Investigating the Role of Substrate Stiffness on Beta-Catenin Activation in Osteoblasts

Cells are exposed to a myriad of signals from their microenvironment and the finely tuned processing of these cues regulates cell survival, proliferation, and differentiation. Traditional belief was that only soluble signaling factors governed cell behavior, but more recently, much attention has been focused on the influence of mechanical and topographical cues. Although many landmark observations have been published in this regard, still little is known about the mechanisms behind cell response to physical cues. This work stems from the previously reported observations that beta-catenin, a key cell signaling molecule involved in bone development, is activated by acute mechanical stress. The main aim of this work was to investigate the role of substrate stiffness on beta-catenin activation in osteoblasts. Here, two polyacrylamide gel platforms are adapted that vary in Young's modulus and act as adhesive substrates for cell attachment. Osteoblasts grown on these polyacrylamide gels attach through cross-linked extracellular matrix proteins and 'sense' the underlying stiffness of the substrate and change their intracellular biochemistry accordingly. It was found in this work that the amount of total beta-catenin increases after 24 hours in osteoblasts cultured on tissue culture plastic and polyacrylamide gels of 40 kPa. Moreover, the number of cell-cell contacts directly influences the amount of total beta-catenin. It was also found that osteoblasts grown on higher stiffness substrates have more active beta-catenin and less degraded beta- catenin compared to lower stiffness substrates. The novel findings reported here advance the proposal that beta-catenin is a participant in mechanosensing and also provides a new platform for investigation and further insight into a mechanism of action

Fluoride Release from Two High-Viscosity Glass Ionomers after Exposure to Fluoride Slurry and Varnish

The effect of brushing with different fluoride slurries on the fluoride release (FR) of different high-viscosity glass ionomer cements (GICs) was investigated. Fifty-eight discs were fabricated from two high-viscosity GICs (GC Fuji IX (F9) and 3M ESPE Ketac-fil (KF)). Five specimens from each brand were used to measure Vickers microhardness and the remaining were randomly assigned to one of four groups (n = 6) based on two-factor combinations: (1) fluoride concentration in the abrasive slurry (275 or 1250 ppm fluoride as NaF) and (2) immersion in a 22,500 ppm fluoride-containing solution. Specimens were brushed for a total of 20,000 strokes over 4 days with daily FR measurement. Data were analyzed using analysis of variance and Bonferroni tests (α = 0.05). Baseline FR and microhardness values were different between the two tested material brands. Exposure to a 22,500 ppm solution was associated with higher FR but not the exposure to 1250 ppm slurries. Brushing and immersion of glass ionomer cements in a 22,500 ppm F solution led to higher FR that was more sustained for KF. Type of the glass ionomer, progressive brushing, and fluoride varnish affected FR but not the fluoride content in the abrasive slurry

The efficacy of an electronic performance support system as a training tool for online faculty

An instructional website was developed as an electronic performance support system (EPSS) to determine whether faculty would use and learn from such a resource. This website summarized pedagogical information about online instruction that users could access 24 hours a day, seven days a week. In Phase I of the study, five college professors with experience teaching online courses evaluated the usability of the website and made suggestions on how it could be improved. Revisions were made to the website to enhance clarity and comprehension in preparation for Phase II of the study. In Phase II, 35 college instructors agreed to use the website to learn about pedagogical information related to teaching online courses. Only two people visited at least 75% of the web pages, limiting the conclusions that could be drawn. Two conclusions, however, seem warranted. First, an EPSS is not the most effective way to deliver non-mandatory faculty education because the primary goal of an EPSS is to enhance performance in a business setting rather than to facilitate learning in the academic setting. Second, any type of faculty development program must be developed from the learner\u27s perspective and include interaction between the participants

How pharmacoepidemiology networks can manage distributed analyses to improve replicability and transparency and minimize bias

Several pharmacoepidemiology networks have been developed over the past decade that use a distributed approach, implementing the same analysis at multiple data sites, to preserve privacy and minimize data sharing. Distributed networks are efficient, by interrogating data on very large populations. The structure of these networks can also be leveraged to improve replicability, increase transparency, and reduce bias. We describe some features of distributed networks using, as examples, the Canadian Network for Observational Drug Effect Studies, the Sentinel System in the USA, and the European Research Network of Pharmacovigilance and Pharmacoepidemiology. Common protocols, analysis plans, and data models, with policies on amendments and protocol violations, are key features. These tools ensure that studies can be audited and repeated as necessary. Blinding and strict conflict of interest policies reduce the potential for bias in analyses and interpretation. These developments should improve the timeliness and accuracy of information used to support both clinical and regulatory decisions

EVALUATION OF MICROTENSILE BOND STRENGTH AND MICROLEAKAGE OF A ONE-STEP SELF-ETCH ADHESIVE

poster abstractNew dental glue (G-aenial Bond-GB) was developed to increase the strength of bonding the white tooth filling to the tooth. An extra roughening step of the tooth surface using a specific acid should help the flow of the glue to the tooth and increases the strength of the bond between the tooth and the filling. Therefore, this study was done to evaluate how strong the bond is between the filling and the tooth using GB, and how much GB leaks and compare both tests with two other glue products and, with and without adding an extra roughening step. For the bond strength test, human molars teeth were divided into 5 groups, each containing 15 teeth. In 3 groups, each glue type was applied on tooth dentin according to company's instructions. In the last 2 groups an extra roughening step using a specific acid was added before applying the glue. The samples were stored in fake saliva where four samples were soaked for 48h and four samples were placed in a machine (thermocycling) that resembles drinking hot and cold beverages where samples are exposed to hot and cold water for 40 days and then the strength of the bond was tested (α=0.05). The broken edges were examined using a light microscope. For the leak test, human molars were divided randomly into the same 5 groups as bond strength test but each containing 11 teeth. A cavity was pre-pared and filled on the check and tongue sides of the tooth. Teeth were then also subjected to thermocylcling and stored for four weeks, soaked in dye for 24 hours and sectioned. The dye penetration was evaluated using light mi-croscopy (α=0.05). Bond strength of GB was significantly higher when an acid roughening step was added. No significant difference in leak of GB was observed

