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

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

Spacer-induced forward osmosis membrane integrity loss during gypsum scaling

We demonstrated forward osmosis (FO) membrane integrity loss during gypsum scaling with the presence of membrane spacer. The gypsum scalant had preferential accumulation adjacent to membrane spacer where the needle-shape gypsum potentially compromised polyamide thin-film composite FO membrane integrity. However, the loss of FO membrane integrity cannot be sensitively detected by in situ measurements of membrane water and salt (NaCl) permeability coefficients. We, for the first time, employed membrane integrity challenge tests to reveal the impaired FO membrane integrity by fluorescent Rhodamine WT tracer and amine-modified latex nanoparticles, respectively. Challenge tests using Rhodamine WT tracer showed that membrane log removal value decreased to 3.5 after three scaling–cleaning cycles, which corresponded to a pinhole size of 0.06 μm2 on the FO membrane. This result was further corroborated by challenge test using latex nanoparticle where the particle size distribution in the permeate became wider and the average particle size increased over the three scaling–cleaning cycles. Both challenge tests were sensitive enough to identify impaired FO membrane integrity. Results reported here have significant implications for achieving better membrane spacer and module design, as well as demanding periodical monitoring of FO membrane integrity in water reuse

Science, technology, engineering, and mathematics (STEM) as a vehicle for supporting service learning

2016-2017 > Academic research: refereed > Refereed conference paper201804_a bcmaVersion of RecordPublishe

The Prevalence and Risk Factors of Paternal Depression from the Antenatal to the Postpartum period and the Relationships between Antenatal and Postpartum Depression among Fathers in Hong Kong

Introduction. Despite the fact that maternal perinatal mental health problems have been extensively studied and addressed to be a significant health problem, the literature on paternal perinatal mental health problems is relatively scarce. The present study aims at determining the prevalence of paternal perinatal depression and identifying the risk factors and the relationship between antenatal and postpartum depression. Methodology. 622 expectant fathers were recruited from regional maternal clinics. The expectant fathers were assessed using standardized and validated psychological instruments on 3 time points including early pregnancy, late pregnancy, and six weeks postpartum. Results. Results showed that a significant proportion of expectant fathers manifested depressive symptoms during the perinatal period. Paternal antenatal depression could significantly predict higher level of paternal postpartum depression. Psychosocial risk factors were consistently associated with paternal depression in different time points. Conclusions. The present study points to the need for greater research and clinical attention to paternal depression given that it is a highly prevalent problem and could be detrimental to their spouse and children development. The present findings contribute to theoretical basis of the prevalence and risk factors of paternal perinatal depression and have implications of the design of effective identification, prevention, and interventions of these clinical problems.published_or_final_versio

Anomalous diffusivity and electric conductivity for low concentration electrolytes in nanopores

The dynamic properties of electrolytes in nanopores were studied using the equilibrium and non-equilibrium molecular dynamic simulations. The realistic primitive model and the restrictive primitive models that were widely used in liquid state theory were applied to the electrolyte model. The electrolytic ions that were found to be immersed in the water were treated as dielectric continuum or macroscopic dielectric continuum. Simulation studies for the discrete solvent primitive model were performed and detailed analysis of the characteristics of the ion radial density functions was done.published_or_final_versio

High-Performance Pentacene Thin-Film Transistor With High-κ HfLaON as Gate Dielectric

published_or_final_versio

High-mobility pentacene OTFT with TaLaO gate dielectric passivated by fluorine plasma

Pentacene thin-film transistor with high-κ TaLaO as gate dielectric has been fabricated and shows a carrier mobility of 0.73 cm2/V s, much higher than that based on pure La2O3 (0.43 cm2/V s) due to the smoother surface of the TaLaO film and thus larger pentacene islands grown on it in the initial stage. Moreover, among various times for fluorine-plasma treatment on the TaLaO gate dielectric, 100 seconds result in the highest carrier mobility of 1.12 cm2/V s due to (1) smoothest oxide surface achieved by fluorine passivation of oxide traps, as measured by AFM and supported by smallest sub-threshold swing and lowest low-frequency noise; (2) the largest pentacene grains grown on the smoothest oxide surface, as demonstrated by AFM. Pentacene islands on on TaLaO or La2O3 gate dielectric with different plasma treatment times.postprin

High-mobility pentacene thin-film transistor by using LaxTa(1-x)Oy as gate dielectric

Pentacene organic thin-film transistors (OTFTs) using LaxTa(1−x)Oy as gate dielectric with different La contents (x = 0.227, 0.562, 0.764, 0.883) have been fabricated and compared with those using Ta oxide or La oxide. The OTFT with La0.764Ta0.236Oy can achieve a carrier mobility of 1.21 cm2 V−1s−1s, which is about 40 times and two times higher than those of the devices using Ta oxide and La oxide, respectively. As supported by XPS, AFM and noise measurement, the reasons lie in that La incorporation can suppress the formation of oxygen vacancies in Ta oxide, and Ta content can alleviate the hygroscopicity of La oxide, resulting in more passivated and smoother dielectric surface and thus larger pentacene grains, which lead to higher carrier mobility.postprin