Correction of Forehead Depressions - Many choices
To answer your question it would be important to understand the nature of your "dent", forehead depression. For example was it from trauma with soft tissue atrophy, were you born that way (congenital), is it due to a bony depression in your skull. A CT scan and certainly an exam would be helpful.
In my experience though fat transfer might work, a more predictable solution would be with a long term filler such as Radiesse. If a bony deformity then "bone...