Holistic Medicine is based on the premise that the body is one unit and how you treat one aspect of that unit has an effect on other aspects. Holistic Dentistry is based on the same notion that what affects the mouth affects the body, and vice versa. If infections of the mouth affect the rest of the body, then dental problems can be seen as causes of other aches and pains as well.
Holistic dentists take off from this premise to consider the impact of dental health in greater depth. For instance, they might discuss nutrition as it affects dental health and include alternative therapies, such as homeopathy, in their practice: treat your gums non-surgically, use antibiotics sparingly as they can disrupt the body, eschew root canals because of concerns about infection, try to use biocompatible dental restoration materials.