissue (control group I, mesiodistal section, x40 magnification; Hematoxylin and eosin staining).
Picture 12. Contact zone of soft tissues with root surface (control group II patient). There is an expressed apical epithelium migration along root surface and into connective tissue; collagen fibers of connective tissue placed in parallel in the area of contact with tooth root are densely infiltrated with neutrophilic granulocytes (oro-facial section, x40 magnification. Hematoxylin and eosin staining).

In flocculent connective tissue in the majority of samples of test group the cells of inflamed reaction were not identified; that was regarded as the absence of immune tension in the new tissues formed under membrane. That's why artificially modeled local conditions for dentogingival attachment reconstruction may be regarded as adequate to the behavior of full regenerative processes without additional stress from antibacterial agent including antibiotics.
At early stages of formation and further remodeling of microstructures after membrane technique usage (not more than 8 months) gum connective tissue is not perfect with peculiar to it normal stromal cell interrelations (Pic.8a); but functionally oriented collagen fibers of the attachment which are perpendicular to the root surface (Pic. 10) can cause the effect of contact inhibition of epithelium growth in apical direction (designated with an arrow).
The growth of epithelial component size of attachment in control group I (Pic.9) in comparison with test group is evidently due to recurrent mobilization of muco-periosteal flaps and their application (stratification) on the surface of the new tissue grown under membrane. Histological picture of the gum coronal zone is characterized by a significant thickness growth of epithelium stratum without a typical structure of this tectorial tissue on stated term (Pic.11).
This all may be the reason for index growth of probation depth of dentogingival sulcus in
control group I in comparison with test one.
In control group II there is minimum of connective tissue capable to attach to the tooth surface after the treatment; dentogingival attachment apparatus which more resembles contact tissue interrelations was mainly represented by epithelium stratum (Pic. 12).
The fibers of the connective tissue in the contact zone with tooth root have parallel (corono-apical) direction. Epithelium migrates along root surface because of the absence of
detergent (restraining) factors. Moreover there is a high cellular density of connective tissue stroma in this part due to expressed leucocytic infiltration demonstrating high level of local non- specific immune protection.

The behavior of osteo-substituting materials (used at present study) during parodontal defect treatment is characteristic. Morphological picture demonstrates the presence of active osteogenesis around microgranules of biositall osteoconductor only in groups where membrane barriers were used (Pic. 13).
This process is in many respects caused by the formation of connective tissue attachment to the root surface under membrane that limits epithelium growth. Connective attachment epithelium and stratified flat keratinizing gum epithelium reconstruct their form in the second place and that's why we can say that epithelium tissue condition is determined by interactions of
connective tissue.

In control group II (where membrane barriers were not used) conversion mechanism of blocks of osteoplastic material was mediated by macrophage phagocytosis (Pic. 14).
Granules of osteosubstituting material had free-lying position in connective tissue without any signs of primary osteoid matrix. Moreover they were limited by fibrous connective tissue elements reminding the structure of a scar.

