Romanian Journal of Medical and Dental Education Vol. 8, No. 10, October 2019

TYPES OF BARRIER-MEMBRANE IN PERIODONTAL THERAPY OF GUIDED TISSUE REGENERATION

Diana Anton1, Irina-Georgeta Sufaru2*, Maria-Alexandra Martu2*, Georgeta Laza Demirbuken1, Raluca Mocanu1, Silvia Martu2

1Phd Student ”Grigore T. Popa” University of Medicine and Pharmacy, Iaşi, Romania, 2”Grigore T. Popa” University of Medicine and Pharmacy, Faculty of Dental Medecine, 16 Universitatii Str., 700115, Iasi, Romania.

Coressponding author: Sufaru Irina Georgeta: [email protected] Martu Maria-Alexandra: [email protected]

Abstract The present resorbable and non-absorbable membranes act as a physical barrier to prevent the fall of the connective and epithelial tissue in defect, favouring the regeneration of periodontal tissues. These conventional membranes have many structural, mechanical and biofunctional limitations. It is clear that the "ideal" membrane for use in periodontal regenerative therapy has not yet been developed. Based on a biomaterial-based approach, it was assumed that a biologically designed and functionally sized nanofibre material closely mimicking native ECM could succeed as the next generation of GTR / GBR membranes for periodontal tissue engineering.

Keywords: guided tissue regeneration, barrier-membrane, periodontal surgery

The strategy of isolating a high-density polytetrafluoroethylene, periodontal defect with a material PTFE (for example, Cytoplast® TXT-200, (resorbable or non-resorbable) which will Osteogenics Biomedical, Lubbock, TX, function as a physical barrier to prevent US) and (2) high density gingival cell invasion led to the creation of polytetrafluoroethylene reinforced with GTR / GBR membranes [1]. These titanium (for example, Cytoplast® Ti-250, membranes must have: (1) Osteogenics Biomedical, Lubbock, TX, biocompatibility to allow integration with USA). host tissues without giving inflammatory PTFE membranes are inert and responses, (2) adequate resorption profile biocompatible, act as a cellular barrier, to match the new tissue formation, (3) provide space for tissue regeneration and appropriate mechanical and physical allow tissue integration. It has been properties to allow for in vivo placement suggested that there is a favourable and sufficient resistance to be able to help correlation between the level of bone prevent membrane collapse and to fulfil regeneration and the protection of space the barrier function [2]. [3]. Studies have shown that titanium The RTG / ROG membranes are reinforcement of high density PTFE divided into two groups, non-resorbable membranes results in a higher regenerative and resorbable, depending on their capacity compared to traditional extended degradation characteristics. PTFE membranes, mainly due to the additional mechanical support provided by Stability / degradation characteristics of the titanium frame to the compression GTR / GBR membranes forces exerted by the superimposed soft The so-called non-resorbable tissue. One of the disadvantages of non- membranes (Table 1) for the RTG / ROG resorbable membranes is the need for procedures currently on the market are (1) additional surgery to remove them, which

6 Romanian Journal of Medical and Dental Education Vol. 8, No. 10, October 2019 involves not only additional pain and leached, usually an inorganic salt (for discomfort, but also an economic burden. example, sodium chloride or organic To eliminate the second surgical sugars) of the desired particle size, is procedure, resorbable barrier membranes combined with a polymer solution in a have been developed [4]. Processing matrix. After evaporation of the solvent, techniques based on either melting (ie, the salt or sugar crystals are dissolved in polymer heated above melting temperature water, which leaves a porous polymeric or melting temperature of glass) or solvent structure [6]. In this technique, the pore casting were used to manufacture polymer size and the porosity level of the based membranes for GTR / GBR membrane / scaffold can be adjusted by applications. Solvent formation / particle adjusting the particle size and salt or sugar leaching and phase inversion [5] are / polymer ratio respectively. common methods of fabricating porous, Unfortunately, the organic solvents three-dimensional, and / or membranous commonly used in this technique can schemes for tissue engineering. In the adversely affect the response of cells and solvent / particulate-lyophilization tissue after implantation. molding method, a porogen which can be

Table 1. List of available membranes Resorption Commercial Composition Mechanical Degradation Biologic degree name resistance rate property Non- Cytoplast High-density N/A Non- Biocompatible resorbable TXT-200 polytetrafluoroethylene degradable (d-PTFE) Cytoplast PTFE reinforced with N/A Non- Biocompatible Ti-250 titanium degradable Synthetic Resolut LT Poly-DL-lactic-co- 11.7 MpA 5-6 months Biocompatible resorbable gliyolic Vicryl Polyglactin 910 N/A 9 months Biocompatible Collagen- Atrisorb Lactid poly-DL and N/A 6-12 months Biocompatible based solvent resorbable AlloDerm Collagen type I from 9.4-21.5 16 weeks Biocompatible human cadaver MPa Bio-Gide Collagen type I from 7.75MPa 24 weeks Biocompatible pig tegument BioMend Collagen type I from 3.5- 18 weeks Biocompatible Extend bovine tendon 22.5MPa Cytoplast Collagen type I from N/A 26-38 weeks Biocompatible RTM bovine tendon

