Evaluation of various low-dose cone-beam computed tomography protocols in the diagnosis of specific condylar defects

This study aimed to determine the identifiability and measurement accuracy of defined bony defects of the temporomandibular joint (TMJ) in cone-beam computed tomographies, depending on different milliampere-second (mAs)-reduced protocols.

Defined artificial defects were prepared on 30 condyles from 15 intact pig heads, with a maximum of surrounding soft tissue preserved. Three-dimensional imaging was performed using ProMax 3D Mid (Planmeca, Helsinki, Finland). The scan protocol with maximum resolution and without mAs-reduction was defined as control. Twenty-six mAs-reduced imaging protocols were analyzed by 1 examiner regarding the protocol-specific measurement accuracy. Defect depth (DD) was divided into 3 categories: I, <2 mm; II, 2-3 mm; and III, >3 mm. The protocol-specific sensitivity and specificity were evaluated in relation to localization and defect size as determined from the results of 3 examiners.

There was a significant difference from the control protocol in DD measurement in 8 mAs-reduced protocols, P <0.001-0.027. In most protocols, there was no significant difference in measurement accuracy concerning defect size and localization. The mean sensitivity reached values between 93.3% and 98.6% and differed significantly among protocols (P = 0.002). The mean specificity amounted to 97.0%-98.1% and did not differ among protocols (P = 0.462). The specificity of DD III (99.1%) was higher than DD I (97.7%) and DD II (97.1%). There was a significant difference in specificity and sensitivity concerning defect localization (P <0.001).

This study showed that mAs-reduced cone-beam computed tomographies protocols are suitable for the analysis of defined osseous TMJ defects. When 3-dimensional TMJ imaging is indicated because of potential erosive defects, validated mAs-reduced scan protocols should be applied instead of high-definition protocols.