4.5.5. Histopathological Analysis

For histopathologic evaluation, tissue samples were processed for paraffin embedding, and 5 μm sections were obtained and stained with hematoxylin and eosin. Tissue samples were evaluated in a light optic microscope by a pathologist with no knowledge about the implant's removal time, thus eliminating bias. Lesions were classified semiquantitatively using the scores described by De Jong et al. (2005) [30], with some modifications. Briefly, classification included the characterization of the capsule involving the implant, the presence of an inflammatory infiltrate, cellular growth within the implant, and polymer's phagocytosis. The intensity of each category was evaluated from mild to severe. The intensity of the inflammatory infiltrates, cellular growth within the implant, and polymer's phagocytosis was evaluated as (1) minimal; (2) moderate; (3) marked; and (4) severe. In addition to scoring as proposed by De Jong et al. (2005) [30], the angioplasia in the capsule involving the polymers was also classified as (1) mild, when few small vases were observed within the fibrotic capsule; (2) moderate, when there were some moderately hyperemic vessels grouped around the capsule; and (3) marked, when diffusely hyperemic vessels were observed within the capsule.

## 4.5.6. Scanning Electron Microscopy (SEM)

Morphological characterization of the materials was performed by SEM. Implant samples with surrounding tissue fragments underwent a dehydration process in an increasing alcohol solution and dried at a critical point. Samples that had the polymer removed from the obtained fragments were dried in an oven at 35 ◦C for 12 h. All samples were mounted on supports and sputtered with gold in a vacuum. The material surfaces were analyzed in a scanning electron microscope (Zeiss EVO 10, Zeiss, Oberkochen, Germany) operated at 10–15 kV. Images were examined with Fiji ImageJ 1.50i software, and the average pore diameter was determined manually from at least 300 pores. For non-circular pores, the greatest distance was considered.
