Advances in magnetoelectric composites for promoting bone regeneration: a review.

Repair of large bone defects is one of the clinical problems that have not yet been fully solved. The dynamic balance of bone tissue is regulated by many biological, chemical and physical environmental factors. Simulating the microenvironment of bone tissue in the physiological state through biomimetic materials is an important development direction of tissue engineering in recent years. With the deepening of research, it has been found that when bone tissue is damaged, its surrounding magnetoelectric microenvironment is subsequently destroyed, and providing a magnetoelectric microenvironment in the biomimetic state will be beneficial to promote bone repair. This review describes the piezoelectric effect of natural bone tissue with magnetoelectric stimulation for bone regeneration, provides a detailed account of the historical development of magnetoelectric composites and the current magnetoelectric composites that are most commonly utilized in the field of tissue engineering. Besides, the hypothesized mechanistic pathways through which magnetoelectric composite materials promote bone regeneration are critically examined, including the enhancement of osteogenesis, promotion of cell adhesion and angiogenesis, modulation of bone immunity, and promotion of nerve regeneration.

Bone augmentation in a titanium cap with a porous surface modified by microarc oxidation.

PURPOSE: To compare bone augmentation on pure titanium-machined surfaces and surfaces that have been modified by microarc oxidation (MAO) using titanium caps. MATERIALS AND METHODS: Twenty caps were manufactured from rods of commercially pure titanium. The control group (CG) consisted of 10 titanium caps with machined inner walls. The test group (TG) consisted of 10 titanium caps that were modified by MAO in an electrolyte solution containing calcium phosphate ions. The two types of titanium caps were fixed on the calvaria of 10 New Zealand rabbits. Each rabbit received two different caps. Although each cap was unfilled, the marrow and blood from the wound of the rabbit skulls could penetrate into the caps. After 4 weeks, the rabbits were sacrificed, and the skulls were removed for observation. The zenith of new bone was measured directly after the caps were removed from the skulls; subsequently, the bone volume was calculated by microcomputed tomography. RESULTS: Little bone augmentation could be observed in the CG caps, and the new bone height of the CG group was inconspicuous. In contrast, the new bone extended along the inner walls of the TG caps. The mean height of new bone of the TG group was 2.3 ± 0.28 mm. The mean volume of new bone in the TG group was 18.63 ± 3.80 mm(3). CONCLUSIONS: New bone formation in a titanium cap surface modified by MAO was greater than that of a nonmodified cap. A titanium cap allowed new bone formation on the MAO surface to be observed and is a promising device for bone augmentation. Additionally, this finding suggests that observation through a titanium cap is a feasible method for biomaterial testing in hard tissue.

The effects of early osseointegration in different implant sites in rabbit tibias.

The aim of this study was to evaluate the early osseointegration of implants with the same surface treatment in different implant sites in rabbit tibias after 4 weeks. A total of 42 acid-etched implants were implanted in three different sites in the tibia: group A was 2.08 ± 0.18 mm below epiphyseal line; group B was 7.00 ± 0.61 mm below the epiphyseal line; group C was 13.01 ± 1.26 mm below the epiphyseal line. After 4 weeks, the average bone-to-implant contact (BIC) values were as follows: group A, 40.02 ± 4.82 %; group B, 28.20 ± 5.41 %; group C, 20.76 ± 3.10 %. The BIC measurements yielded statistically significant differences among group A, group B and group C (P < 0.01); group A demonstrated the best osseointegration. In the present study, the different implantation sites in the selected 20-mm area demonstrated different early osseointegration; the sites located 7 ± 1.5 mm below the epiphyseal line were best suited for observing the effectiveness of early osseointegration among the three sites. The statistical results of the early osseointegration of implants are therefore affected by the location of the implant sites in this 20-mm area.

Bone response to a pure titanium implant surface modified by laser etching and microarc oxidation.

PURPOSE: To compare the bone responses to a pure titanium machined implant surface and one that has been modified by laser etching and microarc oxidation. MATERIALS AND METHODS: Forty-eight threaded implants with a machined surface were manufactured from rods of commercially pure titanium. The control group consisted of 24 implants with a machined surface. The test group consisted of 24 machined-surface implants that were modified by laser etching and treated by microarc oxidation in an electrolyte solution containing Ca2+ and PO43- ions. The implants were analyzed by energy-dispersive x-ray and scanning electron microscopy. Next, the two types of implants were inserted in the tibiae of 12 New Zealand White rabbits; one of the two tibiae received two control implants and the opposite side received two test implants. After 2, 4, and 6 weeks, the rabbits were sacrificed. Prior to sacrifice, all rabbits were injected with fluorescent-labeled achromycin and calcein. Samples were cut and ground for histomorphologic observation, and the mineralization appositional rate and the osseointegration index were measured and analyzed. RESULTS: Proportional spacing craters were found with a diameter of 100 microm and a depth of 80 to 100 microm at intervals of 100 microm around the test surface, and a porous titanium dioxide coating on the surface with pores of 1 to 5 micro in diameter was also produced. Carbon, oxygen, calcium, and phosphonium were detected by electronic probe. The ratio of calcium to phosphonium was 1.418, and the crystal structure of x-ray diffractive patterns indicated pure anatase phases. Compared with the control samples, the mineralization ratio and the osseointegration index of the bone around the test implants were higher (P = .00). CONCLUSIONS: The porous titanium dioxide coating produced by laser etching and microarc oxidation treatment improved the bone response versus that seen around machined titanium implants and enhanced the bone formation rate. It was concluded that the surface chemistry and topography, either separately or together, play an important role in the bone response to implants.

The early osseointegration of the laser-treated and acid-etched dental implants surface: an experimental study in rabbits.

The aim of the study was to evaluate early osseointegration of the laser-treated and acid-etched implant surface after the installation in rabbit tibias for 4 weeks. A total of 56 screw-shaped implants were grouped as follows: group A: implants were turned surface; group B: implants were laser-treated surface; group C: implants were acid-etched; group D: Implants were laser-treated and acid-etched surface. After 4 weeks, the removal torques were: group A: 13.21 +/- 11.30 Ncm; group B: 29.73 +/- 8.32 Ncm; group C: 30.31 +/- 9.45 Ncm; group D: 35.76 +/- 7.58 Ncm; The averages of bone-to-implant contact (BIC) were as follows: group A: 27.30 +/- 6.55%; group B: 38.00 +/- 8.56%; group C: 42.71 +/- 8.48%; group D: 49.71 +/- 9.21%. The removal torque and bone-to-implant contact measurements yielded statistically significant differences between the treated groups and turned group (P < 0.05); The laser-treated and acid-etched surface achieved higher Bone-to-Implant Contact than the laser-treated surface (P < 0.05), but there was no statistically significant difference between the laser-treated and acid-etched surface and the acid-etched surface in bone-to-implant contact (P > 0.05). In the present study, it was concluded that the laser-treated and acid-etched implants had good osteoconductivity and was a potential material for dental implantation.