A morphological study on obliteration of the temporal dorsal bullae using hydroxyapatite granules

The present study deals with morphological observations of temporal dorsal bullae obliterated by implantation of hydroxyapatite granules. The specimens were obtained from guinea pigs 1 year after implantation, and undecalcified tissue sections were examined under a light microscope. The temporal dorsal bullae were found to be completely filled with bone tissue including the hydroxyapatite granules in all animals examined. The bone and hydroxyapatite granules interdigitated tightly without any intervening connective tissue or dead space. The newly formed bone displayed incomplete osteon structures with lamellae surrounding a haversian canal. There was no evidence of inflammation, such as lymphocyte infiltration, in the temporal bullae. The bone formation induced by hydroxyapatite implantation appeared to be a physiological reaction. It was concluded that the hydroxyapatite granules are safe and useful for mastoid obliteration during tympanoplasty.