Conical crowns with electroplated gold copings: retention force changes caused by wear and combined off-axial load

The aim of this study was to examine the wear behavior of conical crowns of gold alloy and zirconium dioxide ceramics facing electroplated gold copings.

Changes in retention force with electroplated copings on conical crowns: a comparison of gold and zirconia primary crowns

The aim of this study was to examine the wear behavior of conical crowns with electroplated gold copings that are used to connect implants and teeth to a removable denture. Gold alloy and zirconium dioxide ceramic crowns were compared.

4D/3D reduction of dualities: mirrors on the circle

We engineer a brane picture for the reduction of Seiberg dualities from 4D to 3D, valid also in the presence of orientifold planes. We obtain effective 3D dualities on the circle by T-duality, geometrizing the non-perturbative superpotential which is an affine Toda potential. When reducing to pure 3D, we define a double-scaling limit which creates a sector of interacting singlets, giving a unified mechanism for the brane reduction of dualities.

Handrub Consumption Mirrors Hand Hygiene Compliance

We assessed handrub consumption as a surrogate marker for hand hygiene compliance from 2007 to 2014. Handrub consumption varied substantially between departments but correlated in a mixed effects regression model with the number of patient-days and the observed hand hygiene compliance. Handrub consumption may supplement traditional hand hygiene observations. Infect. Control Hosp. Epidemiol. 2016;1-4.

Personal neglect-a disorder of body representation?

The cognitive mechanisms underlying personal neglect are not well known. One theory postulates that personal neglect is due to a disorder of contralesional body representation. In the present study, we have investigated whether personal neglect is best explained by impairments in the representation of the contralesional side of the body, in particular, or a dysfunction of the mental representation of the contralesional space in general. For this, 22 patients with right hemisphere cerebral lesions (7 with personal neglect, 15 without personal neglect) and 13 healthy controls have been studied using two experimental tasks measuring representation of the body and extrapersonal space. In the tasks, photographs of left and right hands as well as left and right rear-view mirrors presented from the front and the back had to be judged as left or right. Our results show that patients with personal neglect made more errors when asked to judge stimuli of left hands and left rear-view mirrors than either patients without personal neglect or healthy controls. Furthermore, regression analyses indicated that errors in interpreting left hands were the best predictor of personal neglect, while other variables such as extrapersonal neglect, somatosensory or motor impairments, or deficits in left extrapersonal space representation had no predictive value of personal neglect. These findings suggest that deficient body representation is the major mechanism underlying personal neglect.

Wear of double crown systems: electroplated vs. casted female part

The wear of telescopic crowns is a common problem often reducing the patient's satisfaction with the denture and resulting in a renewal of the denture. The study aims to compare the wear behavior of conical crowns using electroplated copings (group E ) with standard telescopic crowns with cast female parts (group C).

Performance of a new laser fluorescence device for the detection of occlusal caries in vitro

The new device DIAGNOdent pen based on red laser light induced fluorescence was introduced for the detection of approximal and occlusal caries. The aim of this study was to test its performance on occlusal surfaces. The new device comes with two different sapphire fibre tips: a cylindrical tip and a conical tip. The two new sapphire fibre tips were used and compared with the tip currently available with DIAGNOdent (DD). METHODS: The teeth were selected from a pool of extracted permanent human molars, which were stored frozen at -20 degrees C, until use. Prior to being measured the teeth were defrosted and cleaned. One hundred and nineteen teeth were selected and measured with the old tip and with the two new tips of the new device by two independent assessments. The teeth were histologically prepared and assessed for caries extension. RESULTS: Specificity values for D(1), D(2) and D(3) ranged between 0.69 and 0.89, sensitivity between 0.78 and 0.96. There were no statistically significant differences obtained between the two tips of the new and the one tip of the old device (p>0.05). Intra-examiner reliability with kappa values of >0.83 was high. CONCLUSIONS: In this study, the new laser fluorescence device performed on occlusal surfaces as well as the available device.

