It is a general belief that large
cyst-like periapical lesions and apical true
cysts caused by root canal
infection are less likely to heal after nonsurgical
root canal therapy. Nevertheless, there is no direct evidence to support this assumption. A large
cyst-like periapical lesion or an apical true
cyst is formed within an area of
apical periodontitis and cannot form by itself. Therefore, both large
cyst-like periapical lesions and apical true
cysts are of inflammatory and not of neoplastic origin.
Apical periodontitis lesions, regardless of whether they are
granulomas,
abscesses, or
cysts, fail to heal after nonsurgical
root canal therapy for the same reason, intraradicular and/or extraradicular
infection. If the microbial etiology of large
cyst-like periapical lesions and inflammatory apical true
cysts in the root canal is removed by nonsurgical
root canal therapy, the lesions might regress by the mechanism of apoptosis in a manner similar to the resolution of inflammatory apical pocket
cysts. To achieve satisfactory periapical wound healing, surgical removal of an apical true
cyst must include elimination of root canal
infection.