Most synthetic polymer resorbable Their resorption rate is important because membranes for periodontal regeneration these membranes must function for at least on the market are based on either 4-6 weeks to allow successful regeneration polyesters (for example, poly (glycolic) of the periodontal system. In general, acid (PGA), poly (lactic acid) (PLA), poly biodegradation of these polyesters (caprolactone) and their copolymers or involves the non-enzymatic cleavage of collagen derived from tissue [7]. PGA and PLA into the bypassed acids and, Polyester-based membranes (Table 1) are respectively, lactic acids, which are biocompatible, biodegradable, and common end products of digestion. clinically manageable compared to PTFE carbohydrates. membranes and allow tissue integration.

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Milella et al. [8] evaluated the response limits their use in GTR / GBR morphological and mechanical applications. characteristics of polyester based Collagen is a major component of membranes available on the market (for the natural extracellular matrix (ECM). example, Resolut® LT and Biofix®). Collagen-based membranes derived from Although the membranes initially showed tissues of human skin (Alloderm®, high resistance (~ 12-14 MPa), they LifeCell, Branchburg, NJ, USA), bovine completely lost their structural and tendon (Cytoplast® RTM Collagen, City, mechanical properties within 4 weeks of State, USA) or porcine skin (Bio-, incubation in culture medium. The Osteohealth, Shirley, NY, USA) are maximum resistance after 14 days of important alternatives for synthetic exposure decreased significantly (below 1 polymers in GTR / GBR procedures due to MPa). In a study by Li et al. [9], their excellent cell affinity and performed on nano-hydroxyapatite / biocompatibility [10]. However, type I polyamide-66-processed membranes with collagen may have limitations in its use, a porosity gradient, it was suggested that due to the high cost and poor definition of the addition of n-HAp guarantees a its commercial sources, which makes it membrane with good tensile strength (2-3 difficult to control the degradation and MPa). In addition, the reported cellular mechanical properties.

Fig. 1 - (A) AlloDerm® (AD) Macrophotography. AD is a minimally treated, non-cross-linked, freeze- dried dermal matrix collagen-based graft. (B) The SEM image shows the fibrous nature and morphology of the highly porous graft. (C and D) SEM images of the Cytoplast® RTM membrane. (C) general structure of collagen membrane and (D) 3D microstructure of bovine tendon collagen, composed of micro and nano collagen fibres.

AlloDerm® is a lyophilized The biomechanical properties and acellular dermal matrix graft (Figure 1) stability of the collagen matrix can be composed mainly of type I collagen improved by physical / chemical cross- derived from human cadaveric skin. linking, ultraviolet (UV), genipine (Gp), According to its manufacturer, this process glutaraldehyde, 1-ethyl-3- itself does not cause the destruction of the (3dimethylaminopropyl) carbodimide biochemical structural cues necessary to (EDC) hydrochloride. Exogenous cross- maintain tissue regenerative properties and linking agents, such as Gp, have been leaves behind an extracellular collagen reported to not only significantly enhance matrix that provides the basis for tissue the stability of collagen-based tissues, but structure and guides cellular functions also reduce its antigenicity. The formation [11]. of additional inter- or intramolecular crosslinks in collagen fibres enhances the

8 Romanian Journal of Medical and Dental Education Vol. 8, No. 10, October 2019 mechanical properties of biological tissues using film casting, dynamic filtration and [12]. Bottino et al. [7] investigated the synthetic e-spinning (eg PCL) and addition of a natural cross-linking agent, collagen, chitosan [9]. The membranes genipin (Gp), to the AlloDerm® were prepared with or without therapeutic rehydration protocol, demonstrating that it drugs, growth factors and / or calcium affects the mechanical properties and phosphate particles [14]. A material with stability of the collagen matrix. A adequate mechanical, degradation and significant increase in tensile strength biological properties is still required to compared to control was observed when guarantee its in vivo performance for GTR the Gp exposure time increased from 30 / GBR. min to 6 hours. Calorimetric analyses of Most of these methods result in differential scanning revealed a membranes with very low clinical considerable change in the temperature of potential due to their high density (ie, denaturation of the cross-linked samples, handling difficulties) and heterogeneity (ie which coincides with the increase of the non-uniform degradation rate). The e- enthalpy of denaturation. This finding is in spinning technique has shown great agreement with previous investigations membrane processing potential for into the use of a crosslinking agent to periodontal regeneration [13]. E-spinning enhance the stabilization of collagen is a very promising technique for the matrices derived from different biological synthesis of biomimetic nano-matrices, tissues [12]. including membranes for GTR / GBR The critical disadvantages of both applications. PTFE-based resorbable membranes and of resorbable membranes, mainly those based Perspectives in the field of membrane on collagen (for example, insufficient biomaterials mechanical properties, unpredictable While several of the above degradation profiles), have led to the study strategies can be used to successfully of alternative membrane materials. Several develop polymeric biomaterials for research groups have investigated the periodontal tissue regeneration, especially possibility of using membranes with a those based on a stepwise approach, functionally classified structure to hydrogels also offer high versatility in maintain sufficient mechanical properties design and synthesis [15]. Since many during operation, predictable degradation hydrogel systems have already been rate and bioactive properties [13]. Bone examined for tissue engineering purposes, formation would be stimulated by calcium the necessary technology is available and phosphate nanoparticles or growth factors can be used and adapted to periodontal (eg, BMP-2, TGF-β, among others), and tissue engineering needs. The synergistic bacterial colonization would be inhibited combination of hydrogel properties for by antibacterial drugs delivered to the specific periodontal problems is interface soft tissue / membrane [13]. particularly advantageous in these applications. Such hydrogel systems could Membranes designed for area-dependent be designed taking into account the bioactivity specific target values for the selected Numerous research groups have physical, chemical and biological tried to design and develop periodontal properties. For example, the physical- GTR / GBR membranes with the chemical and mechanical properties can be characteristics and properties required by adapted either by interconnection or by combining natural and synthetic polymers. combination with other scaffolding These studies prepared the membranes materials to control degradation behaviour,

