The patient lost the innermost large tooth, it is possible that periodontitis caused the tooth to loosen and eventually fall out. The patient is advised to go to the periodontal department of the dental hospital for an examination and to take x-rays to clarify the condition of periodontitis in the whole mouth. If periodontitis is present in only one tooth, and this tooth is the last molar, that is, the third molar, there is no need for any treatment or restorative treatment. If there are other teeth in the whole mouth that also have periodontitis, basic periodontal treatment is required, and after the treatment is complete, restorative treatment or orthodontic treatment will be performed depending on the situation. If the innermost tooth is lost, it is a functional tooth, the first molar or the second molar is lost, it is recommended that the patient should go to the prosthodontics department for restorative treatment after 2-3 months.