Osteoporosis Prediction Using Machine-Learned Optical Bone Densitometry Data.

Optical bone densitometry (OBD) has been developed for the early detection of osteoporosis. In recent years, machine learning (ML) techniques have been actively implemented for the areas of medical diagnosis and screening with the goal of improving diagnostic accuracy. The purpose of this study was to verify the feasibility of using the combination of OBD and ML techniques as a screening tool for osteoporosis. Dual energy X-ray absorptiometry (DXA) and OBD measurements were performed on 203 Thai subjects. From the OBD measurements and readily available demographic data, machine learning techniques were used to predict the T-score measured by the DXA. The T-score predicted using the Ridge regressor had a correlation of r = 0.512 with respect to the reference value. The predicted T-score also showed an AUC of 0.853 for discriminating individuals with osteoporosis. The results obtained suggest that the developed model is reliable enough to be used for screening for osteoporosis.

Attenuation Aß1-42-induced neurotoxicity in neuronal cell by 660nm and 810nm LED light irradiation.

Oligomeric amyloid-ß 1-42 (Aß1-42) has a close correlation with neurodegenerative disorder especially Alzheimer's disease (AD). It induces oxidative stress and mitochondrial damage in neurons. Therefore, it is used to generate AD-like in vitro model for studying neurotoxicity and neuroprotection against amyloid-ß. A low-level light therapy (LLLT) is a non-invasive method that has been used to treat several neurodegenerative disorders. In this study, the red wavelength (660nm) and near infrared wavelength (810nm) at energy densities of 1, 3, and 5 J/cm2 were used to modulate biochemical processes in the neural cells. The exposure of Aß1-42 resulted in cell death, increased intracellular reactive oxygen species (ROS), and retracted neurite outgrowth. We showed that both of LLLT wavelengths could protect neurons form Aß1-42-induced neurotoxicity in a biphasic manner. The treatment of LLLT at 3 J/cm2 potentially alleviated cell death and recovered neurite outgrowth. In addition, the treatment of LLLT following Aß1-42 exposure could attenuate the intracellular ROS generation and Ca2+ influx. Interestingly, both wavelengths could induce minimal level of ROS generation. However, they did not affect cell viability. In addition, LLLT also stimulated Ca2+ influx, but not altered mitochondrial membrane potential. This finding indicated LLLT may protect neurons through the stimulation of secondary signaling messengers such as ROS and Ca2+. The increase of these secondary messengers was in a functional level and did not harmful to the cells. These results suggested the use of LLLT as a tool to modulate the neuronal toxicity following Aß1-42 accumulation in AD's brain.

Optical bone densitometry insensitive to skin thickness.

Skin thickness, including the adipose layer, which varies from individual to individual, affects the bone density measurement using light. In this study, we proposed a method to measure skin thickness using light and to correct the bias caused by differences in skin thickness and verified the proposed method by experiments using a phantom. We measured simulated skin of different thicknesses and bovine trabecular bone of different bone mineral densities (BMDs) using an optical system consisting of lasers of 850 and 515 nm wavelengths, lenses, and slits. Although the slope of the light intensity distribution formed on the surface of the material when irradiated by the 850 nm laser is affected by the thickness of the skin phantom. The difference of the intensity distribution peaks (δy) between the 850 and 515 nm lasers was strongly correlated with the thickness of the skin phantom. The coefficient of determination between the measurements and the BMD was improved by correcting the 850 nm laser measurements with δy. This result suggests that the method is applicable to optical bone densitometry, which is insensitive to differences in skin thickness.

A Novel Alveolar Distractor Incorporating Nickel-Titanium Alloy Springs: A Preliminary In Vitro Study.

A new design of an alveolar distractor using nickel−titanium (NiTi) open-coil springs was developed and investigated to produce distraction forces against the tensile forces of porcine attached gingiva to simulate human gingiva. We subjected 15 mm long NiTi open-coil springs (Highland and ORMCO) with three levels of forces (light, medium and heavy) to mechanical testing in a 37 ± 1 °C water bath. Ten strips of porcine mandibular attached gingiva were subjected to tensile tests to determine the resistance force. The forces from the springs were compared with the tensile forces from the porcine attached gingiva. Data between groups were analyzed with independent-samples T-tests (p-value < 0.05). The tensile strength and the Young modulus were greater in buccal compared to lingual porcine attached gingiva. Compared to other spring dimensions and companies, forces generated from 0.014 × 0.036″ ORMCO springs were the highest and could overcome the tensile resistance from porcine attached gingiva over the longest distraction range of 1.6 mm. This preliminary in vitro study introduced a new design of an alveolar distractor incorporated with NiTi open-coil springs that could generate light and continuous forces to overcome the resistance from porcine attached gingiva.

