October’s Tip

Do not memorize, understand – Dr. T. Mulligan

The Mulligan Extrusion arch is a two-couple extrusion arch wire used for control of anterior open bite It is commonly made with round wire (a .020 or a .018 SS), attached to the teeth only at the molars and the incisors and is activated for incisor extrusion by a molar tip-forward (off-center, gable) bend. Dr. Mulligan used a .020 ss arch wire, however, the author prefers a .018 SS arch wire – as there is less friction and biding.

The Extrusion arch is activated by one squeeze of the Tweed loop forming pliers – “V” pointing gingivally, just in front of the molar tubes.  This one squeeze creates approximately 45° tip back (off-center bend), if less is desired, squeeze less.  In author’s opinion, it is paramount to apply these bends extra-orally.

Analyzing the result of the tip-back; there is a long arm mesially – pointing in the direction of the force (extrusion of incisors) and creating lingual moment (de-torquing – up righting incisors).  Distally of the tip-back; there is a short arm pointing opposite of the direction of the force (intrusion of the molars) and creating mesial moment (mesially tipping the molars).

Remember, the long arm points in the direction of the force. The short arm points opposite to the direction of the force.

Is not there an analogy between the teeter-totter and the Extrusion arch?

The Mulligan intrusion arch renders the dental arch shorter; the only obvious application may be a dental anterior open bite with a spaced dentition and flared maxillary incisors.