Tip and Torque Accuracy According to the ISO 27020:2019 Norm in Currently Available Pre-Adjusted Orthodontic Brackets

Background: The precision of bracket manufacturing is fundamental to ensure the correct expression of the inbuilt information. The objective of this study was to determine the actual tip and torque values of a pool of stainless steel brackets, pre-adjusted according to the MBT prescription values, and to compare these actual values with those stated by the manufacturers in order to test their compliance with the tolerance limits reported in the ISO 27020:2019 Methods: A sample of 360 stainless steel brackets, from 12 different providers, were evaluated. All brackets had a nominal slot size of 0.022 in., belonged to the upper right central incisor, and were manufactured with the metal injection molding technique (MIM). For each provider, three different batches of the same bracket series were tested. A single-blind design was used for bracket coding. Results: Only five systems displayed torque mean values that matched the declared values (p > 0.05). Only one system did not respect the tolerance limits established in the ISO 27020:2019 norm. The tip values were different from those declared in seven of the assessed systems; however, none exceeded the tolerance limits. The inter-batch variability in most cases was not statistically significant. Conclusions: In most of the assessed systems, there can be a difference between the actual and the declared torque values, while tip information is usually accurately incorporated into the bracket slot. Lack of precision in the manufacturing process can reduce the efficacy of the appliance and force the clinician to compensate for dimensional inaccuracy through wire bending.

An algorithm for scheduling hybrid slot-size to increase traffic density in EPONs

The current basically Ethernet passive optical network (EPON) efficiently supports different service classes, i.e., Giant Prime concern (GP) traffic and Efficiently-best (EE) traffic, in future-generation networks. The difficult task is finding the efficient Dynamic Bandwidth Allocation (DBA) procedure task which suggests service classes of bandwidth simultaneously. This paper suggests improved version to DBA algorithm, Remodeled version-Hybrid division-size/Rate (HDSR) scheme. The modified control message scheduling algorithm is also discussed along with Remodeled-HDSR Algorithm which fits to the proposed scheme. In the modified Remodeled-HSSR scheme, time cycle length is identical classified accordingly with two subparts. In algorithm as explained in order to increase traffic density, the subdivision part of the planned cycle, the traffic conditions are dynamically suggested an improved version for Best effort traffic of multiple ONUs. In the First subdivision part of the span time analysis time will not be compressed, particularly at less buffer status conditions plan buffer status of the HP traffic. The Remodeled control message algorithm which predefined status and is scheduled particularly which controls connecting the sub-parts of the planned cycles of the sequence time and in-turn increases synchronization between two Gate messages to particular ONUs.

Compliance with the ISO 27020:2019 norm of a sample of currently available preadjusted Orthodontic bracket systems. Are the actual dimensions as expected?

Background Determine the exact slot dimension of a sample of a MBT prescription stainless steel conventional brackets from different manufacturers to compare the actual values with the nominal ones declared by the manufacturers and to verify the compliance with tolerance limits given by the ISO 27020:2019. Different batches from each manufacturer were evaluated to determine whether or not they are different in size. In addition, the geometry of the slot walls was assessed. Methods 360 stainless steel preadjusted orthodontic brackets of 12 different manufacturers were assessed. All brackets had a nominal slot size of 0.022 by 0.028 inches, belonged to the right upper central incisor, and were fabricated with the metal injection molding technique (MIM). For each manufacturer, three different manufacturing batches were evaluated. Brackets were coded using a single-blind design. Results All bracket systems in the study group except one displayed a statistically significant difference with the nominal declared value, although only four of the systems did not comply with the tolerance limits established by the ISO 27020:2019. In most of the systems, the slot height was oversized when compared to the nominal one. A significant interbatch variability was found in most of the evaluated systems. Most of the brackets walls were divergent. Conclusions The dimensional accuracy of commercially available metal brackets is not guaranteed. The respect for the norm should be enforced as well as the quality controls along the manufacturing process since orthodontic brackets are a precision medical device.

