Objective: In this study, periapical and panoramic radiographic tests were compared to the clinical examination (after extraction, gold standard) to verify their accuracy in identifying number of roots, root morphology, and presence of root dilaceration in impacted third molars. Methods: In total, 98 third molars were extracted (50 maxillary, 48 mandibular). Three dental surgeons and one radiologist were calibrated to analyze the root characteristics before (radiography) and after extraction.

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... reement between clinical and radiographic findings was analyzed with weighted kappa (κ) statistics. Correlation between radiographic and clinical data was assessed using Spearman correlation test. A 5% significance level was set for all analyses. Results: Upper teeth with single/fused roots and lower teeth with two roots were predominant. Higher agreement and correlation for number of roots and root morphology was observed for periapical (κ=0.258-0.612; R 2 =0.463-0.612; P<0.001) compared with panoramic exam (κ=0.164-0.365; R 2 =0.175-0.417; P<0.01), and for lower compared with upper teeth. For lower teeth, convergent/ parallel roots were predominant in the clinical analysis, while divergent roots were predominant in the imaging tests. For root dilaceration, poor agreement (κ=0.199-0.273) and low correlation (R 2 =0.185-0.306) was observed for either radiographic examinations. Conclusion: The accuracy of radiographic examinations in identifying the root characteristics of impacted third molars was generally low. Compared with the panoramic test, periapical radiography had better agreement and higher correlation with the clinical findings for all root features.