Stainless Steel Crown Success Using the Hall Technique: A Retrospective Study

Background In this retrospective study, the authors evaluated the clinical and radiographic success of stainless steel crowns (SSCs) used to restore primary molars with caries lesions, placed by means of both the traditional technique (involving complete caries removal and tooth reduction before placement of the SSC) and the Hall technique (involving no caries removal, no crown preparation and no use of local anesthetic before placement of the SSC). Methods The authors conducted a retrospective chart review by using the patient records at a private pediatric dental practice at which the Hall technique had been introduced in June 2010 as an alternative treatment to traditional SSC placement. The inclusion criteria were caries lesions on a primary molar with no clinical or radiographic evidence of pulpitis, necrosis or abscess, as well as follow-up of at least six months or until failure, whichever came first. They graded restoration success by using a four-point scale based on presence or loss of the SSC, and whether or not the patient needed further treatment associated with pulpal pathology or secondary caries. They collected and summarized patient demographic information. They used a Kaplan-Meier survival curve along with 95 percent confidence intervals to evaluate clinical success. Results The authors found that 65 (97 percent) of 67 SSCs placed with the Hall technique (mean observation time, 15 months; range, four-37 months) and 110 (94 percent) of 117 SSCs placed with the traditional technique (mean observation time, 53 months; range, four-119 months) were successful. Conclusion Findings of this study show a similar success rate for SSCs placed with the traditional technique or the Hall technique

Microtensile Bond Strength and Microleakage of HEMA-Free One-Step Self-Etch Adhesive

poster abstractThis study evaluated the microtensile dentin bond strength (μ-TBS) and microleakage of a one-step HEMA-free self-etch adhesive (G-aenial Bond-GB) compared to a 2-step self-etch (Clearfil SE-SE) and a 3-step etch and rinse (OptiBond FL-OB) adhesive with and without pre-etching with phosphoric acid. Human molars were divided randomly into 5 groups (n=15), GB and SE (without pre-etching), GB+ and SE+ (with pre-etching), and OB. Eight beams were obtained from each tooth and half of the beams were subjected to μ-TBS testing after 2d. The remaining beams were thermocycled (2,500 cycles), aged for 40d and subjected to μ-TBS testing using a universal testing machine. Failures were analyzed using light microscopy and SEM. Similar groups were used for the microleakage test (n=11). Class V cavities were prepared on the buccal and lingual surfaces of each molar. Teeth were thermocycled (2,500 cycles), aged for 40d, soaked in 1% methylene blue dye for 24h, and sectioned longitudinally from the facial to lingual surface. The dye penetration was scored using light microscopy and an ordinal scale from 0-3. Data was analyzed using Weibull, GEE, and Wilcoxon Rank Sum tests (α=0.05). Phosphoric acid pre-etching significantly increased dentin bond strength. After 40d, the mean bond strength ranged from 28.6-45.7 MPa with a statistical significance of GB, SE<GB+, SE+ & OB. The Weibull Characteristic Strength ranged from 31.5-51.0 MPa and the Weibull Modulus ranged from 2.3-4.1. Cohesive failure ranged from 16%-57% with a statistical significance of GB<SE+ & OB, but GB+ & SE<OB. Phosphoric acid preetching had no significant effect on microleakage. However, significant differences were found between coronal and gingival surfaces for all groups except GB. Pre-etching with phosphoric acid significantly increased dentin bond strength of GB and SE and had no significant effect on microleakage. Materials supplied by GC America and Ultradent

THE EFFECT OF NANO-FILLED RESIN COATING ON FLUORIDE RELEASE IN A NEW CONVENTIONAL GLASS IONOMER CEMENT

poster abstractThe objective of this study was to evaluate fluoride release amounts and patterns from high strength tooth filling material (EQUIA™) which is a con-ventional Glass Ionomer Cement, and investigate whether the application of nano-filled resin-based coating with different thicknesses has any effect on fluoride release from this new material. A total of 120 disc shaped specimens (10 x 2 mm) of EQUIA™ were fabricated according to manufacturer’s in-structions. Samples were subsequently divided into three groups: no resin coating; coated with nano-filled resin-based coat; coated with nano-filled resin-based coat then subjected to abrasion using a mechanical tooth brush-ing machine. Each specimen was soaked individually into a polyethylene container with 20 ml of distilled water and stored at 37ºC. Samples from each group were soaked for four time points; 1 day, 7 days, 14 days and 21 days. Fluoride content was then measured using a fluoride-specific ion elec-trode (Model 9609BNWP, Orion Research, Boston MA, USA). The effects of time and coating on fluoride release were analyzed using two-way analysis of variance (ANOVA), with multiple comparisons performed using the Sidak method at an overall 5% significance level. The distribution of the fluoride release measurements was examined and a natural logarithm transformation of the data was necessary to satisfy the ANOVA assumptions. The time-by-coating interaction was significant (p<0.0001). We can conclude that fluo-ride level significantly increased with time for non-coated and coated then abraded samples only. Application of resin coat significantly reduced fluoride release. Also, subjecting coated samples to tooth brush abrasion increased the fluoride release when compared to coated specimens but was still signifi-cantly less than uncoated samples

Lessons from cardiac transplantation in infancy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73539/1/j.1399-3046.2009.01143.x.pd