H. Alexander

Evaluation of a low-temperature calcium phosphate particulate implant material: Physical-chemical properties and in vivo bone response

A study was conducted to evaluate the osteoconductive ability of a particulate, low-temperature hydroxylapatite (HA(LT)) material (OsteoGen; Impladent, Holliswood, NY). An implantable chamber model was used to determine the ability of this material to encourage bone ingrowth into channels lined with either rough-surfaced titanium or rough-surfaced plasma-sprayed hydroxylapatite. The HA(LT) material increased bone ingrowth into the titanium-lined channels comparable with that in plasma-sprayed hydroxylapatite-coated channels. It was incorporated into ingrowing bone without intervening soft tissue, with the bone bonding directly to the material surface in much the same fashion as it bonds at the plasma-sprayed hydroxylapatite surface. Mechanical testing of the ingrown bone showed no weakness because particles were incorporated. At 12 weeks, the particles began to show signs of dissolution. It was concluded that the HA(LT) material is a biocompatible, osteoconductive material that conducts bone ingrowth in much the same way as high-temperature particulate hydroxylapatite ceramics. This material has the additional desirable property of being slowly resorbable, a beneficial characteristic for many bone-filling applications.

Mechanical modification of dental implants to control bone retention

Abstract Researchers and clinicians have empirically used surface nano- and microtexturing techniques to enhance osseointegration but have never fully understood how these surfaces work. Compiling knowledge gained from cell and molecular biology, and tissue engineering, this chapter presents explanations for observed effects of mechanical modification of surfaces on bone retention around implants. Cell and tissue responses to surfaces are reviewed. Both mechanical and biological explanations are presented. The chapter concludes with what has been done, and what potentially can still be done, to develop surfaces that control hard and soft tissue formation and integration of dental implants.

In vitro degradation of calcium sulfate polymer composites for the reconstruction of bone

We are testing degradation rates of calcium sulfate/polymer composites meant for use as bone graft substitutes. The goal is to demonstrate the potential of composite degradable and biocompatible materials that will resorb slower than pure calcium sulfate. We will determine which composites give us degradation profiles that are appropriate for different types of bone regeneration