The city of Neodentis shone under the glass dome like a pearl encased in an oyster. At first glance, it seemed ordinary: crowds of young people rushed to the neon of the school entrances, robots cleaned the streets and moving billboards displayed advertisements for the latest sonic toothbrushes. However, residents were well aware that their city was unique. They based its entire infrastructure - from power supply to communications - on innovative technologies inspired by... oral hygiene. Anna, a seventeen-year-old student at a biomedical technical school, always felt there was something deeper to it all. Her dad worked in a laboratory on the outskirts of the city, in the bacterial plaque research sector. Every evening, Anna would hear him talk about new discoveries about the oral microflora and its impact on the health of the whole body. Anna, however, usually rolled her eyes. Brushing her teeth, flossing, rinsing - it all seemed like a tedious routine to her. One morning, as the lift carried her to the nineteenth floor of her dormitory, Anna noticed a disturbingly flashing red light on her electric toothbrush. "Not compatible with Smart-Fluor system?" - the message displayed. At the same moment, her holophone rang. Mum hastily said: "Don't forget to bring your dental biofilm sample to school, there will be an inspection today. And remember not to eat anything sweet until the test!". There was an unprecedented atmosphere of anxiety in the school. A group of students were debating in a corner, several teachers were whispering under the display of oral cleanliness results. Even the robots disinfecting the corridors seemed to be working faster than usual. During a cyber biology lesson, Anna heard from a colleague that during the night several people had had disappeared all the data from their personal prophylaxis cards. Without this information, it was impossible to access any city service or even to open the door of a flat. What's more - there was a rumour that someone had seen on CCTV strange shadows moving between blocks of flats after dark, leaving glowing, sticky footprints behind them. In the afternoon, Anna decided to meet her dad at the lab. She moved quickly through sector after sector of the city, analysing in her mind the links between oral hygiene and the functioning of the city's infrastructure. When she arrived, she noticed that the door to the laboratory was wide open and a thin, milky-white layer with a slightly sweet smell spread across the floor. As she approached the entrance, Anna heard someone's hushed voice inside and saw that all the lab screens hung on a single, pulsing message: "Warning: CRITICAL ANOMALY IN FLUOR SYSTEM. Admission by authorised personnel only." Anna tightened her hand on her toothbrush and took a cautious step inside, not yet knowing that she was about to find out first-hand how much oral hygiene could determine the fate of the entire Neodentis.