qat (quat, khat) n. A green-leafed shrub (Catha edulis) whose leaves are chewed with the subsequent release of psychoactive agents. It is usually placed in the mucobuccal fold for several hours and is often accompanied by smoking *tobacco. It is reported to be associated with *periodontitis, *leukoplakia, and *oral cancer.
Further Reading El-Wajeh Y. A. M., Thornhill M. H. Qat and its health effects. Br Dent J 2009;206:17–21.
quadhelix appliance n. A fixed slow-expansion *orthodontic appliance. It is attached to the teeth by *bands cemented to a molar tooth (usually the first molar) on each side of the arch. The spring between the molars is W-shaped and fabricated in 1mm stainless steel wire. In addition to expansion, the appliance can be used to de-rotate rotated molar teeth.
quadrant n. (in statistics) One half of each dental arch. The four quadrants are referred to as upper right, upper left, lower left, and lower right, with thedividing line being themidpoint of the arch.