For panoramic reconstruction images, underestimation and overestimation were 89 and 11%, respectively (Figs. 10 and 12). For cross-sectional images, underestimation and overestimation were 97 and 3%, respectively (Figs. 11 and 12).
No significant difference was found between the error in panoramic reconstruction images and in cross-sectional images (P=0.511) (Fig. 13). However, panoramic reconstruction images showed a wider deviation range than cross-sectional images. Deviations from the gold standard were between 0.01 and 2.1 mm for the panoramic reconstruction images, whereas it was between 0 and 0.99 mm for the cross-sectional slices.
Detection of periodontal disease is important in the prevention of tooth loss [1,2]. In periodontal disease, a precise clinical estimation of the loss of supporting bone is not possible. Radiological diagnostics are an essential aid for making a specific diagnosis and for planning treatment .
CBCT offers many advantages compared with conventional CT. CBCT provides images with higher resolution at a lower cost, shorter examination time, and less radiation dose [14,16,17,22].
Many investigations of the recent CBCT technology have validated its usefulness for several diagnostic purposes, such as implant planning or orthodontics [16,23,24]. However, limited studies have been reported on the advantages of CBCT for periodontal diagnosis [18–20,25,26].
Using CBCT for periodontal assessment may offer new perspectives on periodontal diagnosis and treatment planning [18–20]. Therefore, we thought it is worthwhile to explore the use of CBCT in the assessment of periodontal defects.
Four human dry skulls were used for the measurement of bone height in 148 selected periodontal defects. The CEJ was used as a reference point to assess bone levels. Owing to dehydration of the dry skull, gutta purcha was used as a standardized fiducial to substitute for the faded CEJ.
Gutta purcha facilitated identification of the faded CEJs and allowed standardization of measurement localization. In a clinical setting, identification of CEJs would not be as hard as that with dry skulls (Fig. 7).
When accessibility did not allow the digital caliper to be oriented along the long axis of the tooth, this measurement was dropped. Missed readings were more common on the lingual side than on the buccal side.
The dry skulls were imaged with CBCT. An essential advantage of the CBCT technique is that different views can be retroactively synthesized from the volume data and combined at will. Two-dimensional slices have proven to be the most effective for detailed diagnosis .
Images were viewed with a Planmeca Romexis Viewer 2.2.7.R. Measurements were taken using the digital measurement tool of the software. When the bone height measurement was less than 1.2 mm, the digital measurement tool did not show any reading. Therefore, bone heights less than 1.2 mm were dropped. Recently developed versions of the software do not present the same problem.
Panoramic reconstruction views were used for measuring bone height. They provide the user with an overall view and allow a quick assessment of the periodontal bone. The slice thickness was 5.1 mm, which is large enough to visualize the buccal or lingual fiducials with the alveolar crest on one reconstruction. Therefore, one panoramic view was reconstructed for the buccal measurements and another was constructed for the lingual measurements.
However, panoramic reconstruction images of 5.1 mm would not allow complete exploitation of the acquired three-dimensional CBCT data. Therefore, the selected sites were measured again on coronal and sagittal images of 0.32 mm thickness through the specific fiducials. The highest resolution the CBCT machine used in this study could offer was 0.32 mm slice thickness. CBCT voxel resolutions can range from 0.076 to 0.4 mm .
There was no significant difference between panoramic reconstructed images and the gold standard regarding bone-height measurement (P=0.256). This highlights the accuracy of periodontal bone-level measurements using buccal and lingual panoramic reconstruction images with 5.1 mm slice thickness. The mean error was 0.27 mm. Vandenberghe et al.  used 5.2 mm-thickness panoramic reconstruction images and reported similar results with a mean error of 0.47 mm.
Moreover, there was no significant difference between bone height measurements taken on cross-sectional images and the gold standard (P=0.178). This proves the accuracy of periodontal bone-level measurements using cross-sectional images with 0.32 mm slice thickness. The mean error was 0.3 mm. Vandenberghe et al.  used 0.4 mm-thickness cross-sectional images and reported similar results with a mean error of 0.29 mm. Misch et al.  and Fuhrmann et al.  used 1 mm-thickness cross-sectional images and found similar results (mean error of 0.41 and 0.2, respectively).
