Advanced bone formation in grooves in vitro is not restricted to calcified biological materials.

The aim of this in vitro study was to investigate whether the phenomenon of advanced bone formation in grooves (Bone 18, 115, 1995) is restricted to calcified biological materials. Osteoblasts were released from neonatal rat calvaria by enzyme digestion and cultured in EMEM and 10% FCS. At confluence, they were seeded on to dentine, bone, plastic, titanium, or silicon, which had been grooved using a water-cooled, diamond-edged, slow-speed or high-speed circular saw or reciprocating wire saw, or a rotating dental burr. Cultures were continued for 14-21 days, with a few extended for up to 7 weeks. Osteoblasts were also cultured on grooved dentine and plastic with or without added Stanozolol for 18 days, and bone formation assayed by measuring the total length of bone formed in the grooves in each specimen. Bone formation always occurred first within the grooves and was appositional. It formed on both calcified biological and nonbiological substrates, but developed consistently earlier on the biological substrates, and conformed to both the main grooves and the secondary finer grooving within them. Surface features at scales ranging from the millimeter to nanometer therefore influence the development of bone in vitro and possibly in vivo. The described site-induced bone formation system is valuable as an in vitro assay for biomaterial and pharmaceutical research.