Discussion of results
The efficacy of non-resorbable membrane of polytetrafluoroethylene while using in parodontics was estimated in the present controlled study.
We tested integrative properties of a new biomaterial, tolerance to microbial pollution (in case of barrier exposure), membrane possibilities to support migration of cellular forms and influence on qualitative and quantitative formed in parodontal defects of tissue structures
reinforced be membranes. Teflon regenerative membranes (GoreTex and TefGen) were used in control group.
The results of regenerative therapy of defective parodentium (estimated with the help of standardized clinical indices) were as follows: in 6 - 8 months dentogingival attachment growth while using membranes of our design was on average 4.2 mm (in group with teflon membranes -
2.8 mm), the probation depth decreased by 2.9 mm and 1.4 mm correspondingly. However the gum recession decreased in test group only by 0.2 mm and in parts with teflon membranes - by 0.6 mm.
The dynamics of revealed clinical parameters may be explained by morphological characteristics of new structures of dentogingival attachment formed under membrane. In group with teflon membranes maturation of parodontal attachment apparatus (according to recommendations of creators) is happening under muco-periosteal flap which is mobilized during reoperation after removing of the used barrier. Inspite of the flap deepithelization (although the fullness of procedure is not under control) while adhesion of these tissues the thickness of stratified flat keratinizing epithelium increases minimum twofold. Within the limits of the present study the revealed composition and ratio of tissue structures under maturation prevail. Remodeling of the attachment of connective tissue and its deep layers continue during this period. Thickening of epithelium stratum may be regarded as a compensatory mechanism while returning status quo. The signs of attachment of this epithelium to the root surface were revealed neither clinically nor histologically; that's why the probation depth of dentogingival sulcus in those parts where teflon membranes were used is deep (on average 1.8 mm within the wide range of values of this parameter in control group).
In test group probation depth (with the minimal value of standard deviation) was on average 0.6 mm after regenerative therapy. The parodentium tissues underwent qualitative structural changes connected with parodontal recess liquidation because the residual recess with a low stability to microbial aggression is the main risk factor of the recurrent inflammatory destructive process. Full microstructures of the clinical attachment formed under membrane in test group help to reconstruct the natural form of periodontal tissues in aproximal areas - dentogingival papillae. The real possibility to correspond the leading principle of functional anatomy "form follows function" has been achieved.
The formation of functional biological structures depends at first on mechanical stability of environment (Schenk, 1992). It's known that unstable situation in the focus of regeneration leads to the scar formation. Integration property of the implanted biomaterial is an integral condition for "plug" creation between root surface and barrier to prevent the occurrence of fibrous connective tissue cells and to prevent migration of epithelium in regeneration focus.
Tested material allowed reducing of exposure quantity of barrier surface more than twofold in comparison with control group. The very fact of membrane exposure didn't influence the size of dentogingival attachment growth (4.1 mm against 4.3 mm while test barrier being under muco-periosteal flap). That's why exposure of above-membrane cover soft tissues was not considered as an indication for removing barrier from oral cavity. Only with the occurrence of expressed microbial contamination which induces local inflammatory reaction exceeding the bounds of biomaterial the membranes were removed from the regeneration focus. In the groups studied with the help of guided tissue regeneration method (test and control group I) only half of the total number of exposed barriers were untimely removed. In these areas of parodentium the level of the formed clinical attachment was lower than that while biomaterial exposing: 2.5 mm (0.88) against 4.0 mm (0.45), while the attachment growth was 3.8 mm (0.65) in cases of exposure of membrane barriers in test and control group I. Moreover gum recession size was > 2.5 mm during estimation of the parodentium regenerative therapy results in 6 - 8 months. According to Zucchelli G. data (2002) the GoreTex membrane use (with the same indications and "open" repair) allowed reaching the dentogingival attachment growth 3.6 mm (1.0) with the gum recession 2.5 mm (0.8). Cortellini P. and Tonetti M.S. (2000) fixed the teflon membranes exposure in 70% - 80% cases. It's important to note that native data and results of foreign researchers (while studying teflon membranes) have the same orientation of clinical shifts: dentogingival attachment growth is lower while above-membrane tissues exposure if compared with the "close" repair. The significant decrease of this clinical indication was registered in case of microbial contamination of the exposed surface of our membrane (4.1 mm (0.18) against 3.6 mm (0.92)); while in control group in case of "open" repair and bacterial pollution of exposed surfaces the method efficacy was identical (2.3 mm (0.09) and 2.2 mm (0.84).
The present s tudy showed that membranes оf оur design m ay be "open" into the оral cavity during the repair period and that doesn't cause that degree of microbial contamination of biomaterial surface which is capable to degrade the efficacy of the guided parodentium tissue
regeneration method.
