Vertical Loss Research Articles

Wear behavior of seven artificial resin teeth assessed with three-dimensional measurements

Artificial resin teeth are widely used for removable dental prostheses because of their excellent properties. An evaluation of their wear behavior is important for predicting good clinical performance. The purpose of the study was to examine the wear behavior of 7 different artificial resin teeth with 3-dimensional measurements. The artificial denture teeth tested were 2 composite resin teeth (Yamahachi PX, Huge Kaijing), 3 cross-linked acrylic resin teeth (Cosmo HXL, Premium 8, Vita Lingoform), and 2 conventional acrylic resin teeth (Yamahachi FX, Shengjian). The specimens were subjected to an abrasive tester for masticatory simulation. The wear loss (vertical loss and volume loss) was determined with a confocal laser scanning microscope. Data were analyzed with 1-way ANOVA followed by the Games-Howell post hoc test (α=.05). The mean vertical loss and volume loss for all cross-linked acrylic resin teeth (0.987-1.03 μm, 0.858-0.939 mm(3) × 10(-3)) were higher than for all composite resin teeth (0.636-0.698 μm, 0.507-0.650 mm(3) × 10(-3), P<.001) but lower than those for conventional acrylic resin teeth Yamahachi FX and Shengjian (1.39 μm, 1.24 mm(3) × 10(-3); 12.1 μm, 16.4 mm(3) × 10(-3); P<.001). No significant differences for wear loss were found between the Vita Lingoform group and the other cross-linked acrylic resin teeth (P>.05). The wear behavior of the artificial teeth examined differed with regard to their compositions. The composite resin teeth and high cross-linked acrylic resin teeth found superior wear resistance over the conventional acrylic resin teeth.

Efficacy and safety of vertebral stenting for painful vertebral compression fractures in patients with metastatic disease

Background and Purpose:Painful vertebral compression fractures in cancer patients reduce quality of life and may limit survival. We assessed pain relief, vertebral height restoration, and kyphosis correction following vertebral augmentation using a novel expandable titanium stent implant in cancer patients with painful vertebral compression fractures.Materials and Methods:Patients >18 years of age with metastatic disease who presented symptomatic compression fractures of vertebral bodies T5–L5, with or without a history of osteoporosis, were included in the study. Back pain at presentation, immediately after vertebral stenting, and at 1-, 3-, 6-, and 12-month follow-up was estimated using the visual analog scale (VAS). Vertebral height and local kyphotic angle (alpha angle) were measured on lateral standing X-ray before and 1–3 months after stenting.Results:Forty-one cancer patients with painful vertebral compression fractures underwent vertebral stenting procedures at 55 levels. There was no perioperative mortality and no significant complication. Median preoperative VAS was 8·0 (range 8–10), falling to 2·0 immediately postop (range 1–6, P = 0·000) and 0 at all subsequent follow-up (P ≤ 0·012). Mean preoperative vertical height loss was 25·8% (range 0–84·0%) versus a postoperative mean of 18·0% (range 0–66·0%, P = 0·000). Median pre- and postoperative kyphotic angle improved from 8·3° (range 0·2°–54·0°) to 7·1° (range 0·2°–25·0°, P = 0·000). Wilcoxon signed rank test or student's t-test was used for comparisons.Conclusions:Vertebral augmentation using a novel vertebral stenting system provided immediate and enduring pain relief and improved vertebral height loss and kyphotic angle.

Modelling and fault tolerant control for near space vehicles with vertical tail loss

This work focuses on modelling and fault tolerant algorithm design of a damaged near space vehicle. A novel radial basis function (RBF) neural network backstepping fault-tolerant control methodology is developed for attitude control system with damage, which can make system stable and accurately track the desired signals in the presence of vertical tail loss. First, the changing aerodynamic parameters caused by vertical tail loss are used to model damaged attitude dynamics. Second, in view of the established damaged model, a nominal backstepping controller is designed. Then a RBF neural network technology is designed to update the related parameters, which can compensate effects caused by damage and make the system still stable and track the desired signals. Finally, simulation results are provided to show the effectiveness of the proposed RBF neural network backstepping fault-tolerant control scheme.

