The Oravital™ chair-side oral infection test (BANA) is calibrated to change colour only when a certain threshold level of specific bacteria is detected. The bacteria being tested for are the three most aggressive and relevant to periodontal disease: Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia. When this minimum threshold is reached, the colour of a BANA test strip changes gradually from light blue to aqua blue depending on the levels of the bacteria.