Filling of submembrane space with new viable tissues for reconstruction of form and function of parodentium means keeping of a certain (stated) volume for an adequate period of time during repair process. While guided parodentium tissue regeneration this space and individual for each case defect geometry is determined by the borders of root surface, alveolar process of maxilla and membrane covering them. It's also known that the circuit of formed tissue profile is determined by the circuit of membrane surface.
Following the given statements we tested our membranes with fixity of various degrees and plasticity of different variants and also tried to construct barriers with zone integrative properties distribution. The results of this study (that are not published in press) come to the fact that suggested parameters of fixity and plasticity of our material were balanced both for reliable weigh retention and capability to resist the pressure of surrounding tissues and forces affecting from outside, for instance, mastication.
The results оf оur study s howed that оur biomaterial has оptimal сharacteristics tо be placed in microbial surrounding of oral cavity interacting with humid environment and saliva (protein contamination) and during mechanical stressful moments due to formation of stable epithelium-connective-tissue-membrane connection. Our new macro- and m icrodesign, с hange of the total porosity volume and selection of optimal parameters for biomaterial nuclear chemical processing illustrate its high efficiency.
During new barrier membrane testing we didn't select patients according to the state of health, pernicious habits (smoking) and age requirement. The participants of the study were selected by chance as they came to the Center to get specialized parodontal treatment. 56% of them had diseases of different organs and systems. A special attention was paid to acquiring a habit of oral cavity care. The patients involved into the study achieved a high degree of hygienic motivation due to systematic monitoring of parodentium tissues through the whole period of
study.
Taking into consideration the fact that the patients with pathologies had lower results of membrane technique use (while reconstructing defective parodentium) in comparison with healthy participants the achieved clinical effect of regenerative therapy in test group (according to the statistic whole) was considered to be high and predictable. Even in case of furcation involvement which are the most therapy resistant if compared with intraosteal parodontal recesses dentogingival attachment growth indices were rather high (I degree of involvement) and radically improved clinical situation in case of involvement of molar interroot zones of II degree.
The present work gives histological quality verification of biological structures of parodentium bearing tissues repaired during the process of treatment. In microenvironment created under membrane that makes for migration of cells from maternal vital tissues (bones of alveolar process of maxilla and periodontal ligament) primarily formed connective tissue with a high degree of vascularization and cell forms concentration. While studying biopsy materials of attachment soft tissues formed under membrane we revealed a direct relation between the degree of connective tissue vascularization, quantity and quality of remodeled attachment structures.
Moreover, the time of membrane barriers being in situ determines the shrinkage size of a new tissue profile (in this study designated as gum recession). In comparison with a parallel study of efficacy of a new polypropylene membrane with biocompatible cover (where the
highest shrinkage level of a new tissue was observed during first 2 months after membrane removing from 2-3 weeks (M.D.Perova)) we revealed different laws. Premature explantation of test barrier of tissues (in case of bad microbial pollution) showed recession size of new structures of the attachment; it was 0.3 mm higher than average one in this group. When membrane was in situ during the whole period this index was 0.4 mm lower than average one in test group. In control group premature remove of teflon membranes increased the gum recession size by 0.9
mm on average.
We tried to find explanations to these correlations in interactions of microstructures of a forming dentogingival attachment apparatus in dynamics. In 2 - 3 weeks submembrane space is filled with granulation tissue with soft thin-fibrillar stroma and minimal formation of collagen fibers chaotically oriented. Barrier remove during this period changes the repair situation in case of free access of epithelium cells and gum connective tissue causing the fast process of their apical migration. All this prevents formation of a new connective tissue attachment to the root surface. As the tissue structures (formed under membrane while its being in situ) mature during 6 weeks bundles of collagen fibers along the full thickness in corono-apical direction attach to the "clean" root surface preventing gum recession after barrier remove.

Conclusions
1. Non-resorbable membrane of polytetrafluoroethylene of our design for guided parodentium tissue growth with fundamentally new macro- and microdesign and unique processing by nuclear chemical method demonstrates high and predictable results of clinical treatment.
2. Advantages of this membrane if compared with teflon ones which are used for the same purpose are as follows: more simple explantation at the end of period of being in situ, possibility of the "open" repair during the stated period, high stability to microbial colonies sedimentation on open biomaterial surface, optimal characteristics of barrier rigidity and plasticity, simplified adaptation (modeling) to the parodontal defect form.
3. The present controlled study proved the capability of a new barrier to form a dentogingival attachment of different quality, the structures of which approximate to the normal histoarchitectonics of soft tissues surrounding the tooth that corresponds to the main principle of the functional anatomy "form follows function".

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