FUNDAMENTAL CHARACTERIZATION OF THE DEVELOPED TITA- NIUM DENTAL IMPLANT STRUCTURES

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1 FUNDAMENTAL CHARACTERIZATION OF THE DEVELOPED TITA- NIUM DENTAL IMPLANT STRUCTURES Kossenko A. 1, Astashina N. 2, Antsiferov V. 3, Rogozhnikov A. 2, Rapekta S. 2 1 Ariel University, Laboratory of coatings and nanotechnology. 2 Perm State Medical Academy named after Academician E. A. Wagner for Russian Ministry of Health, Department of Prosthodontics. 3 Scientific Center of Powder Material Science, Perm State Technical University, Perm, Russia. Abstract At present, development of materials and coatings for dental implantation is among the most booming areas of medical material science. One fundamental problem with using titanium-based dental implants is to achieve adequate osseointegration, however, osteogenesis around implanted structures is not always sufficient, especially in soft types of bone tissue (for example, D4 according to С. Mich) [1]. Improved morphology of primary structural materials (titanium alloy) and functional coatings such as hydroxyapatite layer on implant surfaces allows to facilitate their integration. However, it is noted [1] that the main drawback of known coatings is their cracking and scaling after the structure is implanted. Therefore, researchers seek to develop modern approaches to formation of osteoinductive surfaces of implantation systems. To facilitate dental implantation, we improved the production technique of nanostructured titanium in order to form the endosteal portion of an implant, and developed a technique in order to form osteoinductive surface as stable hydroxyapatite layer. Introduction The problem of facilitating dental implantation has been topical for many decades. Loss of teeth results in major morphologic, functional and esthetic defects. This highlights necessity of timely and satisfactory repair of dental defects, using biologically inert materials and state-of-art techniques, which allows to restore integrity and functional unity of dentitions. Currently, dental implantology is one of the most advanced branches in dentistry. Due to its knowledge-intensity and integrative potential, it is in booming growth. New concepts are being developed in implant technology and production [1]. These are improved through comprehensive solution of developmental, technological, biotechnical, material-related problems, and by optimizing the existing processes and designs. For all obvious merits of titanium as a biologically inert material which is not susceptible to oxidation when exposed to corrosive bodily fluids and causes no immune response from living tissues, one fundamental problem with using titanium-based dental implants is to achieve adequate osseointegration [2]. On material interaction level, implanted metallic structures may be rejected since metals generally tend to be repellent towards oxides (bone tissue) and organic matter. Attempts to overcome this obstacle roughening titanium surface are only a limited success: all state-of-art titanium implants are roughened by tapping, however, osteogenesis around implanted structures is not always sufficient [3]. Materials and Methods The proposed method of improving titanium implant osseointegration is based on using nanodisperse titanium as a main structural material, and on developing a mediatory material, hydroxyapatite layer which has good adhesion both to the metal and to bone tissue [4]. We obtained nanodisperse titanium by severe plastic deformation (SPD) of titanium rods, using equal-channel angular extrusion (ECAE)

To assess mechanical properties of the obtained osteoinductive coating (hydroxyapatite layer), we tested the specimens for abrasive wear, using a rabbit s mandible fragment as a rubbing body.

2 To assess mechanical properties of the obtained osteoinductive coating (hydroxyapatite layer), we tested the specimens for abrasive wear, using a rabbit s mandible fragment as a rubbing body. We performed 3 series of experiments: 1 no load, gr load, gr load; then the specimens were examined by SEM. We also performed a full-scale experiment by inserting a hydroxyapatite-coated implant into a pig s mandible in manner conventional for dental implantology, and removing it from bone tissue using Piezosurgery 3 ultrasonic device. The surface change pattern was examined by SEM. Results We developed a dental implant production process based on forming endosteal portions of implants from high-strength rods fabricated from ВТ-5Л alloy and processed by severe plastic deformation. This method allowed to modify grain structure in titanium blanks while preserving their shape and cross-section size. Analysis of data from specimen microhardness measurements and bending tests shows that severe plastic deformation allows to achieve maximums of these values, more than thrice the data from annealed coarse-grained titanium. Ductility values also increase after annealing, as compared to the initial data, and amount to 0.37 mm at 250 C. With the same processing conditions, maximum values are obtained for microhardness and strength. In accordance with the proposed approach, we developed a technique for coating titanium specimens with osteoinductive hydroxyapatite layer. Abrasive testing showed that the rubbing body was sheared by the porous surface spikes while none of its fragments could be found inside the pits (pores). The pores accommodate a sufficient number of hydroxyapatite crystals (Fig. 1, 2, 3). a 1-175

