A Passive Noise Attenuation Earplug Designed to Minimise Unwanted Air Turbine Driven High-Speed Dental Drill Noise.

INTRODUCTION: Air turbine dental drill noise contains high-frequency components that are of concern for patients and dental staff. Meanwhile, verbal communication between the dentist and patient is essential. Conventional active noise-cancelling headphones are ineffective for dental drill noise and simply suppress all sound and hinder communication. METHOD: A compact passive earplug device was designed specifically to attenuate broadband high-frequency noise ranges from 5 to 8 kHz employing an array of quarter wavelength (QW) resonators. This device was 3D printed and tested against white noise to enhance the objectivity of analysis, using a calibrated ear and cheek simulator to effectively measure its performance. RESULTS: The results showed that the resonators produced an average reduction of 27 dB across the targeted frequency range. When compared with two proprietary passive earplugs, this developed passive device prototype was able to attenuate an average of 9 dB more across the target frequency range whilst delivering louder speech signals of 14 dB more. The results also show that using an array of resonators exhibits an accumulated effect of individual resonator performance. CONCLUSIONS: This low-cost passive device could have a place in the dental clinic to reduce unwanted drill noise equivalent to the white noise high frequency spectra tested.

Non-newtonian and flow pulsatility effects in simulation models of a stented intracranial aneurysm.

Three models of different stent designs implanted in a cerebral aneurysm, originating from the Virtual Intracranial Stenting Challenge '07, are meshed and the flow characteristics simulated using commercial computational fluid dynamics (CFD) software in order to investigate the effects of non-Newtonian viscosity and pulsatile flow. Conventional mass inflow and wall shear stress (WSS) output are used as a means of comparing the CFD simulations. In addition, a WSS distribution is presented, which clearly discriminates in favour of the stent design identified by other groups. It is concluded that non-Newtonian and pulsatile effects are important to include in order to avoid underestimating wss, to understand dynamic flow effects, and to discriminate more effectively between stent designs.

Effects of stents under asymmetric inflow conditions.

Patient-to-patient variations in artery geometry may determine their susceptibility to stenosis formation. These geometrical variations can be linked to variations in flow characteristics such as wall shear stress through stents, which increases the risk of restenosis. This paper considers computer models of stents in non-symmetric flows and their effects on flow characteristics at the wall. This is a fresh approach from the point of view of identifying a stent design whose performance is insensitive to asymmetric flow. Measures of dissipated energy and power are introduced in order to discriminate between competing designs of stents.

Molecular mechanisms of the bleaching actions associated with commercially-available whitening oral health care products.

An increased public awareness in dental aesthetics has resulted in the wide availability of techniques of tooth bleaching, both in the dental chair and at home. This article reviews the aetiology of tooth discolouration both at the clinical and the molecular level, together with methods of alleviating such discolouration. Much of the therapeutic and aesthetic actions of commercially-available tooth whiteners, gels, oral rinses and other dentifrices are predominantly dependent on their ability to act as oxidants. A novel method of evaluating these aspects of dentifrice activity is also described: high resolution proton nuclear magnetic resonance (NMR) spectroscopy is a virtually non-invasive, multi component bioanalytical technique that can be employed to study oxidation/reduction reactions at the molecular level and is utilised here to investigate the mechanisms of action of a newly developed dentifrice (Ultrawhite Opal, Janina International). Such methodology also offers much potential for studies concerning the numerous chemical reactions occurring within the oral environment.