title: Tympanic membrane changes after installation of polyethylene grommets. An experimental study in the rat.
abstract: The object of this study was to establish the morphological changes which occur when a polyethylene grommet is implanted in the normal tympanic membrane of experimental animals. We found a serous effusion around the grommet and in the attic during the first weeks after installation. All the grommets had been displaced away from the tympanic memebrane in a medical direction into the middle ear cavity. The displacement was most likely brought about by a squamous cell epithelial and connective tissue hyperplasia, which reached its maximum after 2--3 weeks. Neither atrophy, atelectasis, nor retraction was observed, whether in the pars flaccida or the pars tensa. A greyish, horseshoe-shaped configuration was seen in all specimens in the undisturbed front quadrants. No firm histo-pathological correlation was found to explain these changes. In these studies in the rat, the perforation appeared to heal, although delayed, in the same way as after a central perforation, once the polyethylene grommet had been ejected.
mesh_terms: D000818:Animals; D004848:Epithelium / Q000473:pathology; D005549:Foreign-Body Reaction; D006965:Hyperplasia; D008853:Microscopy; D008855:Microscopy, Electron, Scanning; D011095:Polyethylenes / Q000009:adverse effects*; D019736:Prostheses and Implants / Q000009:adverse effects*; D051381:Rats; D014432:Tympanic Membrane / Q000473:pathology* / Q000648:ultrastructure
chemical_list: D011095:Polyethylenes