Effects of static magnetic fields on bone regeneration of implants in the rabbit: micro-CT, histologic, microarray, and real-time PCR analyses

Objectives The aim of this study was to investigate the effects of static magnetic fields (SMFs) on bone regeneration around titanium implants by CT, histologic analysis, microarrays, and quantitative real-time PCR (qRT-PCR). Materials and methods Neodymium magnets provided the source of SMFs, the specimens were grade 5 titanium implants, and the animals were twenty-seven adult male New Zealand white rabbits. These implants were divided into six groups according to the presence of a magnet and predetermined healing period (1, 4, and 8weeks). Each group comprised six specimens for CT (n=6) and histologic examination, and three specimens (n=3) for microarrays and qRT-PCR, yielding a total of 54 specimens. Results The CT data showed that SMFs increased bone volume fraction (bone volume/total volume, BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th). Histologic observation indicated that SMFs promoted new bone formation and direct bony contact with implants. Microarray analysis identified 293 genes upregulated (>twofold) in response to SMFs. The upregulated genes included extracellular matrix (ECM)-related genes (COL10A1, COL9A1, and COL12A1) and growth factor (GF)-related genes (CTGF and PDGFD), and the upregulation was confirmed by qRT-PCR. Gene Ontology (GO) and pathway analysis revealed the involvement of the mitogen-activated protein kinase (MAPK), Wnt, and PPAR-gamma signaling pathways in implant healing. Conclusions CT, histology, microarrays, and real-time PCR indicate that SMFs could be an effective approach to improving bone regeneration around dental implants.