<prompt> Neurological menifestations of fluorosis occur , when the duration of ingestion is:10 years15 years20 years25 years.  <response>: The fluoride dosage necessary to produce pathological skeletal fluorosis is estimated to be 20-80 mgday for a period of 10 to 20 years. In India, it is most commonly seen in Punjab. Neurological Manifestations of fluorosis occur if the duration of ingestion is more than 20 years. 