EVA mouthguards: how thick should they be?

A major consideration in the performance of mouthguards is their ability to absorb energy and reduce transmitted forces when impacted. This is especially important to participants in contact sports such as hockey or football. The thickness of mouthguard materials is directly related to energy absorption and inversely related to transmitted forces when impacted. However, wearer comfort is also an important factor in their use. Thicker mouthguards are not user-friendly. While thickness of material over incisal edges and cusps of teeth is critical, just how thick should a mouthguard be and especially in these two areas? Transmitted forces through different thicknesses of the most commonly used mouthguard material, ethylene vinyl acetate (EVA) (Shore A Hardness of 80) were compared when impacted with identical forces which were capable of damaging the oro-facial complex. The constant impact force used in the tests was produced by a pendulum and had an energy of 4.4 joules and a velocity of 3 meters per second. Improvements in energy absorption and reductions in transmitted forces were observed with increasing thickness. However, these improvements lessened when the mouthguard material thickness was greater than 4 mm. The results show that the optimal thickness for EVA mouthguard material with a Shore A Hardness of 80 is around 4 mm. Increased thickness, while improving performance marginally, results in less wearer comfort and acceptance.

Treatment outcome in individuals with chronic pain: is the Pain Stages of Change Questionnaire (PSOCQ) a useful tool? Jenny StrongCorresponding Author Contact Information, E-mail The Corresponding Author, a, Kym Westburya, Glen Smithb, Ian McKenziec and William Ryan

The efficacy of psychological treatments emphasising a self-management approach to chronic pain has been demonstrated by substantial empirical research. Nevertheless, high drop-out and relapse rates and low or unsuccessful engagement in self-management pain rehabilitation programs have prompted the suggestion that people vary in their readiness to adopt a self-management approach to their pain. The Pain Stages of Change Questionnaire (PSOCQ) was developed to assess a patient's readiness to adopt a self-management approach to their chronic pain. Preliminary evidence has supported the PSOCQ's psychometric properties. The current study was designed to further examine the psychometric properties of the PSOCQ, including its reliability, factorial structure and predictive validity. A total of 107 patients with an average age of 36.2 years (SD = 10.63) attending a multi-disciplinary pain management program completed the PSOCQ, the Pain Self-Efficacy Questionnaire (PSEQ) and the West Haven-Yale Multidimensional Pain Inventory (WHYMPI) pre-admission and at discharge from the program. Initial data analysis found inadequate internal consistencies of the precontemplation and action scales of the PSOCQ and a high correlation (r = 0.66, P < 0.01) between the action and maintenance scales. Principal component analysis supported a two-factor structure: 'Contemplation' and 'Engagement'. Subsequent analyses revealed that the PSEQ was a better predictor of treatment outcome than the PSOCQ scales. Discussion centres upon the utility of the PSOCQ in a clinical pain setting in light of the above findings, and a need for further research. (C) 2002 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.

Experimental evidence that partner choice is a driving force in the payoff distribution among cooperators or mutualists: the cleaner fish case

Supply and demand largely determine the price of goods on human markets. It has been proposed that in animals, similar forces influence the payoff distribution between trading partners in Sexual selection, intraspecific cooperation and interspecific mutualism. Here we present the first experimental evidence supporting biological market theory in it study on cleaner fish, Labroides dimidiatus. Cleaners interact with two classes of clients: choosy client species with access to several cleaners usually do not queue for service and do not return if ignored, while resident client species with access to only one cleaning station do queue or return. We used plexiglas plates with equal amounts of food to stimulate these behaviours of the two client classes. Cleaners soon inspected 'choosy' plates before 'resident' plates. This supports previous field observations that suggest that client species with access to several cleaners exert choice to receive better(immediate) service.

