Tooth meridian lines are channels or pathways throughout the human body that transport energy. It is said that parts of the human body are connected to teeth through these pathways. Therefore, it is believed that infection or pain in teeth can be linked to health problems in other areas of the body. This concept is also known as Focal Infection Theory and has been linked to conditions such as fatigue, kidney dysfunction, infertility, joint pain, thyroid dysfunction and even cancer.