Muscles of mastication

Why this matters

These four muscles decide whether a patient can open their mouth, and three of the four you will never touch. They are also the muscles a dentist most often injures — the needle that goes too medial, the block that misses, the jaw that will not open two days later.

The big picture

Three of these four muscles cannot be reached, so the moving mandible is the instrument: you read them in millimetres and directions, not with your fingertips. And confidence in this topic runs inversely to reach — the one muscle nobody can touch is the one the teaching drifted around.

The 14 cards in this lesson

1. 01Four muscles, one nerve, one box
2. 02The origin tells you the action
3. 03The zygomatic arch is the watershed
4. 04Both pterygoids, one plate, opposite faces
5. 05Force muscle, excursion muscle
6. 06Who actually produces each movement
7. 07The lateral pterygoid: measured, model, folklore
8. 08Clinical alert — in the lesson
9. 09Clinical alert — in the lesson
10. 10Three from the front, one from the top
11. 11The reversals
12. 12When a muscle sends you to the wrong tooth
13. 13Three of the four cannot be reached
14. 14The patient who does not have TMD

You have got it when

You are ready when you can say which face of which plate each pterygoid takes, name the muscles of a lateral excursion with the sides the right way round, and tell a muscle problem from an abscess using nothing but millimetres.