Short-term bone responses to hydroxyapatite cement.
OBJECTIVE
The purpose of this study was to evaluate the short-term wound healing and repair at the tissue/cement interface with different hydroxyapatite cement formulations.


METHODS
Three groups of Sprague-Dawley rats were implanted with HAC for 3, 7, or 14 days. The medial femur-tibia sites on each leg of the animals were used to create four separate 1.5-mm defects, which were filled with HAC (Bone-Source, Howmedica-Leibinger, Inc.) mixed with either water (W) as a control, an accelerant (0.1 M sodium phosphate, SP), or a stabilizer (1% hydroxypropylmethyl cellulose, HPMC) as diluents. At the appropriate postimplantation times, the animals were euthanized and tissue-implant blocks were prepared for qualitative histopathologic evaluations.


RESULTS
Osseoconduction around and into the HAC was observed with all three cement formulations and the control (unfilled) site by day 7 and continued through day 14. The histologic staining did not reveal resorption lacunae or other cellular activities characteristic of osteoclast degradation of HAC. These results suggests that other processes, perhaps physical-chemical in nature, contributed to the initial degradation of the HAC following surgical placement. Structural stability of HAC was noted when using HPMC as the diluent. However, when either W or SP were employed, dissociation (washout) of the HAC into the surrounding tissue was noted.


CONCLUSIONS
HAC is prone to in situ physical-chemical breakdown before the completion of the setting reaction. Diluents designed to stabilize or accelerate the HAC mixture appeared to improve the handling properties of the HAC without compromising the biological characteristics of the cement.
Morio
Dominic
D
Department of Oral and Maxillofacial Surgery, University of Iowa, Iowa City, IA, USA.
Lew
Daniel
D
Krizan
Kenneth
K
Keller
John C
JC
D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry / Q000494:pharmacology*; D001843:Bone Cements / Q000737:chemistry / Q000494:pharmacology*; D001861:Bone Regeneration / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects* / Q000473:pathology; D002626:Chemistry, Pharmaceutical; D004396:Coloring Agents; D017886:Durapatite / Q000737:chemistry / Q000494:pharmacology*; D005079:Excipients / Q000737:chemistry; D065347:Hypromellose Derivatives; D008747:Methylcellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D023421:Models, Animal; D010012:Osteogenesis / Q000187:drug effects; D010027:Osteotomy; D010710:Phosphates / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014867:Water / Q000737:chemistry; D014945:Wound Healing / Q000187:drug effects
D001672:Biocompatible Materials; D001843:Bone Cements; D004396:Coloring Agents; D005079:Excipients; D010710:Phosphates; D014867:Water; D065347:Hypromellose Derivatives; D008747:Methylcellulose; D017886:Durapatite; C018279:sodium phosphate