When dealing with the radiographic examination of a patient with periodontitis one should keep in mind a crucial equilibrium, which is accurately described by Grondahl; “Whenever radiographic methods are used to acquire information in a clinical context it is of great importance one makes sure that the benefit of using them exceeds
the costs involved.”(9)Therefore, the discussion for the use of intraoral radiography can be divided in two levels of analysis; One relating to the magnitude of the harm caused to the patient due to ionizing radiation and another analyzing the possible benefits from the most accurate radiographic examination needed for a specific purpose.
Before discussing the radiation exposure differences among the two imaging methods, some basic principles of radiology should be discussed for better understanding of the following text. The absorbed dose is the basic physical dosimetric quantity of the radiation exposure. It is measured in a unit termed gray (Gy). However, it is not entirely satisfactory for radiation protection purposes because effectiveness in damaging human tissue differs for different types of ionizing radiation. Consequently, the absorbed dose averaged over a tissue or organ is multiplied by a radiation weighting factor to take account of the effectiveness of the given type of radiation in inducing health effects; the resulting quantity is termed equivalent dose, and it is measured in Sievert (Sv). (13)
There are no formal decrees relating to the exposure doses from radiographic equipment, just guidelines. The International Atomic Energy Agency in 1996 recommended that intraoral dental radiology should be based in a reference dose value of 7 mGy. (12) Still there were no recommendations for the panoramic radiography. In addition, reference dose levels are providing just a framework to reduce the wide variability in patient radiation for the same type of x ray examination among different medical facilities. In the same time, literature exhibits weakness in identifying radiation doses from panoramic devices realistically.(8) Many studies conducted in the past measured doses in phantoms, thus in conditions that are not clinically relevant. (4,10) That’s why everyone could notice wide variation in radiation dose outcomes, from 0,1mGy to 3mGy during radiographic examination. (10) Another black spot of studies' conclusions is the lack of measurements in exposure of tissues like occipital region. (8) Given the fact that estimations of exposure from panoramic radiography are cumulative values from different absorbing tissues, an assumption that measurements underestimate the actual exposure wouldn’t be irrational.
Nevertheless, to date there are many studies comparing the exposure value between intraoral x rays and orthopantomographs. The most optimistic studies (that favour DPGs) indicate that the dose from a panoramic radiograph approximately corresponds to 2-4 intraoral radiographs, or to 1/10 of a full intraoral examination consisted by 20 radiographs(19). How relevant to the dental practice are these calculations of exposure dose? Arua et al found that in 1998, 1.34 diagnostic examinations of 257 different types were performed per person annually in Switzerland. The annual radiation dose per caput was 1mSv and corresponded to the quarter of the total dose received by the population. Dental radiographic examinations had a 43% share in the total radiographic examination, but contributed to just 1% of the total annual exposure.(2) Maybe heretically, due to the findings from the previous study, the hypothesis of considering clinical benefits more than the radiation exposure magnitude could be valid in this particular decision of choosing the appropriate radiographic examination.
Mol’s directions are very helpful for the understanding of the structure of the second level of analysis; “A decision to prescribe any radiograph should only be made if additional information is required and when that information cannot be obtained though methods carrying a lower risk to the patient. “(21)
In terms of clinical interpretation of the radiographic findings, literature seems to reveal more consistent evidence that favour intraoral radiography compared to the panoramic. Unexceptionally panoramic radiographic performance in caries detection is significantly lower compared to periapical or bitewing radiographs. The sensitivity for caries detection is 3 times less than intraoral and below values of 20%. (19) In periodontal aspects this significance is of rather low value. Clinicians are interested more in measurements or identification of bone loss, bone support to root length ratio, infrabony pockets geography description, periodontal ligament enlargement and (for few believers) crestal alveolar lamina dura.
Although hard to find, a very good study was conducted in Greece by Pepelasi et al. (22) They examined more than 1000 infrabony defects with panoramic and intraoral radiographs and compared these measurements with the “golden standard” of open flap measurements during surgical treatment of the defects. They found that small areas of bone destruction were detected 4.7 times more frequently by periapical radiography than by panoramic radiography, though the radiographic detection of any of these sites was very low compared to the identification during surgical exposure. The more sensitive diagnostic value in detection of intrabony defects of intraoral radiographic examination is supported by other studies too. (1, 14, 16, 26, 27, 28) There are of course disagreements in the literature. It is quite reasonable for someone to find bibliographic controversies, but these studies don’t use the gold standard of surgical bone measurement to compare the radiographic findings, but they try to find similarity in radiographic results instead.(5, 6, 15) Regarding the horizontal bone loss measurement, despite the radiographic underestimation that is commonly accepted(1,5,6,11,22,25,26,31) intraoral radiography is more close to the findings from the bone sounding measurement. (22) These findings could be enhanced by the fact the in the premolar areas panoramic imaging is more distorted, affecting the accurate bone to root ratio estimation(29). Attempts to convert the distortion with sophisticated statistical models (30) don’t seem to have clinical relevance.
