Fourier-transform infrared study on effects of ageing, oestrogen level and altered dietary loading on rat mandibular condylar cartilage.

OBJECTIVE: Mandibular condylar cartilage (MCC) of the rat was examined with the Fourier-transform infrared (FITR) spectroscopic imaging to study the effects of ageing, oestrogen level and altered dietary loading on the structure of MCC. MATERIALS AND METHODS: The Sprague-Dawley rats (n = 96) aged 5 and 14 months were divided into 12 subgroups according to age, oestrogen status (ovariectomized [OVX], non-ovariectomized [non-OVX)]) and diet (hard, normal, soft). Specimens of the MCC were examined with FTIR spectroscopic imaging to quantify the distribution of collagens and proteoglycans. MCC was divided sagittally into three segments: anterior, most superior and posterior. From each segment, the collagen and proteoglycan contents at different depths of cartilage were statistically compared between the groups using an N-way analysis of variance (ANOVA). RESULTS: The amount of collagen content was significantly associated with old age in the deep layer of the anterior segment and in the middle layer of the posterior segment of MCC. In the deep layer of the most superior segment, the collagen content also increased with ageing. The amount of proteoglycan content increased significantly when dietary loading increased, and the oestrogen level decreased in the deep layer of the most superior segment of MCC. CONCLUSION: Ageing, oestrogen level and altered dietary loading have a significant effect on the location and content of collagens and proteoglycans of rat MCC. Ageing significantly increased the amount of collagen content in the superior and posterior segments, being highest in the older soft-diet rats. Decreased oestrogen levels and increased dietary loading increased the amount of proteoglycan content.

Mineralization of dental tissues and caries lesions detailed with Raman microspectroscopic imaging.

Dental caries is the most common oral disease that causes demineralization of the enamel and later of the dentin. Depth-wise assessment of the demineralization process could be used to help in treatment planning. In this study, we aimed to provide baseline information for the development of a Raman probe by characterizing the mineral composition of the dental tissues from large composition maps (6 × 3 mm2 with 15 µm step size) using Raman microspectroscopy. Ten human wisdom teeth with different stages of dental caries lesions were examined. All of the teeth were cut in half at representative locations of the caries lesions and then imaged with a Raman imaging microscope. The pre-processed spectral maps were combined into a single data matrix, and the spectra of the enamel, dentin, and caries were identified by K-means cluster analysis. Our results showed that unsupervised identification of dental caries is possible with the K-means clustering. The compositional analysis revealed that the carious lesions are less mineralized than the healthy enamel, and when the lesions extend into the dentin, they are even less mineralized. Furthermore, there were more carbonate imperfections in the mineral crystal lattice of the caries tissues than in healthy tissues. Interestingly, we observed gradients in the sound enamel showing higher mineralization and greater mineral crystal perfection towards the tooth surface. To conclude, our results provide a baseline for the methodological development aimed at clinical diagnostics for the early detection of active caries lesions.

Clinical Super-Resolution Computed Tomography of Bone Microstructure: Application in Musculoskeletal and Dental Imaging.

PURPOSE: Clinical cone-beam computed tomography (CBCT) devices are limited to imaging features of half a millimeter in size and cannot quantify the tissue microstructure. We demonstrate a robust deep-learning method for enhancing clinical CT images, only requiring a limited set of easy-to-acquire training data. METHODS: Knee tissue from five cadavers and six total knee replacement patients, and 14 teeth from eight patients were scanned using laboratory CT as training data for the developed super-resolution (SR) technique. The method was benchmarked against ex vivo test set, 52 osteochondral samples are imaged with clinical and laboratory CT. A quality assurance phantom was imaged with clinical CT to quantify the technical image quality. To visually assess the clinical image quality, musculoskeletal and maxillofacial CBCT studies were enhanced with SR and contrasted to interpolated images. A dental radiologist and surgeon reviewed the maxillofacial images. RESULTS: The SR models predicted the bone morphological parameters on the ex vivo test set more accurately than conventional image processing. The phantom analysis confirmed higher spatial resolution on the SR images than interpolation, but image grayscales were modified. Musculoskeletal and maxillofacial CBCT images showed more details on SR than interpolation; however, artifacts were observed near the crown of the teeth. The readers assessed mediocre overall scores for both SR and interpolation. The source code and pretrained networks are publicly available. CONCLUSION: Model training with laboratory modalities could push the resolution limit beyond state-of-the-art clinical musculoskeletal and dental CBCT. A larger maxillofacial training dataset is recommended for dental applications.

Magnetic-Responsive Carbon Nanotubes Composite Scaffolds for Chondrogenic Tissue Engineering.

