Evaluation of sealing ability of three kinds endodontic materials as root canal sealers / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the apical microleakage of Vitapex (calcium hydroxide based paste) with that of AH-plus and zinc oxide eugenol sealer when used with laterally condensed gutta percha obturation technique.</p><p><b>METHODS</b>One hundred single rooted human anterior teeth were instrumented and randomly divided into three experimental groups (A, B, C) of 30 teeth each and two control groups (D, E) of 5 teeth each. Group A was filled with laterally condensed gutta-percha using Vitapex as sealer. Group B was filled with laterally condensed gutta-percha using AH-plus as sealer. Group C was filled with laterally condensed gutta-percha using zinc oxide eugenol as sealer. Group D was the positive control. Group E was the negative control, which were coated with nail polish to entire root surface. Teeth were then suspended in 2% methylene blue. After this, teeth were demineralized dehydrated and cleared. Linear dye penetration was determined under stereomicroscope with calibrated eye piece.</p><p><b>RESULTS</b>The mean dye penetration for group A, B, C were respectively (0.57 +/- 0.56) mm, (0.79 +/- 0.96) mm and (1.07 +/- 1.12) mm. Group D demonstrated maximum dye penetration. Group E showed no dye penetration. There was no statistically significant difference between group B and group C (P > 0.05). However, there was statistically significant difference between group A and group B, C (P < 0.01).</p><p><b>CONCLUSION</b>This study showed that Vitapex used as endodontic sealer material are better than AH-plus sealer and zinc oxide eugenol sealer.</p>

A multifrequency phase-controlled driving system for ultrasound therapy / 中国医疗器械杂志

Ultrasound therapy is a new type of therapy technology, there are hyperthermia and high intensity focused ultrasound surgery (HIFUS). Compared with a single frequency system, mutiple frequency system has an additional function to combine power patterns of different frequencies. This function increases the availability of power patterns to treat tumors of various shapes and depths. Therefore, we have in this article proposed a system with the ability to drive ultrasonic phased arrays of multiple resonant frequencies for ultrasound hyperthermia and HIFUS. The results show that this system is able to (1) drive multi-element applicators or phased arrays of a single resonant frequency through the multichannel power amplifiers, (2) concurrently drive transducer with different resonant frequencies, (3) adjust the relative phase and output power of each channel for the scanning ultrasonic focus, and (4) operate each channel with good output stability.