An experimental study of bone grafting using rat milled tooth.

PURPOSE: The aim of this study was to develop a novel bone graft material that used extracted teeth. MATERIALS AND METHODS: Thirty-six 10-week-old male Wistar rats were used. The incisors were extracted, immediately frozen and milled, mixed with hydroxypropyl cellulose (HPC), and injected into the socket. The remaining rats received HPC alone, or the socket was left to heal untreated. Socket healing and bone formation in all three groups were evaluated by three-dimensional image analysis from microcomputed tomography examination and histologic observation. RESULTS: Quantitative morphologic measurements demonstrated that bone formation was significantly stimulated in the group that received milled tooth and HPC at 2 and 4 weeks after extraction compared to that of the control (untreated) group, which showed normal healing without any intervention. Histologic observation revealed that the compound of milled tooth and HPC promoted early healing of the socket and initiation of bone formation in the surrounding area. Interestingly, HPC injection alone decreased bone formation and bone mineral content at 2 weeks and then increased bone formation at 4 weeks. CONCLUSION: A bone graft material composed of milled tooth promotes early healing and bone formation, while HPC, which is chemically stable in vivo, affects bone formation in the extraction socket.

High-throughput gene expression analysis in bone healing around titanium implants by DNA microarray.

OBJECTIVE: Bone generation occurs around titanium implants; however, its underlying mechanisms are relatively unknown. We attempt to identify gene transcripts specifically upregulated in in vivo bone healing with titanium implants using DNA microarray. MATERIAL AND METHODS: Titanium implants were placed into rat femurs, and total RNA was extracted from the implant-associated tissue at weeks 1, 2 and 4 of healing. As a control, RNA was extracted from the tissue undergoing osteotomy healing. The RNA samples were hybridized onto oligo DNA microarray. RESULTS: Most of the 20,000 genes tested were expressed similarly in both the implant- and osteotomy-healing groups. Eighty-six genes were upregulated (>2-fold) in the implant-healing group compared with the osteotomy-healing group in at least one time point of healing. Twelve genes were upregulated in the implant healing at week 2 and earlier, while 31 genes were upregulated at week 2 and later. Only one gene was upregulated specifically at week 1, while three genes were consistently upregulated from weeks 1 to 4. The upregulated genes included collagenous and non-collagenous extracellular matrix (ECM)-related genes, proteoglycans and bone resorption-related genes. Pathway analysis revealed the involvement of ECM and receptor interaction in implant healing. CONCLUSIONS: This study provides evidence that a set of gene transcripts is upregulated in the implant healing over the osteotomy healing, which seems to represent the coordinated biological events of long-lasting osteogenesis and bone remodeling required for osseointegration. Further studies are needed to identify the significance and biological roles of the transcripts in osseointegration. Proven reliability and usefulness of microarray technology should encourage future approaches to develop a high-throughput molecular assessment for osseointegration capacity of new implant surfaces.