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The reliability of intra-oral radiographs for analyzing bone levels around dental implants

11/15/2023 in UP FRONT

By Chandur PK Wadhwani, MSD; Paul S. Rosen, DMD, MS; Todd R. Schoenbaum, DDS, MS; Mitra Sadrameli, DMD, MS; and Edward Kwayne Darateew, DDS

Intra-oral radiographs have been used to determine the success of dental implant therapy from the very beginning. They provide a non-invasive inexpensive, readily available and commonly used dental method for evaluating mineralized tissue. Initial success criteria from Albrektsson and others used the standard annual bone loss after the first year of less than 0.2 mm as a guide for implant success1.

The literature is rife with measurements of marginal bone changes over time that vary from zero to fractions of a millimeter. What is the level of certainty that these measurements are reliable?

Radiographs are prone to multiple technique errors, which has led some investigators to recognize that a realistic value for being able to detect real changes in bone levels around implants is 0.5 mm2 but even this requires an almost perfect radiographic technique.

Studies using radiography should be scrutinized for their ability to achieve high quality, standardized serial radiographs.

Fig. 1(A,B): Two seemingly excellent radiographs of the same site were made within 1 minute of each other. They demonstrate the effect of horizontal collimator shift, resulting in a parallax effect (A) where bone appears to be growing over the implant shoulder. 

As clinicians, we must be able to interpret radiographs carefully. Keeping in mind the following may be helpful:

  1. Standardization: Ideally these should be orthogonal images. One way to determine if serial radiographs are comparable is to look at other radiographic fiducial sites. There should be no changes in image shapes related to: Restorations or anatomical sites such as sinus, nerve channels, maxillary midline bone suture, etc. (unless altered during treatment)3. Cropping images reduce our ability to determine if the radiographs are well standardized and should be discouraged.
  2. Image contrast, brightness and sharpness should be standardized across all images. If the implant material looks more opaque, bone density may not be equivalent across the radiographic images. This can lead to misinterpretation of bone levels as bone shows up at differing sites dependent upon pixel value.
  3. Vertical angulation changes of 20 degrees or more can result in the “appearance” of bone changes up to 4.8mm4.
  4. Horizontal tube shifts between images can superimpose bone levels due to parallax producing error up to 1.5mm. This superimposition is also affected by curvature of the maxilla and mandible 5 (Fig. 1).
  5. Bone levels around implants placed sub-crestal are more difficult to interpret as super-imposition or overlap of buccal and palatal bone gives the appearance of bone growth over the surface of the implant5.
  6. Magnification and penumbra6 effects due to the distance of collimator to implant produces errors due to non-sharp imaging, resulting in imprecise measurement.
  7. Implant thread shape cannot be relied upon to show standardization6.
  8. Implant shape and bucco-lingual angulation relative to the sensor and x-ray beam can also produce inaccurances6.
  9. Inter and intra-observer measurements on radiographs are known to have high levels of variability. Studies have shown that in 25% of cases, there is disagreement as to where the bone level exists amongst trained dentists of various specialties and experience. Interesting, even if the same examiner is presented with the same radiograph a few weeks later, 25% did not agree with their first assessment. Females are more consistent with their abilities to read radiographs. This variability in humans assessing imaging has led to the ongoing development of machine learning and reading devices to assist with this8.

What should be required of any study is not only representative images that allow the reader to discern the quality of the research, but also an estimation of the reading error present. If for example, it is considered that radiographs have a limitation in reading of 0.5 mm, then any data outside of this error can be considered, whereas data within this error may just be a flaw in human judgement or “noise”9.

 

References in this article are available via scanning this QR code

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This article was originally published in Academy News.
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