Functionality testing of an innovative biomechanically optimized and surface-modified orthodontic mini-screw-a comparative study.

PURPOSE: The failure rate of orthodontic mini-screws depends strongly on primary stability and, thus, on insertion torque. Further improvement regarding the failure rate might be achieved by modifying the surface coating. Therefore, the aim of the study was to investigate the stability of a newly designed and surface-modified orthodontic mini-screw in beagle dogs. METHODS: Newly designed mini-screws coated either with DOTIZE® or DOTIZE®-copper (DOT GmbH, Rostock, Germany; each: n = 24) were inserted in the mandibles of eight beagle dogs for a duration of 8 months. Insertion and removal torque were measured. These data were compared to values generated by using the artificial bone material Sawbones® (Sawbones Europe AB, Malmö, Sweden). Experiments with and without torque limitation (each: n = 5) were run. The bone-to-implant contact rate and the amount of bone between the threads were examined. Statistical significance was set at P < 0.05. RESULTS: The success rates of the in vivo study reached high levels with 95.3% for the DOTIZE-coated and 90.5% for the DOTIZE-copper-coated screws, whereas the insertion and removal torque did not differ between the coatings. During insertion, a torque limitation of 20 Ncm was necessary to ensure that the recommended limit was not exceeded. The insertion in Sawbones without torque limitation revealed a significantly higher torque compared to torque-limited insertion (18.2 ± 1.3 Ncm, 23.6 ± 1.3 Ncm). Bending occurred (n = 5) in the thread-free part of the mini-screw. CONCLUSIONS: Surface coating might be able to improve the performance of orthodontic mini-screws. The study showed high success rates and stable mini-screws until the end of observation. Further investigations are necessary.

Influence of Test Specimen Geometry and Water Soaking on the In Vitro Cytotoxicity of Orthocryl®, Orthocryl® LC, Loctite® EA 9483 and Polypropylene.

Depending on their composition, plastics have a cytotoxic potential that needs to be evaluated before they are used in dentistry, e.g., as orthodontic removable appliances. Relevant guidelines set out requirements that a potential new resin in the medical field must meet, with a wide scope for experimental design. In the present study, test specimens of different geometries consisting of varying polymers (Orthocryl®, Orthocryl® LC, Loctite® EA 9483, Polypropylene) were soaked for different periods of time, then transferred to cell culture medium for 24 h, which was subsequently used for 24-h cultivation of A549 cells, followed by cytotoxicity assays (WST-1, Annexin V-FITC-propidium iodide (PI) flow cytometry). In this context, a reduction in the cytotoxic effect of the eluates of test specimens prepared from Orthocryl® LC and Loctite® EA 9483 was particularly evident in the Annexin V-FITC-PI assay when the soaking time was extended to 48 h and 168 h, respectively. Consistent with this, a reduced release of potentially toxic monomers into the cell culture medium, as measured by gas chromatography-mass spectrometry, was observed when the prior soaking time of test specimens of all geometries was extended. Remarkably, a significant increase in cytotoxic effect was observed in the WST-1 assay, which was accompanied by a higher release of monomers when the thickness of the test sample was increased from 0.5 to 1.0 mm, although an elution volume adapted to the surface area was used. However, further increasing the thickness to 3.0 mm did not lead to an increase in the observed cytotoxicity or monomer release. Test specimens made of polypropylene showed no toxicity under all test specimen sizes and soaking time conditions. Overall, it is recommended to perform toxicity studies of test specimens using different geometries and soaking times. Thereby, the influence of the different specimen thicknesses should also be considered. Finally, an extension of the test protocols proposed in ISO 10993-5:2009 should be considered, e.g., by flow cytometry or monomer analysis as well as fixed soaking times.

Comparative Sample Preparation Using Focused Ion Beam and Ultramicrotomy of Human Dental Enamel and Dentine for Multimicroscopic Imaging at Micro- and Nanoscale.

(1) Background: The aim of this study was to systematically compare TEM sections of mineralized human enamel and dentine prepared by focused ion beam (in situ lift-out) technique and ultramicrotomy through a combination of microscopic examination methods (scanning electron microscopy and transmission electron microscopy). In contrast with published studies, we compared the TEM preparation methods using the same specimen blocks as those for the ultramicrotomy and FIB technique. (2) Methods: A further evaluation of TEM sample preparation was obtained by confocal laser scanning microscopy and atomic force microscopy. In addition, ultramicrotome- and focused ion beam-induced artefacts are illustrated. (3) Results: The FIB technique exposed a major difference between non-decalcified enamel and dentine concerning the ultrastructural morphology compared to ultramicrotome-prepared sections. We found that ultramicrotomy was useful for cutting mineralized dentine, with the possibility of mechanical artefacts, but offers limited options for the preparation of mineralized enamel. FIB preparation produced high-quality TEM sections, showing the anisotropic ultrastructural morphology in detail, with minor structural artefacts. Our results show that the solution of artificial saliva and glutardialdehyde (2.5% by volume) is a very suitable fixative for human mineralized tissue. (4) Conclusions: The protocol that we developed has strong potential for the preparation of mineralized biomaterials for TEM imaging and analysis.

