Surface microcracks signal osteoblasts to regulate alignment and bone formation.

Microcracks are present in bone and can result from fatigue damage due to repeated, cyclically applied stresses. From a mechanical point, microcracks can dissipate strain energy at the advancing tip of a crack to improve overall bone toughness. Physiologically, microcracks are thought to trigger bone remodeling.

Biaxial flexure testing of calcium phosphate bioceramics for use in tissue engineering.

This study analyzes data from 206 CaP specimens (68 HA, 70 BCP, and 68 beta-TCP) fractured via biaxial flexure testing. Specimens were divided into four groups: (a) Group I, dry; (b) Group II, wet (day 0, immersion time approximately 5-10 s); (c) Group III, after immersion in media for 21 days (day 21); and (d) Group IV, after culturing osteoblasts (OBs) on the surface for 21 days (day 21 with cells). X-ray diffraction verified the presence of minor second phases in HA and beta-TCP while BCP was a biphasic mixture of HA and beta-TCP with minor phases present.

The porosity dependence of the dielectric constant for sintered hydroxyapatite.

Hydroxyapatite (HAp) is the major mineral constituent of bone, and as such, the dielectric properties of HAp are of interest because electromagnetic fields have been shown to accelerate healing in bone fractures. In addition, an interest in the dielectric properties of HAp stems from the suggestion that electrically insulating HAp coatings might be used on implantable devices. In this study, the dielectric constant of polycrystalline hexagonal HAp was measured at nine different frequencies, from 45 kHz to 7.