Posterior "Vibrating" Line ("Ah" Line)

We want to end the denture on soft tissue that does not move. Have the patient say "Ah" and watch the soft palate move upward*. At some point anteriorly the movement ends. We need to record this line of no movement, or little movement.

Seat your recording base in the mouth and hold it in place with your mirror handle. Note the soft tissue contacting the posterior border of your recording base. If when the patient says "Ah" the soft tissue moves away from the recording base (now there is a triangular space posteriorly) then your recording base is too long.

Cut out about a 5mm bullet-shaped section of acrylic on the midline of your posterior border. Have the patient say "Ah" again and watch through the opening where the palate stops moving. Put the recording base on the master cast and put a small dot where the movement ended.

Laterally your border should end at the hamular notch. You can locate it by moving your mouth mirror over the tuberosity until it falls into a soft tissue crevice distally. Mark this on your master cast. Join the three marks and you have the posterior vibrating line.

When you scrape the master cast along the posterior vibrating line, the processed denture will show a raised edge which defines the posterior border of your denture.

There is sometimes a rounded projection of bone disto-lingual to the tuberosity, and the hamular notch. (This is the hamular process or pterygoid hamulus.) Sometimes you can feel the bone just below the mucosa. Never cover this hard tissue with your denture or your pressure spot will end up as a sore spot.

*The soft palate moves upward to close off the nasal cavities when you eat or drink. Otherwise some food and drink would come out your nose.

17. This is a unique skull showing a bony depression in the shape of a cupid's bow. The photo on the right shows that only a portion of this depression (filled with soft tissue) is utilized for the posterior palatal seal. Notice the greater palatine foramen on the medio-lateral border of the tuberosity is within the outline of the posterior palatal seal.

17. The posterior vibrating line extends from hamular notch to hamular notch. It may curve forward, crossing the posterior nasal spine, but missing the posterior border of the bone by a millimeter or two. This may be the only area where the denture is not supported by bone.

1986 Board Question

The sentence in question consists of two main parts: a statement and a reason for the statement. Which of the following describes the sentence?

1. Both statement and reason are correct and related.
2.Both statement and reason are correct but NOT related.
3.The statement is correct but the reason is NOT.
4.The statement is NOT correct but the reason is an accurate statement.
5.NEITHER statement nor reason is correct.

The imaginary line that marks the division between movable and immovable tissues is important in complete denture construction because it indicates where the posterior border of the denture base should be located.

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1999 by Julius Rosen, D.D.S.