Deep-Learning Based Adaptive Ultrasound Imaging From Sub-Nyquist Channel Data.

Traditional beamforming of medical ultrasound images relies on sampling rates significantly higher than the actual Nyquist rate of the received signals. This results in large amounts of data to store and process, imposing hardware and software challenges on the development of ultrasound machinery and algorithms, and impacting the resulting performance. In light of the capabilities demonstrated by deep learning methods over the past years across a variety of fields, including medical imaging, it is natural to consider their ability to recover high-quality ultrasound images from partial data. Here, we propose an approach for deep-learning-based reconstruction of B-mode images from temporally and spatially sub-sampled channel data. We begin by considering sub-Nyquist sampled data, time-aligned in the frequency domain and transformed back to the time domain. The data are further sampled spatially so that only a subset of the received signals is acquired. The partial data is used to train an encoder-decoder convolutional neural network (CNN), using as targets minimum-variance (MV) beamformed signals that were generated from the original, fully-sampled data. Our approach yields high-quality B-mode images, with up to two times higher resolution than previously proposed reconstruction approaches (NESTA) from compressed data as well as delay-and-sum (DAS) beamforming of the fully-sampled data. In terms of contrast-to- noise ratio (CNR), our results are comparable to MV beamforming of the fully-sampled data, and provide up to 2 dB higher CNR values than DAS and NESTA, thus enabling better and more efficient imaging than what is used in clinical practice today.

The effect of resin coating on the shear punch strength of restorative glass ionomer cements.

OBJECTIVE: The aim of the current study was to examine the shear punch strength (SPS) of high-strength glass ionomer cements (HSGICs) in relation to coating applications and duration of coating. MATERIALS AND METHODS: I-Ninety specimens each of Fuji IX GP Fast (FIX Fast), Ionofil Molar AC (IM), Riva Self Cure (R) and Ketac Molar (KM) were prepared and divided into uncoated and coated groups, sub-divided into three sub-groups and incubated for 24 h, 1 week or 8 weeks (distilled water, 37 °C) before SPS. II-Ninety specimens each of uncoated and coated Fuji IX GP Extra were similarly prepared, divided into six sub-groups and incubated for 2 h, 24 h, 1 week, 1 month, 2 months or 3 months (artificial saliva, 37 °C) before SPS. Another 90 specimens were coated for 2 h, 24 h, 1 week, 1 month or 2 months, after which the coating was removed. Specimens were re-incubated in artificial saliva until the end of the 3-month period and then subjected to SPS. RESULTS: None of the materials gained extra strength when coated. Uncoated KM, IM (at all times) and FIX Fast (at 24 h) were stronger. Fuji IX GP Extra achieved 11.5 MPa after 2 h, which increased to 56.7 MPa after 24 h. The highest strength after 3 months was achieved when the coating was retained for 2 h (71.7 MPa). CONCLUSION: A resin coating will not positively affect the SPS of HSGICs. CLINICAL RELEVANCE: There is no need to protect HSGICs from water to gain extra strength unless the coating is retained for 2 h.

A comparison of temperature increases produced by "premium" and "standard" diamond burs: An in-vitro study.

OBJECTIVE: Vital tooth preparations may cause irreversible thermal damage to the pulp. The manufacturing techniques of dental burs may decrease heat production and minimize the risk of overheating and trauma to the dental pulp. Strauss (Raanana, Israel) has introduced "premium" diamond burs, claiming superior efficiency and longevity. We sought to determine the safest preparation methods by performing a comparison of intrapulpal temperature increases caused with "standard" and "premium" burs. METHOD AND MATERIALS: Three types of diamond burs (F1R, F21R, and K2) were tested on extracted human teeth (n = 8 teeth per bur type). Premium and standard manufacturing techniques were compared for each bur type (n = 24 teeth per group; total 48 teeth). An intrapulpal thermocouple was used to measure the temperature during the procedure. Comparisons were analyzed with the t test and one-way ANOVA. P ≤ .05 was considered significant. RESULTS: All premium burs demonstrated lower temperature increases compared to the standard burs (P ≤ .001 for F21R and K2, P = .086 for F1R). The temperature increases with premium burs were similar for different bur shapes, but the temperature increases with standard burs depended on the bur shape (P < .001). CONCLUSION: Using premium diamond burs for tooth preparation may reduce the risk of pulp tissue damage, and thus reduce postoperative pulp-associated complications.

Do dental impression materials play a role in cross contamination?

OBJECTIVE: Dentists are required to institute infectious control procedures. Dental impression materials possessing antimicrobial properties may aid in reducing the risk of cross contamination since impression materials might play a role as carriers. The purpose of this study was to evaluate the antimicrobial properties of four impression materials. METHOD AND MATERIALS: Four impression materials--Orthoprint, Impregum Penta, Aquasil Ultra Monophase, and Permlastic--were evaluated by the direct contact test. The materials were tested in contact with Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, and Candida albicans. The materials were mixed; allowed to set; and examined immediately and after aging for 24, 48, and 72 hours and 1 week. Two-way ANOVA, one-way ANOVA, and Tukey multiple comparison procedures were applied to the results. RESULTS: Impregum Penta presented the broadest antibacterial spectrum of all the materials tested. There was a complete growth inhibition of S aureus and S epidermidis, and it sustained this ability for at least 7 days. It also showed an antifungal effect by partially inhibiting the growth of C albicans, a quality that was seen only immediately after setting. Aquasil Ultra showed an antifungal effect only immediately after setting. Permlastic showed a complete growth inhibition when in contact with C albicans and sustained this ability for at least 7 days. No significant antimicrobial properties were recorded for Orthoprint. When in contact with E faecalis, no significant antibacterial properties were recorded for any of the materials. CONCLUSION: None of the tested materials exhibited a long-lasting or complete antibacterial and antifungal property. Therefore, disinfection of impressions is essential.

