Control of magnesium corrosion and biocompatibility with biomimetic coatings.

The use of magnesium and its alloys as biodegradable metallic implant materials requires that their corrosion behavior can be controlled. We tailored the Mg release kinetics and cell adhesion properties of commercially pure Mg by chemical surface treatments in simulated body fluid, in Dulbecco's Modified Eagle's cell culture medium in the presence or absence of fetal bovine serum (FBS), or in 100% FBS. HeLa cells were cultured for 24 h on these Mg surfaces to characterize their biocompatibility. Cell density on all treated surfaces was significantly increased compared with a polished Mg surface, where almost no cells survived. This low biocompatibility of pure Mg was not caused by the high Mg ion release with concentrations of up to 300 mg/L in the cell culture medium after 24 h, as cells grown on a glass substrate showed no adverse reactions to high Mg ion concentrations. Rather, the most critical factor for cell adhesion was a sufficiently reduced initial dissolution rate of the surface. A comparison among all surface treatments showed that an incubation of the Mg samples in cell culture medium gave the lowest dissolution rate and resulted in the best cell adhesion and spreading behavior.

Complication rates of operatively treated mandibular fractures--the mandibular neck.

BACKGROUND: Surgical treatment of mandibular neck fractures is frequently associated with postoperative complications. This study aims at an in-depth analysis of complication rates of surgically treated mandibular neck fractures. METHODS: All treated patients (264 male, 103 female patients, with 429 mandibular neck fractures) of the Vienna University Clinic of Maxillofacial Surgery in the period of 1995 to 2005 with at least 1 mandibular neck fracture were included. RESULTS: Of surgically treated fractures, 94.8% healed successfully after 1 open reduction, 4.4% had 2, and 0.8% had 3 open reductions. Osteosynthesis failure was 11.3% for 1 miniplate, 6.7% for 2 miniplates, and 8.5% for 1 lag screw. Of the surgically treated, 53 (21.3%) had 1 complication, 12 (4.8%) had 2, and 4 (1.6%) had 3 complications. Comparing isolated and mandibular neck fractures combined with other mandibular fractures the risk of suffering osteosynthesis failure is 3.59 in case of isolated (P = .004). CONCLUSIONS: Predominant causes of revision surgery are osteosynthesis failure, pseudarthrosis, and malposition.

Effect of surface pre-treatments on biocompatibility of magnesium.

This study reports the influence of Mg surface passivation on the survival rate of human HeLa cells and mouse fibroblasts in cell culture experiments. Polished samples of commercially pure Mg show high reactivity in the cell culture medium, leading to a pH shift in the alkaline direction, and therefore cell adhesion and survival is strongly impaired. Passivation of the Mg surface in 1M NaOH can strongly enhance cell survival. The best initial cell adhesion is observed for Mg samples incubated in simulated body fluid (M-SBF), which leads to the formation of a biomimetic, amorphous Ca/Mg-phosphate layer with high surface roughness. This surface layer, however, passivates and seals the Mg surface only partially. Subsequent Mg dissolution leads to a significantly stronger pH increase compared to NaOH-passivated samples, which prevents long-term cell survival. These results demonstrate that surface passivation with NaOH and M-SBF together with the associated changes of surface reactivity, chemistry and roughness provide a viable strategy to facilitate cell survival on otherwise non-biocompatible Mg surfaces.