Impact of particle size and morphology on zinc cation adsorption by hydroxyapatite and dentifrice containing hydroxyapatite / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the influence of particle size and morphology on zinc cation adsorption by hydroxyapatite (HA) and dentifrice containing HA.</p><p><b>METHODS</b>Four HAs with different particle sizes and morphologies, HA-containing dentifrice and blank dentifrice were prepared into suspensions of serial concentrations. Zinc ion solutions with an initial concentration of 10 mg/L was mixed with the suspensions and kept for 24 h for adsorption reaction. The zinc ion concentration in the supernatant was measured by inductively coupled plasma emission spectrometer and the sorption rate of zinc ion was calculated.</p><p><b>RESULTS</b>HA and HA-containing dentifrice with various particle sizes and morphologies were all capable of absorbing zinc ions from simulated waste water, and the adsorption rate of HA-containing dentifrice was 3%-10% higher than that of HA. HA with a particle size of 12 µm and a spherical morphology showed the strongest adsorption ability, followed by short bar-shaped HA with a particle size of 30 µm. Both Langmuir and Freundlich equation could simulate the sorption processes of HA dentifrice, while only Langmuir equation could simulate the sorption processes of HA.</p><p><b>CONCLUSION</b>Incorporation of HA in dentifrice can enhance zinc ion adsorption capacity of the material. The particle size and morphology of HA both affect the adsorption of zinc ions, and 12-µm HA particle with a spherical morphology has the best adsorption ability.</p>

Comparative study of DSC-PWI and 3D-ASL in ischemic stroke patients / 华中科技大学学报（医学）（英德文版）

The purpose of this study was to quantitatively analyze the relationship between three dimensional arterial spin labeling (3D-ASL) and dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI) in ischemic stroke patients. Thirty patients with ischemic stroke were included in this study. All subjects underwent routine magnetic resonance imaging scanning, diffusion weighted imaging (DWI), magnetic resonance angiography (MRA), 3D-ASL and DSC-PWI on a 3.0T MR scanner. Regions of interest (ROIs) were drawn on the cerebral blood flow (CBF) maps (derived from ASL) and multi-parametric DSC perfusion maps, and then, the absolute and relative values of ASL-CBF, DSC-derived CBF, and DSC-derived mean transit time (MTT) were calculated. The relationships between ASL and DSC parameters were analyzed using Pearson's correlation analysis. Receiver operative characteristic (ROC) curves were performed to define the thresholds of relative value of ASL-CBF (rASL) that could best predict DSC-CBF reduction and MTT prolongation. Relative ASL better correlated with CBF and MTT in the anterior circulation with the Pearson correlation coefficients (R) values being 0.611 (P<0.001) and-0.610 (P<0.001) respectively. ROC curves demonstrated that when rASL ≤0.585, the sensitivity, specificity and accuracy for predicting ROIs with rCBF<0.9 were 92.3%, 63.6% and 76.6% respectively. When rASL ≤0.952, the sensitivity, specificity and accuracy for predicting ROIs rMTT>1.0 were 75.7%, 89.2% and 87.8% respectively. ASL-CBF map has better linear correlations with DSC-derived parameters (DSC-CBF and MTT) in anterior circulation in ischemic stroke patients. Additionally, when rASL is lower than 0.585, it could predict DSC-CBF decrease with moderate accuracy. If rASL values range from 0.585 to 0.952, we just speculate the prolonged MTT.

Anatomic study of canal isthmuses of mandibular permanent incisors by micro-CT / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the anatomic feature of the canal isthmus of mandibular permanent incisors by Micro-CT.</p><p><b>METHODS</b>Thirty-three mandibular permanent incisors with two canals were selected through the radiograph in proximal view. These teeth were then scanned using Micro-CT and reconstructed. The scanning layer thickness was 20 microm. We observed the apical 6 mm of the 33 roots, and 300 sections were gained each tooth, giving a total of 9900 sections. The numbers of canals at each level in the apical 6 mm were recorded. The numbers of sections showing isthmuses at each level of the root canals were recorded too. Data were analyzed using the Chi-square statistic to test the null hypothesis that location of the sections in each of the apical 6 mm and presence of the isthmus were independent. The minimum root canal wall thickness was measured in each of the apical 6 mm of the roots.</p><p><b>RESULTS</b>Isthmuses were found to be present at all levels with prevalence from 10.0% to 85.5%. The Chi-square test indicated a significant difference in the distribution of isthmuses with section (P = 0.0O1). The incidence of isthmuses was higher at the apical 3-6 mm level, and the highest incidence (85.5%) was at 5 mm level. There were many more sections containing complete isthmuses (49.7%) than those containing partial isthmuses (4.5%). The thickness of the minimum root canal was less than 0.5 mm.</p><p><b>CONCLUSION</b>The mandibular incisors have a high incidence of isthmus and are narrow in proximal direction. Debridement of the isthmus is a major challenge during surgical and nonsurgical root canal treatment.</p>