9.局部麻醉下，接受下顎大臼齒根管治療，第二天發生張口受限情形，最不可能的原因是？
(A)使用含 1：50,000 epinephrine 之麻醉劑
(B)注射區感染
(C)打到血管，局部出血
(D)打到內翼肌，造成傷害

答案：登入後查看
統計： A(265), B(19), C(27), D(27), E(0) #1032584

詳解 (共 3 筆)

#4843069
局麻代謝一般不會超過12小時,因此不會是...
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#6230639
發生 張口受限（trismus）通常是...
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#7398898

Yes, 1:50,000 epinephrine absolutely exists, although it is rarely used as the primary anesthetic concentration.

Common dental vasoconstrictor concentrations:

Epinephrine concentration Clinical use
1:50,000 Hemostasis during surgery
1:100,000 Most common dental local anesthetic
1:200,000 Lower cardiovascular effect

For example:

  • 2% lidocaine with 1:50,000 epinephrine is available and is often used when strong local vasoconstriction and bleeding control are desired during oral surgery.

Back to the question

Trismus (limited mouth opening) the day after an IAN block is commonly caused by:

✅ (B) Infection in the injection area

  • Can cause inflammation of masticatory muscles.

✅ (C) Hematoma from vessel injury

  • Blood accumulation around muscles can lead to trismus.

✅ (D) Injury to the medial pterygoid

  • One of the most common causes after an inferior alveolar nerve block.
  • The needle may penetrate the medial pterygoid, causing inflammation/spasm.

Why (A) is least likely

1:50,000 epinephrine itself does not cause trismus.

Although high epinephrine concentrations can theoretically:

  • increase local ischemia,
  • delay healing,

they are not a recognized common cause of post-injection trismus.

The usual etiologies tested are:

  • muscle trauma,
  • hematoma,
  • infection.

Therefore:

✅ Answer = (A)

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