Prolonged treadmill training is not able to prevent ovariectomy-induced bone loss.

Introduction: Exercise is widely recognized as prophylaxis for osteoporosis. However, exactly which type of exercise is best to prevent loss of bone mass remains undefined. To find an appropriate form of treadmill exercise that would ameliorate postmenopausal loss of cortical and trabecular structures, we compared various training regimen in ovariectomized (OVX) C57BL/6J mice. Methods: Common to all regimen were training durations of 14 weeks including five 30 min-sessions per week. Two groups-one sham operated, one OVX-served as controls that did not perform any training. Three OVX groups ran at constant speed, either without any incline or at 20° in- and 20° decline, respectively. An additional OVX group ran an interval training, an alternation between intensive tempo sections and so-called slower regeneration phases. Femoral and humeral bone structures were assessed via micro-computed tomography (µCT), biomechanical stability of the femora via 3-point bending test, muscle volumes of the posterior extremities via magnetic resonance imaging (MRI), and bone metabolic parameters via ELISA on peripheral blood. Result: OVX resulted in loss of bone mass and stability and a transient rise in the N-terminal collagen type I pro-peptide (PINP). Training resulted in increased muscle volumes of the heart and the lower extremities as well as increased running velocities. However, none of the exercise programs was able to prevent ovariectomyinduced loss of bone mass. Discussion: These data therefore suggest that axial loading and tensile strain do not suffice as prophylaxis for postmenopausal osteoporosis yet may need to be complemented by low dose pharmaceutics or dietary supplements.

Interval Training Is Not Superior to Endurance Training With Respect to Bone Accrual of Ovariectomized Mice.

Physical exercise is considered to delay bone loss associated with post-menopausal estrogen deficiency in women. However, the optimal training regimen for maximal bone accrual has not yet been defined. We, therefore, turned to ovariectomized (OVX) C57BL/6 mice and directly compared a low intensity endurance training on the treadmill to medium and high intensity interval trainings tailored to the individual performance limits. Trainings lasted 30 min each and were performed five times/week. After a 5-week training period, mice were sacrificed, and the hind legs were analyzed for assessment of (i) biomechanical stability (three-point bending test), (ii) bone microarchitecture [micro-computed tomography (µCT)], (iii) mineral apposition rate (MAR; histomorphometry), and (iv) muscle volume (MRI). Increased running speeds and quadriceps femoris muscle volumes in trained mice confirmed positive impacts on the cardiopulmonary system and myoinduction; however, none of the treadmill training regimens prevented ovariectomy induced bone loss. Our results provide evidence that treadmill training impacts differentially on the various members of the musculoskeletal unit and call for further experiments investigating frequency and duration of training regimens.

Bone char vs. S-enriched bone char: Multi-method characterization of bone chars and their transformation in soil.

To decrease environmental impacts from usage of mineral P fertilizers based on rock phosphate, alternative P fertilizers are urgently necessary but have to be critically evaluated for their characteristics and behaviour or effects in soil. For this reason, bone char (BC) and S-enriched BC (BCplus), original and after one vegetation period in soil, were analysed by wet chemical analyses and XANES spectroscopy. According to X-ray absorption near edge structure (XANES) spectroscopy, both chars were dominated by P bound in hydroxyapatite, which was well reflected by wet chemical P fractionation, where Ca-P was the dominant fraction. Sulfur fractionation of both chars confirmed low percentages of sulfate-S according to XANES analysis but failed to detect elemental S in BCplus. Because S concentrations in BCplus were comparable to that of activated carbon used for biogas desulfurization and sorbed S was dominantly elemental S, BC seems to be well suited for biogas desulfurization. After one year in soil the disappearance of more easily soluble Ca(H2PO4)·2H2O and strongly reduced proportions of sulfates and sulfonates in soil-BCplus compared to BCplus pointed to considerable advantages of BCplus over BC. Taking into consideration the acidic pH of BCplus, the high Ca, P, and S concentrations and the expected microbial induced "in situ digestion" of BC by oxidation of elemental S, it can be concluded that a cascade usage of BC as biogas adsorber and following subsequent usage of BCplus as S/P/Ca/Mg (multi-element) fertilizer could be an alternative to mineral fertilizers based on rock phosphate. The agronomic efficiency and detailed application guidelines must be derived from established and currently running longer-term plot and field experiments.

