Dynamic field testing of coating chemistry candidates by a rotating disk system.

Quick and reliable testing is crucial for the development of new fouling release (FR) coatings. Exposure of these coatings to natural multispecies communities is essential in evaluating their efficacy. To this end, we present a rotating disk setup for dynamic field exposure. To achieve a well-defined flow on the surface of the disk, an easy to use sample mounting system was developed that provides a smooth and even surface. We related the angular velocity of the disk to the wall shear stress on the surface with a hydrodynamic model. The wall shear stress was adjusted to values previously found to be suitable to discriminate dynamic diatom attachment on different coating chemistries in the lab. The effect of the dynamic conditions was shown by comparing polystyrene slides under static and dynamic exposure. Using a set of self-assembled monolayers, the discrimination potential of the assay in a multispecies environment was demonstrated.

Antibacterial, physicochemical and mechanical properties of endodontic sealers containing quaternary ammonium polyethylenimine nanoparticles.

AIM: To evaluate the antibacterial, physicochemical and mechanical properties of two endodontic sealers incorporating quaternary ammonium polyethylenimine (QPEI) nanoparticles at concentrations of 1% and 2% (w/w). METHODOLOGY: The sealers tested were AH Plus and Pulp Canal Sealer EWT in the commercial unmodified form or containing 1% or 2% QPEI. Antibacterial activity was evaluated using a direct contact test (DCT) against Enterococcus faecalis ATCC 29212 and two endodontic isolates (RW35 and RN44). Sealers freshly mixed or set for 7 days were exposed to bacterial suspensions for 10, 30 and 60 min. Setting time, flow test, solubility, apparent porosity, dimensional change following setting, wettability, zeta potential and compressive strength were assessed according to the International Standard Organization 6876:2001 (ISO 6876). RESULTS: DCT results revealed that both freshly prepared sealers had antibacterial effects unaffected by QPEI incorporation. Both unmodified sealers had lost much of their antibacterial effects after 7 days. However, for Pulp Canal Sealer EWT incorporated with 1% and 2% QPEI nanoparticles, the antibacterial effects against all test E. faecalis strains within 30 and 60 min of contact were significantly greater than the unmodified formula. Addition of QPEI resulted in no significant increase in the antibacterial effects of AH Plus after ageing. As for physicochemical and mechanical tests, setting time, wettability and zeta potential were influenced by the presence of QPEI nanoparticles. CONCLUSION: Incorporation of QPEI nanoparticles can improve the long-term antibacterial activity of Pulp Canal Sealer EWT without relevant changes in physicochemical and mechanical properties.

In vitro antimicrobial activity and biocompatibility of propolis containing nanohydroxyapatite.

The high number of biomaterial associated infections demands new strategies to prevent this problem. In this study the suitability of nanohydroxyapatite (nanoHA)-based surfaces containing two Brazilian extracts of propolis (green and red ones) to prevent bacterial growth and biofilm formation, as well as its non-cytotoxic nature, was investigated. Optical density, colony forming units and MTT reduction assay were used to assess the materials' antibacterial activity against planktonic and sessile growth of Staphylococcus aureus. NanoHA matrix was able to absorb both types of propolis and the obtained results revealed the antibacterial effectiveness of the novel materials expressed as the reduction of bacterial growth and biofilm formation ability. Additionally, cell culture tests showed the growth of fibroblasts with high metabolic activity and without membrane damage. Therefore, these nanoHA-based surfaces containing natural products deriving from bees may be a promising bioactive biomaterial to be further studied with the aim of application to orthopaedic or dental devices.

Anti-sessile bacterial and cytocompatibility properties of CHX-loaded nanohydroxyapatite.