3 b c Fig. 1. As-abraded (no load) SEM image with various magnifications. a 1-176

4 b c Fig. 2. As-abraded (400-gr load) SEM image with various magnifications. a 1-177

b c Fig. 3. As-abraded (900-gr load) SEM image with various magnifications.

Examination of hydroxyapatite-coated implant surface after the structure was introduced

retained throughout most of the structure (Fig. 4)

5 b c Fig. 3. As-abraded (900-gr load) SEM image with various magnifications. White colour indicates bone stuck to the specimen. Examination of hydroxyapatite-coated implant surface after the structure was introduced into a pig s bone tissue yielded the following results: hydroxyapatite layer was retained throughout most of the structure (Fig. 4). Fig. 4. SEM image after the full-scale experiment. Hydroxyapatite coating retained. The surface has porous morphology. The pits accommodate intact hydroxyapatite crystals (5)

a b Fig. 5. SEM images after the full-scale experiment with various magnifications: a) 10000; b) 20000. Porous surface structure. Hydroxyapatite crystals inside the pores.

introduce the findings в into clinical dentistry.

6 a b Fig. 5. SEM images after the full-scale experiment with various magnifications: a) 10000; b) Porous surface structure. Hydroxyapatite crystals inside the pores. The above allows to conclude that the implant coated according to the developed process retains most of hydroxyapatite layer when inserted into bone which allows to achieve good osseointegration and introduce the findings в into clinical dentistry. Thus, to facilitate dental implantation, we improved the production technique of nanostructured titanium in order to form the endosteal portion of an implant, and developed a technique in order to form osteoinductive surface as stable hydroxyapatite layer. The developed designs of dental implants are intended to repair dentition defects of various localization. Conclusions 1. High-temperature severe plastic deformation technique allows to obtain a nanodisperse titanium alloy with optimum properties to form endosteal portions of dental implants. 2. The mediatory hydroxyapatite coating has the specified properties: the required strength, crease resistance when the structure is being implanted, well-developed surface and porous morphology, which provides interaction with bone tissue, and furthermore, high adhesion to the implant metal

7 The research was financially supported by the Ministry of Education and Science of Perm Region, research project «Development of biologically inert nanomaterials and high technologies in dentistry within the holiatry program for patients with defects of dentition and jaws». References 1. Mich C.E. Dental Implant Prosthetics P. 2. Musheev I.U., Olesova V.N., Fromovich O.Z. Clinical dental implantology p. 3. Gyunter V.E., Khodorenko V.N., Chekalkin T.L., Olesova V.N. Biocompatibility problems of metallic materials // Dentistry No P Mich C. Hidroxilapatite-coated implants: design considerations and clinical parameters // NY State Dent J 59: 36 41, Kossenko A., Lugovskoy S., Astashina N., Lugovskoy A., Zinigrad M. Effect of Time on the Formation of Hydroxyapatite in Peo Process with Hydrothermal Treatment of the Ti 6Al 4V Alloy // Glass Physics and Chemistry, 2013, Vol. 39, No. 6, pp

ANALYSIS OF EFFICIENCY OF DENTAL IMPLANT OSSEOINTE- GRATION CHARACTERIZED BY VARIOUS SURFACE TYPES.

ANALYSIS OF EFFICIENCY OF DENTAL IMPLANT OSSEOINTE- GRATION CHARACTERIZED BY VARIOUS SURFACE TYPES. Astashina N. 1, Lugovskoy A. 2, Kossenko A. 2, Lugovskoy S. 2, Zinigrad M. 2, Nakonechny F. 2 1 E.A.