Can we use antipsychotics for patients with alzheimer's disease and psychosis knowing that antipsychotics may lead to death in patients with dementia ?

Sometimes, no choice: Antipsychotics are best avoided in managing agitation in dementia. However, if the agitation is the result of actual psychosis i.e., delusions and hallucinations, the risk/benefit ratio often shifts in favor of using antipsychotics, as untreated psychosis itself is a risk of factor for serious injury to self/others. Hope this helps.

Yes, this is a two-edged sword, but often reluctantly we must use antipsychotics to prevent harm to the patient and others in contact with an agitated and potentially violent individual. This is an example of the subtle practice of the "Art of medicine."