How long it takes for middle caries to develop into deep caries varies from person to person, and there is no definite time. Dental caries are caused by poor oral hygiene, bacteria eroding the hard tissues of teeth, causing enamel demineralization and developing into dental caries. Middle caries is the development from caries to superficial dentin. At this time, the pulp can be preserved by timely treatment. By directly covering the pulp and filling it with soluble materials, the further development of dental caries will be prevented. If left untreated, it may develop into deep caries in a month or several months, that is, caries will go deep into dentin and directly damage dental pulp tissue. It is impossible to keep the pulp at this time. Root canal therapy must remove decaying and necrotic pulp tissue, and disinfect, sterilize, rinse and fill the root canal with appropriate materials. consult