The aim of this study was to determine the relationship between loss of radiographic crestal bone height in panoramic, bitewing and periapical radiography and to probe the attachment loss after periodontal treatment. Radiographic and probing measurements were made at baseline and after one year. The population in the study consisted of 21 individuals, 13 females and 8 males, ages 18–59 [mean 35.7] years. A total of 42 interproximal intra-bony defects of 21 mandibular first molar teeth, treatments of which were planned by subgingival curettage procedures, were selected from among 21 subjects who had signed consent forms. Measurements of the distance between the cemento-enamel junction and the alveolar crest were compared with probing crestal bone level and radiographic measurements before and one year after the procedures. The results of probing pocket depths level before and one year after subgingival curettage were different with the mean average being 1.18 ± 1.51 mm. These changes were statistically significant (p < 0.05). Bitewing radiography showed the highest accuracy among radiographic methods in the assessment of the crestal bone level mean average 0.22 ± 0.87 mm (p < 0.05). There was only a slight mean difference compared to panoramic radiography but this was statistically insignificant, mean average 0.20 ± 1.35 mm (p > 0.05), and the periapical radiography had the lowest accuracy of radiographic methods, changed mean average -0.14 ± 1.19.mm (p > 0.05). In summary, we can say that both bitewing and panoramic radiography are preferred to periapical images for crestal bone assesment.