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Objective. The aims of this study were to assess the prevalence of temporomandibular disorders (TMD) amongst adolescents and to contrast the prevalence of TMD according to the DC/TMD clinical examination protocol versus the prevalence of TMD pain according to two screening questions. Material and methods. Two hundred and ten adolescents living in the county of Bergen, Norway, were offered an additional examination for TMD in connection with their regular dental check-up appointment. Five dental clinics were selected with differing socio-economic patient populations, as reflected by stratification of average levels of DMFT, and an equal number of girls and boys were invited to participate. The participants answered two screening questions for TMD pain followed by a clinical examination according to the DC/TMD protocol by five calibrated examiners. Results. Acceptable calibration results were obtained. Approximately 80% of eligible participants consented to partake. According to the criteria of DC/TMD, the prevalence of TMD amongst the study participants was 11.9%, with a peak at 16 years of age. According to the self-reported screening questions for TMD pain, 7.2 % responded positively. Only 7 participants with a TMD diagnosis established according to the DC/TMD clinical examination protocol reported also TMD pain based on answering the two screening questions. Conclusion. The prevalence of TMD is higher for girls than for boys and the prevalence of TMD established according to the DC/TMD criteria was higher than the prevalence of TMD pain estimated by use of screening questions for self-reported pain.

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CO2 injection in hydrate-bearing sediments induces methane (CH4) production while benefitting from CO2 storage, as demonstrated in both core and field scale studies. CH4 hydrates have been formed repeatedly in partially water saturated Bentheim sandstones. Magnetic Resonance Imaging (MRI) and CH4 consumption from pump logs have been used to verify final CH4 hydrate saturation. Gas Chromatography (GC) in combination with a Mass Flow Meter was used to quantify CH4 recovery during CO2 injection. The overall aim has been to study the impact of CO2 in fractured and non-fractured samples to determine the performance of CO2-induced CH4 hydrate production. Previous efforts focused on diffusion-driven exchange from a fracture volume. This approach was limited by gas dilution, where free and produced CH4 reduced the CO2 concentration and subsequent driving force for both diffusion and exchange. This limitation was targeted by performing experiments where CO2 was injected continuously into the spacer volume to maintain a high driving force. To evaluate the effect of diffusion length multi-fractured core samples were used, which demonstrated that length was not the dominating effect on core scale. An additional set of experiments is presented on non-fractured samples, where diffusion-limited transportation was assisted by continuous CO2 injection and CH4 displacement. Loss of permeability was addressed through binary gas (N2/CO2) injection, which regained injectivity and sustained CO2-CH4 exchange. OPEN ACCESSEnergies 2015, 8 4074