Effect of fine particle shot peening on surface friction of stainless steel and ceramic bracket slots.

This study aims to compare the static friction of untreated and fine particle shot peening (FPSP) treated stainless steel and ceramic bracket slots. A total of 60 pieces of stainless steel and 60 pieces of ceramic brackets (Roth prescription, 0.022×0.028 in2) were divided into 3 groups: control (n=20), silica glass bead particle surface treatment (n=20) and stainless steel (SUS316L) particle surface treatment (n=20). Ten brackets of each group were combined with 0.019×0.025 in2 orthodontic stainless steel arch wires and were analyzed for static friction. The remaining 10 brackets of each group were tested for slot surface roughness and hardness. The result shows that stainless steel brackets treated with FPSP exhibited lower static friction, with smoother and harder surfaces than the control group (p<0.05). In contrast, treated ceramic brackets showed no difference from the control group in terms of static friction, roughness, and hardness (p>0.05).

The Effects of Temperature and Time of Heat Treatment on Thermo-Mechanical Properties of Custom-Made NiTi Orthodontic Closed Coil Springs.

Nickel-Titanium (NiTi) springs have been increasingly used in orthodontics; however, no optimum condition of heat treatment has been reported. Therefore, this research was conducted to determine the optimum heat-treatment temperature and duration for the fabrication of NiTi-closed coil springs by investigating their effects on thermo-mechanical properties. As-drawn straight NiTi wires of 0.2 mm diameter were used to fabricate closed coil springs of 0.9 mm lumen diameter. The springs were heat-treated at three different temperatures (400, 450, and 500 °C) with three different durations (20, 40, and 60 min). Electron Probe Micro-Analysis (EPMA) and Differential Scanning Calorimetry (DSC) were used to investigate element composition and thermo-mechanical properties, respectively. Custom-made NiTi closed coil springs composed of 49.41%-Ti and 50.57%-Ni by atomic weight, where their DSC curves of 500 °C presented the obvious endothermic and exothermic peaks, and the austenite finish temperature (Af) were approximately 25 °C. With increasing temperature, deactivation curves presented decreased plateau slopes generating higher superelastic ratios (SE ratios). At 500 °C, closed coil springs showed superelastic tendency with lower stress hysteresis. The thermo-mechanical properties were significantly influenced by heat-treatment temperature rather than duration. The optimum parameter appeared to be 500 °C for 40 min to produce appropriate force delivery levels, relatively low plateau slope, and lower hysteresis for orthodontic use.

Optical bone densitometry robust to variation of soft tissue using machine learning techniques: validation by Monte Carlo simulation.

SIGNIFICANCE: To achieve early detection of osteoporosis, a simple bone densitometry method using optics was proposed. However, individual differences in soft tissue structure and optical properties can cause errors in quantitative bone densitometry. Therefore, developing optical bone densitometry that is robust to soft tissue variations is important for the early detection of osteoporosis. AIM: The purpose of this study was to develop an optical bone densitometer that is insensitive to soft tissue, using Monte Carlo simulation and machine learning techniques, and to verify its feasibility. APPROACH: We propose a method to measure spatially resolved diffuse light from three directions of the biological tissue model and used machine learning techniques to predict bone density from these data. The three directions are backward, forward, and lateral to the direction of ballistic light irradiation. The method was validated using Monte Carlo simulations using synthetic biological tissue models with 1211 different random structural and optical properties. RESULTS: The results were computed after a 10-fold cross-validation. From the simulated optical data, the machine learning model predicted bone density with a coefficient of determination of 0.760. CONCLUSIONS: The optical bone densitometry method proposed in this study was found to be robust against individual differences in soft tissue.

Effects of the secondary shot in the double shot peening process on the residual compressive stress distribution of Ti-6Al-4V.

