The acrylic's design or the addition of internal orthodontic wire changes the resistance of orthodontic plates?

OBJECTIVE: Evaluate resistance of Hawley retainers in three different acrylic configurations in order to evaluate if its format or the addition of internal wire interferes in its resistance. MATERIAL AND METHOD: 45 Hawley retainers were fabricated, divided into three groups (n = 15): Group 1 - acrylic covering the entire hard palate, Group 2 - plate with relief at the deepest region of the palate, leaving it with a "U" conformation and Group 3 - similar to Group 2, with the addition of 0.7mm wire 2cm internally of the acrylic at the region of the palatine ridges. The compressive strength was tested in a universal mechanical testing machine (Stable Microsystems, London, United Kingdom), measuring the applied force until plate rupture occurred. The differences between the formats being compared by the Kruskal-Wallis test. The significance level was set at 5% (α = 0.05). RESULT: Group 1 showed the highest resistance, with a mean of about five times higher than Group 2 and three times higher than Group 3. CONCLUSION: acrylic reduction in dental retainer plates is directly related to the reduction of its compressive strength, the inclusion of orthodontic wire inside the acrylic increases the resistance of the plate, being a good alternative when more comfort is wanted for the patient without loss of the mechanical characteristics of the dental retainers.

Joining of C/SiC Composite and TC4 Alloy Using 70Ag28Cu2Ti Active Brazing Alloy

C/SiC composite and TC4 alloy were successfully brazed using 70Ag28Cu2Ti (wt. %) as filler metal at 820 °C~920 °C for 5 min ~30 min. The effects of brazing parameters on the microstructures, phase composition, shear strength of the brazed joints were investigated by SEM, XRD. The mechanical performances of the brazed joints were measured by a universal mechanical testing machine. The results show that successful joining of C/SiC composite and TC4 alloy owes to interfacial reactions between the brazing alloy and the parent materials, and resultantly produce TiC, Ti5Si3 and Ti-Cu serial compounds at the interfaces; the interfacial structure of the brazed joint is C/SiC composite / TiC / Ti5Si3 /Ag (s.s) +Cu (s.s) / TiCu2 / Ti3Cu4 / TiCu / Ti2Cu / TC4 from C/SiC composite side to TC4 alloy side; the maximum shear strength of the brazed joint is 53.3 MPa at 860°C for 10min.

Influence of Al-10RE Modification on Microstructure and Mechanical Properties of ZL203 Aluminum Alloy

The influence of Al-10RE addition, holding time and holding temperature on the microstructures and mechanical properties of ZL203 aluminum alloy has been studied respectively through using the optical microscope and the universal mechanical testing machine. The experimental results lead to the following conclusions. When Al-10RE addition is 1.0%-1.5%, the holding time is 15 minutes and the holding temperature is 730°C-750°C, the microstructure of Zl203 is perfect. With the increase of Al-10RE addition, the mechanical properties including tensile strength, elongation rate and hardness gradually increase. When the Al-10RE addition is 1.0%-1.5%, the mechanical properties reaches maximum. When the Al-10RE addition is above 1.5%, the mechanical properties decrease with the increase of Al-10RE addition.

Role of Biopolymer in Nacre Heated in Nitrogen Atmosphere

Nacre is one of the most attractive biological materials for its superior mechanical property which is mainly due to the “brick-mortar” microstructure. Nacre samples are heated in N2 atmosphere at 200°C, 400°C and 600°C, separately. The microstructures of the fresh and heated samples are characterized by SEM and XRD, and the three-point bending strengths of these samples are tested by universal mechanical testing machine. TG-DSC curves are performed on the fresh nacre and the demineralized one. The results show that biopolymer plays important roles in maintaining the microstructure, toughening mechanism and the phase transformation of aragonite.

Influence of Quenching Parameters on Mechanical Properties of 7075 Aluminum Alloy

By using the universal mechanical testing machine and SEM, the influence of quenching parameters on the mechanical properties of 7075 aluminum alloy has been studied, and the optimal quenching parameters have been got. The experimental results show that the temperature range of the quenching treatment is too wide. However, the over-burning will occur when the temperature is above 490°C. So the optimal quenching temperature is from 465°C to 475°C. The water temperature and the transfer time are below 40°C and 30s, respectively. The time interval between the quenching and aging treatment is found to have little influence on the mechanical properties of 7075 aluminum alloys.

Study of the Bonding Property between Flanges and Web Plates of Wood I-Joist

Wood I-joists is a kind of wood-based engineering material which was widely used in wood construction. As it is in fact, the property of I-joists are influenced not only by normal stress but also by a part of shear stress when they are taking into application. In this study, the effects of different factors were evaluated on the tensile property of the wood I-joists. The factors include the depth of the tanks on the flanges, the length of joint and different kinds of flanges. The method of control test was used in the process of the experiment design, and tensile shear test were taken during the experiment at the aim of testing the bonding property of the I-joists using a universal mechanical testing machine. Ultimately, it has been discovered that the factor of depth of the tanks and the length of the joint influence the bonding property mostly. So this paper offers the optimal fabrication technology of the I-joists to make it is possible for the increase of reliability when wood I-joists are taken into application.

Optimization Design of the Bonding Property between Flanges and Web Plates of Wood I-Joists

Wood I-joists is a kind of wood-based engineering material which was widely used in wood construction. As it is in fact, the property of I-joists are influenced not only by shear stress but also by a part of normal stress when they are taking into application. In this study, the effects of different factors were evaluated on the tensile property of the wood I-joists. The factors include the depth of the tanks on the flanges, the amount of glue spread and adhesive type. The method of orthogonal test was used in the process of the experiment design, and tensile test were taken during the experiment at the aim of testing the property of the I-joists using a universal mechanical testing machine. Ultimately, it has been discovered that the factor of adhesive type is the most influential one in the three factors which had been listed. So this paper offers the optimal fabrication technology of the I-joists to make it is possible for the increase of reliability when wood I-joists are taken into application.

Porous Scaffold of n-HA/PA66/CS for Tissue Regeneration

Nano-hydroxyapatite/polyamide66/chitosan composite (n-HA/PA66/CS) was prepared by a co-precipitation method and porous scaffolds from n-HA/PA66/CS composite were prepared by means of porogen–leaching method and were characterized by SEM, IR, XRD and universal mechanical testing machine. IR and XRD analyses showed that some chemical bonds existed between n-HA and polymers. Furthermore, macroporous structure of the scaffolds and mechanical strength were tested with a changed ratio of porogens (PVP/NaCl). When the ratio of PVP and NaCl is1: 6, the scaffold processed highly porosity and the pores were interconnected. The compressive strength of the scaffold, can meet the requirement of tissue regeneration.