The demand for engineered scaffolds capable of delivering multiple cues to cells continues to grow as the interplay between cell fate with microenvironmental and external cues is revealed. Emphasis has been given to develop stimuli-responsive scaffolds. These scaffolds are designed to sense an external stimulus triggering a specific response (e.g., change in the microenvironment, release therapeutics, etc.) and then initiate/modulate a desired biofunction. Here, magnetic-responsive carboxylated multi-walled carbon nanotubes (cMWCNTs) are integrated into 3D collagen/polylactic acid (PLA) scaffold via a reproducible filtration-based method. The integrity and biomechanical performance of the collagen/PLA scaffolds are preserved after cMWCNT integration. In vitro safety assessment of cMWCNT/collagen/PLA scaffolds shows neither cytotoxicity effects nor macrophage pro-inflammatory response, supporting further in vitro studies. The cMWCNT/collagen/PLA scaffolds enhance chondrocytes metabolic activity while maintaining high cell viability and extracellular matrix (i.e., type II collagen and aggrecan) production. Comprehensive in vitro study applying static and pulsed magnetic field on seeded scaffolds shows no specific cell response in dependence with the applied field. This result is independent of the presence or absence of cMWCNT into the collagen/PLA scaffolds. Taken together, these findings provide additional evidence of the benefits to exploit the CNTs outstanding properties in the design of stimuli-responsive scaffolds.

Ability of ultrasound imaging to detect erosions in a bone phantom model.

OBJECTIVES: The authors examined the validity, interobserver reliability and interscanner variation in detecting bone erosions with ultrasonography using a custom-made phantom. METHODS: 21 bovine bones were used. Artificial erosions were made into 15 bones and six bones were left as controls. In the processed bones the numbers of erosions, their depths and widths varied between 1-7, 1-4 and 1.5-5 mm, respectively. Each bone was coated with polyvinyl alcohol cryogel to mimic overlying soft tissue and to hide the erosions. Four musculoskeletal sonography experts scanned the 21 blind-coded phantoms using one of the three sets of ultrasound equipment. Finally, quality assurance measurements of the ultrasound equipment was carried out using two additional bone samples. RESULTS: The sonographers detected the erosions successfully with ultrasound. The mean correlation coefficient for a correct result in terms of the number of erosions detected was 0.88 (range 0.75-0.975). The overall Cohen's kappa coefficient for interobserver agreement was 0.683 in terms of discrimination between healthy bones and bones with erosions. The different sets of equipment showed that their overall performance was equal. CONCLUSIONS: The sonographers had good correlations with the number of erosions and they were successful in separating healthy bones from bones with erosions. It seems that neither depth nor width is crucial but that in experimental conditions a 1.5 mm erosion width was the limit for the resolution with current ultrasound equipment. Ultrasound is a valid and reliable method of detecting cortical bone erosions in vitro, when the round erosion is at least 1 mm deep and 1.5 mm wide.

Effects of Estrogen Level, Dietary Loading, and Aging on Types I, II, and X Collagen Expression and Structure of Rat Mandibular Condylar Cartilage.

AIMS: To investigate how estrogen level, dietary loading, and aging affect cartilage structure and the expression of major collagens (types I, II, and X) in rat mandibular condylar cartilage (MCC). METHODS: A total of 96 outbred Sprague Dawley female rats were randomly divided into two groups by ovariectomy (OVX) at 7 weeks old. One week later, the rats in each group were further divided into three subgroups on the basis of food hardness: hard food (diet board), normal food (pellet), and soft food (powder). The rats were sacrificed at the age of 5 or 14 months. The thickness of the fibrous, proliferative, and chondroblastic layers of the mandibular condylar cartilage were measured after toluidine blue staining. Immunohistochemical analysis was performed to evaluate the expression levels of types I, II, and X collagen. A linear regression model was used to investigate the main factors affecting changes in thickness and collagen expression. RESULTS: The expression levels of types II and X collagen were decreased by ovarian estrogen deficiency and increased by dietary loading. Increased dietary loading was the main factor affecting an increase in thickness of the cartilage layers, while aging was the main factor affecting a decrease in thickness of the fibrous layer. A significant age-related increase was found in the expression of type I collagen. There was some degree of interaction between aging and dietary loading that affected the thickness of the chondroblastic layer and the expression of type X collagen. CONCLUSION: The physiologic level of estrogen plays a role in MCC development by promoting the expression of types II and X collagen. Dietary loading is essential to increase the expression of types II and X collagen, as well as the thickness of cellular layers, to maintain the integrity of the MCC. Aging seems to reduce the ability of the MCC to withstand occlusal loading.