Effect of Air-abrasion Preparation on Shear Bond Strength of Orthodontic Brackets to Enamel Surface

Introduction: An optimal orthodontic bonding system must minimize damage to the enamel during conditioning, have enough bond strength to prevent bracket de-bonding during treatment, and allow bracket removal at treatment completion, such that minimal damage is inflicted to the tooth.1 Pumice followed by acid etching has been the standard for many years; however, Groman Inc. (Margate, FL, USA) has stated that using their air-abrasion product will result in a tripling of bond strength. This method claims a three-fold increase in bond strength compared to traditional acid etching techniques by substituting air-abrasion using the EtchMaster® (Groman Inc., Margate, FL) 50 μm aluminum oxide in place of pumice prophy prior to acid etching. The purpose of this study is to see if this combination does in fact triple shear bond strength, and if so, what impact it has on the residual enamel surface after bracket removal, or de-bonding. Methods: Ninety recently extracted bovine incisors were randomly divided into three groups. Each of the three groups underwent different conditioning methods prior to bracket bonding. Group A: pumice + acid etch (N=30), Group B: air-abrasion + acid etch (N=30), and Group C: air-abrasion only (N=30). Enamel surface conditions were characterized using a Quanta 200 Scanning Electron Microscope (SEM) (FEI, Hillsboro, OR) and a SZX7 Stereomicroscope System (Olympus, Center Valley, PA). American Orthodontics Master Series System twin MBT mandibular incisor brackets (Sheboygan, WI, USA) were then bonded to each tooth. Following bonding, teeth were stored for twenty-four hours in water at 37°C +/- 2°C. All groups then underwent thermocycling of five hundred cycles in water baths set at five and fifty-five degrees Celsius. Next, the samples were mounted in dental stone and brackets de-bonded using a universal testing machine (Instron, Canton, MA) to obtain shear bond strength (SBS) values. SEM and optical stereomicroscopy were again utilized to evaluate the enamel surface and determine the adhesive remnant index (ARI) was score of each specimen. Results: The mean of Group A (pumice + acid etch) was 21.52 MPa with a standard deviation of 4.97 MPa. The mean of Group B (air-abrasion + acid etch) was 21.83 MPa with a standard deviation of 7.55 Mpa. The mean of Group C (air-abrasion only) was 8.12 MPa with a standard deviation of 3.05 MPa. Analysis of variance showed a main effect of Group on MPa, F(2, 87) = 60.66, p \u3c 0.001, ηp2= 0.58. Post-hoc analyses using Tukey’s HSD indicated that SBS values were higher for teeth in Group A than for those in Group C (p \u3c 0.001), teeth in Group B had higher SBS values than those in Group C (p \u3c 0.001), but no difference was found for SBS between teeth in Group A and Group B (p =0.981). Results from the Fisher’s Exact test, where we controlled the Type I error using a Bonferroni correction, reveals that ARI scores differed by group (p \u3c 0.001). Stereomicroscope images at 38.75x magnification obtained following enamel conditioning show Groups A (P+AE) and B (AA+AE) are almost indistinguishable; however, Group C (AA) has visual differences. Group C had a speckled reflective property that appeared to be residual aluminum oxide particles. Following de-bond, stereomicroscopic and SEM images showed no enamel defects on the tooth. Conclusions: SBS was not significantly different between Group A (pumice + acid etch) and Group B (air-abrasion + acid etch). SBS was significantly different between Groups A and B, and Group C (air-abrasion only). This means there is not a three-fold increase in SBS when using air-abrasion and acid etch, when compared to pumice and acid etch, as claimed by the manufacturer of the air-abrasion unit used in this study. Additionally, the air-abrasion only group displayed a significantly lower SBS than Group A and B. Air-abrasion only is not a suitable enamel preparation method for orthodontic bonding. Images obtained from the stereomicroscope and SEM reveal no observational damage to the enamel surface topography after de-bonding for any group

Experiment K-6-01. Distribution and biochemistry of mineral and matrix in the femurs of rats

Previous analyses of the composition of mineral and matrix in the bone of young rats following space flight has revealed deficits in calcium, phosphorus, and osteocalcin, a non-collagenous protein, without an associated decrease in collagen. To characterize the location and nature of this mineralization defect in a weight bearing long bone, the femur, researchers attempted to relate the spatial distribution of mineral in situ in the proximal, central and distal thirds of the femoral diaphysis to the biochemical composition of bone from the same area. Biochemical analyses revealed lower concentrations of calcium, phosphorus and osteocalcin but not collagen only in the central third of the diaphysis of the flight animals (F) compared to synchronous controls (S). Collagen concentration was reduced only in the proximal third of the diaphysis, where all 3 crosslinks, expressed as nM/mol collagen were higher in F than S. A new technique, x ray microtomography, with a resolution of 26 microns, was used to obtain semi-quantitative data on mineral distribution in reconstructed sections of wet whole bone. To improve the resolution of the mineral density distribution, images of the surfaces of cut sections were analyzed by backscattered electrons in a scanning electron microscope (BSE). There was good agreement between the results of the two stereochemical techniques which revealed distinct patterns of mineralization in transverse and longitudinal directions of the diaphysis. The novel methodology developed for this flight experiment shows considerable promise in elucidating the biochemical nature of what appear to be regional alterations in the mineralization of long bones of animals exposed to spaceflight

Mean values with cubic characters

We investigate various mean value problems involving order three primitive Dirichlet characters. In particular, we obtain an asymptotic formula for the first moment of central values of the Dirichlet L-functions associated to this family, with a power saving in the error term. We also obtain a large-sieve type result for order three (and six) Dirichlet characters.Comment: 22 pages; greatly shortened, simplified and corrected versio

Baclofen Toxicity Causing Acute, Reversible Dyskinesia.

