(PR136) Segmentation of Periapical Lesions Under CBCT – A Method for Quantifying Lesion Size and Assessing Surgical Outcomes

Objective: Periapical lesions are assessed by linear measurements, most often of a radiolucent region on a radiograph. Cone-beam computed tomography (CBCT) can describe the three dimensions of a lesion in a way that is more representative, but linear measurements are still inadequate for describing lesions that are not perfectly spherical around a root apex. This study aimed to demonstrate the use of 3D segmentation of CBCT scans for the quantitative assessment of endodontic lesion size as a secondary aim of a randomized clinical trial investigating the use of platelet-rich fibrin for bone-grafting during surgical endodontics.

Methods: Endodontic microsurgery was performed for ten participants with CBCT scans exposed before and immediately after surgical treatment. Scans exported as DICOM were processed in ITK-SNAP for semi-automated segmentation of the periapical lesion as well as the postoperative defect caused by osteotomy and root resection. Volumetric measurements were calculated using ITK-SNAP’s proprietary functions.

Results: Pre-operative lesions ranged from as small as 4.8 mm3 to as large as 198.5 mm3 (M = 84.88, SD = 84.96). Post-operative lesions ranged 47.5-258.3 mm3 (M = 145.78, SD = 93.49). Endodontic microsurgery significantly increased the defect size to an average of 4.03 times the original dimensions (paired t-test, p = 0.029).

Conclusion: This study described a method to quantify the extent of periapical defects which cannot be adequately communicated with linear measurements. Furthermore, it demonstrated that endodontic surgery caused a significant increase in defect size; thus, assessment of healing outcomes should consider that this treatment necessitates creating a larger defect than the original lesion.