LIP ADAPTATION TO SIMULATED DENTAL ARCH EXPANSION .2. ONE WEEK OF SIMULATED EXPANSION

An increase in resting lip pressure and the resulting disruption of th e intraoral pressure equilibrium may be responsible for the poor stabi lity found with orthodontically expanded dentitions. Passive expansion strategies seek improved stability by altering lip pressure, thus cre ating a new equilibrium. One of these strategies has been shown to alt er pressure favorably. However, pressure changes associated with conve ntional expansion need to be studied before conclusions regarding the superiority of passive expansion can be drawn. The purpose of this stu dy was to examine lip pressure changes after 1 week of simulated conve ntional expansion. Twenty-two subjects agreed to wear a mandibular exp ansion-simulating stent full-time for 1 week. Resting pressure was mea sured in the midline and right canine areas. Midline lip pressure decr eased significantly after 1 week while pressure in the canine area did not change significantly. This finding suggests an adaptive response that varies according to anatomic location.