Temperature rises beneath resin composite restorations during curing.

PURPOSE: To compare the thermal conductivity of two different composite materials, with five light-cure units, in a series of different material thicknesses and light source distances. METHODS: Two commonly used resin composite restorative materials and three light emitting diodes (LED), one halogen, and one plasma arc lights were selected. The thermal conductivity of the composite materials with different light curing units (LCU) was measured and compared. A K-type thermocouple and digital thermometer were used to assess the thermal conductivity. Materials depths of 1 mm, 2 mm and 4 mm and curing distances of 0 mm, 3 mm and 6 mm were compared. Four-way ANOVA was used to analyze the Ln transformation of the maximal temperature and a Tukey test for multiple comparisons. RESULTS: Significant differences in temperature rise were observed between the two restorative materials. The thermal emission of the LED lights was higher than the other LCU's measured. An inverse ratio was found between material thickness and the measured thermal conductivity and the distance of the light tip from the restorative material.

The influence of 2 condensation techniques on the marginal seal of packable resin composite restorations.

OBJECTIVE: To evaluate the effect of manual condensation versus a combination of manual and mechanical, or automatic, condensation on the gingival marginal seal of packable resin composite restorations. METHOD AND MATERIALS: Two packable composites, Pyramid Dentin (Bisco Dental) and Filtek P-60 (3M Espe), were tested. The study consisted of 37 extracted caries-free human molars and premolars. In each tooth, 2 standardized Class 2 cavities were prepared and restored using the incremental technique; the mesial restoration was condensed by hand instrument, and the distal by a combination of the manual and mechanical condenser (KaVo). Restored teeth were subjected to automatic thermal stresses and cycling load stresses. Teeth were immersed in 0.5% basic fuchsin at 37 degrees C for 96 hours. Samples were sectioned mesiodistally in 3 sections. Dye penetration at the gingival margin was examined. RESULTS: Automatic condensation of Filtek P-60 and Pyramid demonstrated better sealing properties, with a median dye penetration of 0 and 1, respectively (on a dye penetration scale of 0 to 3), compared to manual condensation, median of 2 (P = .043) and 3 (P = .079), respectively. Better sealing ability was shown with P-60 than with Pyramid Dentin when manual condensation was used (P = .037). No significant difference was observed between the 2 products when tested with automatic condensation (P = .066). CONCLUSION: In this in vitro study the combination of manual and automatic condensation resulted in reduced gingival margin microleakage for both packable composites.

A microleakage study of single-bottle adhesives applied to enamel and cementum and aged by both occlusal loading and thermocycling.

OBJECTIVE: To compare enamel and dentin microleakage of three single-bottle dentin-bonding agents (DBA) (One-Step, Single Bond, and Dentamed P&B) on teeth that were then subjected to thermocycling and occlusal loading. METHOD AND MATERIALS: Class 5 cavities were prepared on the buccal and lingual surfaces of 30 extracted human molars and divided into three groups. The occlusal margins were in enamel, and the cervical margins were in cementum. DBA were applied strictly according to the manufacturers' recommendations, and the preparations were restored with resin composite. Specimens were subjected to 2,000 intermittent occlusal loads and 3,000 thermocycles and then immersed in 0.5% basic fuchsin dye for 72 hours. Four consecutive sections were cut for each specimen and examined under a stereomicroscope. The extent of dye penetration was measured and recorded using a nonparametric scale from 0 to 4. RESULTS: The Mann-Whitney U test showed a significant difference at cementum margins between One-Step and Dentamed P&B, as well as between Single Bond and Dentamed P&B, and an insignificant difference between Single Bond and One-Step. There was no significant difference in dye penetration at enamel margins between the three DBA. CONCLUSION: Under combined use of occlusal loads and thermocycling, the sealing ability of single-bottle DBA at dentin margins ranged from good for One-Step to moderate for Single Bond to poor for Dentamed P&B. At enamel margins, all materials performed equally well.

Cavity preparation by Er-YAG laser on pulpal temperature rise.

PURPOSE: To measure the intrapulpal temperature changes in vitro, during cavity preparation and caries removal, using the Opus 20 Er-YAG laser plotted as a function of the laser energy and pulse rate. MATERIALS AND METHODS: Class I and V cavity preparations were made in 175 fresh extracted caries-free human teeth and caries removal was carried out in 42 carious extracted teeth by the Opus 20 Er-YAG laser. K-type thermocouples were inserted into the pulp chambers filled with heat conducting paste. Lasing was carried out at different irradiation energies and pulse frequencies, using air-water spray. Temperature changes in the pulp chamber were measured during lasing. RESULTS: In all groups tested, the maximum temperature rise was lower than 5.5 degrees C, which is considered as critical value for pulp vitality. The highest temperature values were measured during Cl I preparations (3.13 degrees C +/- 1.54 - 4.11 degrees C +/- 1.29), medium values were in Cl V in enamel (2.38 degrees C +/- 1.37 - 4 degrees C +/- 1.07) and the lowest were in cementum (2.10 degrees C +/- 0.61 - 3.61 degrees C +/- 1.15) and during caries removal (1.21 degrees C +/- 0.46 - 3.51 degrees C +/- 0.68).