The following unique case demonstrates an episode of acute dyskinesia secondary to oral baclofen toxicity. We discuss an 80-year-old man with a history of Stage III chronic kidney disease, coronary artery disease, diabetes and stroke who presented to the Emergency Department with new onset of behavioral changes and irregular jerking movements. The patient had been recently prescribed baclofen 10mg twice daily for a back strain he suffered; he subsequently was admitted to the hospital, and his symptoms resolved within 48 hours of admission and discontinuance of baclofen

Novel antibodies directed against the human erythropoietin receptor: creating a basis for clinical implementation

YesRecombinant human erythropoietin (rHuEPO) is an effective treatment for anaemia but concerns that it causes disease progression in cancer patients by activation of EPO receptors (EPOR) in tumour tissue have been contro- versial and have restricted its clinical use. Initial clinical studies were flawed because they used polyclonal antibodies, later shown to lack specificity for EPOR. Moreover, multiple isoforms of EPOR caused by differential splicing have been reported in cancer cell lines at the mRNA level but investigations of these variants and their potential impact on tumour progression, have been hampered by lack of suitable antibodies. The EpoCan consortium seeks to promote improved pathological testing of EPOR, leading to safer clinical use of rHuEPO, by producing well characterized EPOR antibodies. Using novel genetic and traditional peptide immunization protocols, we have produced mouse and rat monoclonal antibodies, and show that sev- eral of these specifically recognize EPOR by Western blot, immunoprecipi- tation, immunofluorescence, flow cytometry and immunohistochemistry in cell lines and clinical material. Widespread availability of these antibodies should enable the research community to gain a better understanding of the role of EPOR in cancer, and eventually to distinguish patients who can be treated safely by rHuEPO from those at increased risk from treatment.Study was supported by the FP7-Health European commission EpoCan grant (282551)

The detection of airborne transmission of tuberculosis from HIV-infected patients, using an in vivo air sampling model

Background. Nosocomial transmission of tuberculosis remains an important public health problem. We created an in vivo air sampling model to study airborne transmission of tuberculosis from patients coinfected with human immunodeficiency virus (HIV) and to evaluate environmental control measures. Methods. An animal facility was built above a mechanically ventilated HIV‐tuberculosis ward in Lima, Peru. A mean of 92 guinea pigs were continuously exposed to all ward exhaust air for 16 months. Animals had tuberculin skin tests performed at monthly intervals, and those with positive reactions were removed for autopsy and culture for tuberculosis. Results. Over 505 consecutive days, there were 118 ward admissions by 97 patients with pulmonary tuberculosis, with a median duration of hospitalization of 11 days. All patients were infected with HIV and constituted a heterogeneous group with both new and existing diagnoses of tuberculosis. There was a wide variation in monthly rates of guinea pigs developing positive tuberculin test results (0%–53%). Of 292 animals exposed to ward air, 159 developed positive tuberculin skin test results, of which 129 had laboratory confirmation of tuberculosis. The HIV‐positive patients with pulmonary tuberculosis produced a mean of 8.2 infectious quanta per hour, compared with 1.25 for HIV‐negative patients with tuberculosis in similar studies from the 1950s. The mean monthly patient infectiousness varied greatly, from production of 0–44 infectious quanta per hour, as did the theoretical risk for a health care worker to acquire tuberculosis by breathing ward air. Conclusions. HIV‐positive patients with tuberculosis varied greatly in their infectiousness, and some were highly infectious. Use of environmental control strategies for nosocomial tuberculosis is therefore a priority, especially in areas with a high prevalence of both tuberculosis and HIV infection

Sociological and Human Developmental Explanations of Crime: Conflict or Consensus

This paper examines multidisciplinary correlates of delinquency in an attempt to integrate sociological and environmental theories of crime with human developmental and biological explanations of crime. Structural equation models are applied to assess links among biological, psychological, and environmental variables collected prospectively from birth through age 17 on a sample of 800 black children at high risk for learning and behavioral disorders. Results show that for both males and females, aggression and disciplinary problems in school during adolescence are the strongest predictors of repeat offense behavior. Whereas school achievement and family income and stability are also significant predictors of delinquency for males, early physical development is the next strongest predictor for females. Results indicate that some effects on delinquency also vary during different ages. It is suggested that behavioral and learning disorders have both sociological and developmental correlates and that adequate educational resources are necessary to ensure channels of legitimate opportunities for high-risk youths

Distributed network organization underlying feeding behavior in the mollusk Lymnaea

The aim of the work reviewed here is to relate the properties of individual neurons to network organization and behavior using the feeding system of the gastropod mollusk, Lymnaea. Food ingestion in this animal involves sequences of rhythmic biting movements that are initiated by the application of a chemical food stimulus to the lips and esophagus. We investigated how individual neurons contribute to various network functions that are required for the generation of feeding behavior such as rhythm generation, initiation ('decision making'), modulation and hunger and satiety. The data support the view that feeding behavior is generated by a distributed type of network organization with individual neurons often contributing to more than one network function, sharing roles with other neurons. Multitasking in a distributed type of network would be 'economically' sensible in the Lymnaea feeding system where only about 100 neurons are available to carry out a variety of complex tasks performed by millions of neurons in the vertebrate nervous system. Having complementary and potentially alternative mechanisms for network functions would also add robustness to what is a 'noisy' network where variable firing rates and synaptic strengths are commonly encountered in electrophysiological recording experiments