Evaluating Static Bone Cysts (SBCs) Through Long-Term Volumetric Analysis Using CBCT: A Study with 6-Month Follow-Up.

BACKGROUND: Salivary gland bone defects are static lesions which are rare entities, generally asymptomatic and found in routine imaging exams. However, in atypical cases or when misdiagnosed, surgical intervention is carried out. Purpose: a) The study is intended to investigate the frequency of SBC's and to describe the radiological characteristics of its subtypes; b) To evaluate the efficacy of volumetric analysis tool in CBCT and; c) To describe the confirmative role of CBCT in the diagnosis of SBC's without the need for surgical intervention.

MATERIAL AND METHODS: The study was conducted on 11 subjects with SBC detected on 3304 panoramic radiographs. CBCT images for each patient were captured at baseline and at an interval of 6 months. Radiographic sub-types of SBC based on the relationship to mandibular canal and bucco-lingual expansion were studied. Files in DICOM format were transferred into OnDemand 3D program (Cybermed Co, Seoul, Korea) and volumes in mm3 of the cavities were measured by 2 observers at both intervals. Inter and intra reliability of volumetric measurements between observers was compared using correlation coefficient and student t test.

RESULTS: There were 8 males and 3 females who had SBC in this study (age range: 22-70 years). According to the relationship of SBC with mandibular canal, most SBCs were Type 1 (63.5 %) followed by Type 2 & 3 (18.5 %) each. The total volume of SBC in patients ranged from 146 mm3 to 650 mm3 (mean: 332.5 mm3). There was no significant difference between observers for volume measurements at baseline and at 6 months interval ( p >0.05).

CONCLUSIONS: Based on the results of this study, CBCT should be considered as a definitive diagnostic modality for volumetric analysis of SBCs. Over diagnosis, unnecessary surgical exploration and agony to patients can be avoided using this tool. Key words: Stafne bone cavity, CBCT, Volumetric analysis, salivary gland, panoramic radiography.