Charge Loss Characteristics of Different Al Contents in a HfAlO Trapping Layer Investigated by Variable Temperature Kelvin Probe Force Microscopy

Kelvin probe force microscopy (KFM) technology is applied to investigate the charge storage and loss characteristics of the HfAlO charge trapping layer with various Al contents. The experimental results demonstrate that with the increase of Al contents in the HfAlO trapping layer, trap density significantly increases. Improvement of data retention characteristic is also observed. Comparing the vertical charge loss and lateral charge spreading of the HfAlO trapping layers, the former plays a major role in the charge loss mechanism. Variable temperature KFM measurement results show that the extracted effective electron trap energy level increases with increasing Al contents in HfAlO trapping layer, which is in accordance with the charge loss characteristics.

Management of shortened dental arches and periodontal health: 5‐year results of a randomised trial

In a multicentre randomised trial (German Research Association, grants DFG WA 831/2-1 to 2-6, WO 677/2-1.1 to 2-2.1.; controlled-trials.com ISRCTN97265367), patients with complete molar loss in one jaw received either a partial removable dental prosthesis (PRDP) with precision attachments or treatment according to the SDA concept aiming at pre-molar occlusion. The objective of this current analysis was to evaluate the influence of different treatments on periodontal health. Linear mixed regression models were fitted to quantify the differences between the treatment groups. The assessment at 5 years encompassed 59 patients (PRDP group) and 46 patients (SDA group). For the distal measuring sites of the posterior-most teeth of the study jaw, significant differences were found for the plaque index according to Silness and Löe, vertical clinical attachment loss (CAL-V), probing pocket depth (PPD) and bleeding on probing. These differences were small and showed a slightly more unfavourable course in the PRDP group. With CAL-V and PPD, significant differences were also found for the study jaw as a whole. For CAL-V, the estimated group differences over 5 years amounted to 0.27 mm (95% CI 0.05; 0.48; P = 0.016) for the study jaw and 0.25 mm (95% CI 0.05; 0.45; P = 0.014) for the distal sites of the posterior-most teeth. The respective values for PPD were 0.22 mm (95% CI 0.03; 0.41; P = 0.023) and 0.32 mm (95% CI 0.13; 0.5; P = 0.001). It can be concluded that even in a well-maintained.patient group statistically significant although minor detrimental effects of PRDPs on periodontal health are measurable.

A Method of Measuring the In Situ Seafloor Sound Speed using Two Receivers with Warping Transformation

We present a method of measuring the in situ superficial seafloor sound speed by using two receivers deployed vertically in sediment, based on the dispersion characteristic of normal modes in shallow water. Warping transformation is adopted to extract the first normal mode from the broadband propagation signals. Some experimental results which could validate the method are shown. One of the advantages of the method is that the seafloor sound speed can be solved directly from the relative vertical transmission loss of the first normal mode without the exact priori information of the environmental parameters such as the sound speed profile, the water-column depth and the source location.

Enamel wear caused by monolithic zirconia crowns after 6 months of clinical use

The purpose of this study was to evaluate enamel wear caused by monolithic zirconia crowns and to compare this with enamel wear caused by contralateral natural antagonists. Twenty monolithic zirconia crowns were placed in 20 patients requiring full molar crowns. For measurement of wear, impressions of both jaws were made at baseline after crown cementation and at 6-month follow-up. Mean and maximum wear of the occlusal contact areas of the crowns, of their natural antagonists and of the two contralateral natural antagonists were measured by the use of plaster replicas and 3D laser scanning methods. Wear differences were investigated by the use of two-sided paired Student's t-tests and by linear regression analysis. Mean vertical loss (maximum vertical loss in parentheses) was 10 (43) μm for the zirconia crowns, 33 (112) μm for the opposing enamel, 10 (58) μm for the contralateral teeth and 10 (46) μm for the contralateral antagonists. Both mean and maximum enamel wear were significantly different between the antagonists of the zirconia crowns and the contralateral antagonists. Gender and activity of the masseter muscle at night (bruxism) were identified as possible confounders which significantly affected wear. Under clinical conditions, monolithic zirconia crowns seem to be associated with more wear of opposed enamel than are natural teeth. With regard to wear behaviour, clinical application of monolithic zirconia crowns is justifiable because the amount of antagonistic enamel wear after 6months is comparable with, or even lower than, that caused by other ceramic materials in previous studies.

