Identification of resected root-end dentinal cracks: a comparative study of visual magnification

The purpose of this in vitro study was to evaluate and compare the effectiveness of visual enhancements as aids in identifying artificially created dentinal cracks in resected root ends. Fifty human maxillary central incisors were decoronated, and the root canals were instrumented to ISO size 50 at the working length. The apical 3 mm of the roots were resected, and cracks were artificially created in the apical dentin with an average load of 5.6 kg using a cylindrical wedge in a miniature drill press. A video microscope at x65 magnification was used to observe the cracks as they developed. Four independent examiners evaluated the root specimens using unaided/corrected vision (group 1), loupes at x3.3 magnification (group 2), a surgical operating microscope at x10 magnification (group 3), and the Orascope at x35 magnification (group 4). The examiners' proficiency at correctly identifying root ends with and without cracks was evaluated. The data were compared to the predetermined standard (27 cracked, 23 not cracked) with a one-tailed Fisher's exact test (alpha = 0.05). Statistically, the Orascope (p = 0.02) was significantly superior, whereas using unaided/corrected vision (p = 0.99), loupes (p = 0.88), or the microscope (p = 0.14) was not significantly better than guessing. The accuracy of correct identification for unaided/ corrected vision, loupes, the microscope, and the Orascope was 39%, 45%, 53%, and 58%, respectively. A two-way analysis of variance of the accuracy of crack identification showed a significant difference among the four visualization techniques (p = 0.0007) and also among the four evaluators (p = 0.006).