Combined periodontic-endodontic lesions are localized, circumscribed areas of bacterial infection originating from either dental pulp, periodontal tissue

Periodontium

Periodontium refers to the specialized tissues that both surround and support the teeth, maintaining them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odons, meaning "tooth." Literally taken, it means that which is "around the tooth"...

s surrounding the involved tooth or teeth or both.

Source of infection

Combined periodontic-endodontic lesions take the form of abscess

Abscess

An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

es and can originate from either or both of two distinct locations and may be informally subclassified as follows:

1. Endo-Perio: infection from the pulp tissue within a tooth may spread into the bone immediately surrounding the tip, or apex, or the tooth root, forming a periapical abscess
   Periapical abscess
   A periapical abscess is the result of a chronic, localized infection located at the tip, or apex, of the root of a tooth.To achieve resolution, endodontic therapy must be performed to debride the root canal or canals and remove pathogens....
   
   . This infection may then proliferate coronally
   Commonly used terms of relationship and comparison in dentistry
   There are numerous commonly used terms of relationship and comparison that refer to different aspects of teeth and are frequently utilized in articles about dentistry...
   
    to communicate with the margin of the alveolar bone and the oral cavity by spreading through the periodontal ligament
   Periodontal ligament
   The periodontal fiber or periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits...
   
   .
2. Perio-Endo: infection from a periodontal pocket may proliferate via accessory canals
   Root canal
   A root canal is the space within the root of a tooth. It is part of a naturally occurring space within a tooth that consists of the pulp chamber , the main canal, and more intricate anatomical branches that may connect the root canals to each other or to the surface of the root.-Root canal anatomy:...
   
    into the root canal of the affected tooth, leading to pulpal inflammation.

Neither the prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

, treatment nor expected treatment outcome depend on the source of the infection.

A combined lesion may also be the result of a fractured tooth.

Treatment

Treatment includes conventional endodontic therapy

Endodontic therapy

Endodontic therapy is a sequence of treatment for the pulp of a tooth which results in the elimination of infection and protection of the decontaminated tooth from future microbial invasion...

 followed by conventional periodontal therapy

Scaling and root planing

The objective of scaling and root planing, otherwise known as conventional periodontal therapy, non-surgical periodontal therapy or deep cleaning, is to remove or eliminate the etiologic agents which cause inflammation: dental plaque, its products and calculus, thus helping to establish a...

. If the lesion is deemed too severe for treatment, the involved tooth may require extraction.