Abstract: Objective: To compare the periodontal ligament (PDL) space for teeth at different pulp statuses with CBCT and periapical radiography. Methods: Two hundred and thirty-four single root teeth without clinical symptoms and positive signs were included. They all had a CBCT scan, a periapical radiograph, and clinical pulp tests. The periapical regions of the CBCT scans and radiographs were scored by modified CBCT-periapical index (CBCT-PAI) and represented as CBCT-PAI and PAI, respectively. The Fisher exact and Chi-squared statistics tested the relationship between CBCT-PAI, PAI, and pulp status. Results: Two hundred and ten teeth had health pulp, and the other teeth were no respond. The CBCT-PAI score was greater than the PAI in 61.9% (130 of 210) teeth. The PDL space of healthy teeth was statistically significant when examined by CBCT and periapical radiography (P<0.01). The difference of PDL on CBCT between teeth with healthy and necrotic pulps was statistically significant (P<0.01). Conclusion: Significant differences were observed between CBCT and periapical radiography in detection the PDL space of healthy teeth. Teeth with necrotic pulps were more likely to have wide PDL when examined by CBCT.

Key words: Cone beam computerized tomography, Diagnosis, Periapical radiography, Periapical lesions