Correlation of ultrasound microscopy and Vickers hardness measurements of human dentin and enamel - A pilot study.

OBJECTIVE: To investigate if Vickers microhardness of dentin and enamel correlated with acoustic velocity c(l) or acoustic reflection from the sample's top (amplitude). METHODS: Eight transversal sections of a sound human tooth were investigated with scanning acoustic microscopy (SAM) and Vickers microhardness measurements. Longitudinal acoustic velocity c(l), amplitude and microhardness MHV were evaluated and for each c(l) test point corresponding amplitude and MHV were linearly interpolated and graphically analyzed. Spearman rank order correlation (rS) was calculated (p<0.05). RESULTS: c(l) was predominantly 6100-7000ms-1 in enamel and 3800-4600ms-1 in dentin and correlated significantly with MHV with 27-420 in enamel and 20-90 in dentin (rs=0,57). Amplitudes significantly correlated with MHV, too, but even better (rs=0,77). SIGNIFICANCE: Acoustic velocity and amplitudes were appropriate to detect microhardness differences of dentin and enamel and certain value ranges of both could be assigned to certain MHV ranges. Further research is needed to differentiate more precisely between the different hard tooth tissues.

In vitro aging behavior of dental composites considering the influence of filler content, storage media and incubation time.

OBJECTIVE: Over time dental composites age due to mechanical impacts such as chewing and chemical impacts such as saliva enzymes and food ingredients. For this research, the focus was placed on chemical degradation. The objective of this study was to simulate hydrolysis by using different food simulating liquids and to assess their impact on the mechanical parameter Vickers microhardness (MHV) and the physicochemical parameter contact angle (CA). METHODS: Specimen of three composites (d = 6 mm, h = 2 mm; n = 435) classified with respect to their filler content (wt%), namely low-filled, medium-filled and highly-filled, were stored for 0, 14, 30, 90 and 180 days in artificial saliva (pH 7), citric acid (pH 3; pH 5), lactic acid (pH 3; pH 5) and ethanol (40%vol; 60%vol) and assessed regarding to MHV and CA. Statistics: Kruskal-Wallis test, stepwise linear regression, bivariate Spearman Rank Correlation (p < 0.05). RESULTS: While stored in artificial saliva, acid and ethanol the CA decreased especially for the low- and medium-filled composites. It was shown that rising the filler content caused less surface changes in the CA. Storage in ethanol led to a significant decrease of MHV of all composites. Regression analysis showed that the effect of in vitro aging on MHV was mainly influenced by the composite material and therefore by filler content (R2 = 0.67; p < 0.05). In contrast, the CA is more influenced by incubation time and filler content (R2 = 0.2; p < 0.05) leading to a higher risk of plaque accumulation over time. Significance: In vitro aging showed significant changes on the mechanical and physicochemical properties of dental composites which may shorten their long-term functionality. In conclusion, it can be stated, that the type of composite material, especially rising filler content seems to improve the materials' resistance against the processes of chemical degradation.

Flexible Automation System for Determination of Elemental Composition of Incrustations in Clogged Biliary Endoprostheses Using ICP-MS.

Automation systems are well established in industries and life science laboratories, especially in bioscreening and high-throughput applications. An increasing demand of automation solutions can be seen in the field of analytical measurement in chemical synthesis, quality control, and medical and pharmaceutical fields, as well as research and development. In this study, an automation solution was developed and optimized for the investigation of new biliary endoprostheses (stents), which should reduce clogging after implantation in the human body. The material inside the stents (incrustations) has to be controlled regularly and under identical conditions. The elemental composition is one criterion to be monitored in stent development. The manual procedure was transferred to an automated process including sample preparation, elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS), and data evaluation. Due to safety issues, microwave-assisted acid digestion was executed outside of the automation system. The performance of the automated process was determined and validated. The measurement results and the processing times were compared for both the manual and the automated procedure. Finally, real samples of stent incrustations and pig bile were analyzed using the automation system.

Fast corroding, thin magnesium coating displays antibacterial effects and low cytotoxicity.

