The causes of tooth soreness and weakness when eating include periodontitis, dentin exposure, apical inflammation, and fissure of the tooth. 1. Periodontitis: If the patient has the symptom of weak teeth when eating, the first consideration is periodontitis. When periodontitis is present, the supporting tissues of the periodontium are damaged and the teeth become loose, so the teeth may feel tender and weak when eating. 2. Dentin exposure: If the patient feels that the teeth are sore and weak when eating, it may be due to dentin exposure. Damage to the enamel of the teeth may lead to dentin exposure, resulting in symptoms of tooth tenderness. 3. Apical inflammation: When a patient suffers from apical inflammation, the symptoms of tooth tenderness may also occur. This is because the force applied to a tooth with apical inflammation stimulates the inflamed tissues at the root tip, resulting in a feeling of tenderness. 4. Cracked teeth: When there is a cracked tooth, the tooth will be cracked, and the uneven force will stimulate the pulp when eating, which will cause the tooth to be sore and weak. If the patient repeatedly appear teeth when eating the symptoms of weakness, should go to the regular hospital in a timely manner, under the guidance of a professional doctor for symptomatic treatment, so as to avoid delays in the condition, resulting in adverse consequences.