Bone induction of human tooth and bone crushed by newly developed automatic mill

Abstract

A novel automatic mill of teeth and bone has been developed for bone engineering. A human frozen-tooth and/or a human frozen-bone block were put into the Zirconium oxide (ZrO2) ceramics vessel of the machine, and crushed for 1 min with 20 saline-ice blocks (1 × 1 × 1 cm3/block) at 12000 rpm of ZrO2 blade. The crushed granules were demineralized completely in 2% HNO3 solution for 20 min, and rinsed in cold saline. We named each biomaterial after the acid treatment and washing, demineralized dentin matrices (DDM), demineralized bone matrices (DBM). Five wisdom teeth (total wet volume: 10.0 g) were crushed, decalcified, and lyophilized. The distribution of freeze-dried DDM granules was fine granules (0.5–1.0 mm: 0.27 g), moderate (1.0–2.0 mm: 0.46 g), and large (2.0–5.0 mm: 0.64 g). The fine granules of human DDM or DBM were implanted into the subcutaneous tissue of 4 week-old nude mice, and their tissue-inductive properties were estimated at 4 weeks after implantation histologically. The explanted samples were demineralized, embedded in paraffin, and sectioned. The specimens were stained with hematoxylin and eosin. We confirmed that DDM induced bone and cartilage independently, and DBM induced cartilage, bone and marrow at 4 weeks in the back skin of nude mice. These results indicated that our material preparation system by the novel mill with a vessel and a blade of ZrO2 under ice-cooling maintained the bone-inducing activity of human dentin and bone.