There are several possibilities for tooth pain when eating hard things: First, periapical inflammation, which is caused by necrosis of the pulp and penetration of the decayed pulp from the apical foramen into the periapical tissue, resulting in inflammation of the periapical area of the tooth. Through effective root canal treatment, the inflammation in the pulp cavity and periapical area can be completely removed, and the tooth will not hurt when eating. Secondly, if the tooth is fractured or hidden cracked due to trauma or other reasons, it will also produce pain when eating. You should visit the hospital and examine the affected tooth carefully to see if it needs to be extracted or restored with a full crown. Third, the bite is unbalanced and has high contact points. You should visit the hospital, check the high points, and use a drill to remove the high points, and the tooth will no longer be painful.