April 2007
Dr Gerhard Steenkamp

As part of your complete dental examination in a dog that had carious lesions on other teeth, you make a survey radiograph of the dog’s left mandibular 1st molar tooth. There is a well-circumscribed radiolucent lesion associated with the apeces of both roots.

a) What is your clinico-radiological diagnosis?
b) How would you manage this case?

Memo:

a A periapical abscess, periapical granuloma or inflammatory periapical cyst (radicular cyst).

b With acute infection of the pulp secondary to trauma, fractures or carious lesions, the inflammation will spread quickly to the periapical tissue.  This is due to the fact that pulp tissue is enclosed in the small environment of the tooth dentine with no room for inflammatory oedema and tissue expansion. The latter soon causes pressure necrosis secondary to the already tissue damaging inflammation in the pulp.  Periapical inflammation can vary from an acute or sometimes chronic dental abscess with puss collecting in the periapical tissue and bone to a mass of chronically inflamed granulation tissue (periapical granuloma) or an epithelium-lined cyst with various degrees of inflammation (periapical/ radicular cyst).  It is also important to remember that the pulp of multirooted teeth are connected, and if one root is infected, both pulpcanals (as in this case) will become infected and may show periapical lesions.

Abscesses my be recognised by puss draining either from the bone directly overlying the apex of the affected tooth, especially in the case of maxillary teeth to puss-draining fistulae opening on the skin, a situation mostly encountered in mandibular teeth. 

It is however impossible to distinguish between a periapical granulomas and periapical cysts (radicular cysts) by clinical and radiographic features only.  Microscopically granulomas consist of vascular granulation tissue with no epithelial lining whilst cysts are typically epithelial-lined lesions filled with debris or inflammatory fluids.  Both can become large lesions of more than 2cm in diameter with cortical expansion of the overlying bone and resorption of the adjacent tooth roots.  In both cases the affected tooth is non-vital. 
Management in all three situations should either be a good endodontic treatment of the tooth where all the necrotic pulp is mechanically removed up to the apex of the tooth and filled with well-described agents or better yet in animals, extraction of such a tooth with curettage of the periapical tissue to ensure complete removal of especially the cyst wall epithelium.  Smaller lesions with less bone involvement tend to do better with endodontic treatment than those with large destructive lesions in which case extraction would always be a better option.  Please remember that all tissue removed from the periapical area should always be submitted for microscopical examination as many neoplastic lesions may also present as a radiolucency in the apical area of a tooth delaying further management of such pathology.