Cavities are a type of chronic, progressive destructive disease caused by bacterial infection of the hard tissues of the teeth. Normally, a cavity should not recur after being filled, but each dental filling material has a certain degree of microleakage. If glass ionomer materials are used, the microleakage is somewhat larger, and after filling, there might be tiny gaps between the edge of the filling material and the tooth, where bacteria can continue to infect, also known as secondary caries, necessitating timely refilling of the tooth. If resin-based materials are used, the microleakage is relatively smaller, and the likelihood of recurrence after the filling is smaller.