There was no statistically significant difference between the panoramic reconstructed images and cross-sectional images (P=0.511). Deviations from the gold standard were between 0.01 and 2.1 mm for the panoramic reconstruction slices and between 0 and 0.99 mm for the cross-sectional slices.
In our opinion, aligning the cross-sectional slices to pass through the points of interest was a lot easier than reconstructing a panoramic image that includes the fiducials of all teeth and the alveolar crest. In addition, the statistics showed the cross-sectional images to be more accurate with a narrower deviation range. Therefore, we recommend the cross-sectional images for any periodontal measurements.
Small or large errors in locating the CEJ and the alveolar crest can, respectively, lead to overestimation and underestimation of disease prevalence . If we considered a 0.5 mm discrepancy acceptable at a clinical level, panoramic reconstructed images were accurate in 76% of the measurements and cross-sectional images were accurate in 82% of the measurements. If we even considered a 1 mm discrepancy acceptable at a clinical level, this leads to 98% accuracy for panoramic reconstructed images and 100% accuracy for cross-sectional images.
In this study, we were able to confirm our hypothesis that CBCT would allow an accurate assessment of bone levels. Statistics show a smaller deviation range from the gold standard for the measurements on 0.32 mm cross-sectional slices (between 0.01 and 2.1 mm) compared with those on the 5.1 mm panoramic reconstruction image (between 0 and 0.99 mm). This finding indicated that the current CBCT system might become more influential in the diagnosis of periodontal diseases.
As the radiation dose of CBCT has been reported to be less than conventional CT, there is a growing concern about the overconsumption of CBCT and its radiation safety [14–16,29].
In our opinion, the use of CBCT should still be carefully justified, and optimized exposure protocols should always be considered. Moreover, specialists in this field must perform the image acquisition and further interpretation. Ludlow et al.  reported dose reduction when using smaller field of view examinations. More studies in the future with a large sample size will determine ideal exposure settings that optimize the image quality for a certain diagnostic task with the lowest radiation exposure possible.
Considering the several advantages, limitations, and risks of CBCT, we would like to suggest that the currently tested model of CBCT should only be used for a relatively more complex periodontal treatment planning, such as prognostic planning and surgery for complex periodontal defects, and the potential use of dental implants.
For proper justification of the applicability of CBCT in periodontal diagnosis, further studies are required for the assessment of various exposure and reformatting protocols and the evaluation of the diagnostic validity during clinical follow-up, especially when surgery is involved. These findings may help in establishing selection criteria for the assessment of periodontal bone loss.
In conclusion, CBCT images allowed accurate measurements of periodontal defects on panoramic reconstruction images of 5.1 mm slice thickness and cross-sectional slices of 0.32 mm thickness. Cross-sectional images showed a more accurate assessment than panoramic reconstruction images, because of the absence of overlapping structures.
1. Slots J. Update on general health risk of periodontal disease Int Dent J. 2003;53(Suppl 3):200–207
2. Oliveira Costa F, Cota LO, Costa JE, Pordeus IA. Periodontal disease progression among young subjects with no preventive dental care: a 52-month follow-up study J Periodontol. 2007;78:198–203
3. Hefti AF. Periodontal probing Crit Rev Oral Biol Med. 1997;8:336–356
4. Jeffcoat MK, Reddy MS. Advances in measurements of periodontal bone and attachment loss Monogr Oral Sci. 2000;17:56–72
5. Quirynen M, Callens A, Van Steenberghe D, Nys M. Clinical evaluation of a constant force electronic probe J Periodontol. 1993;64:35–39
6. Khocht A, Chang KM. Clinical evaluation of electronic and manual constant force probes J Periodontol. 1998;69:19–25
7. Pretty IA, Addy L, Maupomé G. A closer look at diagnosis in clinical dental practice: part 6. Emerging technologies for detection and diagnosis of noncarious dental problems J Can Dent Assoc. 2004;70:621–626
8. Zulqarnain BJ, Almas K. Effect of X-ray beam vertical angulation on radiographic assessment of alveolar crest level Indian J Dent Res. 1998;9:132–138
9. Benn DK. A review of the reliability of radiographic measurements in estimating alveolar bone changes J Clin Periodontol. 1990;17:14–21
10. Eickholz P, Hausmann E. Accuracy of radiographic assessment of interproximal bone loss in intrabony defects using linear measurements Eur J Oral Sci. 2000;108:70–73
11. Schliephake H, Wichmann M, Donnerstag F, Vogt S. Imaging of periimplant bone levels of implants with buccal bone defects Clin Oral Implants Res. 2003;14:193–200
12. Mol A. Imaging methods in periodontology Periodontology 2000. 2004;34:34–48
13. Bragger U. Radiographic parameters: biological significance and clinical use Periodontology 2000. 2005;39:73–90
14. Sukovic P. Cone beam computed tomography in craniofacial imaging Orthod Craniofac Res. 2003;6(Suppl 1):31–36 discussion: 179–182.
