AIM:To determine the accuracy of tomography in the linear measurement of alveolar bone at maxillary sinus/nose location.METHODS:Two dry skulls each marked with 10 pairs of guttaperchas placed on buccal and lingual sides of the maxillary ridge were used in this in vitro study.The distance between the alveolar crest and the sinus/nasal floor was measured on tomographic views,prepared by linear and spiral techniques.The ridges were then sectioned so that each section would include one pair of buccal and lingual guttaperchas.The actual distances directly measured on the sections were compared to those of the equivalent tomographic sections(the magnification co-efficient was applied).Paired t-test was used to statistically analyze the data.RESULTS:The measurement error with the application of linear tomography and spiral tomography wasshown to be 0.455±0.838 mm(P=0.029)and 0.17±0.78 mm(P=0.347),respectively.There was a statistically significant difference between the liner tomography values and actual values(P=0.029).This difference was representative of underestimation.McNamara’s test was used to assess the±1 mm error;73.7%of the linear values and 84.2%of the spiral values were within the±1 mm error limit.Mc Namara’s test did not show any significant differences between the 2methods in this regard(P=0.625).The linear values were significantly different to the actual values(P=0.029)but not to the spiral values(P=0.185).CONCLUSION:Spiral tomography has enough accuracy for the measurement of alveolar ridge height.Although linear tomography somewhat underestimates the actual values it provides satisfactory accuracy. AIM: To determine the accuracy of tomography in the linear measurement of alveolar bone at maxillary sinus / nose location. METHODS: Two dry skulls each marked with 10 pairs of guttaperchas placed on buccal and lingual sides of the maxillary ridge were used in this in vitro study.The distance between the alveolar crest and the sinus / nasal floor was measured on tomographic views, prepared by linear and spiral techniques. ridges were then sectioned so that each section would include one pair of buccal and lingual guttaperchas.The actual discrete directly measured on the sections were compared to those of the equivalent tomographic sections (the magnification co-efficient was applied). Paired t-test was used to analyze analyze the data .RESULTS: The measurement error with the application of linear tomography and spiral tomography wasshown to be 0.455 ± 0.838 mm (P = 0.029) and 0.17 ± 0.78 mm (P = 0.347), respectively. There was a significant difference between the liner tomography valuations es and actual values ​​(P = 0.029). This difference was representative of underestimation. McNamara’s test was used to assess the ± 1 mm error; 73.7% of the linear values ​​and 84.2% of the spiral values ​​were within the ± 1 mm error limit . Mc Namara’s test did not show any significant differences between the 2methods in this regard (P = 0.625). The linear values ​​were significantly different to the actual values ​​(P = 0.029) but not to the spiral values ​​(P = 0.185) .CONCLUSION : Spiral tomography has enough accuracy for the measurement of alveolar ridge height. Although linear tomography somewhat underestimates the actual values ​​it provides satisfactory accuracy.