Due to the "urgently needed" in the title I'm sure your friend has already found and visited a dentist, but in case anyone else is looking for a rec - I go to Norman Dental Center (98 Norman Avenue, Brooklyn, NY 11222 718-389-6666) in Greenpoint and they've been great! Nice office, modern and clean, good services offered and they're all super friendly. I see Dr. Bayer who is really gentle and incredibly nice, and my husband sees another dentist there - I don't remember her name, but he is VERY squeamish when it comes to the dentist and he loves her. I didn't start using them until I had dental insurance so I can't speak to the prices, but they've never ever tried to push something unnecessary on me like some other places have in the past. Hope your friend's mouth is doing ok!
Oh hey, I used to go to Dr. Bayer too when I lived in Greenpoint, and will second that he is super-nice.