Why is this the answer?

The answer is dentist because this clever riddle uses imaginative words to describe the important and helpful work a dentist does inside your mouth every single day. Dentists are like friendly builders and detectives who take care of your teeth. Let us look at the clues one by one, like a detective solving a mystery. The riddle first says, "I dig out tiny caves and store gold and silver in them." The tiny "caves" are actually tooth decay, which is also called a cavity, a small hole a sugar-bug has made in your tooth. The dentist is the one who carefully cleans out that tiny hole, or "digs out the cave." After the hole is cleaned, the dentist fills it up to keep the tooth safe and strong. The riddle calls the filling material "gold and silver," even though today's fillings are usually tooth-colored materials. A long time ago, dentists often used metal mixes that looked silver or gold, so this part of the riddle is a fun, old-fashioned clue about filling a cavity. Next, the riddle mentions building "bridges of silver and crowns of gold." This is another clue about the special repairs a dentist can make for grown-ups. If someone has a missing tooth, a dentist can create a "bridge" to fill the gap. If a tooth is badly broken or worn down, the dentist can put a small, strong cover over it, which is called a "crown." Since these are tiny repairs for the mouth, the riddle says they are "the smallest you could imagine." The word "gold" and "silver" here simply means they are strong and valuable, like a tiny king's crown for your tooth. The riddle is also right when it says, "Sooner or later everybody needs my help." We all need to see the dentist for regular checkups to keep our smiles bright and healthy. And finally, the clue "Yet many people are afraid to let me help them" is also true. Lots of people feel a little nervous about going to the dentist, even though dentists are always very kind and just want to help keep your teeth in great shape!