Osteoconductivity of Two Novel Biodegradable Magnesium Alloys (ZK30A&ZK10A) for Repairing Bone Defect in Dogs

Document Type : Original Article

Authors

1 Associate Professor, Dental Biomaterial Department, Faculty of Dentistry, Alfyoum University, Egypt.

2 Lecturer of Oral Surgery, Faculty of Dentistry, Cairo University, Egypt.

3 Lecturer of Oral Biology, Faculty of Dentistry, Cairo University, Egypt.

Abstract

Background: Magnesium alloys containing zinc and zirconia are promising alloys as biodegradable orthopedic replacement bone
The objective: of this research was to evaluate of the ability of ZK30A and ZK10A Mg-alloys as biodegradable alloplastic bone substitute for bone formation of adequate quality and quantity in repairing bony defects in femoral shaft of dogs.
Materials and Methods: A total of eight skeletally mature mongrel male dogs with an average age 20 ± 2-month-old and weighing 15-18 kg were used in this study. The dogs divided into two groups, group I; contains 8 dogs with type I (ZK30A) alloy plates implanted in holes made in upper right femoral shaft and group II contains the same 8 dogs with type II (ZK10A) alloy plates implanted in holes made in lower right femoral shaft. The quantitative and qualitative assessments of newly formed bone tissue were carried out and assessed by In vivo radiography, scanning electron microscope and EDX for elemental analysis.
Results: radiographic results of bone density of group I showed high bone resorption after three weeks implantation, followed by high rate of bone formation after 6 weeks, then regressed to bone resorption again, finally after 12 weeks bone deposition again insignificant with those at 6 weeks. Whereas group II showed normal pattern of bone resorption till six weeks, followed by bone formation till the end of experiment. Both types of alloys showed bone resorption first after implantation, but they differed in longevity and severity of initial bone resorption; group I was severe for three weeks whereas group II was less in severity for six weeks.. Scanning electron microscopic results of both magnesium alloys (group I and group II) 3 months post-implantation showed new bone formation. Type I(ZK30A) alloys induced new bone in approximate contact to implanted alloy surface. Whereas, type II (ZK10A) alloys induced new bone in close intimate contact and well integrated with implanted alloy surface EDX for elemental analysis of the newly formed bone showed non-significant difference between group I and group II in calcium, Ca/P ratio and zinc. Conclusion: Both Mg-Zn-Zr alloys are liable to form qualified mineral bone. The pattern of osteointegration is directly related to the biodegradation rate and stable corrosive products formation. Mg Zn alloy with higher Zr (ZK10A) showed lower biodegradation tendency and high susceptibility for new bone integrated with orthopedic implant. Mg Zn alloy with lower Zr (ZK30A) showed higher biodegradation tendency and encouraged new bone formation with wide gap distance. ZK10A is promising osteoconductive biodegradable implant.

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