Dataset Information

High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips.

ABSTRACT: Cavitation occurs around dental ultrasonic scalers, which are used clinically for removing dental biofilm and calculus. However it is not known if this contributes to the cleaning process. Characterisation of the cavitation around ultrasonic scalers will assist in assessing its contribution and in developing new clinical devices for removing biofilm with cavitation. The aim is to use high speed camera imaging to quantify cavitation patterns around an ultrasonic scaler. A Satelec ultrasonic scaler operating at 29 kHz with three different shaped tips has been studied at medium and high operating power using high speed imaging at 15,000, 90,000 and 250,000 frames per second. The tip displacement has been recorded using scanning laser vibrometry. Cavitation occurs at the free end of the tip and increases with power while the area and width of the cavitation cloud varies for different shaped tips. The cavitation starts at the antinodes, with little or no cavitation at the node. High speed image sequences combined with scanning laser vibrometry show individual microbubbles imploding and bubble clouds lifting and moving away from the ultrasonic scaler tip, with larger tip displacement causing more cavitation.

SUBMITTER: Vyas N

PROVIDER: S-EPMC4775067 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips.

Vyas Nina N Pecheva Emilia E Dehghani Hamid H Sammons Rachel L RL Wang Qianxi X QX Leppinen David M DM Walmsley A Damien AD

PloS one 20160302 3

Cavitation occurs around dental ultrasonic scalers, which are used clinically for removing dental biofilm and calculus. However it is not known if this contributes to the cleaning process. Characterisation of the cavitation around ultrasonic scalers will assist in assessing its contribution and in developing new clinical devices for removing biofilm with cavitation. The aim is to use high speed camera imaging to quantify cavitation patterns around an ultrasonic scaler. A Satelec ultrasonic scale ...[more]

PMID: 26934340

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Project description:We present 1?-resolution ALMA observations of the circumnuclear disk (CND) and the interstellar environment around Sgr A*. The images unveil the presence of small spatial scale 12CO (J=3-2) molecular "cloudlets" (?20,000 AU size) within the central parsec of the Milky Way, in other words, inside the cavity of the CND, and moving at high speeds, up to 300 km s-1 along the line-of-sight. The 12CO-emitting structures show intricate morphologies: extended and filamentary at high negative-velocities (vLSR ?-150 km s-1), more localized and clumpy at extreme positive-velocities (vLSR ?+200 km s-1). Based on the pencil-beam 12CO absorption spectrum toward Sgr A* synchrotron emission, we also present evidence for a diffuse molecular gas component producing absorption features at more extreme negative-velocities (vLSR <-200 km s-1). The CND shows a clumpy spatial distribution traced by the optically thin H13CN (J=4-3) emission. Its motion requires a bundle of non-uniformly rotating streams of slightly different inclinations. The inferred gas density peaks, molecular cores of a few 105 cm-3, are lower than the local Roche limit. This supports that CND cores are transient. We apply the two standard orbit models, spirals vs. ellipses, invoked to explain the kinematics of the ionized gas streamers around Sgr A*. The location and velocities of the 12CO cloudlets inside the cavity are inconsistent with the spiral model, and only two of them are consistent with the Keplerian ellipse model. Most cloudlets, however, show similar velocities that are incompatible with the motions of the ionized streamers or with gas bounded to the central gravity. We speculate that they are leftovers of more massive molecular clouds that fall into the cavity and are tidally disrupted, or that they originate from instabilities in the inner rim of the CND that lead to fragmentation and infall from there. In either case, we show that molecular cloudlets, all together with a mass of several 10 M ?, exist around Sgr A*. Most of them must be short-lived, ?104 yr: photoevaporated by the intense stellar radiation field, G 0?105.3 to 104.3, blown away by winds from massive stars in the central cluster, or disrupted by strong gravitational shears.

Dataset Information

High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips.

Publications

High Speed Imaging of Cavitation around Dental Ultrasonic Scaler Tips.

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