A PROSPECTIVE-STUDY OF LIP ADAPTATION DURING 6 MONTHS OF SIMULATED MANDIBULAR DENTAL ARCH EXPANSION

The stability of dental arch expansion with conventional orthodontic t reatments is disappointing. An increase in labial soft tissue pressure resulting from the expansion may contribute to this instability. An 8 -month study of lip pressure changes resulting from lip bumper wear ha s been conducted, but no long-term studies have been conducted on pres sure changes resulting from conventional expansion using fixed applian ces. The purpose of the current study was to investigate changes in la bial soft tissue pressures when conventional expansion was simulated. Twenty-two subjects wore a stent simulating mandibular dental arch exp ansion. They were instructed to wear the stent full-time. Lip pressure was recorded initially at 1 week, and monthly for 6 months. A repeate d measures ANOVA was used for statistical analysis. A statistically si gnificant (P less than or equal to 0.05) increase in pressure was docu mented after initial insertion of the expansion-simulating stent. The increase was not maintained, suggesting an adaptation of the labial so ft tissues.