Not my area but the following results from google search may give some ideas
http://www.radiustoothbrush.com/inde...n=Custom&ID=28
Extract
"the bristles (made elsewhere I assumed) are fused with heat and the resulting tuft is placed into a molding machine with others and the molding machine makes the handle, head and the tufts into one. In fusion bristling the bristles are polished before the injection molding stage"