At the age of five and a half, loose teeth may be due to tooth replacement or inflammation of the root tip of the teeth. 1. Replacement of milk teeth: at the age of five and a half, permanent teeth begin to erupt one after another, and milk teeth begin to be replaced and the symptoms of loose teeth will appear; generally no special treatment is needed, and can be left to fall off on its own. 2. Inflammation of the root tip of the tooth: when apical periodontitis occurs due to dental caries or dental trauma, it will lead to inflammatory resorption of the alveolar bone at the root tip of the tooth, which will lead to the symptoms of loose teeth; it is necessary to go to the doctor in time to carry out root canal treatment to eliminate inflammation at the root tip in order to effectively treat the above symptoms. Therefore, five and a half years old loose teeth is not necessarily a symptom of tooth replacement, it is recommended to consult a doctor for a clear diagnosis and treatment.