Purpose: This study aimed to analyze radiographs of dentigerous cysts containing high-density areas within lowdensity areas to identify their characteristic radiographic features. Materials and Methods: This retrospective study included histopathologically confirmed cases of dentigerous cysts inpatients who underwent computed tomography (CT). The analyses included demographic data, the position of the lowdensity area relative to the impacted tooth, and the number, size, and location of the high-density area within the lowdensity region. Group comparisons were performed for each analytical factor. Results: The patients were classified into 550 cases of dentigerous cysts without high-density areas and 34 cases with high-density areas within the low-density regions. In the group with high-density areas, the low-density regions more frequently extended beyond the cementoenamel junction toward the center of the tooth root. In addition, many lesions exhibited high-density areas with a maximum diameter of less than 3 mm, contact with the tooth crown, and involvement of impacted teeth. Conclusion Lesions displaying high-density features, such as a maximum diameter <3 mm, contact with the tooth crown, and association with impacted teeth, are likely dentigerous cysts. These findings suggest that dentigerouscysts containing high-density areas differ from other lesions with calcified components. Although such cases are rare,recognizing them is important for understanding the disease spectrum.

Purpose: This study aimed to investigate inter-observer reliability among observers with different levels of proficiency and the diagnostic imaging reliability of cone-beam computed tomography (CBCT) images of the retromolar canal. Materials and Methods: CBCT images of 307 patients were assessed for the presence of retromolar canals (RMCs) by 3 observers independently. Diagnoses were made twice by each observer at intervals of more than 3 weeks. Inter-observer reliability was assessed using the kappa coefficient. One observer had no experience in diagnosis using CBCT images. Therefore, a specialist in diagnostic imaging explained the CBCT images for interpretation and practiced diagnostic imaging together with this observer, while the other observer interpreted the images independently. Thereafter, the observers re-evaluated the images. Results: The interobserver kappa coefficients (including bilateral RMCs) calculated at the first reading were low, ranging from 0.21 to 0.61. Their values ranged from 0.95 (right side) to 1.00 (left side) after one-on-one practice with a diagnostic imaging specialist, while the values ranged from 0.65 (right side) to 0.66 (left side) without one-on-one practice. Conclusion Diagnostic accuracy was improved through diagnostic imaging practice. To improve the anatomical interpretation of images, it is important to practice diagnostic imaging with a specialist in diagnostic imaging. One-on-one instruction about diagnostic imaging was an effective method of training.