Correlation Between Interimplant Distance and Crestal Bone Loss in Internal Connection Implants with Platform Switching

The aim of this study was to investigate the influence of interimplant distance of internal connection implants with platform switching on crestal bone loss using radiographic evaluation. The present study included patients missing two consecutive teeth in the posterior quadrant and receiving internal connection implants. Digital periapical radiographs were taken at the time of superstructure connection and at the time of more than 1 year of loading. Bone level change was measured on the modified image using a digital subtraction program. The crestal bone loss between implants and the horizontal and vertical loss of peri-implant marginal bone were evaluated, and the influence of interimplant distance on crestal bone loss was analyzed at α = .05. A total of 10 pairs of implants having ≤ 3 mm of interimplant distance was included in this study (group 1). The other 15 pairs of implants having > 3 mm of interimplant distance were selected as a control group (group 2). After the mean 19.3 months of observation, the mean crestal bone loss between implants was -0.26 ± 0.14 mm in group 1 and -0.23 ± 0.29 mm in group 2 (P > .05). There was no significant difference between the interimplant distance and the crestal bone loss according to the regression analysis (P = .765). The mean horizontal and vertical marginal bone loss was -0.18 ± 0.25 mm and -0.15 ± 0.18 mm, respectively, in group 1 and -0.17 ± 0.31 mm and -0.11 ± 0.33 mm, respectively, in group 2. There were no significant differences between outside and inside bone loss of implants in horizontal and vertical change (P > .05). Within the limitations of the short-term study, the interimplant distance did not affect the crestal bone loss with internal connection implants with platform switching. The horizontal and vertical marginal bone loss was found to be too small to result in overlapping loss of the interimplant crestal bone.

Tilted Implant Concept for Full Mouth Immediate Loading Restoration

Tilted Implant Concept for Full Mouth Immediate Loading Restoration

Relationship Between the Buccal Bone Plate Thickness and the Healing of Postextraction Sockets With/Without Ridge Preservation

In 48 postextraction sites, sockets were grafted with bovine bone mineral plus collagen membrane (test) or had spontaneous healing (control). After 4 months, horizontal ridge width reduction was 0.71 mm in the test group and 4.04 mm in the control group, while vertical ridge loss was 0.58 mm and 1.67 mm, respectively. No correlation was found between the thickness of the buccal bone wall and the alveolar bone loss in the test group, while an inverse correlation was found in the control group. Ridge preservation compensated for postextraction alveolar ridge resorption irrespective of the buccal plate thickness, whereas leaving the extraction socket undisturbed may result in alveolar bone loss.

Phylogenetic analysis of LSU and SSU rDNA group I introns of lichen photobionts associated with the genera Xanthoria and Xanthomendoza (Teloschistaceae, lichenized Ascomycetes)

We studied group I introns in sterile cultures of selected groups of lichen photobionts, focusing on Trebouxia species associated with Xanthoria s. lat. (including Xanthomendoza spp.; lichen-forming ascomycetes). Group I introns were found inserted after position 798 (Escherichia coli numbering) in the large subunit (LSU) rRNA in representatives of the green algal genera Trebouxia and Asterochloris. The 798 intron was found in about 25% of Xanthoria photobionts including several reference strains obtained from algal culture collections. An alignment of LSU-encoded rDNA intron sequences revealed high similarity of these sequences allowing their phylogenetic analysis. The 798 group I intron phylogeny was largely congruent with a phylogeny of the Internal Transcribed Spacer Region (ITS), indicating that the insertion of the intron most likely occurred in the common ancestor of the genera Trebouxia and Asterochloris. The intron was vertically inherited in some taxa, but lost in others. The high sequence similarity of this intron to one found in Chlorella angustoellipsoidea suggests that the 798 intron was either present in the common ancestor of Trebouxiophyceae, or that its present distribution results from more recent horizontal transfers, followed by vertical inheritance and loss. Analysis of another group I intron shared by these photobionts at small subunit (SSU) position 1512 supports the hypothesis of repeated lateral transfers of this intron among some taxa, but loss among others. Our data confirm that the history of group I introns is characterized by repeated horizontal transfers, and suggests that some of these introns have ancient origins within Chlorophyta.