Double shot peening is the development of shot peening by shooting large media as a first shot and re-shooting again with smaller media as a second shot in order to achieve high residual compressive stress and hardness at the surface, while the in-depth effect can still be maintained. This research aims to examine the effect of media type and media size when used in the second shot of double shot peening on hardness, roughness, and residual stress to identify the suitable conditions and compare them with single shot peening, such as conventional shot peening and fine shot peening, which was used as the first shot and second shot. Ti-6Al-4V was used as the substrate material, while various diameter sizes of silica and SUS304 media were selected as the media for the second shot in the process. The results showed that in the case of the larger size of silica media in the second shot of double shot peening, the hardness and residual compressive stress on the surface clearly increased more than with the smaller media due to the higher Almen intensity, which affected impact energy. On the other hand, when shooting with SUS304 media as a second shot, the increment of residual compressive stress and hardness, including roughness reduction on the surface, showed less effect than was the case for silica media, due to the lower Almen intensity, which affected the impact energy transfer. This research found that the condition of shooting with 80 µm of silica media as the second shot could generate the highest hardness and residual compressive stress on the surface, which increased by 14% and 53%, respectively, while roughness was decreased by 20% when compared with single shot peening.

Quantitative Strengthening Evaluation of Powder Metallurgy Titanium Alloys with Substitutional Zr and Interstitial O Solutes via Homogenization Heat Treatment.

The decomposition behavior of ZrO2 particles and uniform distribution of Zr and O solutes were investigated by employing in situ scanning electron microscope-electron backscatter diffraction (SEM-EBSD) analysis and thermogravimetric-differential thermal analysis (TG-DTA) to optimize the process conditions in preparing Ti-Zr-O alloys from the pre-mixed pure Ti powder and ZrO2 particles. The extruded Ti-Zr-O alloys via homogenization and water-quenching treatment were found to have a uniform distribution of Zr and O solutes in the matrix and also showed a remarkable improvement in the mechanical properties, for example, the yield stress of Ti-3 wt.% ZrO2 sample (1144.5 MPa) is about 2.5 times more than the amount of yield stress of pure Ti (471.4 MPa). Furthermore, the oxygen solid-solution was dominant in the yield stress increment, and the experimental data agreed well with the calculation results estimated using the Hall-Petch equation and Labusch model.

Influence of Mouthwash Rinsing on the Mechanical Properties of Polymeric Ligature Ties Used for Dental Applications.

Mouthwashes are used during dental treatments to mitigate the complications caused by poor oral hygiene. However, these solutions also affect the properties of dental appliances, including those used in orthodontics. This point has been investigated in this study focusing on the changes in mechanical properties of polymeric orthodontic ligature ties. Commercial ties from four brands were characterized in terms of their maximum forces and displacement, delivery forces, molecular structures, and microscopic morphology. These properties were compared against the ties, which were rinsed with commercial mouthwashes from three manufacturers. The results showed that mouthwash rinsing significantly reduced the maximum bearable forces of ligature ties by up to 73.1%, whereas the reduction in their maximum displacement was up to 74.5% across all tested brands. Significant changes in microscopic morphology of ligature ties were observed after mouthwash rinsing, but not their molecular structure. Furthermore, mouthwash rinsing also reduced the delivery forces from ligature ties by between 20.9 and 32.9% at their first deformation cycle. It can be concluded from this study that mouthwashes have significant impact on the mechanical properties of polymeric orthodontic ligature ties and could also potentially affect the overall efficacy of orthodontic and other dental treatments.

Comparison of cold-hardening bending and direct electric resistance heat treatment on the mechanical properties and transformation temperature of NiTi archwire: An in vitro study.

OBJECTIVES: The aim of this investigation was (1) to compare the effects of cold-hardening bending and direct electric resistance heat treatment (DERHT) methods; and (2) to compare the effects of offsets and angulations on the mechanical properties and thermal analysis of NiTi alloy archwire. METHODS: Nickel-titanium (NiTi) archwires (Ormco, Glendora, CA), 0.016×0.022-inch, were bent by cold-hardening bending and DERHT methods into 1-mm, 2-mm, or 3-mm offset for a 3-point bending test, and at angles of 30°, 45°, or 60° to the horizontal plane for testing the change in transformation temperature (Af) measured by differential scanning calorimetry (DSC). The data were analysed using ANOVA followed by the Scheffe post-hoc test. RESULTS: The 3-point bending test results of the cold-hardening bending and DERHT methods were not significantly different between the 1-mm, 2-mm and 3-mm offset groups (95% CI: -0.05 to 0.97; P=0.082, 95% CI: -0.65 to 0.74; P=0.983 and 95% CI: -0.61 to 0.98; P=0.813, respectively). Increasing the offset resulted in a significantly decreased force in the 3-point bending test (P<0.001). The Af temperatures of the cold-hardening bending and DERHT methods were not significantly different for the 30°, 45°, and 60° bending angulations (95% CI: -1.93 to 1.39; P=0.876, 95% CI: -1.2 to 0.87; P=0.878, 95% CI: -2.24 to 1.18; P=0.636, respectively). Af temperatures were not influenced by different bending angulations. CONCLUSIONS: NiTi archwire shape can be modified by using both cold-hardening and DERHT bending methods, because the mechanical properties and Af temperature are not affected. However, the bending distance has an effect on the mechanical properties.

