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

Introduction: 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.

Methods: 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.

Results: 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).

Conclusions: 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.