Establishment of the micro-stress sensor measurement system for invisible aligner technique / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To design and build the micro-stress sensor measurement system for invisible aligner technique.</p><p><b>METHODS</b>A measurement system based on silicon-on-insulator piezoresistive stress sensor was developed. A four-point-bending based experimental apparatus was constructed to calibrate the piezoresistive coefficients of this stress sensor. A chemical-mechanical polishing process was developed for thinning the stress sensor dies. A packaging solution using flexible printed circuit to get signals out was designed.</p><p><b>RESULTS</b>The developed silicon stress sensor chip was 7.0 mm × 6.0 mm × 0.1 mm in size, and 13 sensor rosettes and 4 calibration rosettes were fabricated in one sensor. And a main testing PCB and a Lab View program were designed to carry out the automation measurement of the stress sensor. The stress state during the process was obtained through this test system. And measuered the stress of the 13 sensor unit.</p><p><b>CONCLUSIONS</b>A stress measurement system was established for measuring stress during orthodontic treatment with invisable aligner.</p>

Properties of NiTi wires with direct electric resistance heat treatment method in three-point bending tests / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the mechanical properties of Ni-Ti wires with direct electric resistance heat treatment (DERHT) method in three-point bending tests.</p><p><b>METHODS</b>Two superelastic Ni-Ti wires (wire A: Smart SE, wire B: SENTALLOY SE, 0.406 mm × 0.559 mm) and 2 heat-actived Ni-Ti wires (wire C: Smart SM, wire D: L&H TITAN, 0.406 mm × 0.559 mm) were selected. They were heat-treated using the DERHT method by a controlled electric current (6.36 A) applied for different period of time [0 (control), 1.0, 1.5, 2.0, 2.5 seconds). Then, a three-point bending test was performed under controlled temperature (37°C) to examine the relationships between the deflection and the load in the bending of wires.</p><p><b>RESULTS</b>After DERHT treatment, the plateau in the force-deflection curve of superelastic Ni-Ti wires and heat-activated Ni-Ti wires were increased. When the wires were heated for 2.0 seconds and deflected to 1.5 mm, the loading force of A, B, C and D Ni-Ti wires increased from (3.85 ± 0.11), (3.62 ± 0.07), (3.28 ± 0.09), (2.91 ± 0.23) N to (4.33 ± 0.07), (4.07 ± 0.05), (4.52 ± 0.08), (3.27 ± 0.15) N respectively.</p><p><b>CONCLUSIONS</b>DERHT method is very convenient for clinical use. It is possible to change the arch form and superelastic force of NiTi wires. The longer the heating time is, the more the superelastic characteristics of the wires are altered.</p>

Study on the thickness-change of different thickness thermoplastic materials after thermoforming and saliva immersion / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To survey and compare the thickness-change of different thickness thermoplastic materials under different test condition and make sure the relationship between the thickness-change and the material initial thickness in order to provide a guide in selecting the suitable thickness thermoplastic in practice.</p><p><b>METHODS</b>To choose Biolon, the thickness include 1.0 mm, 0.75 mm, 0.5 mm. Used Electron Vernier caliper to measure the thickness-change of different thickness thermoplastic materials under different processing mode. The data was analyzed by SPSS 10.0.</p><p><b>RESULTS</b>After thermoforming the thickness of thermoplastic became thinner, the thickness of Biolon 0.75 mm decreased by 0.14 mm, Biolon 1.0 mm decreased by 0.22 mm and Biolon 0.5 mm decreased by 0.14 mm. After saliva immersion the thickness became thicker. The thickness of Biolon 0.75 mm increased by 0.02 mm, Biolon 1.0 mm increased by 0.03 mm and Biolon 0.5 mm increased by 0.02 mm.</p><p><b>CONCLUSION</b>1)The influence of different processing mode to the thickness-change had relation to the material initial thickness. 2)The Biolon 0.75 mm had certain superiority in thickness stability compared to the homogeneous brand through the above research.</p>

Differential scanning calorimetry analyses of phase transformations in different nickel-titanium orthodontic wires / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used nickel-titanium (NiTi) orthodontic arch wires selected from several manufacturers.</p><p><b>METHODS</b>Differential scanning calorimetry (DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used NiTi alloys (types: 0.406 mm, 0.406 mm x 0.559 mm).</p><p><b>RESULTS</b>The austenite finish temperatures of A, B, D NiTi wires were 22.4 CT, 21.9 degrees C, 22.5 degrees C, respectively. No phase transformation was detected during oral temperature. It indicated that these types of NiTi wires did not possess shape memory property. For C and H NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The austenite finish temperatures of E, G and I NiTi wires were 34.3 degrees C, 36.6 degrees C, 38.5 degrees C, respectively, which were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting that the NiTi wires listed above had good shape memory effect. Although F NiTi wire also showed martensitic-austenitic structures at room temperature, its austenite finish temperature (61.5 degrees C) was much higher than oral temperature.</p><p><b>CONCLUSIONS</b>The transformation phase temperatures and transformation behavior were varied among different NiTi alloys, leading to variability in shape memory effect.</p>

Phase transformation analysis of varied nickel-titanium orthodontic wires / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The shape memory effect of nickel-titanium (NiTi) archwires is largely determined by the phase transition temperature. It is associated with a reversible transformation from martensite to austenite. The aim of this study was to characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used clinical NiTi orthodontic arch wires selected from several manufacturers.</p><p><b>METHODS</b>Differential scanning calorimetry (DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used clinical NiTi alloys (types: 0.40 mm (0.016 inch), 0.40 mm x 0.56 mm (0.016 inch x 0.022 inch)).</p><p><b>RESULTS</b>The austenite finish temperatures (Af) of 0.40 mm Smart, Ormco and 3M NiTi wires were lower than the room temperature, and no phase transformation was detected during oral temperature. Therefore, we predicted that these types of NiTi did not possess shape memory property. For 0.40 mm and 0.40 mm x 0.56 mm Youyan I NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The Af of 0.40 mm x 0.56 mm Smart, L&H, Youyan II Ni-Ti wires were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting the NiTi wires listed above have good shape memory effect. Although the 0.40 mm x 0.56 mm Damon CuNiTi wire showed martensitic-austenitic structures at oral temperature, its Af was much higher than the oral temperature. It means that transformation from martensite to austenite for this type of NiTi only finishes when oral temperature is above normal.</p><p><b>CONCLUSION</b>The phase transformation temperatures and transformation behavior varied among different commonly used NiTi orthodontic arch wires, leading to variability in shape memory effect.</p>