I highly recommend
Dr. W. R. A. P. P. Rajapaksha. I myself did a nerve filling and it cost only 15k a year back. On top of that, he is easily the best. But getting an appointment is quite difficult though. You need to call on a Saturday and if you are lucky enough, the call will go through and you'll get an appointment in the next week.
https://maps.app.goo.gl/1kiVfpRJh5dXaXJ98