Bedri Onur Kucukyildirim

Effect of platelet-rich plasma for treatment of Achilles tendons in free-moving rats after surgical incision and treatment

OBJECTIVE The purpose of this study is to investigate, both histopathologically and biomechanically, the effect of platelet-rich plasma (PRP) on surgically repaired Achilles tendon rupture recovery in rats. METHODS The study included 25 17-month-old male Sprague-Dawley rats with an average weight of 500-550 g. Five rats were used as donors, while 20 rats were separated as PRP group (n=10) and control group (n=10). The Achilles tendons of the rats were cut transversely, and PRP was administered to the PRP group, while the control group received serum physiologically to create the same surgical effect. In previous studies, it was shown that this serum does not affect tendon recovery. Fifteen and 30 days post-treatment, the rats were sacrificed, and their Achilles tendons were extracted and examined histopathologically and biomechanically. RESULTS Based on the obtained findings, it was observed that the histopathologic Movin and Bonar scores of PRP group on the 15th and 30th day post-treatment were significantly lower than those of the control group (p=0.019, p=0.017, respectively), while no significant difference was found in maximum force (Fmax) values in biomechanical measures on the 15th and 30th day post-treatment. CONCLUSION It is thought that PRP use in Achilles tendon ruptures positively affects histopathological recovery in the early period, but that it does not produce the same biomechanical effect. We believe that PRP use for qualified tendon recovery is histopathologically beneficial.

Surface Roughness Changes and Corrosion on Nickel Titanium Orthodontic Wires Compared to Stainless Steel Wires in Various Artificial Salivas

Abstract Nickel titanium shape memory alloy and stainless steel orthodontic wires were exposed to three different artificial saliva solutions which are modified Fusayama, modified Fusayama with 1g/l NaF addition and modified Fusayama with 1.7 % H3PO4 addition. Under conditions similar to oral cavity temperature, corrosion behaviours were observed by using weight loss method and by macro surface photographic observations. Also, surface roughness of wires were investigated and compared. Consequently, it was determined that corrosion rates of all NiTi wires exposed to the modified Fusayama solutions with NaF addition are higher because of galvanic interaction of NiTi and hydrogen embrittlement of titanium. Also, surface roughness of NiTi wires were increased in modified Fusayama solution with NaF addition.

Investigation of the biomechanical and histopathological effects of autologous conditioned serum on healing of Achilles tendon

Objective The aim of this study to evaluate the effects of autologous conditioned serum (ACS) on the healing of transected rat Achilles tendons via the assessment of biomechanical and histological parameters. Methods The study was conducted on 45 male Sprague–Dawley rats. Five rats were used as donors for ACS preparation. Animals were randomly assigned to the experimental or control group. In both groups, the Achilles tendon was cut transversally and then sutured. In the placebo control and ACS-treated groups, saline or ACS, respectively, was injected into the repair zone three times after surgery. Ten rats from each group (ACS group, n = 20; control group, n = 20) were euthanized at days 15 and 30 after surgery for histopathological (n = 5) and biomechanical (n = 5) testing. The histopathological findings were interpreted using the Bonar and Movin scales. Tendon remodelling was evaluated via the immunohistochemical staining of collagen type 3. Biomechanical effects were assessed by tensile testing. Results The Bonar and Movin scale scores were significantly better in the ACS-treated group on both day 15 (p = 0.003 and p = 0.003, respectively) and day 30 (p = 0.005 and p = 0.004, respectively). The immunohistochemical density of collagen type 3 was significantly lower in the ACS-treated group on day 30 (p = 0.018). The type 1/3 collagen ratios of the groups were similar on days 15 and 30, as determined by Sirius Red staining (p = 0.910 and p = 0.133, respectively). In the biomechanical assessment results, the ACS-treated groups maximum load to failure values were significantly higher on day 15 (p = 0.049). Conclusion Injection of ACS had a positive effect on the histopathological healing of rat Achilles tendons on days 15 and 30 and on biomechanical healing on day 15. ACS treatment contributed to lowering the collagen type 3 density by day 30. According to our study, ACS may be favourable for the treatment of human Achilles tendon injuries and tendinopathies.

The Effect of Aging Under Loading on the Phase Transformation Behavior of Near-Equiatomic NiTi Shape Memory Alloy

The phase transformation temperature of nickel titanium (NiTi) shape memory alloy (SMA), which is commonly used in biomaterial fields, is strongly influenced by aging heat treatments. In this study, we apply a new aging heat treatment under loading conditions to near-equiatomic NiTi SMA wires to investigate its effect on phase transformation temperatures. We determine changes in the phase transformation temperatures via differential scanning calorimetry measurements. We analyze transformation temperatures, hysteresis properties, and enthalpy changes and discuss significant results with the help of micrographs. Moreover, we evaluate our results using two-way analysis of variance, axiomatic design methods, and customary analysis in order to make reliable inferences. We observe a significant difference between first and second heating-cooling cycle results for NiTi SMA samples on the basis of austenitic transformation temperatures. Consequently, we are able to theorize correlations between design parameters and functional requirements.

Lubrication Effects during Biaxial Stretch Forming of Galvanized Steel Compared to Interstitial-Free Steel

Abstract In this study, the effect of lubrications in biaxial forming zone was investigated and their performances in stretch forming process were compared. Two different ultra low carbon steel sheets which are extensively used in the industries, interstitial-free steel and galvanized steel, were tested. Three different lubrications were tested and changes in the right hand of the forming limit diagrams of the materials with different lubricants were determined by using out-of-plane formability test as well as limiting dome heights were obtained for each lubricant. Moreover, strain distributions of samples, which were stretched with dry and different lubricants, were evaluated experimentally and the effectiveness of lubricants is compared. As a result, it was observed that deep-drawing oil has the highest performance among all lubricants. Furthermore, galvanized steel has lower formability under all conditions when compared to interstitial-free steel.

Creep Behaviour of NearEquiatomic Nickel-Titanium Wires

Abstract The creep behaviour of near-equiatomic (50.8 at.-% Ni) NiTi wire with a diameter of 0.49 mm is studied between 82 MPa and 127 MPa tensile stress as well as in a temperature range of 575 °C to 650 °C. For 600 °C and between 82–107 MPa a stress exponent of n = 4.5 as well as for 82 MPa between 600–625 °C an activation energy of Q = 300 kJ mol-1 have been found, these results have been compared with previous creep studies. In contrast to previous studies, this investigation has been performed with high stresses for thin NiTi wires. Moreover, fracture surfaces and ductility of wires have been investigated. The main reasons for the various results are discussed.

Surface Roughness Changes on β-Titanium Orthodontic Wires after Corrosion in Various Artificial Saliva Solutions

Abstract β-Titanium orthodontic wires are exposed to three different artificial corrosive environments, modified Fusayama, modified Fusayama with 0.1 % NaF addition, and modified Fusayama with 1.7 % H3PO4 addition, which are similar to the oral cavity conditions. Corrosion behaviours of wires are observed by using weight loss method and scanning electron microscope observations. Afterwards, surface roughness of wires is investigated in details. Consequently, it is determined that corrosion rate of β-titanium wires exposed to the modified Fusayama solutions with H3PO4 addition is higher because of the acidity of this saliva. Furthermore, maximum increase in surface roughness and skewness are observed in the same environment. Hydrogen embrittlement of titanium is also an important factor for the corrosion of wires.