Tissue response to facial contour augmentation with dense and porous hydroxylapatite in rhesus monkeys.
Using extraoral incisions, subperiosteal pockets were created bilaterally over the zygomatic and mandibular areas in six rhesus monkeys. One side of each anatomic site received a dense block of hydroxylapatite (HA) implant, and the contralateral side received an equivalent-sized block of porous HA implant. Monkeys were killed at 3, 6, and 12 months, and the implants were manually tested for mobility. The implants were then retrieved in block specimens. Half of each specimen was decalcified, embedded in paraffin, and stained. The other half was embedded in plastic, and sections were stained or carbon coated for scanning electron microscope histometry. The dense HA implants showed complete fibrous encapsulation and they popped out when cut in half. The porous HA implants were attached to the underlying cortex by bone ingrowth. The porous implant volume sampled within 2.5 mm of underlying cortex contained 33.0% HA matrix and 35.7% bone. The surface area of the porous HA matrix (4.8 mm2/mm3) was 54.3% covered by bone ingrowth. It is hypothesized that micromotion may have accounted for the lack of osseointegration of the dense HA specimens. In contrast, the early ingrowth of fibrous tissue into the porous HA block might be responsible for reducing micromotion to levels acceptable for ingrowth of bone. The contrasting biologic response of implant sites to two variants of the same implant material supports the value of comparative studies to permit informed surgical selection decisions.
el Deeb
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Department of Oral and Maxillofacial Surgery, University of Minnesota School of Dentistry, Minneapolis 55455.
Holmes
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RE
D000818:Animals; D003238:Connective Tissue / Q000033:anatomy & histology; D017886:Durapatite; D004867:Equipment Design; D005260:Female; D006882:Hydroxyapatites; D007091:Image Processing, Computer-Assisted; D008253:Macaca mulatta; D008334:Mandible / Q000033:anatomy & histology / Q000601:surgery*; D010012:Osteogenesis; D019736:Prostheses and Implants; D013499:Surface Properties; D013997:Time Factors; D014945:Wound Healing; D015050:Zygoma / Q000033:anatomy & histology / Q000601:surgery*
D006882:Hydroxyapatites; D017886:Durapatite