The Selçuk type headgear-timer (STHT) is described and tested under laboratory conditions first and then in a controlled patient study. The timing device was compared with real time measurements for 4 months. Accuracy was determined to be absolute (100%). The STHT was determined to be independent of force variables, easy to construct, rugged, and inexpensive. In the clinical test, 10 patients were instructed to wear the extraoral appliance for 16 hours a day. After a 2-month treatment period, the timing mechanisms were introduced to the patients and a subsequent 2-month treatment period was initiated. At the end of the second period, headgear wear was increased 26%. This significant improvement in patient compliance with the STHT timing device, attached to a standard breakaway type headgear, has the likelihood of enhancing treatment results. A foolproof method of assessing actual duration of wear is now available. (Am J Orthod Dentofac Orthop 1997;111:87-92.)
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