Pressure from the lips on the teeth during speech

Pressure on the teeth from the labial soft tissues during the articulation of a given sentence was measured in 24 children, 8 to 14 years old, with normal incisor relationships. The points of measurement were labial in the midlines between the maxillary and mandibular central incisors and between the right maxillary canine and first premolar (the modiolus point). A mouthpiece was attached to the teeth at these three positions and connected via a water-filled system to an extraoral pressure transducer. A microphone recorded the volume and speed of articulation while the activity of the lip muscles was surveyed by electromyography. The maximal pressure during pronunciation of the consonant /p/, the pressure at rest (RP), the speech posture pressure (SPP), the time pressure integral (TPI), and the mean speech pressure (MSP) during articulation were analyzed. Maximal pressure during pronunciation of /p/ and TPI were highest at the modiolus, second highest at the lower midline, and lowest at the upper midline. RP and SPP were highest at the lower midline. SPP was 2 to 3 times higher than RP, and MSP was 4 to 7 times higher than RP. The pressures during articulation recorded at the lower midline were closely correlated with those at the modiolus, with weaker correlations between the upper and lower midlines and between the upper midline and modiolus. There was a close correlation between RP and SPP. SPP, MSP, and TPI may, along with RP, contribute to the positions of the teeth.