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INTEGRAL METHODS OF DEVELOPING MEDICAL IMPLAN-

TATION SYSTEMS BASED ON CARBON COMPOSITE MATE-

RIAL AND TITANIUM

V. Antsiferov1, N. Astashina

2, M. Kachenyuk

1, G. Rogozhnikov

2

1 Scientific Center of Powder Material Science, Perm State Technical University,

Perm, Russia 2 Perm State Medical Academy, Ministry of Health Perm, Russia

Keywords: implant, carbon materials, titanium alloys

INTRODUCTION

Increasing efficiency of holiatry of patients with acquired maxillary defects re-

mains one of focal problems in modern dentistry. This problem is gaining importance

due to increase in number of patients who were operated for neoplasms, occupational

and civilian injuries. Maxillary defects inevitably result in functional disorders, as well

as changes in a person’s appearance. WHO report, Global Goals for Oral Health 2020,

notes that treatment of patients with acquired defects in maxillae and mandibular joints

must become a critical strategic objective of modern dentistry [1].

The problem of developing efficient methods for bridging maxillary defects has

remained topical for many years [2, 3, 4, 5,6]. The main key to solve this focal prob-

lem is to develop novel implantation systems made of biologically compatible materi-

als which allow to secure prosthodontic structures with high quality, restore aesthetic

and functional parameters of maxillofacial area.

Among the most promising materials are carbon composite materials which

combine biological compatibility and mechanical strength comparable to mandibular

bone tissue property. High surface roughness and porosity of carbon composite materi-

al allow bone tissue to spread into the implantation-bone block, however, such surface

structure does to allow to form an anatomical head of the mandibular joint or ensure

normal function of the latter. The scientists of Ye. A. Vagner Perm State Medical

Academy and the Scientific Center of Powder Material Science for Perm National Re-

search University have developed and implantation system based on CCM and titani-

um, to be used in mandibular arthroplasty and bridging mandibular defects (Fig. 1).

Fig. 1. Implantation System Used to Bridge Mandibular Defects and in Mandibular

Arthroplasty

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EXPERIMENTAL

Uglekon-M carbon composite material (CCM) was joined to titanium pins using

a previously tested [7] compound of 70 % of mechanically activated (MA) titanium

sponge (TS) and 30 % of titanium hydride. The slip was prepared by mixing the pow-

ders, adding about 50 vol. % of ethyl alcohol, and grinding. The slip was applied onto

the CCM hole surface and the titanium pin. After screwing the pin into the CCM, the

junction was also impregnated with the slip.

As we found previously [7], the CCM and the titanium pin cannot be joined se-

curely enough if the pin and the hole are smooth. So, the hole and the pin fabricated

had embossed surface. For the shape combinations used, see Table 1.

Table 1. Shapes of the Components Being Joined

No. Pin connector profile CCM hole profile Drawing

1 Thread M5 Thread M5 Figure 3, a

2 Thread M5 Thread M6 Figure 3, b

3 Grooves Thread M6 Figure 3, c

a) b) c)

Fig. 2. Pin-to-CCM Jointing Versions

The structures were heat-treated in СНВЭ-1.3.1/16 furnace, under vacuum.

The junction strength was tested in Heckert FP-10 tensile machine, at load rate of

2 mm/min. The cyclic loading strength was tested in Instron 5885H tensile machine, at

load rate of 2 mm/min. During the cycle, the load varied from 400 N to 100 N, fol-

lowed by fracture strength test.

RESULTS AND DISCUSSION

Titanium Pin-to-CCM Junction Strength Testing

Testing the strength of joining pins with various surface shape to CCM with vari-

able threads found that maximum strength of 5.8 MPa can be achieved by combining

M5 pin thread to M5 CCM hole thread. Other configurations of parts being joined

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showed lower strength. Therefore, only M5+M5 version was used in further testing.

Junction using titanium slip was also shown to be stronger than M5 threaded connec-

tion without it (Fig. 3).

Using a threaded connection enhances strength via two factors. The major con-

sideration is ability of the thread to withstand axial load. Moreover, titanium-to-CCM

contact area is increased by a factor of 1.6 at the expense of the thread surface.

Heat treatment causes the titanium slip to interact both with the pin material and

with CCM. This produces titanium carbides which are fused into the titanium pin ma-

terial (Fig. 4).

Fig. 3. Strengths of Various Junctions, as Sintered at 1100 °C and Unsintered

Large thread surface area brings about further increase in strength with respect to the

strength of the thread itself. Moreover, contacts arising at the pin-to-CCM interface

prevent the pin from loosening.

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Fig. 4. Titanium Pin-to-CCM Joint as Heat-Treated at 1200º C.

On the Left: Thread Surface, on the Right: Pin Cut Surface

Higher increase allows to see that the thread surface includes two heterogeneous

phases (Fig. 5). The first phase is titanium which underwent structural changes via

atomic diffusion during heat treatment, and carbon-in-titanium solid solutions. The

second phase is titanium carbide produced by mutual diffusion of titanium and carbon.

Titanium-carbide grains demonstrate sharp angles and faces, and darker colour in the

image. In the first stage, titanium-based, and then titanium-carbide-based solid solu-

tions are formed at elevated temperature in titanium slip-to-CCM contact areas. High

activity of the dispersion-based slip causes them to consolidate with the titanium pin at

much lower temperatures than melting point of titanium and formation points of eutec-

tic titanium-carbon melts.

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Fig. 5. Enlarged Detail: Titanium Pin-to-CCM Joint as Heat-Treated at 1200º C

Sintering temperature-to-junction strength relationship is given in Figure 6. If

sintered at 1100 °C, the junction strength is the lowest, as sintering temperature is in-

creased to 1200 °C, the junction strength is increased to 9.2 MPa.

Fig. 6. Sintering Temperature-to-Junction Strength Relationship

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1000 cycles of cyclic loading up to 400 N does not result in strength degradation

which remains at 9.1 MPa (Fig. 7).

Increase in cycles to 10,000 causes a certain decrease in strength (to 7.3 MPa).

It should be noted that cyclic loading does not bring about elongation of the

structure in excess of 0.03 mm, which indicates absence of fractures at the material

contact interface.

Fig. 7. Cyclic Testing of M5+M5 Sample Sintered at 1200 °C. Cycles: 1000

CONCLUSIONS

1) Optimum surface configuration was determined for the joinable parts of the com-

bined implantation system. Maximum component coupling strength is observed if M5

threads are used.

2) CCM-to-titanium pin junction strength was found to depend directly on the sinter-

ing temperature. The strength is minimum at 1100 °C, it increases as temperature is

raised. Maximum junction strength was 9.2 MPa.

3) Effect of cyclic loads on CCM-to-titanium pin junction strength was tested. No ap-

preciable decrease in strength is observed in case of up to 1000 cycles. If the cycles are

increased to 10,000, the strength is decreased to 7.3 MPa.

The research was financially supported by the Ministry of Education of Perm Region,

research project – «Development of biologically inert nanomaterials and high technol-

ogies in dentistry within the holiatry program for patients with defects of dentition and

jaws».

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