Artifacts in orthodontic bracket systems in cone-beam computed tomography and multislice computed tomography

The purpose of this study was to quantify artifacts caused by different bracket systems in cone-beam computed tomography (CBCT) and multislice computed tomography (MSCT) scans.

Orthodontic brackets of four different systems were consecutively bonded to the surface of a residual molar on a human cadaveric mandible. One MSCT system and three CBCT units were used to scan each of the four bonded brackets, in addition to obtaining a blank reference scan of the tooth surface. All datasets were registered to the reference dataset using visualization software (Analyze 11.0® by AnalyzeDirect). Artifact-related reductions in image quality were expressed in percent of theoretical maximum standard deviations (SD) obtained for the gray values of the adjacent voxels, with higher percentages correlating more pronounced artifacts.

Both the SD percentages for three defined line profiles and their mean values were almost invariably higher with the MSCT system than with the CBCT units. Looking into the individual SD percentages, two of the CBCT units (Pax Zenith 3D® and Picasso Trio®; both Vatech) produced higher values than the MSCT system (SOMATOM Definition AS+®; Siemens) in some line profiles. The titanium bracket, in particular, was associated with marked differences between the two scanner technologies, as the mean artifact intensities from this bracket were particularly high with the MSCT unit and relatively low with the CBCT units. The artifact intensities observed with the other three bracket systems varied widely depending on which scanner was used.

Different artifact intensities were noted depending on the composition of the bracket system and on the scanner technology (MSCT/CBCT). While the artifacts manifested themselves differently with different scanners, their adverse effects were comparable. However, given the variable severity of the artifacts observed depending on the materials scanned and the scanners used, a blanket recommendation for or against MSCT or CBCT units cannot be given on the basis of this study.