CMC has become aware of a potential safety issue regarding the ProSeries Aluminum Lock Carabiner. A crack may appear on the base of the key lock gate as illustrated below. This crack is easily identified with a visual inspection.
Vortex Full Crack [Crack Serial Key
CMC has become aware of an issue regarding the ProTechTM Aluminum Key- Lock Carabiner. A defect in the manufacturing process resulted in a small population of carabiners having surface cracks that could impact the minimum breaking strength (MBS) of the product.
The Hyflex EDM file (HEDM; Coltene / Whaledent AG, Switzerland) using electrical discharge machining (EDM) manufacturing process create a rough and hard surface of the file, resulting in superior fracture resistance and improved cutting efficiency (7). HEDM file has a tip size of 25 with a constant 0.08 taper in the apical 4mm of the instrument but reduces progressively upto 0.04 taper in the coronal portion. It has 3 different cross-sectional zones with a triangular cross-section at top, trapezoidal in middle part and rectangular in the apical part of the instrument working portion (8). It was reported that, this variable cross-sectional design contributes to lesser dentinal cracks formation (5).
One hundred non-carious, mandibular first molar teeth were radiographed in both directions to ensure that all the mesial roots had two separate canals. Teeth having root canal systems with reduced pulp spaces, pulp stones or calcified canals were discarded. All roots were inspected under 12X magnification to ensure that they did not have root caries, hypercementosis, open apices, cracks or craze lines. Collected teeth were recently extracted and their use in research was approved by the local biomedical research ethics committee (D158601033). Only teeth in which radii of curvature ranged between 2.5mm to 6.3mm and the angle of root canal curvature between 50 to 200 (moderately curved) were selected. As a result, only 60 specimens with moderate mesial root curvatures were selected and stored in 0.1% thymol solution at 50C. Sample size was estimated using G* Power 3.1 software (Heinrich Heine, Dusseldorf, Germany). Twelve samples were indicated as the minimum ideal size required for observing the effect of instruments on root dentin with an alpha error probability of 0.05.
For all the 60 selected teeth, coronal part of the tooth was removed 1mm above the cemento-enamel junction, using a flexible diamond disk. The mesial roots were resected by placing a vertical cut at the furcation area and the distal roots were discarded. Baseline images were taken with a micro-CT scanner (X-radia Versa 500, Ziess, Germany), to detect the presence of pre-operative microcracks or craze lines in the root dentin. The long axis of the roots were adjusted so that they are perpendicular to the X-ray beam to provide scans in the same sagittal plane. The scanning was performed according to the following parameters: a rotation of 3600 in vertical axis with a rotational step of 0.50, and the camera exposure time of 500 milliseconds. The specimens were imaged at an isotropic resolution of 30μm, and filtered with 1mm thick aluminium filter. Three dimensional images were generated and reconstructed using the software (Scout and ScanTM control system 10.7.3679.13921 Ziess, Germany).
Incidence of incomplete microcracks formation was significantly high for Hyfex EDM (P= 0.0232) and vortex blue (P=0.0447) systems when compared to NiTi flex files ( Table 3, Table 4). No significant difference was found between the groups in craze lines and complete cracks formation.
Commonly used in-vitro method to evaluate the post-instrumentation microcracks formation is by assessing the pictures taken under magnification after sectioning of the root (13,14). Limitations of the sectioning method is the possibility of having false positive results, as extraction and sectioning procedures might create or propagate existing dentinal defects. Micro-computed tomography method could be applied both quantitatively and qualitatively for three dimensional assessment of root canal system. Micro-CT enables the visualization of the pre-existing defects and their precise location throughout the root and this improves the validity of the experiment because each specimen acts as its own control (15,16).
Moderately curved roots were selected in the study, as it was demonstrated that shaping the root canals with a smaller radius and greater curvature increased the incidence of dentinal microcracks formation (10). Due to constricted anatomical configuration of mandibular molar mesial canals, more stresses may develop on the dentinal surface during mechanical preparation, increasing the potential to develop cracks (15).
