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The balanced development of compulsory education, with a focus on the goal of educational equality, is both a matter of policy orientation and a practical educational issue. At present, people are mostly concerned with the unbalanced state of development of compulsory education, its causes, and issues regarding its administration. Various modes of production, policy choices, and institutional arrangements during different periods have been the practical, historical causes of differences in regional compulsory education, differences between urban and rural areas, and differences between schools. A direct consequence of the unbalanced development of compulsory education has been the emergence of irregularities in school selection. During the process of school selection, the strength of family and school social capital is increasingly influential, and it has increasingly negative effects: circumventing the policy of going to school near home, aggravating differences between families because of family and school social capital, and therefore damaging the prospect of educational equality. On this account, we present a constructive proposal for government policy to reduce the detrimental effects of social capital by means of reasonable policy choices and institutional arrangements. With prerequisite balanced allocation of school resources for compulsory education, the government reduces the role that family and social capital play in school selection and constructs a benignly competitive environment wherein school social capital works to placate social issues aroused by the intervention of the social capital of families and schools in school selection.

The purpose of this study was to investigate the three-dimensional displacement of the cantilever fixed partial denture (CFPD) under an oblique loading. One Beagle dog was used in this experiment. The CFPD, which used the second premolar and the first molar as abutments and the second molar as pontic, was made in vitro fresh mandible of the Beagle dog, and the digital laser speckle (DLS) technique was employed to measure the three-dimensional displacement of the CFPD under the oblique loading for the first time. We found that when an oblique loading was exerted on the pontic, the displacement of CFPD was the greatest, and the displacement of the abutment near the pontic was smaller than that of the pontic but greater than that of the abutment far from the pontic. We also found that when an oblique loading was exerted on the abutment, the displacement of the directly loaded abutment was greater than that of the other abutment and the pontic. Under the oblique loading, the displacement increased with increasing of load. The experiment demonstrated that it would be advisable for the clinicians to avoid oblique loading, especially the oblique loading of the pontic when using the CPDF. The DLS technique may be one kind of methods for measuring the three-dimensional displacements of the small and irregular objects.

All-ceramic crowns and bridges have been widely used for dental restorations owing to their excellent functionality, aesthetics and biocompatibility. However, the premature clinical failure of all-ceramic crowns and bridges may easily occur when they are subjected to the complex environment of oral cavity. In the oral environment, all-ceramic materials are prone to aging. Aging can lead all-ceramic materials to change color, to lower bending strength, and to reduce anti-fracture toughness. There are many factors affecting the aging of the all-ceramic materials, for example, the grain size, the type of stabilizer, the residual stress and the water environment. In order to analyze the aging behavior, to optimize the design of all-ceramic crowns and bridges, and to evaluate the reliability and durability, we review in this paper recent research progress of aging behavior for all-ceramics restoration materials.

The influence of alumina addition on mechanical behavior and fracture properties of all-ceramics zirconia dental materials was evaluated. Samples containing 0, 5, 10, 15 wt.% Al 2 O 3 particles were prepared by cold isostatic pressing (200 MPa) and sintered at 1500°C for 5 h. Commercial powders were investigated by bulk density and phase formation using Archimedes principle and X-ray diffraction (XRD). Bending strength and fracture load were determined at room temperature by three-point bending test. In order to study the fracture, we took points on the crack path under microscope, plotted points on coordinates and used software "Origin" to general fitting curves. Scanning electron microscopy (SEM) and atomic force microscope (AFM) were introduced to estimate the particle size of powders and observe the fracture surfaces. No density difference was observed for a given alumina content. The majority phases of ceramics were t-zirconia and α-alumina before breaking while m-zirconia, t-zirconia and α-alumina coexisted on the cross section of cracked samples. Zirconia containing 10% alumina had the best mechanical properties, the most tortuous crack propagation and the least obvious crack distribution. This observation may provide a reference for the materials selection, shape design and production process of all-ceramic crown and bridge.