In vitro comparison of commercial and ultrafine-grained titanium osteosynthesis miniplates used on mandibular fractures.

BACKGROUND: Implants called miniplates, with different geometries, are used for the treatment of a fractured or diseased mandible. Generally, Ti-based miniplates in various quantities and with various geometries are fixed into the bone tissue according to the location and shape of the fracture by embedding. OBJECTIVES: The aim of this study was to increase the strength of the material used in the production of miniplates by means of the equal-channel angular pressing (ECAP) treatment, and to provide a highrigidity fixation system with fewer miniplates. MATERIAL AND METHODS: In this study, the ECAP method, which is one of the methods of severe plastic deformation, was applied at 4 passes at 300°C in route Bc to increase the strength of pure Ti. Then, miniplates were produced with 2 different geometries (regular and long) and 2 different properties of the Ti material (untreated and ECAP-treated). The produced miniplates were placed in the fracture line formed in the angular region of an artificial, synthetic-bone mandible. The 2-point and 3-point bending and torsion tests were conducted on these fixation systems. RESULTS: As a result, after the ECAP process, the yield and tensile strength of pure Ti increased by 65%, while elongation decreased by 13%. After the ECAP process, the grain size of the material was reduced from 110 µm to 200 nm. CONCLUSIONS: This study showed that the fixation system became more rigid due to using ECAP-treated miniplates, and this ensured lesser displacement of the fixation system.

Dose-dependent effect of radiation on resorbable blast material titanium implants: an experimental study in rabbits.

BACKGROUND: Radiotherapy is a commonly used treatment modality in head and neck cancer; however, it also negatively affects healthy structures. Direct damage to oral soft and hard tissue frequently occurs with radiotherapy. In this study, we aimed to evaluate the effect of radiotherapy on bone surrounding titanium dental implants via biomechanical and molecular methods. MATERIALS AND METHODS: Fifty-four implants were inserted in the left tibiae of 18 adult male New Zealand rabbits (3 implants in each rabbit). After 4 weeks of the implant surgery, the left tibiae of 12 rabbits were subjected to a single dose of irradiation (15 Gy or 30 Gy). Four weeks after the irradiation, rabbits were sacrificed and removal torque test was done for the biomechanical evaluation. Bone morphogenetic protein-2 (Bmp-2) and fibroblast growth factor-2 (Fgf-2) expression analyses were performed with Real-time PCR. Statistical analysis was done using SPSS. RESULTS: The control group showed significantly higher removal torque value than the 15 and 30 Gy irradiation groups, and the 15 Gy irradiation group had higher removal torque value than the 30 Gy irradiation group (p < .001). The 15 Gy and 30 Gy irradiation groups had significantly lower Bmp-2 and Fgf-2 mRNA expressions than the control group (p < .001). In addition, the 30 Gy irradiation group had significantly lower Bmp-2 (p < .01) and Fgf-2 mRNA expressions (p < .001) than the 15 Gy group. CONCLUSION: Radiotherapy with 15 and 30 Gy doses can adversely affect osseointegration of implants by reducing the quality of bone and impairing the bone-to-implant contact. The mechanism of action seems to be related to alterations in Bmp-2 and Fgf-2 mRNA expressions.

Failure analysis of the cement mantle in total hip arthroplasty with an efficient probabilistic method.

Accurate prediction of long-term behaviour of cemented hip implants is very important not only for patient comfort but also for elimination of any revision operation due to failure of implants. Therefore, a more realistic computer model was generated and then used for both deterministic and probabilistic analyses of the hip implant in this study. The deterministic failure analysis was carried out for the most common failure states of the cement mantle. On the other hand, most of the design parameters of the cemented hip are inherently uncertain quantities. Therefore, the probabilistic failure analysis was also carried out considering the fatigue failure of the cement mantle since it is the most critical failure state. However, the probabilistic analysis generally requires large amount of time; thus, a response surface method proposed in this study was used to reduce the computation time for the analysis of the cemented hip implant. The results demonstrate that using an efficient probabilistic approach can significantly reduce the computation time for the failure probability of the cement from several hours to minutes. The results also show that even the deterministic failure analyses do not indicate any failure of the cement mantle with high safety factors, the probabilistic analysis predicts the failure probability of the cement mantle as 8%, which must be considered during the evaluation of the success of the cemented hip implants.

Treatment of isolated diaphyseal fractures of the radius with an intramedullary nail in adults.

BACKGROUND: The goal of the radius diaphysis fractures in surgical treatment is restoration of bone length, rotation correction and to secure fixation that allows early mobilization. The purpose of this study is evaluating the results of intramedullary (IM) radius nail for the treatment of isolated adult diaphyseal fractures of the radius. MATERIALS AND METHODS: We retrospectively reviewed adults with isolated fractures of the radius, who were treated with closed or mini open reduction with a IM radius nail between May 2008 and November 2011 and who were followed for a least 1 year. Patients with a Galeazzi fracture, a pathological fracture, or patients with nonunion after previous surgeries were excluded. All patients were allowed full range of motion without any external support. Primary outcomes were Grace and Eversmann rating, Disabilities of the Arm, Shoulder and Hand (DASH) scores. RESULTS: Twenty-three enrolled patients (mean age 34 years; 17 men) had 23 isolated radius fractures. Mean time to fracture union was 12 weeks (range 10-13 weeks) for radius fractures. No patient had nonunion, deep infections, or radioulnar synostosis. Follow-up ranged from 12 to 42 months. Grace and Eversmann ratings of 21 patients were excellent or good, and 2 patients were medium. Mean DASH score was 4.2 points (range 0-13.3). CONCLUSIONS: Our experience indicates that this new IM radius nail may be considered as an alternative to plate osteosynthesis for fractures of the radius diaphysis in adults. IM nailing of radius fractures provides reliable bony union and excellent postoperative clinical results in adults.