[Correction of the projection center of rotation based on the sinogram using translation matching method].

The accurate position of the center of rotation (COR) is a key factor to ensure the quality of computed tomography (CT) reconstructed images. The classic cross-correlation matching algorithm can not satisfy the requirements of high-quality CT imaging when the projection angle is 0 and 180°, and thus needs to be improved and innovated. In this study, considering the symmetric characteristic of the 0° and flipped 180° projection data in sinogram, a novel COR correction algorithm based on the translation and match of the 0° and 180° projection data was proposed. The OTSU method was applied to reduce noise on the background, and the minimum offset of COR was quantified using the L1-norm, and then a precise COR was obtained for the image correction and reconstruction. The Sheep-Logan simulation model with random gradients and Gaussian noise and the real male SD rats samples which contained the heterogenous tooth image and the homogenous liver image, were adopted to verify the performance of the new algorithm and the cross-correlation matching algorithm. The results show that the proposed algorithm has better robustness and higher accuracy of the correction (when the sampled data is from 10% to 50% of the full projection data, the COR value can still be measured accurately using the proposed algorithm) with less computational burden compared with the cross-correlation matching algorithm, and it is able to significantly improve the quality of the reconstructed images.

Biomimetic remineralization of demineralized enamel with nano-complexes of phosphorylated chitosan and amorphous calcium phosphate.

Remineralization of enamel plays a crucial role in the progression of carious process and the management of early caries lesion. Based on the influence of phosphorylated proteins in biomineralization, the objective of this study was to synthesize nano-complexes of phosphorylated chitosan and amorphous calcium phosphate (Pchi-ACP), and evaluate their ability to remineralize enamel subsurface lesions in vitro. Pchi was synthesized using a previously established chemical method. The biomimetic remineralizing solution containing nano-complexes of Pchi-ACP was prepared by adding CaCl2 and K2HPO4 into Pchi-ACP solution (0.5 % w/v) in sequence. The final concentrations of calcium and phosphate ions were 10 and 6 mM, respectively. The nano-complexes of Pchi-ACP were characterized by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). During testing the enamel lesions were treated with Pchi-ACP and fluoridated remineralizing solutions, respectively. The remineralizing of enamel lesions was examined with field emission electron microscope (FE-SEM) and Micro-CT. ACP was stabilized by Pchi to form nano-complexes that were soluble in water. The size of Pchi-ACP nano-complexes particles was determined to be less than 50 nm. XRD and SAED results confirmed their amorphous phases. FE-SEM and Micro-CT results showed that the remineralizing effect of Pchi-ACP on enamel lesions was similar to that of fluoride. However, the remineralizing rate of Pchi-ACP treatment was significantly higher than that of fluoride treatment (P < 0.05). This study highlighted the potential of nanoparticles functionalized with a natural analogue involved in biomineralization, to remineralize early enamel caries.

Oriented and Ordered Biomimetic Remineralization of the Surface of Demineralized Dental Enamel Using HAP@ACP Nanoparticles Guided by Glycine.

Achieving oriented and ordered remineralization on the surface of demineralized dental enamel, thereby restoring the satisfactory mechanical properties approaching those of sound enamel, is still a challenge for dentists. To mimic the natural biomineralization approach for enamel remineralization, the biological process of enamel development proteins, such as amelogenin, was simulated in this study. In this work, carboxymethyl chitosan (CMC) conjugated with alendronate (ALN) was applied to stabilize amorphous calcium phosphate (ACP) to form CMC/ACP nanoparticles. Sodium hypochlorite (NaClO) functioned as the protease which decompose amelogenin in vivo to degrade the CMC-ALN matrix and generate HAP@ACP core-shell nanoparticles. Finally, when guided by 10 mM glycine (Gly), HAP@ACP nanoparticles can arrange orderly and subsequently transform from an amorphous phase to well-ordered rod-like apatite crystals to achieve oriented and ordered biomimetic remineralization on acid-etched enamel surfaces. This biomimetic remineralization process is achieved through the oriented attachment (OA) of nanoparticles based on non-classical crystallization theory. These results indicate that finding and developing analogues of natural proteins such as amelogenin involved in the biomineralization by natural macromolecular polymers and imitating the process of biomineralization would be an effective strategy for enamel remineralization. Furthermore, this method represents a promising method for the management of early caries in minimal invasive dentistry (MID).

Biomimetic remineralization of demineralized dentine using scaffold of CMC/ACP nanocomplexes in an in vitro tooth model of deep caries.

Currently, it is still a tough task for dentists to remineralize dentine in deep caries. The aim of this study was to remineralize demineralized dentine in a tooth model of deep caries using nanocomplexes of carboxymethyl chitosan/amorphous calcium phosphate (CMC/ACP) based on mimicking the stabilizing effect of dentine matrix protein 1 (DMP1) on ACP in the biomineralization of dentine. The experimental results indicate that CMC can stabilize ACP to form nanocomplexes of CMC/ACP, which is able to be processed into scaffolds by lyophilization. In the single-layer collagen model, ACP nanoparticles are released from scaffolds of CMC/ACP nanocomplexes dissolved and then infiltrate into collagen fibrils via the gap zones (40 nm) to accomplish intrafibrillar mineralization of collagen. With this method, the completely demineralized dentine was partially remineralized in the tooth mode. This is a bottom-up remineralizing strategy based on non-classical crystallization theory. Since nanocomplexes of CMC/ACP show a promising effect of remineralization on demineralized dentine via biomimetic strategy, thereby preserving dentinal tissue to the maximum extent possible, it would be a potential indirect pulp capping (IPC) material for the management of deep caries during vital pulp therapy based on the concept of minimally invasive dentistry (MID).

[Diffraction enhanced imaging of condylar cartilage of osteoarthritic rats].

OBJECTIVE: To observe the images of early lesions of condylar cartilage of osteoarthritic rats in synchrotron radiation diffraction enhanced imaging (DEI). METHODS: The animal model of temporomandibular joint osteoarthrosis was established in rat following the method of partial resection of the joint disc. The changes of osteoarthritic condylar cartilage in different pathological stages were observed by DEI and compared with those in situ histopathological sections. RESULTS: With DEI, straight and orbicular lines were detected in condylar cartilage 45 to 60 days after discs resection. The lines were confirmed by histopathology to be collagen degradation and tiny fissure formation inside the cartilage. CONCLUSIONS: DEI is capable of imaging the early stages of pathological changes of excised condylar cartilage such as collagen degradation and tiny fissure formation, and this technique is of potential value to clinical application.