Nondestructive inspection of metal specimen using tone-burst vibro-acoustography.

Even though the pulse-echo ultrasonic technique is commonly used for the assessment of metal structures, it has some inherent limitations. Vibro-acoustography (VA) is a relatively new ultrasonic technique which has demonstrated a great potential in revealing defects in objects, however it is traditionally used to analyze the integrity of specimens made of low-stiffness materials. This work presents the evaluation of the performance of VA technique for the inspection of a steel structure, which was manufactured with defects of known geometry on its inner surface. All the inspection process was done automatically, from the data acquisition to the image processing for characterizing the defects. Experimental results show that VA was able to identify and characterize even the smallest defects in the structure, with a diameter of 2 mm. In addition, the results show that VA was able to characterize the artificial defects in the steel structure with almost the same errors as the traditional pulse-echo method, which indicates a potential use of VA in the inspection of materials with high mechanical stiffness.

Accuracy of digital technologies for the scanning of facial, skeletal, and intraoral tissues: A systematic review.

STATEMENT OF PROBLEM: The accuracy of the virtual images used in digital dentistry is essential to the success of oral rehabilitation. PURPOSE: The purpose of this systematic review was to estimate the mean accuracy of digital technologies used to scan facial, skeletal, and intraoral tissues. MATERIAL AND METHODS: A search strategy was applied in 4 databases and in the non-peer-reviewed literature from April through June 2017 and was updated in July 2017. Studies evaluating the dimensional accuracy of 3-dimensional images acquired by the scanning of hard and soft tissues were included. RESULTS: A total of 2093 studies were identified by the search strategy, of which 183 were initially screened for full-text reading and 34 were considered eligible for this review. The scanning of facial tissues showed deviation values ranging between 140 and 1330 µm, whereas the 3D reconstruction of the jaw bone ranged between 106 and 760 µm. The scanning of a dentate arch by intraoral and laboratorial scanners varied from 17 µm to 378 µm. For edentulous arches, the scanners showed a trueness ranging between 44.1 and 591 µm and between 19.32 and 112 µm for dental implant digital scanning. CONCLUSIONS: The current digital technologies are reported to be accurate for specific applications. However, the scanning of edentulous arches still represents a challenge.

Computer-aided analysis of digital dental impressions obtained from intraoral and extraoral scanners.

STATEMENT OF PROBLEM: The internal and marginal adaptation of a computer-aided design and computer-aided manufacturing (CAD-CAM) prosthesis relies on the quality of the 3-dimensional image. The quality of imaging systems requires evaluation. PURPOSE: The purpose of this in vitro study was to evaluate and compare the trueness of intraoral and extraoral scanners in scanning prepared teeth. MATERIAL AND METHODS: Ten acrylic resin teeth to be used as a reference dataset were prepared according to standard guidelines and scanned with an industrial computed tomography system. Data were acquired with 4 scanner devices (n=10): the Trios intraoral scanner (TIS), the D250 extraoral scanner (DES), the Cerec Bluecam intraoral scanner (CBIS), and the Cerec InEosX5 extraoral scanner (CIES). For intraoral scanners, each tooth was digitized individually. Extraoral scanning was obtained from dental casts of each prepared tooth. The discrepancy between each scan and its respective reference model was obtained by deviation analysis (µm) and volume/area difference (µm). Statistical analysis was performed using linear models for repeated measurement factors test and 1-way ANOVA (α=.05). RESULTS: No significant differences in deviation values were found among scanners. For CBIS and CIES, the deviation was significantly higher (P<.05) for occlusal and cervical surfaces. With regard to volume differences, no statistically significant differences were found (TIS=340 ±230 µm; DES=380 ±360 µm; CBIS=780 ±770 µm; CIES=340 ±300 µm). CONCLUSIONS: Intraoral and extraoral scanners showed similar trueness in scanning prepared teeth. Higher discrepancies are expected to occur in the cervical region and on the occlusal surface.