Mei-Shun went to see Dr. M, her home dentist for final check after three-time cleaning today. Their regular meeting has been biannual so far, yet changed into 4 month — dental score of the patient worsened. It is partly caused by her hesitation to use floss on one of Ame-chan twins. Since it has glass fiber core, the owner felt like keeping it untouched while another is removable, easy to clean.