accuracy and reliability of linear measurements using tangential projection and cone beam computed tomography

background: providing a cross-sectional image is essential for preimplant assessments. computed tomography (ct) and cone beam ct (cbct) images are very expensive and provide high radiation dose. tangential projection is a very simple, available, and low-dose technique that can be used in the anterior portion of mandible. the purpose of this study was to evaluate the accuracy of tangential projection in preimplant measurements in comparison to cbct. materials and methods: three dry edentulous human mandibles were examined in five points at intercanine region using tangential projection and cbct. the height and width of the ridge were measured twice by two observers. the mandibles were then cut, and real measurements were obtained. the agreement between real measures and measurements obtained by either technique, and inter- and intra-observer reliability were tested. results: the measurement error was less than 0.12 for tangential technique and 0.06 for cbct. the agreement between the real measures and measurements from radiographs were higher than 0.87. tangential projection slightly overestimated the distances, while there was a slight underestimation in cbct results. conclusion: considering the low cost, low radiation dose, simplicity and availability, tangential projection would be proper for preimplant assessment in edentulous patients when limited numbers of implants are required in the anterior mandible, and there is no need for more complicated image modalities.  key words: cone beam computed tomography, dental implant, radiograph