how did aunt polly extract Tom's tooth ?

This is actually a Chapter 6 question. From the text;

One of them's loose, and it aches perfectly awful."

"There, there, now, don't begin that groaning again. Open your mouth. Well -- your tooth is loose, but you're not going to die about that. Mary, get me a silk thread, and a chunk of fire out of the kitchen."

Tom said:

"Oh, please, auntie, don't pull it out. It don't hurt any more. I wish I may never stir if it does. Please don't, auntie. I don't want to stay home from school."

"Oh, you don't, don't you? So all this row was because you thought you'd get to stay home from school and go a-fishing? Tom, Tom, I love you so, and you seem to try every way you can to break my old heart with your outrageousness." By this time the dental instruments were ready. The old lady made one end of the silk thread fast to Tom's tooth with a loop and tied the other to the bedpost. Then she seized the chunk of fire and suddenly thrust it almost into the boy's face. The tooth hung dangling by the bedpost, now.

Tom'sTeeth Got Loose because he becoming a big boy