"True" Versus "Bay" Apical Cysts: Clinical, Radiographic, Histopathologic, and Histobacteriologic Features

J Endod. 2020 Sep;46(9):1217-1227. doi: 10.1016/j.joen.2020.05.025. Epub 2020 Jun 14.


Introduction: This study compared the main clinical, radiographic, and histologic features of true and bay apical cysts.

Methods: The study material comprised 95 biopsy specimens of apical periodontitis lesions obtained attached to the root tip of both untreated and root canal-treated teeth. Clinical and radiographic data were recorded. Specimens were obtained by extraction or periradicular surgery and were meticulously processed for histopathologic and histobacteriologic methods. All cases diagnosed as apical cysts (n = 23) were divided into the true and bay types, which were then compared for tooth location, patient's sex, lesion size, severity of clinical symptoms, presence of a sinus tract, previous abscess episodes, and prevalence of bacteria in the main root canal lumen and ramifications, on the outer root surface, and within the cyst cavity.

Results: Eleven specimens were classified as true (48%) and 12 (52%) as bay cysts. Bacteria were found in all specimens, regardless of the histopathologic diagnosis. Planktonic bacteria were observed in the main root canal in all true cysts and in 11 of 12 (92%) bay cyst cases. Biofilms were detected in the main canal in 10 cases from each diagnostic group and were frequently observed in ramifications. Extraradicular biofilms occurred in a few specimens only. Bacteria were visualized within the cavity of both true (4/11, 36%) and bay (6/12, 50%) cyst specimens. The severity of histologic inflammation was always high. There were no significant differences between true and bay cysts for all the clinical, radiographic, histopathologic, and histobacteriologic parameters assessed.

Conclusions: Except for the morphologic relationship of the cyst cavity with the root canal space, true and bay cysts exhibited no other significant differences in the various parameters evaluated. The 2 cyst types were always associated with an intraradicular infection and sometimes with an extraradicular infection. Findings question the need to differentiate true and bay cysts and do not support the assumption that true cysts are self-sustainable entities not maintained by infection.

Keywords: Apical periodontitis; bay apical cyst; biofilm; endodontic infection; true apical cyst.

MeSH terms

  • Biofilms
  • Dental Pulp Cavity
  • Humans
  • Periapical Periodontitis*
  • Radicular Cyst*
  • Root Canal Therapy
  • Tooth Apex