A morphological study of drill holes applied with mitomycin-C in hydroxyapatite orbital implants

For maximum motility of the prosthesis, the hydroxyapatite orbital implant should be drilled and coupled to the prosthesis via a motility peg. However, problems of peg extrusion have been reported to occur in 25-30% of cases. In this animal study, serial histopathological changes within the drill hole after hydroxyapatite implantation were observed and the effect of mitomycin-C (MMC) was evaluated as a new method of hole maintenance. A hole was drilled into each hydroxyapatite implant 20 weeks after enucleation and different concentrations of MMC solution were applied. The morphological changes of the holes were evaluated with proliferating cell nuclear antigen. In the control group (non-MMC-treated), all the motility pegs were extruded showing occluded holes. In the groups treated with 0.5 and 1.0 mg/ ml MMC, all the motility pegs were maintained in position with the holes at ample depth and width. However, toxicity, such as conjunctival ulcer and implant exposure around the hole, was observed in the 1.0 mg/ml MMC group. A 0.5 mg/ml MMC application for 5 min to the drill hole effectively reduced the risk of peg extrusion in this albino rabbit model.