Missing teeth are ideally replaced by dental implants. Alternatively, dental bridges are another way to replace missing teeth. Your existing teeth are used to literally create a bridge to cross the area where your tooth is missing. Bridges are made from strong non metal tooth color Zirconia / porcelain to ensure that they are natural looking and durable.
If you are missing a tooth you should strongly consider having it replaced. Besides the aesthetic disadvantage of missing a tooth, it could also cause structural changes to your mouth and jaw, as well as making it difficult to eat or speak properly.