15. Ludlow JB, Davies Ludlow LE, Brooks SL, Howerton WB. Dosimetry of 3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT Dentomaxillofac Radiol. 2006;35:219–226
16. Scarfe WC, Farman AG, Sukovic P. Clinical applications of cone-beam computed tomography in dental practice J Can Dent Assoc. 2006;72:75–80
17. White SC, Pharoah MJ Oral radiology: principles and interpretation. 20086th ed St. Louis Mosby
18. Misch KA, Yi ES, Sarment DP. Accuracy of cone beam computed tomography for periodontal defect measurements J Periodontol. 2006;77:1261–1266
19. Vandenberghe B, Jacobs R, Yang J. Diagnostic validity (or acuity) of 2D CCD versus 3D CBCT-images for assessing periodontal breakdown Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2007;104:395–401
20. Tyndall DA, Rathore S. Cone-beam CT diagnostic applications: caries, periodontal bone assessment and endodontic applications Dent Clin N Am. 2008;52:825–841
21. Newman MG, Takei H, Klokkevold PR, Carranza FA Carranza's clinical periodontology. 200610th ed Philadelphia, PA WB Saunders
22. Zoller JE, Neugebauer J, Dreiseidler T, Haak R, Hey J, Braumann B Cone-beam volumetric imaging in dental, oral and maxillofacial medicine: fundamentals, diagnostics and treatment planning. 20081st ed Berlin, Germany Quintessence Publishing
23. Dreiseidler T, Mischkowski RA, Neugebauer J, Ritter L, Zöller JE, Keeve E. Pre-surgical cone beam assessment in dental implantology. Proceedings of the 8th Congress of the European Association for Cranio-Maxillofacial Surgery; Sep; Barcelona; 2006.
24. Ziegler CM, Woertche R, Brief J, Hassfeld S. Clinical indications for digital volume tomography in oral and maxillofacial surgery Dentomaxillofac Radiol. 2002;31:126–130
25. Mol A, Balasundaram A. In vitro cone beam computed tomography imaging of periodontal bone Dentomaxillofac Radiol. 2008;37:319–324
26. Grimard BA, Hoidal MJ, Mills MP, Mellonig JT, Nummikoski PV, Mealey BL. Comparison of clinical, periapical radiograph and cone-beam volume tomography measurement techniques for assessing bone level changes following regenerative periodontal therapy J Periodontol. 2009;80:48–55
27. Lohse AK, Scarfe WC, Shaib F, Farman AG. Obstructive sleep apnea-hypopnea syndrome: clinical applications of cone beam CT Aust Dent Pract. 2009:122–132
28. Fuhrmann RA, Bucker A, Diedrich PR. Furcation involvement: comparison of dental radiographs and HR-CT-slices in human specimens J Periodontal Res. 1997;32:409–418
29. Hagtvedt T, Aalokken TM, Notthellen J, Kolbenstvedt A. A new low-dose CT examination compared with standard-dose CT in the diagnosis of acute sinusitis Eur Radiol. 2003;13:976–980
Keywords:© 2011 Egyptian Associations of Oral and Maxillofacial Surgery
cone beam computed tomography; periodontal defects; periodontal diagnosis