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Purpose: The present study evaluated the marginal gap of lithium disilicate crowns fabricated through three different wax pattern techniques; Conventional, Milling and 3D-printing. Materials and Methods: Thirty stone models were replicated from a stainless-steel model representing a prepared tooth; ten were sent to make conventional wax patterns while the remaining were sent to a digital dental scanner. The computer aided design was completed and STL (Standard Tessellation Language) files were sent to either milling or 3D-printing machines. All wax patterns (n = 30) were pressed, and a stabilizing instrument was used to secure the crowns on the master model. The marginal gap was measured at 18 points for each crown using a digital microscope (µm) (n = 540) and compared using One-way ANOVA (p ≤ 0.05). Results: There was a significant difference in the marginal gap value between all three groups (p < 0.01) where the milled group showed the least mean gap (28.87 ± 30.18 µm), followed by 3D printed (47.85 ± 27.44 µm), while the highest mean marginal gap was found in the conventional group (63.49 ± 28.05 µm). Conclusion: Milled and 3D-printed wax patterns produced better fitting crowns compared to conventional techniques.

A new fusion of geophysical scanners is developed for detection of the near-surface buried objects, such as iron pipes, pieces of metal, and rocks. The new fusion was built up in a cart that integrates three kinds of geophysical instruments including an EM-61 metal detector, magnetometer, and OhmMapper. For the new system, we have innovate an electric control unit and adapted all the original connection cables to efficiently and simultaneously collect the electromagnetic field, magnetic intensity, and apparent resistivity on the surface of ground. We also modified and complement DOS-based computer programs to automatically measure the three kinds of data, record the surveying positions, and transfer the data from the system to a host computer for integration of the mapping images. The new system has been tested at a synthetic field site where five different objects are previously buried. The experimental results show successes in mapping these near-surface targets and prove that the new system archives saving surveying time, obtaining comprehensive data, reducing human interventions and number of human operators. It may become a new efficient and effective tool of geophysical exploration for detection of the near-surface buried objects.

Summary “Modern distributed DC/IP surveys can collect large amounts of broadband electrical data. This allows geophysicists to apply true 3D geometries which opens the door to high resolution 3D information about the spectral complex resistivity response of the earth and possibly mineral discrimination. However, these arrays also increase the computational complexity of solving the inverse problem. In addition, the increase in the frequency range of the collected data along with the complex wire paths raises the chances of incurring inductive coupling, which can hide the complex resistivity response. In this paper we present the results of a spectral induced polarization (SIP) survey completed over a prospective target in Saudi Arabia. The field SIP data were inverted using the generalized effective-medium theory of induced polarization (GEMTIP) in conjunction with an integral equation-based modeling and inversion method. These methods can replicate all inductive coupling and EM effects, which removes a significant barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted, and several drill holes sited. The drill holes intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project.”

In this study, three field programs have been conducted to determine the distribution and structure of volcanic landforms (lava flows, cinder cones, eruptive centers), and collect samples for analytical studies (age determination, mineral and whole composition, isotope geochemistry). The first expedition was to Harrat Lunayyir, where recent seismic activity has indicated the possibility for developing new volcanic systems. The second expedition targeted Harrat Hutaymah, as a remarkable area for providing an extraordinary range of mantle and crustal xenoliths, which are rock fragments carried up from great depths (40–70 km) by magmas that fed lava flows and cinder cones.

The Saudi Arabian Glass Earth Pilot Project is a geophysical exploration program to explore the upper crust of the Kingdom for minerals, groundwater, and geothermal resources as well as strictly academic investigations. The project began with over 8000 km2 of green-field area. Airborne geophysics including electromagnetic (EM), magnetics, and gravity were used to develop several high priority targets for ground follow-up. Based on the results of airborne survey, a spectral induced polarization (SIP) survey was completed over one of the prospective targets. The field data were collected with a distributed array system, which has the potential for strong inductive coupling. This was examined in a synthetic study, and it was determined that with the geometries and conductivities in the field survey, the inductive coupling effect may be visible in the data. In this study, we also confirmed that time domain is vastly superior to frequency domain for avoiding inductive coupling, that measuring decays from 50 ms to 2 s allow discrimination of time constants from 1 ms to 5 s, and the relaxation parameter C is strongly coupled to intrinsic chargeability. We developed a method to fully include all 3D EM effects in the inversion of induced polarization (IP) data. The field SIP data were inverted using the generalized effective-medium theory of induced polarization (GEMTIP) in conjunction with an integral equation-based modeling and inversion methods. These methods can replicate all inductive coupling and EM effects, which removes one significant barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted and compared with results of drill hole set up in the survey area. The drill hole intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project.

This study shows the results of mapping numerous cavities and distress which appeared and detected in Qassim area, Saudi Arabia. This phenomenon was observed near a school building and residential area and became a serious risk to occupants and residents. The survey was carried out applying geotechnical techniques which included advancing rotary boreholes to depths of 23 m to 30 m with sampling and testing. The evaluation process also included resistivity imaging profiles using 2D electrical resistivity measurements. Results obtained from this research showed a thick top layer of silty clayey sand soil rich of gypsum and carbonate presenting a hazardous and high-risk soil type. The percentage of fines that are likely to be washed out as a result of chemical disintegration and exposure to significant hydraulic gradient was of great concern. Assessment was made using combined geotechnical and geophysical approach in addition to chemical tests. Based on the data collected and analysis of test results a practical solution was suggested to solve this problem. The use of “cut-off wall” in order to reduce the level of subsurface scour and cajuvity formation were found appropriate. The depth of the cut off wall was determined based on the subsurface geological profile. Advantages of this approach and concerns need to be considered in adopting typical solutions that are presented.

Recent developments in large-scale geophysical inversions made it possible to invert the results of entire airborne geophysical surveys over large areas into 3D models of the subsurface. This paper presents the methods for and results of the interpretation of the data acquired by a multiphysics airborne geophysical survey in Saudi Arabia. The project involved the acquisition, processing, and interpretation of airborne electromagnetic, gravity, and magnetic geophysical data over an 8000 square kilometer area. All the collected data were carefully analyzed and inverted in 3D models of the corresponding physical properties of the subsurface, including 3D density, magnetization vector, and conductivity models. This paper summarizes the interpretation of all geophysical data sets collected during the field airborne survey. The goal of the paper is to demonstrate how the advanced 3D modeling and inversion methods can be effectively used for interpretation of multiphysics airborne survey data and to study and analyze the potential of the survey area for natural resource exploration in Saudi Arabia.

The presence of natural voids and cavities in subsurface karstic limestones causes severe problem for civil engineering and environmental management. The presence of such features hinders the extension of urbanizations particularly in the new metropolitan. The eastern part of Saudi Arabia contains various types of karstic limestone, sinkholes, solution cavities and voids. In this context, geophysical methods particularly electrical resistivity technique is used as a cost-effective solution for investigating subsurface caves, voids, and shallow weathered zones. 2-D electrical resistivity data sets have been acquired along seven profiles in the new urbanization at Al Hassa area. Data processing has been carried out taking into consideration the response of synthetic models, which simulates physical models of the most common karstic features in the area. The results are very useful to determine the extension of shallow weathered zones and to locate different cavities underneath them. The hard limestone bedrock can also be detected and traced along the surveyed profiles.