Morphogenesis of the peri-implant mucosa: an experimental study in dogs

PURPOSE: The objective of the present experiment was to study the morphogenesis of the mucosal attachment to implants made of c.p. titanium. MATERIAL AND METHODS: All mandibular premolars were extracted in 20 Labrador dogs. After a healing period of 3 months, four implants (ITI Dental Implant System) were placed in the right and left sides of the mandible. A non-submerged implant installation technique was used and the mucosal tissues were secured to the conical marginal portion of the implants with interrupted sutures. The sutures were removed after 2 weeks and a plaque control program including daily cleaning of the remaining teeth and the implants was initiated. The animals were sacrificed and biopsies were obtained at various intervals to provide healing periods extending from Day 0 (2 h) to 12 weeks. The mandibles were removed and placed in the fixative. The implant sites were dissected using a diamond saw and processed for histological analysis. RESULTS: Large numbers of neutrophils infiltrated and degraded the coagulum that occupied the compartment between the mucosa and the implant during the initial phase of healing. At 2 weeks after surgery, fibroblasts were the dominating cell population in the connective tissue interface but at 4 weeks the density of fibroblasts had decreased. Furthermore, the first signs of epithelial proliferation were observed in specimens representing 1-2 weeks of healing and a mature barrier epithelium occurred after 6-8 weeks of healing. The collagen fibers of the mucosa were organized after 4-6 weeks of healing. CONCLUSION: It is suggested that the soft-tissue attachment to implants placed using a non-submerged installation procedure is properly established after several weeks following surgery.

CT radiation dose for computer-assisted endoscopic sinus surgery: dose survey and determination of dose-reduction limits

BACKGROUND AND PURPOSE: Computer-assisted navigation is increasingly used in functional endoscopic sinus surgery (FESS) to prevent injury to vital structures, necessitating preparative CT and, thus, radiation exposure. The purpose of our study was to investigate currently used radiation doses for CT in computer-assisted navigation in sinus surgery (CAS-CT) and to assess minimal doses required. MATERIALS AND METHODS: A questionnaire inquiring about dose parameters used for CAS-CT was sent to 30 radiologic institutions. The feasibility of low-dose registration was tested with a phantom. The influence of CAS-CT dose on technical accuracy and on the practical performance of 5 ear, nose, and throat (ENT) surgeons was evaluated with cadaver heads. RESULTS: The questionnaire response rate was 63%. Variation between minimal and maximal dose used for CAS-CT was 18-fold. Phantom registration was possible with doses as low as 1.1 mGy. No dose dependence on technical accuracy was found. ENT surgeons were able to identify anatomic landmarks on scans with a dose as low as 3.1 mGy. CONCLUSIONS: The vast dose difference between institutions mirrors different attitudes toward image quality and radiation-protection issues rather than being technically founded, and many patients undergo CAS-CT at higher doses than necessary. The only limit for dose reduction in CT for computer-assisted endoscopic sinus surgery is the ENT surgeon's ability to cope with impaired image quality, whereas there is no technically justified lower dose limit. We recommend, generally, doses used for the typical diagnostic low-dose sinus CT (120 kV/20-50 mAs). When no diagnostic image quality is needed, even a reduction down to a third is possible.

The use of extraoral implants for distal-extension removable dentures: a clinical evaluation up to 8 years

PURPOSE: This retrospective study reports the clinical outcome following placement of extraoral implants in severely resorbed posterior ridges to support distal-extension removable dentures. MATERIAL AND METHODS: Consecutively treated patients with partially or completely edentulous ridges, with available bone height in the posterior region of 6 mm or less, were included in the study. Implants originally intended for extraoral use (Straumann) were placed in second molar regions and allowed to heal for 4 to 6 months before abutment connection. At recall appointments, the peri-implant hard and soft tissues were evaluated. Complications with implant components, as well as mechanical and structural failures of the prostheses, were recorded. Two-year survival rates were calculated and life table analyses undertaken. RESULTS: Twenty-nine patients (19 women and 10 men; average age 61.2 years, range, 44 to 75 years) were included in the study. Forty-seven extraoral implants in 26 patients were placed in the second molar site of the mandible. Two extraoral implants in 2 patients failed during the osseointegration phase, yielding an 8-year cumulative success rate of 91.8%. The mean distance from the extraoral implants to the most distal tooth/implant was 28.1 mm (range, 16.7 to 39.2 mm). Twenty-three extraoral implants were restored with magnets, 18 with ball anchors, and 4 with conical cylinders. Replacement of abutments and retention elements was necessary in 2 patients. Four abutments in 2 patients were disconnected from the restorations. CONCLUSIONS: Within the limits of the employed research design, extraoral implants may be used successfully to provide support for distal-extension removable dentures in severely resorbed posterior alveolar ridges.