Friction behavior of the wire material Gummetal®

Objectives Gummetal® (Maruemu Works, Osaka, Japan), a new orthodontic wire material successfully used in clinical applications since 2006, is biocompatible and exhibits exceptionally high elasticity, nonlinear elastic behavior, plasticity and strength. Systematic comparisons of friction behavior are lacking; thus, the friction of Gummetal® in the binding modus was compared to commonly used low friction wires. Materials and methods In vivo tests were run with Gummetal®, CoCr (cobalt-chromium Elgiloy®, Rocky Mountain Orthodontics, Denver, CO, USA), β‑Ti (β-Titanium TMA®, Ormco, Orange, CA, USA), NiTi (nickel–titanium, NiTi-SE, Dentalline, Birkenfeld, Germany), and stainless steel (SS; Ref. 251-925, 3M Unitek, Monrovia, CA, USA) [dimensions: 0.014 inch (0.35 mm), 0.016 inch (0.40 mm), 0.016 × 0.022 inch (0.40 × 0.56 mm), and 0.019 × 0.025 inch (0.48 × 0.64 mm)—β-Ti not available in the dimension 0.014 inch]. These were combined with Discovery® (Dentaurum, Ispringen, Germany), Micro Sprint® (Forestadent, Pforzheim, Germany), Clarity™ (3M Unitek), and Inspire Ice™ (Ormco) and slots in the dimension 0.022 inch (0.56 mm) and, except for the 0.019 × 0.025 inch wires, in the dimension 0.018 inch (0.46 mm). They were ligated with a 0.010 inch (0.25 mm) steel ligature (Smile Dental, Ratingen, Germany). Brackets were angulated by applying a moment of force of 10 Nmm against the wire, which was pulled through the slot at 0.2 mm/s. Results In 660 tests using 132 bracket–wire combinations, friction loss for Gummetal® was comparable to and, in a few combinations with Micro Sprint®, significantly lower (p < 0.05) than SS and CoCr. The friction for Gummetal® was significantly lower (p < 0.05) than NiTi, and β‑Ti. In some bracket–wire combinations, lower friction was found with round wires compared to rectangular wires, except for the combination with Inspire Ice™, which was higher but not significant. Slot size did not have a significant effect on friction in most combinations. Conclusion The low friction associated with Gummetal® wires during arch-guided tooth movement will be a valuable addition to the armamentarium of orthodontists.

Experimental evaluation of orthodontic bracket slot deformation to simulated torque

In orthodontic fixed appliance therapy, the archwire torque used to refine the teeth position during the treatment imparts significant forces inside the bracket slot. The objective of this study was to measure the torque relevant bracket slot deformation in Stainless Steel (SS) brackets during various degree of archwire twist. Standard edgewise brackets 0.018-inch (in.)/0.022-in. each 20 no. and 0.016 × 0.022, 0.017 × 0.025, 0.019 × 0.025, and 0.021 × 0.025 in. archwires each 10 no. were used. A novel experimental setup consisting of loading fixture and torque key mounted on a Vision Measuring System (VMS) were used to measure the brackets slot deformation. The Top Slot and Middle Slot Deformations (TSD and MSD) of the brackets for 35° angle of twist in 0.016 × 0.022 in. archwire in 0.018-in. slot, 0.019 × 0.025 in. archwire in 0.022-in. slot and for 30° angle of twist in 0.017 × 0.025 in. archwire in 0.018-in. slot and 0.021 × 0.025 in. archwire in 0.022-in. slot were measured. Results showed that the mean TSD and MSD were higher when the archwire size, the slot size and the angle of twist were greater. In the evaluated bracket-archwire combinations, the TSD were higher than MSD and the bracket slots were elastically deformed within the clinically required 35° angle of twist in the archwire. Clinicians should be aware of this torque relevant bracket slot deformation which might be a factor for torque loss and suitably incorporate archwire angle of twist.

