Mega-city construction engineering to residential satisfaction: new insights from Yan' an of China.

Introduction: The contradiction among population, economy and urbanization has gradually intensified, and the Mountain Excavation and City Construction (MECC) project is one of the special solutions. Nevertheless, there are few comparative studies on the project index studies and effect of MECC projects on residential satisfaction. To remedy this deficiency, this study base on the Yan'an new district (YND) reconstruction project, attempting to analyze the specific influencing factors prerelocation and post-relocation from the perspective of residential satisfaction. Methods: After conducting reliability and validity analysis on each dimension, multiple linear regression and paired t-test were used to analyze and compare the questionnaire data. Results: The results show that the residential satisfaction index of the YND is indeed higher than that of the Yan'an old district (YOD). Concurrently, the decisive factors of residential satisfaction are also different. Specifically, the interpersonal communication, supporting facilities, community environment and economic income are significant in the YOD, but only the aspect of supporting facilities is negative significant. The supporting facilities, community environment, economic income and urban development are all positive significant in the YND. The satisfaction factors of middle-aged people in YOD and YND have the most significant differences, and the significance of each dimension is different. Discussion: The research results of this study provide a comparative perspective at the micro-level for evaluating China's urban construction, and it supplies specific directions for future urban development and the improvement of old cities through the new residential satisfaction index.

Effects of customized resin base on bonding strength of spherical self-ligating brackets.

PURPOSE: Fabricating resin bases has become an easy and economical method to achieve the customization of brackets. This study aimed to assess the effect of the resin base on bonding strength of spherical self-ligating brackets. METHODS: A defined amount of adhesive was bonded to the bracket base and constituted the new resin base. The thickness of the adhesive was measured and controlled at 0.5, 1.0, 1.5 and 2.0 mm, and a group without a resin base was used as a control. Sixty extracted human premolars were randomly divided into five groups. The brackets in each group were bonded to the specimen, and debonding tests were conducted. The shear bond strength (SBS) was calculated according to the measured debonding force in relation to the base area. The adhesive remnant index (ARI) score and the residual location of the fractured resin base were recorded. Enamel damage was also analyzed by scanning electron microscopy. After assessing for data normality and homogeneity, statistical comparisons between the groups and correlations among parameters were determined. P < 0.05 was regarded as significant. RESULTS: The correlation analysis revealed an inverse correlation between the resin base thickness and the SBS (Coeff = -0.719, P < 0.01). The highest SBS was 9.33 MPa, in the control group, which was significantly greater than the lowest SBS (6.03 MPa), in the 2.0-mm group (P < 0.05). Multiple comparisons analysis revealed no differences in SBS between the 1.0-, 1.5- and 2.0-mm groups. Nonparametric analysis found that only the ARI score in the 0.5-mm group (2.92) was significantly different (P < 0.05) from that in the control group (1.25). As the thickness of the resin base increased, the fractured resin base tended to remain at the bracket base, and the risk of enamel damage decreased. CONCLUSIONS: As the thickness of the resin base increased, the bonding strength of the spherical bracket decreased. However, the required clinical bonding strength was still satisfied when the thickness was less than 2.0 mm. The existence of a resin base could protect the enamel surface from damage caused by debonding. The customization of spherical brackets by tailoring a resin base can be applied in clinical practice because of the clinically acceptable bonding strength.