9 Romanian Journal of Medical and Dental Education Vol. 8, No. 10, October 2019 sustained drug release and protein / cell must be adjusted to engage in tissue adhesion. In addition, since the hydrogels engineering of the periodontium. are conductive enough to migrate cells However, because in vitro and in throughout most of the scaffold, biological vivo degradation cannot always be properties such as bioactivity can be compared, flexibility is required in regulated and biomolecules (eg, growth regulating degradation times, if deemed factors) can be added to guide, enhance or necessary. Hydrogel systems that provide prevent cell adhesion and growth [16]. such flexibility in regulating degradation Many researchers have explored properties usually consist of polymer ways to control and improve the networks that incorporate hydrolyzed or mechanical properties of hydrogels but the enzymatically degradable crosslinkers or control of mechanical strength during degradable units within the polymer initial degradation is unclear. The rate of column. degradation will influence the mechanical The biological properties of properties, as well as the mechanisms of hydrogels can be most efficiently surface or body degradation. The regulated if the bioactive modification is possibilities of improving the mechanical performed on hollow gel or bio-inert strength of the hydrogels lie in the matrices such as polyethylene glycol or in generation of interpenetrated (IPN) or a biopolymeric hydrogel when the nanocomposite hydrogel networks [17]. biomolecules are incorporated in the Such elastomeric hydrogels have superior hydrogel or covalently attached to the mechanical properties compared to their polymer column [15]. Within a hydrogel, polymeric controls. Often, a combination biomolecules, such as growth factors, can of different crosslinking mechanisms be soluble or immobilized by physical allows the generation of mechanical interactions that provide the ability to strength, resistance and self-healing control cell migration. characteristics, all of which are suitable Taken together, the current parameters for use as a periodontal technology and results from the literature regeneration membrane. suggest that both e-spun nanomaterial and Making these degradable hydrogels biologically active hydrogel combinations, should allow target values in terms of functionally classified, have significant mechanical strength (for example 5-8 potential for use in periodontal tissue MPa) and the rate of degradation (for engineering. example, 4-6 weeks) [18]. Control of Future directions include, of swelling or shrinkage of hydrogel course, the rational design of hydrogels networks in changing physiological that require not only the control of conditions is essential for maintaining degradation and mechanical properties, but mechanical properties over time. This also the consideration of biological problem can usually be minimized by variables. Although in vitro results with e- adapting the synthetic procedures or by spun scaffolds show promise for creating a formulating hydrogels with biomolecules, biologically active synthetic membrane, salt or nanoparticles [17]. there is a significant limitation associated Maintaining biocompatibility with these scaffolds. Due to the dense during degradation is most important for packing of e-spun nanofibres during the designing functional hydrogel networks. spinning process, the resulting matrix has The hydrogels, as well as their degradation pore sizes that are usually small to allow products, must be biocompatible and, as cell infiltration into the body [19] and mentioned earlier, the degradation profile limits tissue growth and vascularization in vivo. Although techniques such as the salt

10 Romanian Journal of Medical and Dental Education Vol. 8, No. 10, October 2019 leaching method and the selective removal while facilitating the removal of cellular of soluble fibres [20] could improve cell waste products. infiltration into the fibrous matrix, Therefore, in order to accelerate endanger structural and mechanical the application of periodontal regeneration integrity, or result in macroscopic therapies, the next step should be to delamination of the layer. To maximize perform in vivo pre-clinical implantation periodontal regeneration, the implant must tests to evaluate the behaviour of barrier support bone cell infiltration from the bone membranes in animal models, to determine defect. In addition, vascularization of their biomechanical integrity and biomaterial / cellular construction is an biodegradation, healing, properties essential step in tissue healing, as this vascular as well as regeneration and process ensures the survival of the remodelling. nutrients and oxygen needed by bone cells,

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