问题 单项选择题

患者,女,30岁,牙体缺损拟行冠修复,牙体预备后常规制取印模,在用石膏灌注工作模型时,以下做法正确的是()

A.石膏粉与水调和后,发现水量过多,再次加入石膏粉继续调拌

B.灌注模型时从右侧逐渐到左侧

C.灌注时避免震荡

D.组织面最好选用熟石膏

E.模型在灌注后15分钟不可修整,24小时则容易修整

答案

参考答案:B

解析:石膏粉与水调和后,若发现水粉比例不合适,应重取量调和。此时再加入石膏粉或水,会造成结晶中心反应的时间和数量不一致,形成晶体间凝聚力减少的不均匀块状物,使凝固时间不同步,导致石膏强度降低。灌注模型时应从一侧逐渐到另一侧,震荡缓慢灌注,排除气泡,充分显示牙体及周围组织的解剖结构。组织面最好灌注超硬石膏,其他部分用普通石膏,以保证模型的强度。石膏模型在15分钟内产生初凝,1小时内基本凝固,24小时完全凝固,其强度达到最高。初凝时,石膏逐渐变稠,失去表面光泽和可塑性,此时能用刀切割,但到终凝阶段时,则不易用器械修整。

单项选择题
单项选择题

Alcohol has a peculiar relationship to happiness. We drink to celebrate, but because alcohol works as a depressant, it ends up deadening feelings. Not surprisingly, there’s an observable connection between alcoholism and depression, and even though it’s not always clear which leads to which, everyone knows you can’t drink like a Sterling Cooper employee for too long before becoming a perpetual sad sack.
But if alcohol can lead to depression, does that mean abstaining (戒除) from alcohol will make you happier A new study suggests that the opposite actually tends to be true. In fact, those who never drink are at significantly higher risk for not only depression but also anxiety disorders, compared with those who consume alcohol regularly.
The study, which was published recently in the journal Addiction, looked at more than 38,000 people in Norway. Researchers, led by Jens Christoffer Skogen of the University of Bergen in Norway, asked the participants how much they had drunk in the previous two weeks; the research team also asked them various questions to measure their levels of anxiety and depression.
People in the top fifth percentile (百分点) of drinkers had the highest odds for ’anxiety. But it was abstainers who were at the highest risk for depression--higher even than the heaviest of drinkers. Why
One reason is that the abstainers in the study sample were more likely to have chronic illnesses, and people with chronic illnesses are more prone to melancholy. Also, "some people assume it’s healthier not to drink," says Skogen--which may be particularly true of those who have chronic illnesses. Finally, some abstainers were formerly heavy drinkers--alcoholics who had to give up the bottle. It makes sense that they would have more psychological distress than others, but only 14% of the abstainers in the Norway study fit this category.
The most powerful explanation seems to be that abstainers have fewer close friends than drinkers, even though they tend to participate more often in organized social activities. Abstainers seem to have a harder time making p friendship bonds, perhaps because they don’t have alcohol to lubricate their social interactions. After all, it’s easier to reveal your worst fears and greatest hopes to a potential friend after a Negroni or two.
So does this mean we should all have a cocktail Maybe, but Skogen says he doesn’t believe his study should encourage abstainers to become drinkers. Rather, "he says doctors might want to investigate why abstaining patients don’t drink and explain that in societies where alcohol use is common, not drinking may lead them to feel left out. Sometimes, you should just say yes.

According to Jens Christoffer Skogen’s study, ______ are at the least risk for depression.

A. those who quit alcohol after some time
B. those who have never drunk alcohol
C. those who drink alcohol heavily

D. those who drink alcohol regularly