The method for cleaning dental plaque biofilm from the teeth includes the steps of applying a liquid gellable composition to the teeth, the composition including a positively charged polymer such as chitosan, the liquid composition having a viscosity which results in coverage of substantially all of the exposed areas of the teeth. The base unit is configured to mount to a vehicle and to faithfully transmit vehicle motion to an attached sensor. The gate insulating film is formed by depositing an oxide film in a second sputtering apparatus connected to the first apparatus through a gate valve. Thus, it is possible to provide the disk cartridge, the disk recording medium device and the disk recording andor reproducing apparatus in which dusts, smudges and so on are difficult to enter the disk compartment.