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[en] This study investigated maxillary third molars and their relation to the maxillary sinus using panoramic radiography and cone-beam computed tomography (CBCT). A total of 395 maxillary third molars in 234 patients were examined using panoramic radiographs and CBCT images. We examined the eruption level of the maxillary third molars, the available retromolar space, the angulation, the relationship to the second molars, the number of roots, and the relationship between the roots and the sinus. Females had a higher frequency of maxillary third molars with occlusal planes apical to the cervical line of the second molar (Level C) than males. All third molars with insufficient retromolar space were Level C. The most common angulation was vertical, followed by buccoangular. Almost all of the Level C molars were in contact with the roots of the second molar. Erupted teeth most commonly had three roots, and completely impacted teeth most commonly had one root. The superimposition of one third of the root and the sinus floor was most commonly associated with the sinus floor being located on the buccal side of the root. Eruption levels were differently distributed according to gender. A statistically significant association was found between the eruption level and the available retromolar space. When panoramic radiographs showed a superimposition of the roots and the sinus floor, expansion of the sinus to the buccal side of the root was generally observed in CBCT images
[en] The purpose of this study was to examine the inferior expansion of the maxillary sinus floor following maxillary molar extraction. Cone beam computed tomographic images of 59 subjects were used to evaluate the height difference of the maxillary sinus floor between extraction sites and contralateral dentate sites. The height of the maxillary sinus floor was defined as the vertical distance to the Frankfort plane from the level of the anterior nasal spine to the most inferior point of the sinus floor. We examined the difference in sinus pneumatization according to the number of missing teeth and the vertical relationship of the molar roots to the sinus floor. The inferior expansion of the maxillary sinus floor was 1.20 ± 1.86 mm on the maxillary first molar and 1.90 ± 2.42 mm on the maxillary second molar. Increased expansion was observed in cases where two proximate molars were extracted. There was no significant difference in sinus pneumatization following extraction according to the vertical relationship of the molar roots to the sinus floor. The results of this study confirm that sinus pneumatization occurs following maxillary molar extraction. In situations where pneumatization can affect treatment after molar extraction, three-dimensional radiography should be considered.
[en] The author observed a case of osteogenic sarcoma in a 11-year-old female with complaint of painful swelling on face in right side. The observed results were as follows: 1. Large hematoma was observed, and patient complained painfull swelling on c/c site. 2. Predisposing factor of osteogenic sarcoma was not clear, but patient had history of extraction before patient visiting infirmary of our dental collage. 3. Serologic findings were not specific, and serum aldaline level was normal. 4. Radiographic findings were as follows: a. Diffuse faint radiopacit in the lesion. b. Bony destruction and increased radiopacity in right antrum. c. Displacement of multiple teeth on involved area(i. e no 12, 15, 55, 16, 17, 18) d. Increased periodontal space in single tooth(no 13) e. Destruction of bony crypt on involved teeth(no 13, 14, 15, 17, 18) f. Loss of lamina dura of three teeth in involved area(no 11, 12, 16) 5. Computed tomographic findings were as follows: a. Large calcific and heterogenous component mass in the Rt. maxillary sinus, and this mass extending to Rt. maxilla, alveolar bone, ethmoid sinus. b. Soft tissue bulging in to Rt. side nasal cavity and oral cavity. c. Bone destruction of maxillary sinus wall and Rt. alveolar bone.
[en] The invention relates to a method and an apparatus for simultaneously drilling a bore and testing the sub-soil formations thus passed through. The apparatus according to the invention is characterized in that it contains a non-rotating injection head supported by a hoisting hook and carrying the rod driving a train of drilling rods carrying a drilling bit and a test probe adapted to receive signals emitted by the sub-soil formation in the process of drilling, said head being connected through a cable to a recording device. This cable is inserted in the non-rotating portion of the injection head through a packing which can be untightened and which prevents the drilling sludges from leaking while at the same time locking the cable so as to prevent same from rotating while the drilling rods are in the process of rotating. Such an apparatus is suitable, in particular, for using a probe adapted to measure pressure, or the specific gravity of an electric feature or the radioactivity of the sub-soil formations passed through
[fr]L'invention concerne un procede et un appareil pour le forage d'un puits et l'essai simultane des formations traversees. L'appareil selon l'invention est caracterise par une tete d'injection non rotative supportee par le crochet de levage et supportant la tige d'entrainement d'un train de tiges de forage portant un trepan et une sonde d'essai pour recevoir des signaux provenant de la formation foree et connectee par un cable a l'appareil d'enregistrement. Le cable penetre dans la partie non rotative de la tete d'injection a travers un presse-etoupe pouvant etre desserre et empechant les fuites de la boue de forage et fixant en meme temps le cable pour empecher sa rotation pendant la rotation du train de tiges de forage. Un tel appareil convient en particulier pour l'utilisation d'une sonde mesurant la pression, la densite, une caracteristique electrique ou la radioactivite des formations traversees
[en] Electronic total station can simultaneously measure angle and distance, together with the appropriate calculation methods and operating skills, able to efficiently complete the survey work, this paper based on practical experience, theoretical analysis, based on total station introduced in setting out a few boring in the skills and the measurement of total station in the construction layout for accuracy. (authors)
[en] A method is derived to determine principal stress magnitude and orientation at a particular location by using calculated secondary principal stresses that were obtained from overcoring stress relief measurements. A computer program based on this method is used to calculate the principal stress at various locations in Rainier Mesa, Nevada Test Site, using previously reported secondary principal stress values. (U.S.)