Bacterial colonisation and biofilm formation are characteristics of implant-associated infections. In search of candidates for improved prosthetic materials, fast corroding Mg-based coatings on titanium surfaces were examined for their cytotoxic and antimicrobial properties. Human osteoblasts and Staphylococcus epidermidis were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg45Zn5Ca, applied via magnetron sputtering. Uncoated titanium samples served as controls. S. epidermidis was quantified by counting colony forming units. The biofilm-bound fraction was isolated via ultrasonic treatment, and the planktonic fraction via centrifugation. Biofilm-bound S. epidermidis was significantly decreased by approximately four to five orders of magnitude in both Mg- and Mg45Zn5Ca-coated samples after seven days compared to the control. The osteoblast viability was within the tolerance threshold of 70% stated in DIN EN ISO 10993-5:2009-10 for Mg (~80%) but not for Mg45Zn5Ca (~25%). Accordingly, Mg-coated titanium was identified as a promising candidate for an implant material with antibacterial properties and low cytotoxicity levels. The approach of exploiting fast corrosion contrasts with existing methods, which have generally focused on reducing corrosion.

Can nasal decongestants improve eustachian tube function?

OBJECTIVE: To evaluate the effect of nasal decongestants on eustachian tube (ET) opening. STUDY DESIGN: A prospective nonrandomized study. SETTING: A tertiary referral center. PATIENTS: Twenty-four patients (44 ears) with intact eardrums, 39 patients (43 ears) having a noninfected eardrum defect, and six patients with an upper airway infection. INTERVENTIONS: Nasal or intratympanal (in perforated ears) application of a nasal decongestant (xylometazoline 0.1%). MAIN OUTCOME MEASURES: Change of tube opening quality (yes or no; better or worse) measuring tube opening parameters (pressure, latency) using the Estève method and pressure equalization tests (swallowing at negative and positive external ear canal pressures). RESULTS: In most cases, nasal decongestion or intratympanal use of decongestants have no effect on ET opening. Improvement in tube opening is rather an exception and, in a minority of patients, a reduced ET function was evident. CONCLUSION: Our acute studies revealed no improvement in eustachian ventilatory tube function with the administration of nasal decongestants.

Linking a neural mass model with a 3D model of the human brain to reproduce EEG signals.

Electroencephalography (EEG) is often employed to measure electrical activity in the living human brain. Simulation studies can help unravel how the brain electrical activity pattern generates the EEG signal, still a widely unresolved question. This article describes a method to simulate brain electrical activity by using neuronal populations of a neural mass model. Implementing these populations in a finite element model of the head offers the opportunity to investigate the influence of each group of neurons to the scalp potential. This model is based on structural magnetic resonance imaging data to specify tissue composition, and diffusion tensor imaging data to model local anisotropy. We simulated the EEG signals of five neuronal populations generating α waves in the visual cortex. Our results indicate that radially oriented sources dominate over tangential sources in the generation of the scalp signal. Investigating the influence of anisotropic conductivity, we found small differences in topography and phase and larger ones for the potential amplitude compared with an isotropic conductivity distribution. The outcome of this article is a fast method based on superposition of sources for simulating time-dependent EEG signals, which can be used for further studies of neurodegenerative diseases.

No influence of simultaneous bone-substitute application on the success of immediately loaded dental implants: a retrospective cohort study.

PURPOSE: To examine the influence of bone-substitute application during implantation on the success of immediately placed and loaded dental implants. MATERIALS AND METHODS: A total of 147 consecutive patients (age, 16.5-80.4 years) were provided with 696 immediately loaded implants. The mean follow-up time was 34.1 months. Of these implants, 50.4% (n=351) were immediately placed into extraction sockets. A total of 119 implants were added by simultaneous bone-substitute application (NanoBone, Artoss GmbH, Rostock Germany), whereas the other implants were placed in healed bone. Univariate and multivariate analysis was performed using IBM SPSS V.20. RESULTS: The overall implant success rate was 96.1%. Implants with simultaneous bone replacement had a hazard ratio of 0.877 (p=0.837); 95% CI, 0.253-3.04). Factors found to be statistically significant modifiers of success on multivariate analysis (p<0.05) included type of superstructure (p<0.001), implant-abutment connection (p<0.001), membrane use (p=0.010), and jaw (p=0.026). None of the other factors investigated were significant modifiers. CONCLUSIONS: The present study demonstrates high success rates for immediately loaded implants and their superstructures independent of the simultaneous application of bone substitute. The declared aim of socket preservation, the prevention avoiding bone loss, is achieved in the immediate implant placement scenario under immediate-loading conditions.

Section plane selection influences the results of histomorphometric studies: the example of dental implants.

