Effects from changes to the Medicare Benefits Schedule in 2014 on cone beam computed tomography and panoramic radiography scans across Australia.

INTRODUCTION: This study examines the effects of the new Medicare Benefits Schedule (MBS) operating from 1st November 2014 on the number of Medicare rebated panoramic radiography (PR) and cone beam computed tomography (CBCT) scans. METHODS: Data for rebated PR and CBCT scans were extracted from Medicare Australia Statistics online for four 12-month periods: November 2011-October 2012, November 2012-October 2013, November 2013-October 2014 and December 2014-November 2015. RESULTS: There was a reduction in the number of CBCT scans rebated across Australia under the new MBS. Nationally, December 2014-November 2015 showed a 65.3% reduction in the number of CBCT scans when compared to the peak in the previous 12 months under the old MBS. The number of rebated PR scans remained constant. CONCLUSION: The new MBS implemented on 1st November 2014 resulted in a reduction in the number of rebated CBCT scans, but had no effect on rebated PR scans. Overall, there has been considerable cost savings for Medicare due to the change in MBS. Additionally, the reduction in the number of rebated CBCT scans has resulted in a substantial reduction in the ionising radiation load to the Australian community as a whole, but especially the younger age groups.

Accuracy of angular measurements and assessment of distortion in the mandibular third molar region on panoramic radiographs.

OBJECTIVE: The objective of this study was to examine distortion on panoramic radiographs by assessing the accuracy of angular measurements in the mandibular third molar region on panoramic radiographs using computed tomography (CT). METHODS: Images from patients referred to a radiology practice for low-dose CT scans of their lower third molars were used in this study. The angle between the long axes of the second and third molars was assessed on panoramic radiographs and the corresponding CT images. Apparent tilting of the tooth across the arch on the panoramic image and the bucco-lingual inclination on CT were also recorded and compared. RESULTS: Eighty-eight patients had 163 mandibular third molars. The mean difference between the panoramic measurements and the CT measurements was -1.44 degrees, indicating that on the panoramic radiograph the third molar appeared less mesially inclined on average. This pattern was present in most cases, but in 64 cases the third molar appeared more mesially inclined on the panoramic radiograph. It was not possible to predict the direction of the discrepancy based on the radiographic findings. The discrepancy between the 2 measurements was greater if the third molar appeared tilted across the arch on the panoramic image, and tilted teeth showed a higher bucco-lingual inclination on reformatted CT images. CONCLUSIONS: Distortions inherent in panoramic imaging because of projection geometry produce discrepancies in the angular measurements in the mandibular third molar regions on panoramic radiographs. Interpretation of third molar angulation from panoramic radiographs is often unreliable and may not accurately reflect the true orientation of the tooth. Apparent tilting of the tooth across the arch on the panoramic radiograph exacerbates the problem and appears to correlate with the bucco-lingual inclination of the third molar as visualized on reformatted CT images.