Biomaterials in reconstructive middle ear surgery.

Biomaterials are a necessity in modern otosurgery, but none is usefull for all applications. Surface properties, particularly structural characteristics, critically influence the quality of the implant-biological interface. Micropores promote fixation whereas polished surfaces tend to resist it. Prior to the introduction of any new biomaterials, safety precautions must be adhered to rigorously. We showed that osteoblast-like cells grew from human stapedes. This model detected cytotoxicity but it did not show difference in growth when several biomaterials were compared. Hence, animal studies are necessary to evaluate the complicated interactions of mucosa, bone, ventilation and possibly infection with respect to the placement of middle ear prostheses. Nevertheless, animal study results must be interpreted cautiously. In the future therefore, it is clear that rigorously controlled pilot introduction in humans will be required after the biomaterial has passed detailed in-vitro and in-vivo experimental test examinations. The use of plastics often leads to foreign body reaction in the middle ear. Teflon used in stapes prostheses as the only exception, has proved valuable as a result of its low surface energy, and consequently, the avoidance of prosthetic epithelialisation. Most ceramics are biocompatible, but glasses are degradable and therefore of no use in potentially infected ears. Titanium and gold are playing an increasingly important role. However, it should be noted that gold may cause damage to the inner ear, when used as stapes prosthesis. The use of ionomeric cement resulted in fatal complications, when it came in contact with cerebrospinal fluid and consequently, the use of this material has been completely abandoned.