My father is 75 & suffering from dementia. Is there any treatment to this disease?

Symptom relief. With good geriatric psychiatric cares my of the symptoms can be decreased. Adapting the environment can help optimize functioning. An occupational therapist is an expert at maximizing functioning and improving safety.
Treatment. There is treatment but not a cure. If this hasn't already been done, he would benefit from seeing a geriatric specialist, neurologist or geriatric psychiatrist. Take care.