A small crack in the lower incisor indicates that the tooth is cracked, so you can choose between filling and root canal treatment according to the pain condition. 1. Filling and restoration: If the tooth is painful when stimulated by hot, cold, sour or sweet, it means that the hidden crack reaches the dentin, so first cover the hidden crack with calcium hydroxide, and then fill it with light-curing composite resin. 2. Root canal treatment: if the tooth has night pain or biting pain, it means that the hidden crack reaches the tooth nerve or the root tip of the tooth, it is better to carry out root canal treatment on the tooth, and then carry out crown restoration after two weeks to prevent the tooth from splitting. Teeth cracks and pain, it is best to go to the hospital in a timely manner, after a professional physician’s examination, to clarify the degree of hidden cracks in the teeth, and then choose the most reasonable method of treatment.