Comparison of friction forces between stainless orthodontic steel brackets and TiNi wires in wet and dry conditions.

In sliding mechanics, frictional force is an important counter-balancing element to orthodontic tooth movement, which must be controlled in order to allow application of light continuous forces. The purpose of this study was to compare the frictional forces between a stainless steel bracket and five different wire alloys under dry and wet (artificial saliva) conditions. TiNi, TiNiCu, TiNiCo, commercial wires A and commercial wires B with equal dimensions of 0.016×0.022'' were tested in this experiment. The stainless steel bracket was chosen with a slot dimension of 0.022''. Micro-hardness of the wires was measured by the Vickers micro-hardness test. Surface topography of wires was measured by an optical microscope and quantified using surface roughness testing. Static and kinetic friction forces were measured using a custom-designed apparatus, with a 3-mm stretch of wire alloy at a crosshead speed of 1mm/min. The static and dynamic frictions in the wet condition tended to decrease more slowly than those in the dry condition. Therefore, the friction of TiNiCu and commercial wires B would increase. Moreover, these results were associated with scarred surfaces, i.e. the increase in friction would result in a larger bracket microfracture. From the results, it is seen that copper addition resulted in an increase in friction under both wet and dry conditions. However, the friction in the wet condition was less than that in dry condition due to the lubricating effect of artificial saliva.

Improvement of mechanical and biological properties of TiNi alloys by addition of Cu and Co to orthodontic archwires.

The purpose of this study was to investigate improved performances of TiNi in order to promote tooth movement. Special attention was paid to the effect on the clinical properties of TiNi of adding Cu and Co to this alloy. Ti49.4Ni50.6, Ti49Ni46Cu5 and Ti50Ni47Co3 (at %) alloys were prepared. Specimens were cold-rolled at 30% reduction and heat-treated at 400°C for 60min. Then, the test results were compared with two types of commercial archwires. The findings showed that superelasticity properties were confirmed in the manufactured commercial alloys at mouth temperature. The difference of stress plateau in TiNi, TiNiCo and commercial wires B at 25°C changed significantly at various testing temperatures due to the combination of martensite and austenite phases. At certain temperatures the alloys exhibited zero recovery stress at 2% strain and consequently produced zero activation force for moving teeth. The corrosion test showed that the addition of Cu and Co to TiNi alloys generates an increase in corrosion potential (Ecorr) and corrosion current densities (Icorr). Finally, we observed that addition of Cu and Co improved cell viability. We conclude that addition of an appropriate amount of a third alloying element can help enhance the performances of TiNi orthodontic archwires.

The effect of light-emitting diode irradiation at different wavelengths on calcification of osteoblast-like cells in 3D culture.

This study aimed to investigate the effect of four different light-emitting diode (LED) wavelengths on calcification and proliferation of osteoblast-like cells in vitro. MC3T3-E1 cells were seeded within three-dimensional collagen scaffolds and irradiated daily by LED light with peak emission wavelengths of 630-, 680-, 760- and 830-nm at constant fluency of 3.1 J/cm(2) (irradiance intensity 2 mW/cm(2)). Cultures were measured for calcium content at day 0, 7, 14, 21, 28, 35 and 42. The significant enhancement in calcium content was observed at the early stage of culture (days 7 and 14) (p<;0.05). After that, the calcium content of irradiated groups was similar to that of the controls group. This suggests the transient effect of light irradiation on osteoblastic cell calcification. Only 680-nm irradiated samples revealed a significant enhancement of calcium content until the late stages of culture (from days 21 to 42) (p<;0.001). The cyclin D mRNA expression that was investigated 3 hours after stimulation at day3 also show that the 680-nm LED irradiation can enhance cyclin D expression more than others. For enhancing bone mineralization, LED irradiation at the 680-nm is more effective than those at 630-, 760- and 830-nm. Further studies should be investigated in order to obtain the most effective parameters of LLLI on bone regeneration in clinical setting.