Design, Fabrication, and Testing of a Modular Magnetic Field Microsensor on a Flexible Polymer Foil
In contrast to existing microelectromechanical systems (MEMS), this paper describes the development, fabrication, and testing of an anisotropic magnetoresistance (AMR) microsensor using a 7 μm thick polymer foil as substrate material. The modular magnetic field micro sensors are fabricated on a standard 4 in Si Wafer due to handling purposes during the sensor fabrication process. To enable a release of the micro sensors at the end of the fabrication process, initial investigations concentrated on the proof of principle applying a deep reactive-ion etching (DRIE) process to structure the Si wafer. The DRIE process was used to structure Si frames, which serve as carriers for the modular magnetic field micro sensors. For the evaluation of the fabricated modular magnetic field micro sensors, electrical resistance measurements were accomplished. The aim of these investigations was the characterization of the magnetic field dependence of the electrical resistance. The electrical output signal of the AMR sensors were subsequently compared to electrical resistance measurements of AMR sensors fabricated on a Si substrate and served as reference. The measurement results show a marginal effect of the substrate material on the characteristics of the AMR sensors.
Modular Eddy Current Micro Sensor
In order to provide a contactless measurement technique to examine products during the fabrication process, a modular design of an eddy current micro sensor was developed and fabricated in thin-film technology. The sensor consists of two parts, a single-turn excitation coil and an anisotropic magneto-resistance (AMR) sensor. The AMR sensor detects the change of the magnetic field induced in a sample by the excitation coil. Initial investigations were conducted to prove the capability of the completed eddy current micro sensor. A defect was created on the surface of a Cu probe. The electrical output signal of the AMR sensor was subsequently compared to optical measurements of the surface profile of the crack. There is a high correlation between the optical measurements and to those of the eddy current micro sensor.
Assessment of fractures in endodontically treated teeth restored with and without root canal posts using high-resolution cone beam computed tomography
Background Root fractures are a diagnostic challenge for dentists in endodontic treatment. This study aimed to determine the relationship between the characteristics of tooth fractures and the presence of root canal posts in endodontically treated teeth using high-resolution cone beam computed tomography (CBCT). Material and Methods Fifty high-resolution CBCT scans of endodontically treated teeth with a diagnosis of fracture were obtained, of which 30 were from women and 20 were from men. These scans were acquired with three Veraviewepocs 3D units and one 3D Accuitomo 170 unit, with a 40 × 40-mm field of view and 125 μm voxel size. The variables assessed included the type of fracture, extent of fracture, type of retention, post length, cause of endodontic failure, location of the lesion, and time required to detect the fracture (difficulty score). For data analysis, the chi-squared test, Student’s t-test, and multiple linear regression (α <0.05) were used. Results No association was found between the type of fracture and type of retention or between the type of fracture and its extent (P>0.05). On the other hand, the type of fracture significantly influenced the time required for its detection. Additionally, the most difficult plane for detecting the fracture and the difficulty score were associated, with statistically significant results. Conclusions The type of fracture in endodontically treated teeth was not associated with the type of post used for restoration. All of the CBCT systems used to detect tooth fracture showed the same efficiency. Key words:Cone-Beam CT, Tooth Fracture, Root Canal Post.