Hand Ni-Ti instrumentation caused minimal increase (1.66%) in dentinal defects formation at coronal level. Use of gates glidden drills for coronal root canal flaring might have resulted in the formation of these defects. Similar findings were observed in the previous studies (20,21) where the samples prepared with gates glidden drills exhibited microcracks. To complete a preparation with rotary Ni-Ti files significantly more rotations are required as compared to hand files contributing to the formation of more dentinal defects. In accordance with the observations of the previous studies (11,14) both the rotary systems demonstrated significant increase in the percentage of dentinal defects after canal instrumentation. Contrary to this finding Bayram et al. (5) claimed that the instrumentation with Vortex Blue and HyFlex EDM rotary files developed no new microcracks and they attributed this finding to the heat treated structure of these instruments, which gives extra flexibility to the files. Straight root canals were used in their study, whereas moderately curved mesial roots (50 to 200) used in the present study might explain the possible reason for increase in dentinal microcracks formation. These findings differ from the observations by De-Dues et al. studies (15,17,18), where they found lack of correlation between dentinal microcracks formation and root canal preparations with rotary systems.
In the present study most of the cracks were located at the cervical and midroot regions. The reason for this finding might be explained by previous in vivo strain gauge experiment results (23), that reported the occurrence of maximum functional strain distribution at the coronal and mid- root surfaces.
In the present study both the Ni-Ti rotary systems exhibited higher percentage of incomplete cracks. Similar findings were observed in Burklein S et al.(13) study where they found incomplete cracks in the range of 15% to 25%. The current study results are correlating with the findings of Arias et al. (24), in that the microcracks formed after root canal instrumentation were in the mesio-distal directon. Based on the investigations on VRF in endodontically treated teeth, Sugaya et al. (25) reported that most apical fractures may be in mesiodistal or buccolingual direction and generally VRF have been reported to be in buccolingual direction.
Going back to our code by doing a few stepi, we reach at 00000000004016FA. You can also see we have another condition here stating jg crackme_xor. 40172F. If you take a look at the RBX register, it has a number loaded as 10.
After the Aloha 737-200 accident, in which a 12ft x 8ft section of the upper fuselage tore away in flight, all 737's with over 50,000 cycles must have their lap joints reinforced with external doublers. This tired old aircraft is a 737-200 and the patching is clearly visable. This modification takes about 15,000 man hours and unfortunately has sometimes been the source of another problem - scoring. This is when metal instruments instead of wooden ones have been used to scrape away excess sealant or old paint from the lap joints which create deep scratches which may themselves develop into cracks.
KIRO 7 Eyewitness News Investigative Reporter Chris Halsne discovers a big new problem for Boeing, centered on "lap-joint metal fatigue". The problem is called "scoring". During assembly, workers lay a bead of sealant along this lap joint. It makes the jet more aerodynamic. A year or two flying you around and many jets have to get repainted. Powerful chemical strippers melt the sealant, so some maintenance crews have been putting on caulk then, according to the Federal Aviation Administration, have been cutting away the excess with a box cutter. That can ruin the integrity of the metal along the entire aircraft lap joint. The FAA recently grounded three passenger jets due to "scribe marks" and has identified 32 more Boeing planes with damaging box cutter-type cuts along the lap joint. "When we found this, we jumped on it right away," said FAA spokesperson Mike Fergus. Fergus says they have no idea yet how many more jets are affected by scoring. "With the contraction and expansion of thousands of flight hours, the scratch has the potential, not a guarantee, the potential of turning into a crack. That in turn may have safety factor. That's our issue. If it's safety, we're interested," Fergus said.
Scoring of some lap joints is just the latest chapter in Boeing's long battle with the design and maintenance of its riveted seams. "With that type of structure, whatever is occurring between the two sheets is not readily visible," said Earl Brown, a certified jet engine and airframe mechanic. Brown says the FAA has been warning airlines to inspect -- and re-inspect often -- the lap joints of thousands of still-operating older model Boeing jets. "If we can catch a problem when it's still just a crack and fix it, then we don't have to worry about something coming apart, breaking. The potential for breaking is there if a crack develops. It's pretty much inherent in the design of the airplane and the materials used," Brown said. The scoring issue has been kept quiet until now, but other huge maintenance nightmares include hundreds of previously "patched" or repaired planes. 2ff7e9595c
Comments