A histomorphometric study of the tissue reaction around hydroxyapatite implants irradiated after placement.
OBJECTIVE
The tissue reaction around hydroxyapatite (HA) implants irradiated at 3 different time points after placement was histologically and histomorphometrically analyzed to further determine the relation between irradiation and tissue reaction.


METHODS
Cylindrical high-density HA implants were placed in the mandibles of 48 Japanese white rabbits. The mandible was then irradiated with a single 15-Gy dose 5, 14, or 28 days after implantation. The rabbits were sacrificed on days 7, 14, 28, or 90 after irradiation. Nonirradiated rabbits with implants were used as controls. Nondecalcified specimens stained with toluidine blue were used for histologic analysis and histomorphometric measurements.


RESULTS
In the rabbits irradiated 5 days after implantation, the HA-bone contact occurred later than in the controls. The bone-implant contact surface ratio was lower than in the controls at each time of sacrifice because of necrosis of the newly formed bone just after irradiation. The HA-bone contact in rabbits irradiated 14 and 28 days after implantation was similar to that of the controls. Bone remodeling was suppressed in the rabbits in each group sacrificed 90 days after irradiation.


CONCLUSIONS
Therapeutic irradiation shortly after implantation inhibits direct contact between the HA implant and the surrounding bone. Bone contact occurring before irradiation was minimally affected. Regardless of the interval between implantation and irradiation, postimplantation irradiation inevitably delays bone remodeling.
Kudo
M
M
First Department of Oral and Maxillofacial Surgery, School of Dentistry, Showa University, Tokyo, Japan.
Matsui
Y
Y
Ohno
K
K
Michi
K
K
D000818:Animals; D001672:Biocompatible Materials / Q000528:radiation effects; D001853:Bone Marrow / Q000473:pathology / Q000528:radiation effects; D001857:Bone Matrix / Q000473:pathology / Q000528:radiation effects; D016723:Bone Remodeling / Q000528:radiation effects; D004396:Coloring Agents; D017886:Durapatite / Q000528:radiation effects; D008297:Male; D008334:Mandible / Q000473:pathology / Q000528:radiation effects*; D009336:Necrosis; D010006:Osteoblasts / Q000473:pathology / Q000528:radiation effects; D010011:Osteocytes / Q000473:pathology / Q000528:radiation effects; D019736:Prostheses and Implants; D011817:Rabbits; D011829:Radiation Dosage; D013499:Surface Properties; D013997:Time Factors; D014048:Tolonium Chloride; D014945:Wound Healing / Q000528:radiation effects
D001672:Biocompatible Materials; D004396:Coloring Agents; D014048:Tolonium Chloride; D017886:Durapatite