A monolithic smoothing-gap algorithm for contact-impact based on the signed distance function

A new algorithm has been developed for smoothing the surfaces in finite element formulations of contact-impact. A key feature of this method is that the smoothing is done implicitly by constructing smooth signed distance functions for the bodies. These functions are then employed for the computation of the gap and other variables needed for implementation of contact-impact. The smoothed signed distance functions are constructed by a moving least-squares approximation with a polynomial basis. Results show that when nodes are placed on a surface, the surface can be reproduced with an error of about one per cent or less with either a quadratic or a linear basis. With a quadratic basis, the method exactly reproduces a circle or a sphere even for coarse meshes. Results are presented for contact problems involving the contact of circular bodies. Copyright (C) 2002 John Wiley Sons, Ltd.

A pilot study of the manual force levels required to produce manipulation induced hypoalgesia

Objective. A pilot investigation of the influence of different force levels on a treatment technique's hypoalgesic effect. Design. Randomised single blind repeated measures. Background. Optimisation of such biomechanical treatment variables as the point of force application, direction of force application and the level of applied manual force is classically regarded as the basis of best practice manipulative therapy. Manipulative therapy is frequently used to alleviate pain, a treatment effect that is often studied directly in the neurophysiological, paradigm and seldom in biomechanical research. The relationship between the level of force applied by a technique (e.g. biomechanics) and its hypoalgesic effect was the focus of this study. Method. The experiment involved the application of a lateral glide mobilisation with movement treatment technique to the symptomatic elbow of six subjects with lateral epicondylalgia. Four different levels of force, which were measured with a flexible pressure-sensing mat, were randomly applied while the subject performed a pain free grip strength test. Results. Standardised manual force data varied from 0.76 to 4.54 N/cm, lower-upper limits 95 Cl, respectively. Pain free grip strength expressed as a percentage change from pre-treatment values was significantly greater with manual forces beyond 1.9 N/cm (P = 0.014). Conclusions. This study, albeit a pilot, provides preliminary evidence that in terms of the hypoalgesic effect of a mobilisation with movement treatment technique, there may be an optimal level of applied manual force.

Comparison of tafenoquine (WR238605) and primaquine in the post-exposure (terminal) prophylaxis of vivax malaria) in Australian Defence Force personnel

On return from duty in North Solomons Province (including Bougainville Island), Papua New Guinea, 586 Australian Defence Force personnel received either primaquine (14-d) or tafenoquine (3-d) post-exposure malaria prophylaxis. Within 12 months, 6 of the 214 volunteers receiving primaquine and 7 of 378 receiving tafenoquine had developed vivax malaria. Overall, volunteers preferred the shorter course of tafenoquine.

(-)-CGP 12177 increases contractile force and hastens relaxation of human myocardial preparations through a propranolol-resistant state of the beta1-adrenoceptor

Two forms of the activated beta(1)-adrenoceptor exist, one that is stabilized by (-)-noradrenaline and is sensitive to blockade by (-)-propranolol and another which is stabilized by partial agonists such as (-)-pindolol and (-)-CGP 12177 but is relatively insensitive to (-)-propranolol. We investigated the effects of stimulation of the propranolol-resistant PI-adrenoceptor in the human heart. Myocardium from non-failing and failing human hearts were set up to contract at 1 Hz. In right atrium from non-ailing hearts in the presence of 200 nM (-)-propranolol, (-)-CGP 12177 caused concentration-dependent increases in contractile force (-logEC(50)[M] 7.3+/-0.1, E-max 23+/-1% relative to maximal (-)-isoprenaline stimulation of beta(1)- and beta(2)-adrenoceptors, n=86 patients), shortening of the time to reach peak force (-logEC(50)[M] 7.4+/-0.1, E-max 37+/-5%, n=61 patients) and shortening of the time to reach 50% relaxation (t(50%), -logEC(50)[M] 7.3+/-0.1, E-max 33+/-2%, n=61 patients). The potency and maxima of the positive inotropic effects were independent of Ser49Gly- and Gly389Arg-beta(1)-adrenoceptor polymorphisms but were potentiated by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (-logEC(50)[M] 7.7+/-0.1, E-max 68+/-6%, n=6 patients, P