患儿9岁，左上侧切牙牙齿变色就诊。检查：冠折牙本质暴露，牙齿变色。冷热测无反应，X线片示根尖喇叭口，骨硬板不连续。下列各项中哪项最重要（）。
A.拔髓，不要出根尖孔
B.彻底去除根管内感染物质，消除炎症，保护牙 * *
C.根管内不要封FC等刺激性大的药物
D.用氢氧化钙糊剂充填，不要超填
E.定期复查，更换糊剂
参考答案：B
解析：牙髓破坏后，根尖端存活的牙 * * 可化生成牙本质细胞，使牙根继续发育。
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| Perhaps you ride a bicycle to school. Riding a bicycle can be great fun. Do you know how to ride a bicycle 1 ? Careful boys and girls learn to ride their bicycle well 2 they go out on the road. How can you tell 3 you are a good rider? If you can ride a bicycle in a straight line, you can ride well. If you can't ,you should practise riding 4 a safe place. To be safe on a bicycle, you 5 to use both hands and both feet. 6 your feet on the pedals and your hands on the handle bars at all times. Do you have a basket on your bicycle? If so, put your books and packages in it. Then you can 7 both hands on the handle bars. You know that your bicycle is built for one person. It is not safe to carry anyone 8 you. 9 is this so? Keep 10  safe by safety rules when you ride on a bicycle. Watch where you are going at all times. | |||
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