一下颌第二磨牙，MOD银汞充填，剩余颊舌壁硬组织强壮，但牙冠高度仅约4mm。若全冠修复，以下增加固位的措施错误的是（）。
A．龈下边缘
B．适当增加龈边缘宽度
C．设计嵌体冠
D．增加钉洞或箱型辅助固位形
E．在轴壁上制备倒凹
参考答案：E
解析：
为增加全冠的固位力，可以通过选择龈下边缘，适当增加龈边缘宽度、设计嵌体冠利用洞型固位、增加钉洞或箱型辅助固位形等方法。但在轴壁上制备倒凹会影响全冠就位，是不正确的。
| 用括号内所给单词的适当形式填空。 | |
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| 1. I like soft______ because it can make people look good. 2. Jim always gets good grades because he studies in the ______ way. 3. It was______ that mom gave a new schoolbag to my brother, but I got nothing. 4. The train station is quite______ before the Spring Festival. 5. They ______hands and said "Goodbye" to each other. |