Non-invasive imaging of the crystalline structure within a human tooth

The internal crystalline structure of a human molar tooth has been non-destructively imaged in cross-section using X-ray diffraction computed tomography. Diffraction signals from high-energy X-rays which have large attenuation lengths for hard biomaterials have been collected in a transmission geometry. Coupling this with a computed tomography data acquisition and mathematically reconstructing their spatial origins, diffraction patterns from every voxel within the tooth can be obtained. Using this method we have observed the spatial variations of some key material parameters including nanocrystallite size, organic content, lattice parameters, crystallographic preferred orientation and degree of orientation. We have also made a link between the spatial variations of the unit cell lattice parameters and the chemical make-up of the tooth. In addition, we have determined how the onset of tooth decay occurs through clear amorphization of the hydroxyapatite crystal, and we have been able to map the extent of decay within the tooth. The described method has strong prospects for non-destructive probing of mineralized biomaterials.     

Increase in central striatal dopamine transporters in patients with Shwachman–Diamond syndrome: Additional evidence of a brain phenotype

Patients with Shwachman–Diamond syndrome (SDS) do not only experience well‐described physical features like skeletal abnormalities and hematological dysfunctions, but recent studies also suggested attention and working memory deficits in SDS. Indeed, a recent structural magnetic resonance imaging (MRI) study demonstrated smaller brain regions in SDS. Regarding attention and working memory, however, an important role for the neurotransmitter dopamine is well established. Therefore, in this study we assessed in vivo dopamine transporters (DATs; a specific marker of dopaminergic cells expressed in nerve terminals) and performed structural MRI in SDS. In 6 and 5 young SDS patients, respectively, we were able to acquire DAT single photon emission computed tomography (SPECT) and MRI examinations, and the data were compared to age‐matched control data. Striatal DAT binding was significantly increased in SDS patients as compared to controls. In addition, we observed significantly smaller volumes particularly posteriorly and caudally located in the brain: the corpus callosum, brainstem, and cerebellum. Also the thalamus was smaller in SDS patients than in controls. In conclusion, our data replicate earlier findings on smaller brain regions in SDS. In addition, our novel molecular imaging data suggest that SDS patients may have a dysregulated dopaminergic system. These findings may be of relevance to increase our understanding of behavioral and cognitive deficits in SDS. © 2012 Wiley Periodicals, Inc.     

No Effect of Hole Geometry in Microfracture for Talar Osteochondral Defects

Background

Débridement and bone marrow stimulation is an effective treatment option for patients with talar osteochondral defects. However, whether surgical factors affect the success of microfracture treatment of talar osteochondral defects is not well characterized.

Questions/purposes

We hypothesized (1) holes that reach deeper into the bone marrow-filled trabecular bone allow for more hyaline-like repair; and (2) a larger number of holes with a smaller diameter result in more solid integration of the repair tissue, less need for new bone formation, and higher fill of the defect.

Methods

Talar osteochondral defects that were 6 mm in diameter were drilled bilaterally in 16 goats (32 samples). In eight goats, one defect was treated by drilling six 0.45-mm diameter holes in the defect 2 mm deep; in the remaining eight goats, six 0.45-mm diameter holes were punctured to a depth of 4 mm. All contralateral defects were treated with three 1.1-mm diameter holes 3 mm deep, mimicking the clinical situation, as internal controls. After 24 weeks, histologic analyses were performed using Masson-Goldner/Safranin-O sections scored using a modified O’Driscoll histologic score (scale, 0–22) and analyzed for osteoid deposition. Before histology, repair tissue quality and defect fill were assessed by calculating the mean attenuation repair/healthy cartilage ratio on Equilibrium Partitioning of an Ionic Contrast agent (EPIC) micro-CT (μCT) scans. Differences were analyzed by paired comparison and Mann-Whitney U tests.

Results

Significant differences were not present between the 2-mm and 4-mm deep hole groups for the median O’Driscoll score (p = 0.31) and the median of the μCT attenuation repair/healthy cartilage ratios (p = 0.61), nor between the 0.45-mm diameter and the 1.1-mm diameter holes in defect fill (p = 0.33), osteoid (p = 0.89), or structural integrity (p = 0.80).

Conclusions

The results indicate that the geometry of microfracture holes does not influence cartilage healing in the caprine talus.

Clinical Relevance

Bone marrow stimulation technique does not appear to be improved by changing the depth or diameter of the holes.