For most people there exists a balance between the host defenses and the oral micriobiota but if the host defenses are compromised like during minor illness such as influenza or an upper respiratory tract infection, pericoronitis results. Another common cause is entrapment of food beneath the gum flap (also called an operculum). Pericoronitis can present as a mild infection or severe infection. In its mildest form it is just a localized tissue swelling and soreness whereas in severe forms the swelling is slightly larger even sometimes creating trismus (difficulty opening the mouth). Occasionally, an impacted tooth causes sufficient pressure on the roots of adjacent teeth causing it to resorb. An impacted tooth occupies space that is usually filled with bone. This weakens that area of bone and renders the jaw more susceptible to fracture. When impacted teeth are retained completely within the alveolar process, the associated follicular sac is also retained along with it. Though in most persons the dental follicle maintains its original size sometimes it may undergo cystic degeneration and become a dentigerous cyst or a keratocyst. Symptoms
Most commonly the individual complains of food getting lodged beneath the gums and a soreness that is usually confused with throat infections. In slightly milder forms a swelling is visible and mouth opening becomes difficult in severe cases. Pain is invariably present. Management
Impacted teeth might be extracted or left alone, depending on the dentist (and the health authoritys guidelines in that country) and the situation.
Extraction might be contraindicated and might be simple or surgical, often depending on the location of the teeth. In some cases, for aesthetic purposes, a surgeon may wish to expose the canine. This may be achieved through open or closed exposure. Studies show no advantage of one method over another. Laser can be used to uncover superficially impacted teeth with no bleeding and quick recovery

References
See also
Impacted wisdom teeth