Use of a Checklist During Observation of a Simulated Cardiac Arrest Scenario Does Not Improve Time to CPR and Defibrillation Over Observation Alone for Subsequent Scenarios

Theory: Immersive simulation is a common mode of education for medical students. Observation of clinical simulations prior to participation is believed to be beneficial, though this is often a passive process. Active observation may be more beneficial. Hypotheses: The hypothesis tested in this study was that the active use of a simple checklist during observation of an immersive simulation would result in better participant performance in a subsequent scenario compared with passive observation alone. Methods: Medical students were randomized to either passive or active (with checklist) observation of an immersive simulation involving cardiac arrest prior to participating in their own simulation. Performance measures included time to cardiopulmonary resuscitation (CPR) and time to defibrillation and were compared between first and second scenarios as well as between passive and active observers. Results: Seventy-nine simulations involving 232 students were conducted. Mean time to CPR was 18 seconds (SD = 11.6) for those using the checklist and 24 seconds (SD = 15.8) for those who observed passively (M difference = 6 seconds), t(35) = 1.46, p =.153. Time to defibrillation was 94 seconds (SD = 26.4) for those using the checklist and 92 seconds (SD = 23.8) for those who observed passively (M difference = –2 seconds), t(38) =.21, p =.837. Time to CPR was 24 seconds (SD = 15.8) for passive observers and 31 seconds (SD = 21.0; M difference = 7 seconds), t(35) = 1.13, p =.265, for their first scenario counterparts. Time to CPR was 18 seconds (SD = 11.6) for active observers and 36 seconds (SD = 26.2; M difference = 18 seconds), t(24) = 2.81, p =.010, for their first scenario counterparts. Time to defibrillation was 92 seconds (SD = 23.8) for passive observers and 125 seconds (SD = 32.2; M difference = 33 seconds), t(33) = 3.63, p =.001, for their first scenario counterparts. Time to defibrillation was 94 seconds (SD = 26.4) for the active observers and 132 seconds (SD = 52.9; M difference = 38 seconds), t(28) =.46, p =.008, for their first scenario counterparts. Conclusions: Observation alone leads to improved performance in the management of a simulated cardiac arrest. The active use of a simple skills-based checklist during observation did not appear to improve performance over passive observation alone.     

Domain-Specific Relationships in Sexual Measures of Impulsive Behavior

Impulsivity is an important construct for understanding sexual behaviors, but behavioral and self-report measures of impulsivity often are not correlated. One possible explanation for this is that there is little shared variance in the measures because behavioral measures index impulsivity by asking questions about monetary preferences, while self-report measures index impulsivity by asking about a broad range of real-world outcomes (including those of a sexual nature) largely unrelated to money-related preferences. Undergraduate students (total N?=?105; female n?=?77, male n?=?28) completed laboratory measures—delay discounting (DD) and probability discounting (PD)—for two different outcomes—money and sexual activity. Participants also completed the Delaying Gratification Inventory (DGI), which measures difficulty with delaying gratification (i.e., impulsivity) across different domains, including money and physical pleasures. Findings indicated that DD and PD for money were not related to any of the DGI subscales. However, DD for sexual activity was significantly related to the DGI Physical Pleasures subscale, but not other subscales. These findings suggest that the relationship between behavioral and self-report measures of impulsive choice may be stronger when both are measuring domain-specific rather than domain-general behavioral patterns, but further research is warranted.     

