Insights into surface treatment methods of titanium dental implants

Titanium is the most widely used material for dental implants, due to its desirable properties, e.g., high biocompatibility, low density, high stiffness and strength, etc. More importantly, titanium implants may osseointegrate with living bone, meaning that new bone grows directly onto the surface of the implant, without any intermediate soft tissue layer. A successfully osseointegrated implant generally has a strong bonding to the adjacent bone; consequently, it usually functions well and remains stable for long service period. It also has been clinically proven that surface treatment methods can improve the rate and quality of titanium implants’ osseointegration. This article focuses on two such methods, i.e., surface roughening and hydroxyapatite (HA) coating. In addition, we discuss a promising new methodology, which attempts to modify the surface charge of titanium materials. This paper focuses on the current best surface treatment methods for titanium dental implants developed and improved in the past two decades, i.e., 1990–2010.postprin

Effects of surface charges on dental implants: past, present and future

Osseointegration is a major factor influencing the success of dental implantation. To achieve rapid and strong, durable osseointegration, biomaterial researchers have investigated various surface treatment methods for dental subgingival titanium (Ti) implants. This paper focuses on surface-charge modification on the surface of titanium dental implants, which is a relatively new and very promising methodology for improving the implants' osseointegration properties. We give an overview on both theoretical explanations on how surface-charge affects the implants' osseointegration, as well as a potential surface charge modification method using sandblasting. Additionally, we discuss insights on the important factors affecting effectiveness of surface-charge modification methods and point out several interesting directions for future investigations on this topic.published_or_final_versio

A novel effect of sandblasting on titanium surface: static charge generation

Recent advances in biomaterials research suggest that electrical charges on a dental implant surface significantly improve its osseointegration to living bone, as a result of selective osteoblast activation and fibroblast inhibition. This study aims at investigating the possibility of using sandblasting to modify the electrical charges on the surface of titanium materials. Our experiments used Al 2O 3 grits to blast on CP2 titanium plates, for durations between 3 and 30s. After sandblasting, Ti surfaces were measured for their electrostatic voltage. The results indicate a novel finding, i.e. negative static charges are generated on the titanium surface, which may stimulate osteoblast activity to promote osseointegration around dental implant surface. This finding may at least partially explain the good osseointegration results of sandblasted titanium dental implants, in addition to other known reasons, such as topological changes on the implants surface. However, the static charges accumulated on the titanium surface during sandblasting decayed to a lower level with time. It remains a challenging task to seek ways to retain these charges after quantification of desired level of negative charges needed to promote osteoblast activity for osseointegration around dental implants. © 2012 Copyright Taylor and Francis Group, LLC.postprin

A comparison of MISiC Schottky-diode hydrogen sensors made by NO, N 2O, or NH 3 nitridations

MISiC Schottky-diode hydrogen sensors with gate insulator grown in three different nitridation gases (nitric oxide (NO), N 2O, and NH 3) are fabricated. Steady-state and transien-t-response measurements are carried out at different temperatures and hydrogen concentrations using a computer-controlled measurement system. Experimental results show that these nitrided sensors have high sensitivity and can give a rapid and stable response over a wide range of temperature. This paper also finds that N 2O provides the fastest insulator growth with good insulator quality and hence the highest sensitivity among the three nitrided samples. The N 2O- nitrided sensor can give a significant response even at a low H 2 concentration of 48-ppm H 2 in N 2, indicating a potential application for detecting hydrogen leakage at high temperature. Moreover, the three nitrided samples respond faster than the control sample. At 300°C, the response times of the N 2O, NO, and NH 3-nitrided sample to the 48-ppm H 2 in N 2 are 11, 11, and 37 s, respectively, as compared to 65 s for the control sample without the gate insulator. © 2006 IEEE.published_or_final_versio

Sensing characteristics of a novel NH 3-nitrided schottky-diode hydrogen sensor

A novel NHi-nitrided Schottky-diode hydrogen sensor has been successfully fabricated Measurements have been performed to investigate the sensitivity, stability and response speed of the sensor at different temperatures and hydrogen concentrations. It can respond to hydrogen variation very quickly and can give significant response ewn at low hydrogen concentration. The studied device exhibits high sensitivity of 350 % at 300 °C when 800 ppm IJ in N2 gas is introduced. The sensitivity is 15 times greater than that of the Pt-SiC sensor. The excellent hydrogen-sensing characteristics of this novel sensor make it very suitable for detecting hydrogen leakage in high-temperature environment. The effects of hydrogen adsorption on the barrier height and hydrogen reaction kinetics are also investigated. ©2004 IEEE.published_or_final_versio

High Performance Algorithms for Counting Collisions and Pairwise Interactions

The problem of counting collisions or interactions is common in areas as computer graphics and scientific simulations. Since it is a major bottleneck in applications of these areas, a lot of research has been carried out on such subject, mainly focused on techniques that allow calculations to be performed within pruned sets of objects. This paper focuses on how interaction calculation (such as collisions) within these sets can be done more efficiently than existing approaches. Two algorithms are proposed: a sequential algorithm that has linear complexity at the cost of high memory usage; and a parallel algorithm, mathematically proved to be correct, that manages to use GPU resources more efficiently than existing approaches. The proposed and existing algorithms were implemented, and experiments show a speedup of 21.7 for the sequential algorithm (on small problem size), and 1.12 for the parallel proposal (large problem size). By improving interaction calculation, this work contributes to research areas that promote interconnection in the modern world, such as computer graphics and robotics.Comment: Accepted in ICCS 2019 and published in Springer's LNCS series. Supplementary content at https://mjsaldanha.com/articles/1-hpc-ssp