[en] The objective of drillhole ER-12-1 was to determine the hydrogeology of paleozoic carbonate rocks and of the Eleana Formation, a regional aquitard, in an area potentially downgradient from underground nuclear testing conducted in nearby Rainier Mesa. This objective was addressed through the drilling of well ER-12-1 at N886,640.26 E640,538.85 Nevada Central Coordinates. Drilling of the 1094 m (3588 ft) well began on July 19, 1991 and was completed on October 17, 1991. Drilling problems included hole deviation and hole instability that prevented the timely completion of this borehole. Drilling methods used include rotary tri-cone and rotary hammer drilling with conventional and reverse circulation using air/water, air/foam (Davis mix), and bentonite mud. Geologic cuttings and geophysical logs were obtained from the well. The rocks penetrated by the ER-12-1 drillhole are a complex assemblage of Silurian, Devonian, and Mississippian sedimentary rocks that are bounded by numerous faults that show substantial stratigraphic offset. The final 7.3 m (24 ft) of this hole penetrated an unusual intrusive rock of Cretaceous age. The geology of this borehole was substantially different from that expected, with the Tongue Wash Fault encountered at a much shallower depth, paleozoic rocks shuffled out of stratigraphic sequence, and the presence of an altered biotite-rich microporphyritic igneous rock at the bottom of the borehole. Conodont CAI analyses and rock pyrolysis analyses indicate that the carbonate rocks in ER-12-1, as well as the intervening sheets of Eleana siltstone, have been thermally overprinted following movement on the faults that separate them. The probable source of heat for this thermal disturbance is the microporphyritic intrusion encountered at the bottom of the hole, and its age establishes that the major fault activity must have occurred prior to 102.3+0.5 Ma (middle Cretaceous)
[en] Reliable forecasting of stability and deformation parameters of 'Ukrytie' fundament determine its operation. Necessary data were obtained on the base of characteristic values of soils which resulted from engineering-geological research
[en] One of the most profound changes in our perspective of the solar system resulting from the first quarter century of planetary exploration by spacecraft is the recognition that planets, including Earth, were bombarded by cosmic projectiles for 4.5 aeons and continue to be bombarded today. Although the planetary cratering rate is much lower now than it was during the first 0.5 aeons, sizeable Earth-approaching asteroids and comets continue to hit the Earth at a rate that poses a finite risk to civilization. The evolution of this planetary perspective on impact cratering is gradual over the last two decades. It took explorations of Mars and Mercury by early Mariner spacecraft and of the outer solar system by the Voyagers to reveal the significance of asteroidal and cometary impacts in shaping the morphologies and even chemical compositions of the planets. An unsettling implication of the new perspective is addressed: the risk to human civilization. Serious scientific attention was given to this issue in July 1981 at a NASA-sponsored Spacewatch Workshop in Snowmass, Colorado. The basic conclusion of the 1981 NASA sponsored workshop still stands: the risk that civilization might be destroyed by impact with an as-yet-undiscovered asteroid or comet exceeds risk levels that are sometimes deemed unacceptable by modern societies in other contexts. Yet these impact risks have gone almost undiscussed and undebated. The tentative quantitative assessment by some members of the 1981 workshop was that each year, civilization is threatened with destruction with a probability of about 1 in 100,000. The enormous spread in risk levels deemed by the public to be at the threshold of acceptability derives from a host of psychological factors that were widely discussed in the risk assessment literature
[en] Twenty-nine intervals in 10 core holes were hydraulically fractured in N, E, and T tunnels, Nevada Test Site, during 1974. Certain pressures were determined and related to the ambient stress field, but the orientation of the hydraulic fractures was not measured. These data and data from previous investigations in G tunnel indicated that both the magnitude of the hydraulic pressures and the direction of fracturing are independent of the orientation of the core holes. The maximum and minimum principal compressive stresses determined by the hydraulic fracturing methods are good approximations of those determined by nearby overcore methods. The data show that a good approximation of the magnitudes of the maximum and minimum principal stress axes can be obtained from several hydrofractured intervals in one core hole. Furthermore, if fracture orientation can be measured, then the direction of minimum principal compressive stress can be determined and the orientation of the plane of the maximum and intermediate principal compressive stresses can also be determined