Final answer:
Dentists can restore a severely decayed and endodontically treated primary tooth using a stainless steel crown or a glass ionomer restoration.
Step-by-step explanation:
Dentists restore severely decayed and endodontically treated primary teeth using different methods. One common method is to use a stainless steel crown. This is a durable and long-lasting option that covers the entire tooth to protect it and restore its function. Another option is a glass ionomer restoration, which is a tooth-colored filling material that bonds to the tooth and releases fluoride to help prevent further decay. Both of these options are commonly used by dentists to restore severely decayed and endodontically treated primary teeth.