What are prons nd cons of using silver diamine fluoride to treat cavity.why it is used so rarely and dentist often use traditional way of drilling to fight cavity?

SDF is a desensitizing agent and can arrest the formation of carious lesions, but it will not rebuild a broken down tooth. That's what traditional restorations are designed to do. ref: https://www.ada.org/resources/research/science-and-research-institute/oral-health-topics/silver-diamine-fluoride

SDF is used mostly in children and where there is no full time dental operations. Children are scared and this treatment causes no pain. The SDF will keep the cavities from getting larger and when the child is older and less afraid, than the cavities can be filled.