Usability of three boron compounds for enhancement of flame retardancy in polyethylene-based cable insulation materials

It is known that for the production of halogen-free cable insulation materials based on polyethylene, very high amounts of traditional metal hydroxide flame retardants such as 65 wt% aluminum hydroxide are required to fulfill international directives. In this respect, the aim of this study was to reveal possible enhancement effects of three boron compounds on the flame retardancy of two cable insulation materials: low-density polyethylene and its blend with ethylene vinyl acetate both loaded with aluminum hydroxide. For this purpose, a certain fraction of aluminum hydroxide was replaced with various amounts of zinc borate, boron oxide, and boric acid. The materials were compounded by the melt mixing method with a twin-screw extruder, while specimens were shaped by compression and injection molding. Limiting oxygen index, UL-94 vertical burning and mass loss cone calorimeter analyses indicated that replacement of certain amount of aluminum hydroxide with boron compounds could lead to certain levels of enhancement in many flame retardancy parameters. Residue analyses revealed that these improvements were basically due to further contribution of boron compounds to the physical barrier mechanism of aluminum hydroxide in both gas and condensed phases.

Analysis of vertical radiation loss and far-field pattern for microcylinder lasers with an output waveguide

Vertical radiation loss and far-field pattern are investigated for microcylinder lasers by 3D FDTD simulation and experimentally. The numerical results show that an output waveguide connected to the microcylinder resonator can result in additional vertical radiation loss for high Q coupled modes and affect the far field pattern. The vertical radiation loss can be controlled by adjusting the up cladding layer thickness. Furthermore, two lobes of vertical far-field patterns are observed for a 15-μm-radius microcylinder laser connected with an output waveguide, which confirms the vertical radiation loss.

Effect of bar cross-section geometry on stress distribution in overdenture-retaining system simulating horizontal misfit and bone loss

This study evaluated the influence of cross-section geometry of the bar framework on the distribution of static stresses in an overdenture-retaining bar system simulating horizontal misfit and bone loss. Three-dimensional FE models were created including two titanium implants and three cross-section geometries (circular, ovoid or Hader) of bar framework placed in the anterior part of a severely resorbed jaw. One model with 1.4-mm vertical loss of the peri-implant tissue was also created. The models set were exported to mechanical simulation software, where horizontal displacement (10, 50 or 100μm) was applied simulating the settling of the framework, which suffered shrinkage during the laboratory procedures. The bar material used for the bar framework was a cobalt—chromium alloy. For evaluation of bone loss effect, only the 50-μm horizontal misfit was simulated. Data were qualitatively and quantitatively evaluated using von Mises stress for the mechanical part and maximum principal stress and μ-strain for peri-implant bone tissue given by the software. Stresses were concentrated along the bar and in the join between the bar and cylinder. In the peri-implant bone tissue, the μ-strain was higher in the cervical third. Higher stress levels and μ-strain were found for the models using the Hader bar. The bone loss simulated presented considerable increase on maximum principal stresses and μ-strain in the peri-implant bone tissue. In addition, for the amplification of the horizontal misfit, the higher complexity of the bar cross-section geometry and bone loss increases the levels of static stresses in the peri-implant bone tissue.

Augmented Corticotomy Combined With Accelerated Orthodontic Forces in Class III Orthognathic Patients: Morphologic Aspects of the Mandibular Anterior Ridge With Cone-Beam Computed Tomography

This study used cone-beam computed tomography to evaluate morphologic changes of the mandibular anterior ridge after using augmented corticotomy plus accelerated orthodontia to decompensate mandibular incisors in patients with surgical skeletal Class III. Fourteen patients (8 men, 6 women; mean age, 26.14 yr) with skeletal Class III were treated before orthognathic surgery with a technique that combined corticotomy, bone grafting, and accelerated orthodontic forces to decompensate the lower incisors. Three-dimensional cone-beam computed tomograms were taken before treatment (T0) and at the completion of presurgical orthodontic treatment (T1). Measurements of the amount of vertical alveolar bone changes and horizontal bone thickness at the midroot and root apex levels of the mandibular incisors were evaluated. All patients showed significant proclination of the mandibular incisors at T1. The mean alveolar bone thickness from T0 to T1 increased buccally at the midroot and apex levels, showing statistically significant horizontal bone augmentation at the labial side of the lower anterior mandibular teeth (P < .05). The mean amount of vertical bone change did not show any significant vertical loss of alveolar bone. This new combined technique provided adequate decompensation of the mandibular incisors by increasing horizontal bone thickness in the labial aspect of the mandibular anterior area, without any vertical bone loss. This approach decreases the risk of the typical periodontal complications associated with traditional orthodontics, such as marginal bone loss and gingival recession.

