Buying a new brush every time your old one loses bristles can be an inconvenience. People with thick, coarse hair experience this often, usually after just a few months of using the same hairbrush. The most common cause for a worn-out hairbrush is the loss of the bristles. Regular use can pull the bristles right out of the brush, rendering it ineffective for use. Fortunately, you can repair some types of brushes (metal or plastic bristle brushes) if you notice the bristles falling out.
Comb your fingers through your hair and search the floor for any fallen bristles. Once you collect all the errant bristles, store them in a safe place (such as a plastic container or a sandwich bag) until you are ready to repair the brush.
Examine the ends of the bristles to see whether they have a locking mechanism. If there is nothing on the end but a straight bristle, the locking mechanism that held the bristle in place broke off. If you find such bristles, throw them away because you will be unable to properly replace them on the head of the brush.
Look closely at the head of the brush. There are small holes that hold the protruding bristles all over the surface of the brush. Locate the areas with a hole but no bristle so you know where to stick the detached bristles (unless damage to the hole makes it impossible to reattach the bristle).
Force the end of the bristle into the head of the brush anywhere you see an empty bristle hole. The bristles have a protrusion on the end of them that you must force through the head in order to make them stick in place. Be careful not to press the bristle in so far that it actually sinks into the head of the brush and will not reemerge.
Run the brush through your hair a few times to ensure the bristles will stay in place. If the bristles fall out, pick it back up and force it into place.