Incremental anisotropic damage theory and its numerical analysis

2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Pentacene thin-film transistors with HfO2 gate dielectric annealed in NH3 or N2O

Pentacene-based Organic Thin-Film Transistor (OTFT) with HfO 2 as gate dielectric is studied in this work. The HfO2 dielectric was prepared by RF sputtering at room temperature, and subsequently annealed in N 2O or NH 3 at 200 °C. The OTFTs were characterized by IV measurement and 1/f noise measurement. The OTFTs show small threshold voltage and can operate at as low as 3 V. Results indicate that the OTFT annealed in NH 3 shows higher carrier mobility, larger on/off current ratio, smaller sub-threshold swing and smaller Hooge parameter than the OTFT annealed in N 2O. Therefore, NH 3-annealed HfO 2 is a promising gate dielectric for the fabrication of high-performance OTFTs. © 2008 IEEE.published_or_final_versio

Efficacy of High Dose Vitamin D Supplements for Elite Athletes.

PURPOSE: Supplementation with dietary forms of vitamin D is commonplace in clinical medicine, elite athletic cohorts and the general population, yet the response of all major vitamin D metabolites to high doses of vitamin D is poorly characterized. We aimed to identify the responses of all major vitamin D metabolites to moderate and high dose supplemental vitamin D3. METHODS: A repeated measures design was implemented in which 46 elite professional European athletes were block randomized based on their basal 25[OH]D concentration into two treatment groups. Athletes received either 35,000 or 70,000 IU.week vitamin D3 for 12 weeks and 42 athletes completed the trial. Blood samples were collected over 18 weeks to monitor the response to supplementation and withdrawal from supplementation. RESULTS: Both doses led to significant increases in serum 25[OH]D and 1,25[OH]2D3. 70,000 IU.week also resulted in a significant increase of the metabolite 24,25[OH]2D at weeks 6 and 12 that persisted following supplementation withdrawal at week 18, despite a marked decrease in 1,25[OH]2D3. Intact PTH was decreased in both groups by week 6 and remained suppressed throughout the trial. CONCLUSIONS: High dose vitamin D3 supplementation (70,000 IU.week) may be detrimental for its intended purposes due to increased 24,25[OH]2D production. Rapid withdrawal from high dose supplementation may inhibit the bioactivity of 1,25[OH]2D3 as a consequence of sustained increases in 24,25[OH]2D that persist as 25[OH]D and 1,25[OH]2D concentrations decrease. These data imply that lower doses of vitamin D3 ingested frequently may be most appropriate and gradual withdrawal from supplementation as opposed to rapid withdrawal may be favorable

Effects of reduced energy availability on bone metabolism in women and men

Background: The short-term effects of low energy availability (EA) on bone metabolism in physically active women and men are currently unknown. Purpose: We evaluated the effects of low EA on bone turnover markers (BTMs) in a cohort of women and a cohort of men, and compared effects between sexes. Methods: These studies were performed using a randomised, counterbalanced, crossover design. Eleven eumenorrheic women and eleven men completed two 5-day protocols of controlled (CON; 45 kcal·kgLBM-1.d-1) and restricted (RES; 15 kcal.kgLBM-1·d-1) EAs. Participants ran daily on a treadmill at 70% of their peak aerobic capacity (VO2 peak) resulting in an exercise energy expenditure of 15 kcal·kgLBM-1·d-1 and consumed diets providing 60 and 30 kcal·kgLBM-1·d-1. Blood was analysed for BTMs [β-carboxyl-terminal cross-linked telopeptide of type I collagen (β-CTX) and amino-terminal propeptide of type 1 procollagen (P1NP)], markers of calcium metabolism [( parathyroid hormone (PTH), albumin-adjusted calcium (ACa), magnesium (Mg) and phosphate (PO4)] and regulatory hormones [sclerostin, insulin-like growth factor 1 (IGF-1), triiodothyronine (T3), insulin, leptin, glucagon-like- peptide-2 (GLP-2)]. Results: In women,β-CTX AUC was significantly higher P=0.03) and P1NP AUC was significantly lower (P=0.01) in RES compared to CON. In men, neither β-CTX (P=0.46) n or P1NP (P=0.12) AUCs were significantly different between CON and RES. There were no significant differences between sexes for any BTM AUCs (all P values>0.05). Insulin and leptin AUCs were significantly lower following RES in women only (for both P=0.01). There were no differences in any AUCs of regulatory hormones or markers of calcium metabolism between men and women following RES (all P values>0.05). Conclusions: When comparing within groups, five days of low EA (15 kcal·kgLBM-1·d-1) decreased bone formation and increased bone resorption in women, but not in men, and no sex specific differences were detected