The identification of features like enlarged periodontal ligament and crestal alveolar lamina dura can be made only with intraoral x ray. The clinical significance of these features is unclear. Old studies with not quite methodological design implicate the periodontal ligament enlargement with trauma from occlusion.(32,33,34). Other studies indicate the possible diagnostic value of presence of crestal alveolar lamina dura. Specifically, Rams concludes that absence of crestal alveolar lamina dura as a diagnostic test yields high values of sensitivity for periodontal stability, but low specificity.(25) In other words, the presence of lamina dura in the radiograph of a periodontal patient indicates the presence of stability, but the lack of it does not preclude any form of disease activity.
Mol’s directions are very helpful to decide whether additional radiographic examination is required upon a previous one. “A decision to prescribe any radiograph should only be made if additional information is required and when that information cannot be obtained though methods carrying a lower risk to the patient. “(21)
One has to remember that intraoral radiographic examination is not valid in every aspect of periodontal evaluation. There is no evidence to indicate the use of intraoral radiography for early bone loss detection in supportive periodontal therapy. (17,23,24,31) Clinical measurements are more efficient in this aspect. Some though disagree with these findings suggesting that studies with different findings could be justified by the fact that the magnitude of periodontal changes could be within the range of errors of the measuring techniques. (10) However, sequentially taken radiographs, when examined by eye, are able to reveal changes in bone only after 30-50% of the bone mineral has been resorbed. (35)
To conclude, although the trend of new studies (especially from the Gotenburg university group) (19,20) on periodontal radiography focuses in reduction of radiation exposure dose, clinical significance of radiographic findings seems to engage larger proportion in decision making for the choice of imaging examination, in realistic conditions. Otherwise, any periodontal patient consultation would be conducted after CT examination. There are many studies to suggest better diagnostic accuracy with CT examination compared to both previously analysed techniques(7,18) (for review Mol(21) and Hausmann(10) give many details).
1. Akesson L, Hakansson J, Rohlin M. (1992) Comparison of panoramic and intraoral radiography and pocket probing for the measurement of the marginal bone level. Journal of Clinical Periodontology, 19, 326.
2. Aroua A, Burnand B, Decka I, Vader JP, Valley JF. (2002) Nationwide survey on radiation doses in diagnostic and interventional radiology in Switzerland in 1998. Health Physics, 83, 46.
3. Bragger U. (2005) Radiographic parameters: biological significance and clinical use. Periodontology 2000, 39(1), 73-90.
4. Danforth DA and Dennis E. Clark. (2000) Effective dose from radiation absorbed during a panoramic examination with a new generation machine. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 89(2), 236.
5. Eickholtz P, Kim TS, Benn DK, Staedle HJ. (1998) Validity of radiographic measurement of interproximal bone loss. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 85, 99.
6. Eickholz P, Hausmann E. (2000) Accuracy of radiographic assessment of interproximal bone loss in intrabony defects using linear measurements. European Journal of Oral Sciences, 108, 70.
7. Fuhrmann RA, Wehrbein H, Langen HJ and Diedrich PR. (1995) Assessment of the dentate alveolar process with high resolution computed tomography. Dentomaxillofacial Radiology, 24(1), 50-54.
8. González L, Vañó E, Fernández R. (2001) Reference doses in dental radiodiagnostic facilities. Journal of British Radiology 74, 153.
9. Grondahl HG. (2003). Radiographic examination. Clinical periodontology and implant dentistry, pp 838.
10. Hausmann E. (2005). Radiographic and digital imaging in periodontal practice. Journal of Periodontology, 71, 497-503.
11. Jun JH, Hwang SJ, Kim CS, Cho KS, Chai JK, Kim CK, Choi SH. (2005) The correlation between the bone probing, radiographic and histometric measurements of bone level after regenerative surgery. Journal of Periodontal Research, 40(6), 453-460.
12. The Institute of Physics and Engineering in Medicine. (1997) Recommended standards for the routine performance testing of diagnostic X-ray imaging systems, IPEM Report 77. York: IPEM.
13. International Atomic Energy Agency. (1996) International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Safety series No 115 Vienna: IAEA.
14. Kiefer H, Lambrecht TJ, Roth J. Strahlenexposition von analogen und digitalen Zahnstaten und Panoramaschichtaufnahmen. Schweiz Monatsschr Zahnmed 2004; 114, 687.
