The aim of this in vivo study is to evaluate the influence of apical periodontitis (AP) on the accuracy of Dentaport ZX, Raypex 5, and i-Root electronic root canal length measurement devices.

Thirty-two single-rooted teeth scheduled for extraction, consisting of 16 teeth with AP and 16 teeth with normal periapex (NP), were selected. Access cavity was prepared and coronal portion of the canal was flared. Electronic working length (EWL) was determined by each ERCLMD according to each manufacturer's instructions. Each tooth was extracted and actual working length (AWL) was determined by inserting a size 15 K-file until the tip could be seen at a position tangential to the major foramen and then 0.5 mm was subtracted from the measurement. The distance from the AWL to the file tip was calculated and compared between the two groups by t-test. The accuracy of each ERCLMD within ±0.5 mm was compared between the groups by Fisher's test. Statistical significance was set at P < .05.

Inclusion Criteria:

• single-rooted teeth
• clinical pulp necrosis and periapical index scores of 3, 4 or 5
• pulp vitality and a periapical index score of 1

Exclusion Criteria:

• Teeth with metal restorations
• Teeth with prosthetic crowns
• Teeth with pulp calcification
• Teeth with previous endodontic treatment