When apical inflammation occurs in a tooth that has been filled, clinically, it is necessary to check how long the apical inflammation occurs after the filling is completed, and if the apical inflammation occurs just after the filling is completed, it does not take a long time to produce the apical inflammation. Generally, it means that there is a mistake in the judgment of the situation of the tooth when filling the tooth, and there is already a state of end-stage pulpitis and early apical inflammation, and the patient still has a slight pain when filling the tooth to the patient, so the situation of apical inflammation will occur at this time. In other cases, the caries in the corresponding area is not removed when the filling is placed, and the caries in the inner area develops further, gradually forming apical inflammation. There is also a special case where a filling has been placed, but due to the presence of caries in other parts of the filling, there is a risk of apical inflammation developing step by step. All in all, it is not true that a tooth will never break down again after a filling has been placed, and it is important to be vigilant in preventing the possibility of further lesions on the filled tooth.