Final answer:
Cochlear implants effectively restore hearing for individuals with a nonfunctional cochlea by bypassing damaged hair cells and directly stimulating the auditory nerve. However, they cannot restore hearing if the auditory nerve itself is abnormal, as the nerve's function is crucial for the implant to work. Damage to the middle ear bones might not be directly treated by the implant, but it can still be effective if the inner ear and auditory nerve are intact.
Step-by-step explanation:
Cochlear implants are designed to restore hearing in individuals with a nonfunctional cochlea. They convert sounds into electrical impulses that stimulate the auditory nerve. To address the question of which type of hearing loss would not be restored by a cochlear implant, it's important to understand the implant's reliance on a functioning auditory nerve to transmit sound signals to the brain.
Hearing loss due to absence or loss of hair cells in the organ of Corti can be overcome by cochlear implants because they bypass the damaged cells and stimulate the nerve. In contrast, hearing loss resulting from an abnormal auditory nerve cannot be addressed by a cochlear implant because the device depends on a functional nerve to relay the signals. Similarly, hearing loss due to a fracture of the cochlea may be alleviated by the implant if the auditory nerve is intact. Finally, hearing loss resulting from damage to bones of the middle ear, typically of a conductive nature, might not be directly treated by cochlear implants, but these devices can still be effective if the inner ear and auditory nerve remain functional.