15. Kullman L, Al-Asfour A, Zetterqvist L, Andersson L. (2007) Comparison of radiographic bone height assessments in panoramic and intraoral radiographs of implant patients. International Journal of Oral Maxillofacial Implants, 22(1), 96-100.
16. Liñares A, Cortellini P, Lang NP, Suvan J, Tonetti MS; European Research Group on Periodontology (ErgoPerio). (2006) Guided tissue regeneration/deproteinized bovine bone mineral or papilla preservation flaps alone for treatment of intrabony defects. II: radiographic predictors and outcomes. Journal of Clinical Periodontology, 33(5), 351-358.
17. Machtei EE, Hausmann E, Grossi SG, Dunford R, Genco RJ. (1997) The relationship between radiographic and clinical changes in the periodontium. Journal of Periodontal Research, 32 (8), 661-666.
18. Mengel R, Candir M, Shiratori K, Flores de Jacoby L. (2005) Digital volume Tomography in the Diagnosis of Periodontal Defects: An in vitro study of Native pig and human mandibles. Journal of Periodontology 76(5), 665.
19. Molander B, Ahlqwist M, Grondahl HG. (1995) Panoramic and restrictive intraoral radiography in comprehensive oral radiographic diagnosis. European Journal of Oral Sciences, 103, 191.
20. Molander B, H-G Gröndahl HG, and Ekestubbe A. (2004) Quality of film based and digital panoramic radiography. Dentomaxillofacial Radiology, 33, 32-36.
21. Mol A (2004). Imaging methods in periodontology. Periodontology 2000; 34, 34.
22. Pepelasi EA, Diamanti-Kipioti A. (1997) Selection of the most accurate method of conventional radiography for the assessment of periodontal osseous destruction. Journal of Clinical Periodontology, 24, 557.
23. Persson RE, Tzannetou S, Feloutzis AG, Bragger U, Persson GR, Lang NP. (2003) Comparison between panoramic and intraoral radiographs for the assessment of alveolar bone levels in a periodontal maintenance population. Journal of Clinical Periodontology, 30, 833-889.
24. Pilgram TK, Hildebolt CF, Yokoyama-Crothers N, Dotson M, Cohen SC, Hauser JF, Kardaris E. (1999) Relationships between longitudinal changes in radiographic bone height and probing depth measurements: Data from post menopausal women. Journal of Periodontology, 70(8), 829-833.
25. Rams TE, Listgarten MA, and Slots J. (1994) Utility of radiographic lamina dura in predicting periodontitis disease activity. Journal of Clinical Periodontology, 21, 571-576.
26. Tonetti M, Pini-Prato G, Cortellini P. (1993) Periodontal regeneration of human intrabony defects. IV. Determinants of healing response. Journal of Periodontology, 63, 934.
27. Tonetti MS, Pini Prato G, Williams RC, Cortellini P. (1993) Periodontal elimination of human infrabony defects. III. Diagnostic strategies to detect bone gain. Journal of Periodontology 64, 114.
28. Tsitoura E, Tucker R, Suvan J, Laurell L, Cortellini P, Tonetti M. (2004) Baseline radiographic defect angle of the intrabony defect as a prognostic indicator in regenerative periodontal surgery with enamel matrix derivative. 31 (8), 643-647.
29. Tugnait A, Clerehugh V, Hirschmann PN (2000) The usefulness of radiographs in diagnosis and management of periodontal diseases: a review. Journal of Dentistry, 28, 219-226.
30. Yitschaky M, Haviv Y, Aframian DJ, Abed Y, and Redlich M. (2004) Prediction of premolar tooth lengths based on their panoramic radiographic lengths. Dentomaxillofacial Radiology, 33, 370.
31. Zybutz M, Rapoport D, Laurell L, Persson GR. (2000) Comparisons of clinical and radiographic measurements of inter-proximal vertical defects before and 1 year after surgical treatments. Journal of Clinical Periodontology, 27(3), 179.
32. Ericsson I & Lindhe J. (1983) Lack of significance of increased tooth mobility in experimental periodontitis. Journal of Periodontology, 55(8), 447-452.
33. Kantor M, Polson AM & Zander HA. (1976) Alveolar bone regeneration after removal of inflammatory and traumatic factors. Journal of Periodontology, 47(12), 687-695.
34. Lindhe J & Ericsson I. (1982) The effect of elimination of jiggling forces on periodontally exposed teeth in the dog. Journal of Periodontology, 53(9), 562-567.
35. Reddy M. (1992) Radiographic methods in the evaluation of periodontal therapy. Journal of Periodontology, 63, 1078-1084.
No comments:
Post a Comment