Nanohydroxyapatite possesses exceptional biocompatibility and bioactivity regarding bone cells and tissues, justifying its use as a coating material or as a bone substitute. Unfortunately, this feature may also encourage bacterial adhesion and biofilm formation. Surface functionalization with antimicrobials is a promising strategy to reduce the likelihood of bacterial infestation and colonization on medical devices. Chlorhexidine digluconate is a common and effective antimicrobial agent used for a wide range of medical applications. The purpose of this work was the development of a nanoHA biomaterial loaded with CHX to prevent surface bacterial accumulation and, simultaneously, with good cytocompatibility, for application in the medical field. CHX (5-1500 mg/L) was loaded onto nanoHA discs and the materials were evaluated for CHX adsorption and release profile, physic-chemical features, antibacterial activity against Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis, and cytocompatibility toward L929 fibroblasts. Results showed that the adsorption of CHX on nanoHA surface occurred by electrostatic interactions between the cationic group of CHX and the phosphate group of nanoHA. The release of CHX from CHX-loaded nanoHA showed a fast initial rate followed by a slower kinetics release, due to constraints caused by dilution and diffusion-limiting processes. NanoHA.50 to nanoHA.1500 showed strong anti-sessile activity, inhibiting bacterial adhesion and the biofilm formation. CHX-nanoHA caused a dose- and time-dependent inhibitory effect on the proliferation of fibroblasts for nanoHA.100 to nanoHA.1500. Cellular behavior on nanoHA.5 and nanoHA.50 was similar to control. Therefore, CHX-loaded nanoHA surfaces appear as a promising alternative to prevention of devices-related infections.

Clinical heterogeneity of autosomal recessive spastic paraplegias: analysis of 106 patients in 46 families.

BACKGROUND: Hereditary spastic paraplegias (HSPs) are a heterogeneous group of neurodegenerative disorders characterized by progressive and predominant spasticity of the lower limbs, in which dominant, recessive, and X-linked forms have been described. While autosomal dominant HSP has been extensively studied, autosomal recessive HSP is less well known and is considered a rare condition. OBJECTIVE: To analyze the clinical presentation in a large group of patients with autosomal recessive HSP from Portugal and Algeria to define homogeneous groups that could serve as a guide for future molecular studies. RESULTS: Clinical features in 106 patients belonging to 46 Portuguese and Algerian families with autosomal recessive HSP are presented, as well as the results of molecular studies in 23 of these families. Five phenotypes are defined: (1) pure early-onset families, (2) pure lateonset families, (3) complex families with mental retardation, (4) complex families with mental retardation and peripheral neuropathy, and (5) complex families with cerebellar ataxia. Six additional families have specific complex presentations, each of which is unique in the present series. Pyramidal signs in the upper limbs and pes cavus are frequent findings, while pseudobulbar signs, including dysarthria, dysphagia, and brisk jaw jerks, are more frequent in the complex forms. The complex forms have a poorer prognosis, while pure forms, particularly those with early onset, are more benign. One Algerian pure early-onset kindred was linked to the locus on chromosome 8, previously reported in 4 Tunisian families. Two of the Portuguese kindreds with complex forms (one with mental retardation and the other associated with hypoplasia of the corpus callosum) showed linkage to the locus recently identified on chromosome 16. CONCLUSIONS: Although autosomal recessive HSP represents a heterogeneous group of diseases, some phenotypes can be defined by analyzing a large group of patients. The fact that only one Algerian family was linked to chromosome 8 suggests that this is a rare localization even in kindreds with the same ethnic background. Linkage to chromosome 16 was found in 2 clinically diverse Portuguese kindreds, illustrating that this locus is also rare and may correspond to different phenotypes.

In vitro evaluation of Midwest Caries ID: a novel light-emitting diode for caries detection.

