The difference between moderate and deep caries mainly includes the different depth of the lesion, the different symptoms, and the different treatment methods. Caries, also known as tooth decay, is a disease that leads to progressive destruction of the hard tissues of the dentin under the action of multiple factors such as bacterial infection. According to the different depths of lesions, caries can be categorized into shallow, medium and deep caries, and the difference between medium and deep caries mainly includes: 1. Depth of lesion: medium caries caries reaches the superficial layer of dentin, and the cavity is shallow; while deep caries has reached the deep layer of dentin, and the cavity is deeper. 2. Symptoms: intermediate caries can be sensitive to external stimuli such as cold, heat, sweet, acid, etc., and the symptoms will disappear after the stimuli are removed; while deep caries can have more obvious pain reaction to external stimuli than intermediate caries, and there will be obvious pain when touched by the dentist’s probe or toothpick and other objects. 3. Treatment: The main treatment for intermediate caries is filling after cushioning; while deep caries requires appeasement treatment or indirect pulp capping before filling.