Histopathologic Evaluation of Polymer Supports for Pintucci-Type Keratoprostheses: an Animal Study

Purpose: To report histopathological findings for different types of polymers proposed as support for a Pintucci-type keratoprosthesis. Methods: Six polymers, including three types of polyesters (#1-3), one type of polytetrafluoroethylene (PTFE, #4), polyethylene (#5), and expanded polytetrafluoroethylene (ePTFE, #6) were evaluated. Four samples of each material were placed under the orbicularis oculi muscles of 12 rabbits. After five weeks, the samples were removed and evaluated histopathologically. Fibrovascular tissue ingrowths were investigated in terms of tissue penetration depth into the materials (graded as none, mild, moderate, and intense) and fibrovascular ingrowth area at the ultimate level of tissue penetrance. ImageJ software was used to calculate fibrovascular tissue area between the material fibers, and the mean area values were compared between the materials. Results: Polyester materials #1 and #3 demonstrated intense fibrovascular tissue penetration with a large fibrovascular ingrowth area; no overt tissue ingrowth was observed into material #6. The mean area of penetrated fibrovascular tissues was significantly different between materials (P < 0.001). Materials #2, #4, and #5 showed moderate fibrovascular tissue ingrowth and the area of presented fibrovascular tissue at the paracentral parts of material #4 was significantly smaller than that of materials #1 (P = 0.02) and #3 (P = 0.01). Conclusion: Two polyester materials that had relatively large pore sizes demonstrated a deep and large area of fibrovascular ingrowth. Given that material #3 is thicker and more consistent than material #1, the former can be used as the appropriate material for supporting the Pintucci-type keratoprosthesis.

Double-setting alpha-tricalcium phosphate cement provided with interconection channels in rabbits after enucleation: A potential implant for the anophthalmic socket

The purpose of this study was to evaluate the macroscopy and microstructure of a double setting alpha-tricalcium phosphate bone cement sphere provided with interconnection channels (alpha-TCP-i), as well as the integration of the implant with the rabbits' orbital tissue, through macroscopic analysis and histopathology. The external and internal surfaces of the alpha-TCP-i were evaluated macroscopically and by electron microscopy. Twelve New Zealand rabbits received 12mm implants of alpha-TCP-i following enucleation of the left eye. The clinical assessment was undertaken daily during the first 15 days, followed by fortnightly assessment until the end of the study period. For the morphological analysis, exenteration was performed in 3 animals per experimental period (15, 45, 90 and 180 days). The external and internal surfaces of the implant appeared solid, smooth and compact, with six channels which interconnected centrally. The micro-architecture was characterized by the formation of columns of hexagonal crystals. No signs of infection, exposure, dehiscence of sutures or extrusion of the implant were noted in any of the animals during the entire period of the study. The morphological evaluation demonstrated the presence of a thin capsule around the implant, from whence appeared fibro-vascular projections, which penetrated it through the interconnecting channels. In the first days after the insertion of the implant, an intense inflammatory reaction was noted. At 180 days, however, there were no signs of inflammation. The alpha-tricalcium phosphate cement implant was well tolerated in this rabbit model and appeared to be relatively inert with some fibrovascular ingrowth through the large channels.

Nuclear Bone Scintigraphy (NBS): A Valuable Tool Depicting Osseointegration at the Sites of Dental Grafts

Hydroxyapatite (HA) implants were used as grafting materials to fill some of the root resections in three patients. Two of the patients had previous root resections without implant insertion. Being implanted to the resection sites, the porous structure of HA serves as a framework for vascular and soft tissue ingrowth. Previous reports on the utilization of three phase nuclear bone scintigraphy (NBS) to evaluate the degree of fibrovascular ingrowth into HA dental implants after surgery are scarce. Three cases are described in which bone scintigraphy was performed at 6 months after implant insertion. The images revealed technetium-99m methylenediphosphonate (99mTc-MDP) uptake at dental implant sites consistent with vascularization and osteoconduction. The current results strongly indicate that osseointegration is complete. This study demonstrates that NBS is a valuable test in the follow up of osseointegration rate at implantation sites and HA is found to be a good biomaterial for grafting purposes showing high osseointegration rates.