25 0:03:56 Multiple choice question Among the premolars, which of the following teeth has the highest proportion of having double root canals: ()
A. Maxillary first premolar
B. Maxillary second premolar
C. Mandibular first premolar
D. Mandibular second premolar
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26 0:08:09选择题 关于下颌第一磨牙的髓腔形态的描述不正确的是:()
A. 髓室近远中径大于颊舌径大于髓室高度
B. 髓室顶形凹,最凹处约与颈缘平齐
C. 舌侧髓角高度约近牙冠中1/3
D. 颊侧和远中髓角较低,位于牙冠颈1/3或颈缘附近
E. 近中根管为双管型者占13%
26 0:08:09 Multiple choice question Which of the following descriptions about the pulp cavity of the mandibular first premolars is incorrect: ()
A. The mesiodistal diameter of the pulp chamber is larger than the buccolingual diameter, and the buccolingual diameter is larger than the height of the pulp chamber.
B. The roof of the pulp chamber is concave. The bottom of the concavity is nearly at level with the cervical margin.
C. The height of the lingual pulp horn nearly reaches the middle third of the crown.
D. The pulp horns of buccal cusps and distal cusp are relatively low, and are located at cervical third of the crown or near the cervical line.
E. The double-root canals account for 13% among the mesial root canals.
27. 0:02:36 选择题 根管横断面可呈C字形的牙齿为:()
A. 上颌第一磨牙
B. 上颌第二磨牙
C. 上颌第三磨牙
D. 下颌第一磨牙
E. 下颌第二磨牙
27 0:02:36 Multiple choice question Which of the following teeth can have C-shaped cross section at the root canal? ()
A. Maxillary first molar
B. Maxillary second molar
C. Maxillary third molar
D. Mandibular first molar
E. Mandibular second molar
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