Hoda Abbaspour Tehrani Fard - Private Dentist, Tehran Iran.
Ladan Hafezi - Assistant professor, Oral and Maxillofacial Radiology Department., Dental School, Islamic Azad University of Medical Sciences, Tehran, Iran.
Amirreza Mehdizadeh - Post-graduate Student, Oral and Maxillofacial Radiology Department, Dental School, Islamic Azad University of Medical Sciences, Tehran, Iran
Niloofar Ghadimi - Post-graduate Student, Oral and Maxillofacial Radiology Department, Dental School, Islamic Azad University of Medical Sciences, Tehran, Iran
Afsoon Jalali Ara - Post-graduate Student, Oral and Maxillofacial Radiology Department, Dental School, Islamic Azad University of Medical Sciences, Tehran, Iran
Ahmadreza Talaipour - Professor, Oral, and Maxillofacial Radiology Department, Dental School, Islamic Azad University of Medical Sciences, Tehran, Iran.

Background: Due to the importance of CBCT linear measurement accuracy and the lack of standard axial plane inclination, this study aimed to investigate the effect of axial plane inclination changes on linear measurement accuracy in reconstructed maxillary CBCT images. Materials and Methods: In the present experimental (in-vitro) study, CBCT images were obtained from ۳ dry human maxillae. In this study, radiopaque markers (gutta-percha) were used as landmarks. First, real measurements were made by a practitioner using a digital caliper. Then, CBCT was taken in ۵ different inclinations of the axial plane (parallel to the occlusal plane as the standard plane and ±۷ ̊and ±۱۴ ̊). One observer performed radiographic linear measurements. The linear measurements were a total of ۵۴۰ samples according to ۳۶ markers and ۵ different inclinations and ۳ replications. Physical and radiographic linear measurements were compared to evaluate the accuracy of linear measurements on ۵ different inclinations. Data were analyzed using SPSS software version ۱۶ and ANOVA test. Results: A total of ۵۴۰ samples with ۵ different inclinations were evaluated. The actual size of the marker length, inclinations estimation and difference estimation showed that the maximum and minimum differences were related to inclinations of -۷ ̊ by ۰.۰۰۹ and inclinations of +۷ ̊ by ۰.۰۰۲, respectively. However, ANOVA test showed that this estimate of differences in various inclinations was not statistically significant (P >۰.۰۵). Conclusion: It seems that changing the inclination from ۰ to -۱۴ does not affect estimating the real differences of marker length with the inclination. Therefore, it can be concluded that all vertical measurements are accurate clinically.

Cone beam computed tomography, Linear measurements, Maxilla