A generalized anisotropic quadric yield criterion and its application to bone tissue at multiple length scales

Nonlinear computational analysis of materials showing elasto-plasticity or damage relies on knowledge of their yield behavior and strengths under complex stress states. In this work, a generalized anisotropic quadric yield criterion is proposed that is homogeneous of degree one and takes a convex quadric shape with a smooth transition from ellipsoidal to cylindrical or conical surfaces. If in the case of material identification, the shape of the yield function is not known a priori, a minimization using the quadric criterion will result in the optimal shape among the convex quadrics. The convexity limits of the criterion and the transition points between the different shapes are identified. Several special cases of the criterion for distinct material symmetries such as isotropy, cubic symmetry, fabric-based orthotropy and general orthotropy are presented and discussed. The generality of the formulation is demonstrated by showing its degeneration to several classical yield surfaces like the von Mises, Drucker–Prager, Tsai–Wu, Liu, generalized Hill and classical Hill criteria under appropriate conditions. Applicability of the formulation for micromechanical analyses was shown by transformation of a criterion for porous cohesive-frictional materials by Maghous et al. In order to demonstrate the advantages of the generalized formulation, bone is chosen as an example material, since it features yield envelopes with different shapes depending on the considered length scale. A fabric- and density-based quadric criterion for the description of homogenized material behavior of trabecular bone is identified from uniaxial, multiaxial and torsional experimental data. Also, a fabric- and density-based Tsai–Wu yield criterion for homogenized trabecular bone from in silico data is converted to an equivalent quadric criterion by introduction of a transformation of the interaction parameters. Finally, a quadric yield criterion for lamellar bone at the microscale is identified from a nanoindentation study reported in the literature, thus demonstrating the applicability of the generalized formulation to the description of the yield envelope of bone at multiple length scales.

The influence of yield surface shape and damage in the depth-dependent response of bone tissue to nanoindentation using spherical and Berkovich indenters

Prevention and treatment of osteoporosis rely on understanding of the micromechanical behaviour of bone and its influence on fracture toughness and cell-mediated adaptation processes. Postyield properties may be assessed by nonlinear finite element simulations of nanoindentation using elastoplastic and damage models. This computational study aims at determining the influence of yield surface shape and damage on the depth-dependent response of bone to nanoindentation using spherical and conical tips. Yield surface shape and damage were shown to have a major impact on the indentation curves. Their influence on indentation modulus, hardness, their ratio as well as the elastic-to-total work ratio is well described by multilinear regressions for both tip shapes. For conical tips, indentation depth was not statistically significant (p<0.0001). For spherical tips, damage was not a significant parameter (p<0.0001). The gained knowledge can be used for developing an inverse method for identification of postelastic properties of bone from nanoindentation.

Radiometric Method for Emissivity Retrieval in High Reflective Materials

High reflective materials in the microwave region play a very important role in the realization of antenna reflectors for a broad range of applications, including radiometry. These reflectors have a characteristic emissivity which needs to be characterized accurately in order to perform a correct radiometric calibration of the instrument. Such a characterization can be performed by using open resonators, waveguide cavities or by radiometric measurements. The latter consists of comparative radiometric observations of absorbers, reference mirrors and the sample under test, or using the cold sky radiation as a direct reference source. While the first two mentioned techniques are suitable for the characterization of metal plates and mirrors, the latter has the advantages to be also applicable to soft materials. This paper describes how, through this radiometric techniques, it is possible to characterize the emissivity of the sample relative to a reference mirror and how to characterize the absolute emissivity of the latter by performing measurements at different incident angles. The results presented in this paper are based on our investigations on emissivity of a multilayer insulation material (MLI) for space mission, at the frequencies of 22 and 90 GHz.