Implant-abutment assemblies are usually subject to long-term cyclic loading. To evaluate the dynamic fatigue performance of implant-abutment assemblies with different tightening torque values, thirty implant-abutment assemblies (Zimmer Dental, Carlsbad, CA, USA) were randomly assigned to three tightening groups (24 Ncm; 30 Ncm; 36 Ncm), each consisted of 10 implants. Five specimens from each group were unscrewed, and their reverse torque values recorded. The remaining specimens were subjected to a load between 30N～300N at a loading frequency of 15 Hz for 5×10 6 cycles. After fatigue tests, residual reverse torque values were recorded if available. In the 24 Ncm tightening group, all the implants fractured at the first outer thread of the implant after fatigue loading, with fatigue crack propagation at the fractured surface showed by SEM observation. For the 30 Ncm and 36 Ncm tightening groups, a statistical significant difference (p<0.05) between the unloaded and loaded groups was revealed. Compared with the unloaded specimens, the specimens went through fatigue loading had decreased reverse torque values. It was demonstrated that insufficient torque will lead to poor fatigue performance of dental implant-abutment assemblies and abutment screws should be tightened to the torque recommended by the manufacturer. It was also concluded that fatigue loading would lead to preload loss.

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Since the twenty-first century, new things are emerging in the market economy; the Internet is one of them. Internet of things (IoT) is a new thing, which combines computer, Internet, and mobile communication network after the third wave of information industry, the development of huge application prospect, has been listed as one of the five emerging strategic industries. With the rapid development of digital technology and market economy, to accelerate the competition in the market economy, intense competition in IoT industry also exists. Effect of human resource management to a certain extent determines the strength of the market competitiveness of an enterprise; the research about human resource management of the IoT industry is carried out in this paper, by analysis of the basic characteristics of the Internet industry and combining Internet enterprise competitiveness, and it is directly related to human resource of a number of factors and applies the AHP method to establish the Internet enterprise human resources management quality and the effect of the evaluation model. Finally, an IoT enterprise is taken as the study object, the human resources management quality assessment model studied in this paper is used to evaluate enterprise’s human resources management, and its existing human resources management strategy and its optimization are studied, which provide certain theory support to enhance its market competitiveness.

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