Wear of two denture teeth materials in vivo—2-year results

Objective(1) To quantify wear of two different denture tooth materials in vivo with two study designs, (2) to relate tooth variables to vertical loss. MethodsTwo different denture tooth materials had been used (experimental material=test; DCL=control). In study 1 (split-mouth, 6 test centers) 60 subjects received complete dentures, in study 2 (two-arm, 1 test center) 29 subjects. In study 1 the mandibular dentures were supported by implants in 33% of the subjects, in study 2 only in 3% of the subjects. Impressions of the dentures were taken and poured with improved stone at baseline and after 6, 12, 18 and 24 months. Each operator evaluated the wear subjectively. Wear analysis was carried out with a laser scanning device. Maximal vertical loss of the attrition zones was calculated for each tooth cusp and tooth. A mixed linear model was used to statistically analyse the logarithmically transformed wear data. ResultsDue to drop-outs and unmatchable casts, only 47 subjects of study 1 and 14 of study 2 completed the 2-year recall. Overall, 75% of all teeth present could be analysed. There was no statistically difference in the overall wear between the test and control material for either study 1 or study 2. The relative increase in wear over time was similar in both study designs. However, a strong subject effect and center effect were observed. The fixed factors included in the model (time, tooth, center, etc.) accounted for 43% of the variability, whereas the random subject effect accounted for another 30% of the variability, leaving about 28% of unexplained variability. More wear was consistently recorded in the maxillary teeth compared to the mandibular teeth and in the first molar teeth compared to the premolar teeth and the second molars. Likewise, the supporting cusps showed more wear than the non-supporting cusps. The amount of wear did not depend on whether or not the lower dentures were supported by implants. The subjective wear was correct in about 67% of the cases if it is postulated that a wear difference of 100μm should be subjectively detectable. SignificanceThe clinical wear of denture teeth is highly variable with a strong patient effect. More wear can be expected in maxillary denture teeth compared to mandibular teeth, first molars compared to premolars and supported cusps compared to non-supported cusps.Laboratory data on the wear of denture tooth materials may not be confirmed in well-structured clinical trials probably due to the large inter-individual variability.

Prestress Loss of a New Vertical Prestressing Anchorage System on Concrete Box-Girder Webs

A new, double-tensioned prestressing steel strands anchorage system (DTPSSAS), characterized by low prestress loss caused by prestressing tendon retraction, is described. When it is used for short prestressing tendons in concrete box-girder webs, this anchorage system significantly reduces prestress loss. To investigate its efficiency in reducing prestress loss, a rectangular thin plate using the DTPSSAS was devised and tested; the results demonstrated that the average rate of instantaneous prestress loss decreased from 32.35% after the first tension to 2.68% after the second tension. Further, long-term observations of prestress loss with the DTPSSAS were conducted in the laboratory and in a field test. Based on the field test of a continuous concrete box-girder bridge, the average loss rate of instantaneous prestress loss to the control tensile stress of two strands in the web is 7.61%, and the average rate of prestress loss at 150 days is 10.53%. Concurrently, the time-dependent prestress loss was calculated with Models GL2000 and CEB-FIP90 for different concrete shrinkage and creep prediction by the step-by-step calculation method. In comparison with the laboratory test results, the calculated results with the two models were greater than the test values. In addition, the effect of stress redistribution caused by the constraint of reinforcing bars to concrete shrinkage and creep was evaluated. The results revealed that the stress redistribution effect increased the vertical compressive prestress loss of concrete, indicating that the time-dependent compressive prestress loss rate of concrete was greater than the tensile prestress loss rate of prestressed tendons. In this regard, bridge engineers may need to pay attention to the stress redistribution phenomenon in vertical prestressing design.