Fluoride: benefits and risks of exposure

This summarizes current knowledge of the benefits and risks of fluoride ingestion. The preponderance of evidence indicates that fluoride can reduce the incidence of dental caries and that fluoridation of drinking water can provide such protection. Due to the ubiquitous nature of exposures to fluoride sources other than drinking water, it is currently impossible to draw firm conclusions regarding the independent effect of fluoride in drinking water on caries prevalence using an ecologic study design. Moderate dental fluorosis occurs in 1 to 2% of the population exposed to fluoride at 1 mg/l in drinking water and in about 10% of the population at 2 mg/l; moderate/severe fluorosis occurs in variable percentages ranging up to 33% of the population exposed to fluoride at 2.4 to 4.1 mg/l in drinking water. The issue of whether moderate or severe dental fluorosis represents an adverse health effect is still controversial. There is no evidence of skeletal fluorosis among the general U.S. population exposed to drinking water fluoride concentrations lower than 4 mg/l. Radiographically detected osteosclerosis after chronic exposure to fluoride in drinking water at 8 mg/l was not associated with clinical symptoms. Reports of crippling skeletal fluorosis associated with low concentrations of fluoride in drinking water in tropical countries have been attributed to other dietary factors. The available data suggest that some individuals may experience hypersensitivity to fluoride-containing agents. Further studies on hypersensitivity are required. There is no evidence of increased incidence of renal disease or renal dysfunction in humans exposed to up to 8 mg fluoride per liter in drinking water. Structural changes in kidneys of experimental animals have been detected at doses exceeding 1 to 5 mg fluoride per kilogram per day. Based on four case reports, individuals with renal insufficiency who consume large volumes of naturally fluoridated water at 2 to 8 mg/l are possibly at increased risk of developing skeletal fluorosis. Studies on the effects of fluoride in individuals with renal insufficiency are needed. There is no evidence that chronic exposure to concentrations of fluoride reported to be greater than 2 mg/l in drinking water increases human cancer mortality or incidence. A study of lifetime exposure to fluoride on cancer incidence in rats and mice has been completed, but assessment for cancer has not been completed. There is no evidence that fluoride is genotoxic except in some in vitro assays at cytotoxic concentrations. There is no in vivo evidence that fluoride affects human cellular enzyme activities.(ABSTRACT TRUNCATED AT 400 WORDS)     

Behaviour of primary incisor caries: a micromechanical study

OBJECTIVES: To date, there has been no attempt to assess the mechanical properties of the entirety of a smooth-surface carious lesion in primary teeth, despite the fact that these lesions are not only common, but clinically challenging. Therefore, the aim of this study was to describe the hardness and modulus of elasticity across smooth surface lesions of primary incisors. STUDY DESIGN: An in vitro study of the micromechanical properties of primary incisors. MATERIALS AND METHODS: Carious primary incisor teeth were set in resin, sectioned and polished. A series of indentations using the ultra-micro-indentation system were conducted in fully hydrated carious and sound dentine from the minimally affected pulpal region towards the tooth surface. A single set of indentations were duplicated for sound dentine. RESULTS: Although the mechanical properties of the carious dentine varied between the test teeth, the median hardness of the surface, middle and inner (pulpal) region of the carious dentine was 0.01, 0.10 and 0.28 GPa, respectively. The modulus of elasticity of the surface, middle and inner (pulpal) carious dentine was 0.12, 2.16 and 5.98 GPa, respectively. The mechanical properties of the sound dentine varied less, and were consistent between the pulpal and surface regions. Examination of the individual series of indentations indicated that, although the majority of the test teeth showed a decrease in the mechanical properties from the 'unaffected dentine' to the surface of the lesion, in the last 300-500 microm, both the hardness and modulus of elasticity showed a dramatic increase. CONCLUSIONS: This study has confirmed that the carious process has a deleterious effect on the mechanical properties of dentine in primary incisors. This, in turn, increases the likelihood of restorative failure. However, the slight increase in mechanical properties seen at the surface of the carious lesion suggests an increase in mineral content.     

The hardness and modulus of elasticity of primary molar teeth: an ultra-micro-indentation study

Objective: Baseline information on the mechanical properties of and the effect of load upon dental hard tissue is important in the development of successful dental materials. Existing methods of measuring such properties of tissue are subject to significant experimental error. This study reports on the use of an Ultra-Micro-Indentation System (UMIS) to measure the hardness and elastic modulus of primary enamel and dentine.

Methods: Primary molar teeth were sectioned, set in resin and polished. Thirty indentations were made in enamel and dentine using a Berkovitch indentor, 15 of which were subject to a load of 50 mN and 15 to a load of 150 mN. An automated computerised system converted the force/penetration graph for each indentation in to a hardness vs depth graph from which values for the mean hardness and elastic modulus were calculated.

Results: Primary enamel had a mean hardness of 4.88±0.35 GPa whilst the hardness of dentine was 0.92±0.11 GPa The elastic modulus for enamel was 80.35±7.71 GPa and that of dentine 19.89±1.92 GPa. Using linear regression analysis a significant relationship could be shown between the hardness and the elastic modulus for both enamel and dentine when loaded to 150 mN but only for dentine at 50 mN (P<0.05). In general the elasticity of tooth structure increased as the hardness increased.

Conclusion: The UMIS offers a simple and reproducible method of measuring basic mechanical properties of small samples of enamel and dentine.