The term, odontogenic infection refers to an infection that originates in the tooth proper or in the tissues that closely surround it; said infection then progresses along the periodontia down to the apex, involving periapical bone and from this area, it then spreads through the bone and periosteum towards near-by or more distant structures. The relevance of this type of infection lies in that it can cause infections that compromise more distant structures (via direct spread and distant spread), for example, intracraneal, retropharyngeal and pulmonary pleural infections. Dissemination by means of the bloodstream can lead to rheumatic problems and deposits on the valves of the heart (endocarditis), etc. The conditions or factors that influence the spread of infection are dependent on the balance between patient-related conditions and microorganism-related conditions. The virulence of the affecting germs is dependent upon their quality and quantity and is one of the microbiological conditions that influences the infection. It is this virulence that promotes infectious invasion and the deleterious effects the microbe will have on the host. Patient-related conditions include certain systemic factors that determine host resistance, which may be impaired in situations such as immunodeficiency syndrome or in brittle diabetes, as well as local factors that will also exert their impact on the spread of the infection.