Chitosan-phosphorylated chitosan polyelectrolyte complex hydrogel as an osteoblast carrier.

To simulate extra-cellular matrix, a novel three-dimensional scaffold of polyelectrolyte complex (PEC) hydrogel as an osteoblast carrier was synthesized. First, chitosan, a natural glycosaminoglycan, was modified by phosphorylation to obtain a water-soluble phosphorylated chitosan (P-content: 10.7 mass%). The PEC hydrogel was then formed from equal volumes of 0.173 mass% phosphorylated chitosan in water and 1 mass% chitosan in 1% (V/V) acetic acid solution. Rat osteoblasts were seeded in the hydrogel. The PEC hydrogel had a three-dimensional hierarchically-porous structure and good cytobiocompatibility for osteoblasts in vitro. It is concluded that the PEC hydrogel is a promising material as an osteoblast carrier.

Biomimetic mineralization of dentin induced by agarose gel loaded with calcium phosphate.

A novel biomimetic mineralization system was designed to induce a layer of hydroxyapatite on a demineralized dentin surface. This system was constructed as follows. A layer of 0.5% agarose gel containing 0.26M Na(2) HPO(4) was used to cover acid-etched dentin slices, followed by a layer of agarose gel without phosphate ions. Then a neutral 0.13M CaCl(2) solution was added onto the ion-free gel surface. The mineralization system (dentin-agarose gel containing phosphate ions-CaCl(2) solution) was kept in a water bath at 37°C, and the gel and CaCl(2) solution were replaced at various intervals. The results showed that the deposited hydroxyapatite crystals densely packed to each other, completely covered the dentin surface, and occluded the dentinal tubules after 10 days of biomimetic mineralization in vitro. Therefore, this method may provide the experimental basis for dentin remineralization and for a new method to treat dentin hypersensitivity and dental caries.

Comparisons of condylar movements with the functional occlusal clutch and tray clutch recording methods in CADIAX system.

AIM: The purpose of this study is to compare the effects of the two clutches on recording the condylar movement. METHODOLOGY: Ten subjects (6 women, 4 men; mean age 25.4 years) participated in the study. The mandibular movement, sagittal condylar inclination angle, and transversal condylar inclination angle of each subject were recorded with the CADIAX using the two clutches, respectively. The characteristics of the tracings of the protrusion, opening, and mediotrusion were analyzed with the t-test statistics at a = 0.05 level. The Kappa values were calculated for an assessment of the congruence of the tracings. RESULTS: The results showed that the contour, direction, and dimension of the tracings in the two clutches were approximately same, but the tracings determined by the functional occlusal clutch were more regular and congruent. In the group segment recorded with the tray clutch, opening/closing paths of one subject showed crossed and time curves of three subjects appeared peak-like changes of velocity, but none were statistically different (P>0.05). CONCLUSION: The research suggests that the functional occlusal clutch should be preferred in the evaluation of the mandibular function, as the tracings with the tray clutch are more likely to produce false positive results.

In vitro odontoblast-like cell differentiation of cranial neural crest cells induced by fibroblast growth factor 8 and dentin non-collagen proteins.

During tooth development, cranial neural crest (CNC) cells represent a population of pluripotent stem cells that give rise to various dental tissues. This study aimed to investigate whether CNC cells could differentiate into odontoblast-like cells by in vitro induction. CNC cells were isolated from explants of cranial neural tubes and cultured in serum-free Dulbecco's modified Eagle's medium (DMEM)/F12 medium which contained fibroblast growth factor 8 (FGF8) and dentin non-collagen proteins (DNCP). The initiation of controlled differentiation was determined using histological assays, and the expression of specific gene phenotypes was detected using immunocytochemical staining and reverse transcription--polymerase chain reaction (RT--PCR). The first branchial arch phenotype of the CNC cells demonstrated negative Hoxa2 expression and positive vimentin expression in the presence of 100 ng/ml FGF8. Following DNCP induction, the CNC cells became bipolar, demonstrated high alkaline phosphatase (ALP) activity, and formed mineralized nodules. In addition, the expression of DSPP, DMP1, and collagen type I confirmed the odontoblast phenotype. The results indicate that the tissue-specific cellular differentiation (odontoblast-like cells) of early-stage embryonic-derived cells (such as CNC cells) can be induced by adult extracellular matrix proteins (such as DNCP). CNC cells may be used as a valuable cell model for research on dental tissue differentiation and regeneration.

[Evaluation of a model of temporomandibular disorders established by transzygomatic arch traction of the mandibular ramus in rabbits].

OBJECTIVE: To evaluate a model of temporomandibular disorders established by transzygomatic arch traction of the mandibular ramus in rabbits. METHODS: Fifteen adult New Zealand rabbits were subjected to traction in the postero-superior direction unilaterally using elastic force and six rabbits used as the control. Histopathologic change of the disc, joint space and cartilage was observed through Hematoxylin and Eosin staining. RESULTS: Anterior disc displacement or disc deformity in four experimental rabbits was observed on the traction side 2 weeks after operation. At 4 weeks, fibrous adhesions in joint compartment were found in five experimental rabbits. The condyles or articular eminences of some experimental rabbits showed irregularities on the cartilage surface. In the 6 th week, bad disc deformity in four rabbits and severe fibrous adhesions in five rabbits was observed on the traction side, and subchondralbone and calcified cartilage became irregular. In control group, All articular structures were normal. CONCLUSIONS: A animal model of temporomandibular disorders can be established by transzygomatic arch traction of the mandible.

[The distribution of collagen I, II, X and alkaline phosphatase in the development of condylar cartilage of fetal mouse mandible].

OBJECTIVE: The purpose of this study was to investigate the distribution of collagen I, II , X, alkaline phosphatase (ALP) and their roles during initiation of condylar cartilage of the fetal mouse. METHODS: Coronary sections of mandible of mouse embryo aged from 14th to 18th day were studied under light microscope after stained by immunohistochemical method with antibody of types I, II, X collagen and ALP. RESULTS: On the 14th day of mouse embryo, it was found that mesenchymal cells condensation continuous with the periosteum. Type I collagen and ALP were positive behind the terminal of the ossifying mandibular periosteum where future condylar will form. On the 15th day, positive staining for types I, II collagen was found in mesenchymal cells around hypertrophic cells and type X collagen was detected in hypertrophic cells. ALP was positive in both mesenchymal cells and hypertrophic cells. On the 16th day, type I collagen was observed from periosteal osteogenic cells and mesenchymal cells of the fibrous cell layer to the upper hypertrophic cell layer while Type II collagen was restricted from the lower polymorphic cell layer to the bottom of the hypertropic cell layer. Type X collagen was positive in the hypertrophic cell layer. ALP was positive in periosteal osteogenic cells and hypertrophic chondral cells, but not in the polymorphic cell layer. CONCLUSION: Development of condylar cartilage is different from that of limb bone. Types I, II, X collagen are expressed in the condylar chondrocyte on the early stage of endochondral ossification. The histology evidence supports the conjecture that condylar cartilage is derived from differentiated mesenchymal cells of the preperiosteum or periosteum of the mandible where ALP is positively expressed.