Precision of identifying cephalometric landmarks with cone beam computed tomography in vivo.

The study aims were to assess the precision and time required to conduct cephalometric analysis with cone-beam computed tomography (CBCT) in vivo on both three-dimensional (3D) surface models and multi-planar reformations (MPR) images. Datasets from 10 patients scanned with CBCT were used to create two types of images: 1. axial, coronal, and sagittal MPR images and 2. 3D surface models. Eleven observers identified 22 cephalometric landmarks on 3D surface models first and then using 3D in combination with MPR images twice independently. Tracing time was recorded in both methods. Precision was defined as the absolute difference between an observer's repeated measurements and the mean of all measurements per landmark. Inter- and intra-observer agreements were defined as the absolute difference of the observers' measurements from each other and from their repeated measurements averaged over all landmarks, respectively. The precision of measurements ranged between 0.29 ± 0.17 and 2.82 ± 7.53. Adding MPR alongside, 3D surfaces improved the precision of tracing for 15 of 22 of the landmark but it took on average twice as much time. Mean time required to trace one patient was 6:03 ± 2:48 and 10:41 ± 4:01 minutes for 3D and 3D + MPR, respectively (P = 0.0001).

Detecting bone loss along dental implants by subtraction of panoramic radiographs.

OBJECTIVES: To test an extended subtraction method for measuring changes in bone along dental implants depicted on non-standardized panoramic radiographs. MATERIAL AND METHODS: The measuring method consisted of a subtraction module extended with modules correcting gray values, correcting geometry and defining the region of interest mesial and distal of dental implants. It was applied to an archive of panoramic radiographs of implant patients who had been monitored up to 16 years. RESULTS: Significant loss of gray value was demonstrated at a constant rate of 0.6 units per month throughout the study. This indicates gradual bone loss on the mesial and/or distal sides of the implants. Females were found to lose bone at a higher rate than males. Smokers and non-smokers, and various implant strategies yielded the same rate of bone loss. CONCLUSIONS: The measuring method is a helpful tool to monitor changes around implants even when non-standardized radiographs are being used. Whereas changes of marginal bone level are increased five to eight times during the first year after surgery, the present method shows gradual loss of bone during 15 years after surgery.

Dementia in a woman with Prader-Willi syndrome.

We report on a 58-year-old woman with Prader-Willi syndrome (PWS) and dementia. This case report illustrates a new research area in older adults with PWS. Dementia might be associated with PWS. In the case of dementia, more clinical studies are warranted to observe whether premature Alzheimer changes or indications of other dementia forms indeed occur more prevalent in people with PWS.