Stock Assessment of Lates niloticus in Upper Victoria Nile and its Impact on Uganda’s Economy

This study investigated the growth, mortality, recruitment, and catch estimates of Nile perch, Lates niloticus (Linnaeus, 1758), in Upper Victoria Nile, basing on total catches and length-frequency data collected between 2008 and 2018. The asymptotic length (L∞) had a value of 93.45 cm TL, growth curvature (K) was 0.446 year-1, total mortality (Z) was 1.85year-1, natural mortality (M) was 0.79 year-1, fishing mortality (F) was 1.09 year-1, exploitation rate (E) was 0.59 and growth performance index(ᴓ) of (L∞) was 3.604. There were two peaks recruitment period, a minor one in March and a major one in August. These respectively accounted for 12.8 and 26.3 percent of the total catch. The optimum sustainable yield (E0.5), maximum sustainable yield (Emax) and, economic yield (E0.1) was 0.278, 0.421 and 0.355 respectively. The findings suggest that there is a decline in the population of Lates niloticus in Upper Victoria Nile. Therefore, strict management of the fishery by adhering to the recommended slot size of 50-85 cm TL and curtailing use of illegal gears is needed. This will be possible through enforcement of regulations, monitoring, control and surveillance in order to ensure sustainability of the Nile perch fishery and ecosystem restoration in the Upper VictoriaNile.Keywords: Lates niloticus; Catch rates; Growth parameters, Upper Victoria Nile.

Development of Plasma Sprayed Coatings to Improve the Erosion Resistance of Wire Wrapped Screens

The installation of sand screens in wells can fail in one of two ways: by causing an unacceptable high pressure drop in the near wellbore area or by losing the ability to retain particles. Four mechanisms can lead to a failure: plugging, corrosion, erosion and mechanical deformation. To increase the lifetime under erosive conditions, a coating for wire wrapped screens was developed and tested. Erosion occurs, when formation particles hit the screen surface with high velocities or by continuous production of fines through the screen openings. The screen openings must keep a specified size in order to control the formation sand or gravel pack. If the opening size increases due to erosion, more particles are produced and erosion increases. A newly developed coating is put on the outside (i.e. facing the formation) of standard wire wrapped screens to make the slots resistant against erosion. The coating consists of ceramic or hard metal and is applied by plasma spraying. An extensive development and verification program was conducted to guarantee defined slot widths, corrosion resistance and mechanical strength of coating and screen. A test facility was built to investigate the erosion resistance of sand screens. It consists of a flow loop to circulate a slurry of water and particles through 2″ coupons. Samples of standard wire wrapped, metal mesh and coated screens were tested. The tests were conducted with flow velocities of up to 18.5 m/s and particles of up to 100 micrometer for up to 60 h. The screens where compared under consideration of optical criteria, mass loss and functionality. The coated screens showed no sign of wear on the outside and kept their initial slot size. The slots of uncoated wire wrapped screens more than doubled in some places, when eroded under the same conditions. To test the functionality of the samples, sand retention tests were conducted before and after erosion. Since there were no changes in slot width, the coated screens show the same retention capabilities before and after erosion, while metal mesh screens that were eroded under the same conditions lost their ability to retain sand. The newly developed coating improves the resistance against erosion, is able to withstand corrosive well environments and has mechanical properties suitable to be safely installed in any well. Therefore the coating has the ability to improve the lifetime of screens under erosive conditions.

SCREENING OF JUICES THROUGH ROTARY AND DSM SCREEN

During the year 2008, DSM screen having slot size 0.7mm installed at mill house for screening of mixed juice and DSM screen with slot size 0.35mm working for screening of clear juice were replaced by two rotary screens of 0.5mm slot size for mixed juice and 0.2mm slot size for clear juice. after initial operational difficulties both the screens worked satisfactorily, not only clarity of clear juice increased but bagacillo particle in juices decreased which resulted less scale formation in juice heaters, evaporator tubes and back liner of continuous centrifugal. Also, e-circulation/ overflow of juice at the 2 mills was considerably reduced, resulting in improved mill working.