Facial augmentation with Proplast and nonporous hydroxylapatite in rhesus monkeys

Using an extra-oral approach, subperiosteal pockets were created bilaterally over zygomatic and mandibular areas in six Rhesus monkeys. One side of each anatomic site received a Proplast I implant and the contralateral a nonporous hydroxylapatite (NPHA) block. Two animals were killed postoperatively at 3, 6, and 12 months, and the implants retrieved en bloc for histologic evaluation. Clinical evaluation showed the Proplast implants more stable than NPHA implants. Histologic evaluation for Proplast implants demonstrated complete encapsulation, fibrous tissue infiltration, fragmentation of implants, and some giant cell reaction. The NPHA implants were completely encapsulated with fibrous tissues, and no giant cell response, fragmentation, biodegradation, or bone formation was observed. We concluded that the Proplast was more stable than NPHA implants, but the NPHA produced less inflammatory cell and giant cell reaction.