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Passage Bone Growth and Remodeling During Fracture Healing Are Often Slow

Question 116

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Bone growth and remodeling during fracture healing are often slow and have potentially poor outcomes, including malunion or nonunion at the fracture site. Magnesium bone implants can aid in bone formation and safely biodegrade in the body according to the following reaction:Mg(s) + 2H₂O(l) → Mg(OH) ₂(s) + H₂(g) Reaction 1 Corrosion of magnesium metal in aqueous mediumHowever, magnesium metal tends to degrade too quickly and forms hydrogen gas pockets in the body. Corrosion is slowed as the metal naturally forms a protective layer of magnesium hydroxide in a process called passivation. Magnesium hydroxide is less soluble than magnesium metal, and its dissolution is described by the endothermic reaction:
$Passage Bone growth and remodeling during fracture healing are often slow and have potentially poor outcomes, including malunion or nonunion at the fracture site. Magnesium bone implants can aid in bone formation and safely biodegrade in the body according to the following reaction:Mg(s) + 2H2O(l) → Mg(OH) 2(s) + H2(g) Reaction 1 Corrosion of magnesium metal in aqueous mediumHowever, magnesium metal tends to degrade too quickly and forms hydrogen gas pockets in the body. Corrosion is slowed as the metal naturally forms a protective layer of magnesium hydroxide in a process called passivation. Magnesium hydroxide is less soluble than magnesium metal, and its dissolution is described by the endothermic reaction: Reaction 2 Solubility equilibrium of Mg(OH) 2 in water at 25°CAlthough passivation slows down the corrosion rate, it must be slowed even further to adequately facilitate bone reformation.Researchers are interested in the differences in the corrosion rates of magnesium metal protected by different biocompatible coatings. They compared 10-mm magnesium disks coated with compounds of various cation and anion combinations, with solubility results shown in Table 1. The coated disks were immersed in simulated body fluid (SBF) at room temperature for 50 hours.Table 1 Solubility for Biocompatible Inorganic Salts Given in mmol/100mL of Pure Water at 25°C Adapted from Huan ZG, Leeflang MA, Zhou J, Fratila-apachitei LE, Duszczyk J. In vitro degradation behavior and cytocompatibility of Mg-Zn-Zr alloys. J Mater Sci Mater Med. 2010;21(9) :2623-35. -Magnesium hydroxide begins to precipitate onto the magnesium metal surface when which of the following expressions is true? A) [Mg2+][OH−]2 > 8.9 × 10−12 B) [OH−] < 1 × 10−7 C) [Mg2+] = 8.9 × 10−12 D) [OH−] = [Mg2+]$ Reaction 2 Solubility equilibrium of Mg(OH) ₂ in water at 25°CAlthough passivation slows down the corrosion rate, it must be slowed even further to adequately facilitate bone reformation.Researchers are interested in the differences in the corrosion rates of magnesium metal protected by different biocompatible coatings. They compared 10-mm magnesium disks coated with compounds of various cation and anion combinations, with solubility results shown in Table 1. The coated disks were immersed in simulated body fluid (SBF) at room temperature for 50 hours.Table 1 Solubility for Biocompatible Inorganic Salts Given in mmol/100mL of Pure Water at 25°C
$Passage Bone growth and remodeling during fracture healing are often slow and have potentially poor outcomes, including malunion or nonunion at the fracture site. Magnesium bone implants can aid in bone formation and safely biodegrade in the body according to the following reaction:Mg(s) + 2H2O(l) → Mg(OH) 2(s) + H2(g) Reaction 1 Corrosion of magnesium metal in aqueous mediumHowever, magnesium metal tends to degrade too quickly and forms hydrogen gas pockets in the body. Corrosion is slowed as the metal naturally forms a protective layer of magnesium hydroxide in a process called passivation. Magnesium hydroxide is less soluble than magnesium metal, and its dissolution is described by the endothermic reaction: Reaction 2 Solubility equilibrium of Mg(OH) 2 in water at 25°CAlthough passivation slows down the corrosion rate, it must be slowed even further to adequately facilitate bone reformation.Researchers are interested in the differences in the corrosion rates of magnesium metal protected by different biocompatible coatings. They compared 10-mm magnesium disks coated with compounds of various cation and anion combinations, with solubility results shown in Table 1. The coated disks were immersed in simulated body fluid (SBF) at room temperature for 50 hours.Table 1 Solubility for Biocompatible Inorganic Salts Given in mmol/100mL of Pure Water at 25°C Adapted from Huan ZG, Leeflang MA, Zhou J, Fratila-apachitei LE, Duszczyk J. In vitro degradation behavior and cytocompatibility of Mg-Zn-Zr alloys. J Mater Sci Mater Med. 2010;21(9) :2623-35. -Magnesium hydroxide begins to precipitate onto the magnesium metal surface when which of the following expressions is true? A) [Mg2+][OH−]2 > 8.9 × 10−12 B) [OH−] < 1 × 10−7 C) [Mg2+] = 8.9 × 10−12 D) [OH−] = [Mg2+]$ Adapted from Huan ZG, Leeflang MA, Zhou J, Fratila-apachitei LE, Duszczyk J. In vitro degradation behavior and cytocompatibility of Mg-Zn-Zr alloys. J Mater Sci Mater Med. 2010;21(9) :2623-35.
-Magnesium hydroxide begins to precipitate onto the magnesium metal surface when which of the following expressions is true?

A) [Mg²⁺][OH⁻]² > 8.9 × 10⁻¹²
B) [OH⁻] < 1 × 10⁻⁷
C) [Mg²⁺] = 8.9 × 10⁻¹²
D) [OH⁻] = [Mg²⁺]

Passage Bone Growth and Remodeling During Fracture Healing Are Often Slow

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