OBJECTIVES: This study was designed to determine and statistically analyze bone-to-implant contact (BIC) values for human specimens segmented in at least two different locations. MATERIALS AND METHODS: Samples of human bone with fractured osseointegrated implants were obtained from six patients. Sections were prepared, dehydrated, and resin infiltrated. Undecalcified bone sections were produced using the thin-section technique according to Donath, ultimately obtaining a section thickness of approximately 20 µm. Fifteen specimens were available for histomorphometry. The bone sections were digitized and analyzed. The bone-to-metal contact (BMC) parameter was determined histomorphometrically. The BMC was returned in terms of the visibly bone-covered implant surfaces as a percentage of the total implant surface shown. RESULTS: The values obtained for the six implants were arranged as six maximum-distance pairs and tested for significance using the t-test for dependent samples. The mean difference in BIC was 11.69±9.79%. The two-sided test showed a significant difference (p=0.033). CONCLUSION: The accidental or deliberate choice of section plane for a bone-implant block has an influence on the BIC value. To make BIC values more comparable, a standardization of section planes is desirable.

Experiments on the mechanism of underwater hearing.

CONCLUSION: The findings suggest that underwater sound perception is realized by the middle ear rather than by bone conduction, at least in shallow water conditions. OBJECTIVE: To prove whether underwater sound perception is effected by bone conduction or by conduction via the middle ear. METHODS: Five divers, breathing through snorkels, were tested in a swimming pool, to determine whether a sound was louder when the acoustic source placed was in front of the head in comparison with a lateral application facing the ear region. The second experiment investigated whether sound perception is influenced by ear protection plugs in underwater conditions. Also, the effect of a 5 mm thick neoprene hood was determined, with and without an additional perforation in the ear region. RESULTS: Sounds were louder when applied from a position laterally facing the ear, louder without than with a protection plug, louder without than with a neoprene hood on, and louder when the neoprene hood had a perforation in the region of the ear than with an intact hood.

Bacterial activity and bacterioplankton diversity in the eutrophic River Warnow--direct measurement of bacterial growth efficiency and its effect on carbon utilization.

The influence of bacterial activity and diversity on bacterial growth efficiency was investigated in a flatland river. Eutrophic River Warnow drains predominantly agricultural land and is heavily loaded with nutrients, dissolved and particulate organic matter (DOM and POM), especially humic substances. Although the water column bacterial community consists of many inactive or damaged cells, bacterioplankton sustained a high bacterial secondary production of 0.2-14.5 µg C L(-1) h(-1) and a high DNA synthesis (thymidine uptake) of 6.1-15.5 µg C L(-1) h(-1). The direct and short-term measurement of bacterial respiration (by optodes) revealed high respiration rates especially in summer leading to directly estimated bacterial growth efficiencies (BGE) of 2-28%. These values are compared to calculations based only on bacterial production, which considerably overestimated BGEs. From all these data, River Warnow can be characterized as a strongly remineralizing system. River Warnow was dominated among others by Cytophaga/Flavobacteria and Actinobacteria which are typical for organic rich waters because of their ability to degrade high molecular weight compounds. However, community composition did not significantly affect BGE.

New and fast method to quantify respiration rates of bacterial and plankton communities in freshwater ecosystems by using optical oxygen sensor spots.

A new method of respiration rate measurement based on oxygen luminescence quenching in sensor spots was evaluated for the first time for aquatic bacterial communities. The commonly used Winkler and Clark electrode methods to quantify oxygen concentration both require long incubation times, and the latter additionally causes signal drift due to oxygen consumption at the cathode. The sensor spots proved to be advantageous over those methods in terms of precise and quick oxygen measurements in natural bacterial communities, guaranteeing a respiration rate estimate during a time interval short enough to neglect variations in organism composition, abundance, and activity. Furthermore, no signal drift occurs during measurements, and respiration rate measurements are reliable even at low temperatures and low oxygen consumption rates. Both a natural bacterioplankton sample and a bacterial isolate from a eutrophic river were evaluated in order to optimize the new method for aquatic microorganisms. A minimum abundance of 2.2 x 10(6) respiring cells ml(-1) of a bacterial isolate was sufficient to obtain a distinct oxygen depletion signal within 20 min at 20 degrees C with the new oxygen sensor spot method. Thus, a culture of a bacterial isolate from a eutrophic river (OW 144; 20 x 10(6) respiring bacteria ml(-1)) decreased the oxygen saturation about 8% within 20 min. The natural bacterioplankton sample respired 2.8% from initially 94% oxygen-saturated water in 30 min. During the growth season in 2005, the planktonic community of a eutrophic river consumed between 0.7 and 15.6 micromol O(2) liter(-1) h(-1). The contribution of bacterial respiration to the total plankton community oxygen consumption varied seasonally between 11 and 100%.