INTRODUCTION: Traditional detection techniques have limits in diagnosing occlusal caries. Thus, more accurate methods are needed. This study evaluates the ability of the Midwest Caries ID (Midwest) to detect caries. METHODS: Two hundred sixty-four extracted, nonrestored premolars and molars were cleaned and stored in 0.2% sodium azide. Teeth were divided into three groups of 88. One examination site on each occlusal surface was chosen. Each site was inspected by a calibrated examiner via visual, Midwest, and histologic exams. First, a visual exam was performed following the International Caries Detection and Assessment guidelines. Next, the same site was inspected using the Midwest device. Finally, the tooth was sectioned mesiodistally through the site. The half with greater caries progression was visualized under a stereomicroscope (64×). Histologic appearance was scored based on the Downer system. Data were analyzed using Kendall tau-b, partial correlation coefficients, and the receiver operating characteristics curve. RESULTS: Overall, the Midwest scoring assessment correlated with histologic assessments (tau = 0.32; p<0.0001), but the visual exam had a stronger correlation (tau = 0.53; p<0.0001) with the histologic exam. The sensitivity and specificity of the Midwest was also reported at 0.56 and 0.84, compared with 0.92 and 0.43, respectively, for the visual exam. CONCLUSIONS: Midwest Caries ID is a novel caries detection device that has limitations and should not be used as the sole means to detect occlusal caries.

Effect of silver diamine fluoride on microtensile bond strength to dentin.

The aim of this in vitro study was to investigate the effect of the cariostatic and preventive agent silver diamine fluoride (SDF) on the microtensile bond strength of resin composite to dentin. Forty-two caries-free, extracted molars were flattened occlusally and apically using a diamond saw, and the exposed occlusal dentin was polished with a series of silicon carbide papers, all under water irrigation. The teeth were then randomly divided into six groups of seven teeth each that were treated as follows: 1) Peak SE self-etch bonding agent; 2) 12% SDF + Peak SE; 3) 38% SDF + Peak SE; 4) Peak LC etch-and-rinse bonding agent; 5) 12% SDF + Peak LC; and 6) 38% SDF + Peak LC. Four-millimeter buildups of Amelogen Plus were incrementally placed on all teeth; after a 24-hour storage period in distilled water, the specimens were sectioned perpendicular to the adhesive interface to produce beams of cross-sectional surface area measuring approximately 1 mm(2). The beams were placed on a microtensile testing machine, which utilized a single-speed pump motor and force gauge at 20 kgf × 0.01 second to record maximum tensile force before failure occurred. Two-way analysis of variance and post hoc Tukey tests were performed to compare the effects of the SDF on microtensile bond strength, with statistical significance set at α = 0.05. None of the experimental groups treated with different concentrations of SDF showed a significant difference in bond strength compared to the control groups, and there was no significant difference in bond strength between self-etch and etch-and-rinse groups. However, the effect of SDF on self-etch bonded teeth compared to etch-and-rinse bonded teeth was statistically significant (p=0.0363), specifically at the 12% concentration. SDF does not adversely affect the bond strength of resin composite to noncarious dentin.

Effect of bur type and conditioning on the surface and interface of dentine.

The purpose of this in vitro study was to evaluate the surface and resin-dentine interface characteristics of permanent tooth dentine cut with diamond or carbide burs and treated with phosphoric acid (PA) or an acidic conditioner. Labial surfaces of permanent incisors were prepared into dentine with high-speed carbide or diamond burs and divided into two halves. Phosphoric acid 36% was applied on one half and non-rinse conditioner (NRC) was applied on the other half. Ten randomly selected scanning electron microscopy (SEM) fields from each specimen (n = 15) were evaluated. Occlusal surfaces of third molars were divided in two halves for evaluation of the resin-dentine interface. The halves were randomly assigned to one of each conditioner and restored with Prime & Bond NT/Spectrum. Ten specimens were analysed by SEM to evaluate hybrid layer formation and interfacial seal. We observed that surfaces prepared with carbide bur presented less residual smear plugs (P < 0.05) than surfaces prepared with diamond burs. Surfaces conditioned with NRC, which is a smear layer modifier, presented more residual smear plugs than surfaces conditioned with PA (P < 0.05). Treatment with PA resulted in more sealed interfaces than specimens treated with NRC. Within the limitations of this study the results showed that carbide burs leave a surface that is more conducive to bonding than diamond burs.