CHEMICAL EFFECTS ON PWR SUMP STRAINER BLOCKAGE AFTER A LOSS-OF-COOLANT ACCIDENT: REVIEW ON U.S. RESEARCH EFFORTS

Industry- or regulatory-sponsored research activities on the resolution of Generic Safety Issue (GSI)-191 were reviewed, especially on the chemical effects. Potential chemical effects on the head loss across the debris-loaded sump strainer under a post-accident condition were experimentally evidenced by small-scale bench tests, integrated chemical effects test (ICET), and vertical loop head loss tests. Three main chemical precipitates were identified by WCAP-16530-NP: calcium phosphate, aluminum oxyhydroxide, and sodium aluminum silicate. The former two precipitates were also identified as major chemical precipitates by the ICETs. The assumption that all released calcium would form precipitates is reasonable. CalSil insulation needs to be minimized especially in a plant using trisodium phosphate buffer. The assumption that all released aluminum would form precipitates appears highly conservative because ICETs and other studies suggest substantial solubility of aluminum at high temperature and inhibition of aluminum corrosion by silicate or phosphate. The industry-proposed chemical surrogates are quite effective in increasing the head loss across the debris-loaded bed and more effective than the prototypical aluminum hydroxide precipitates generated by in-situ aluminum corrosion. There appears to be some unresolved potential issues related to GSI-191 chemical effects as identified in NUREG/CR-6988. The United States Nuclear Regulatory Commission, however, concluded that the implications of these issues are either not generically significant or are appropriately addressed, although several issues associated with downstream in-vessel effects remain.

Nitrogen Budget in a Lowland Coastal Area Within the Po River Basin (Northern Italy): Multiple Evidences of Equilibrium Between Sources and Internal Sinks

Detailed studies on pollutants genesis, path and transformation are needed in agricultural catchments facing coastal areas. Here, loss of nutrients should be minimized in order to protect valuable aquatic ecosystems from eutrophication phenomena. A soil system N budget was calculated for a lowland coastal area, the Po di Volano basin (Po River Delta, Northern Italy), characterized by extremely flat topography and fine soil texture and bordering a network of lagoon ecosystems. Main features of this area are the scarce relevance of livestock farming, the intense agriculture, mainly sustained by chemical fertilizers, and the developed network of artificial canals with long water residence time. Average nitrogen input exceeds output terms by ~60kgNha(-1)year(-1), a relatively small amount if compared to sub-basins of the same hydrological system. Analysis of dissolved inorganic nitrogen in groundwater suggests limited vertical loss and no accumulation of this element, while a nitrogen mass balance in surface waters indicates a net and significant removal within the watershed. Our data provide multiple evidences of efficient control of the nitrogen excess in this geographical area and we speculate that denitrification in soil and in the secondary drainage system performs this ecosystemic function. Additionally, the significant difference between nitrogen input and nitrogen output loads associated to the irrigation system, which is fed by the N-rich Po River, suggests that this basin metabolizes part of the nitrogen excess produced upstream. The traditionally absent livestock farming practices and consequent low use of manure as fertilizer pose the risk of excess soil mineralization and progressive loss of denitrification capacity in this area.

Infiltration properties of paddy fields under intermittent irrigation

Puddling and recurring intermittent irrigation, common praxis in wet rice cultivation, modify the soil structure and therewith cause a temporal variation of the infiltration properties. This study attempts to evaluate the temporal variation of the infiltration rates of plough pan (vertical infiltration) and paddy fields’ surrounding bunds (bund infiltration) by analyzing (i) the infiltration rate as a function of time, (ii) the relationship between ponding water depth and infiltration rate, and (iii) the influence of cultivation age on vertical water loss and cross-flow through bunds. Two experimental fields with respective cultivation ages of 30 (A) and 7 (B) years were investigated. The results revealed that the time series of vertical infiltration rate (IRv) was with time consistency and the persistency of the bund infiltration was uncertain. The mean infiltration rate into the plough pan of A and B was 3.34 and 1.01 cm d−1, respectively. A total water depth of 230 and 85 cm would be, respectively, lost in A and B through the plough pan during rice growing season. The correlation coefficient between ponding water depth and IRv was −0.48 and −0.81 in A and B, respectively, demonstrating that the dynamic IRv in the old paddy field was less affected by the drying and wetting cycles. It is concluded that rice paddies which have been taken into cultivation since only a few decades may contribute to water losses. Maintenance of equilibrium condition between ponding and drying stages and careful preparation of bunds may reduce water loss.