Objective: The purposes of this electromyographic study were to examine whether levator veli palatini muscle activity during speech can be changed with placement of a speech appliance and to clarify whether or not the change is related to the type of speech appliance used.
Design: Electromyography (EMG) was performed during production of speech samples in two conditions: with placement and with removal of a speech appliance. Speech samples were the vowel /omega/ and consonant-vowel (omega) syllables, including nasal, plosive, fricative, and affricate consonants.
Setting: Division for Oral-Facial Disorders, Faculty of Dentistry, Osaka University Dental Hospital, Japan.
Participants: Subjects were six patients with repaired cleft palate and velopharyngeal inadequacy (VPI); three routinely wore a palatal lift prosthesis to correct borderline VPI, and the other three wore a speech appliance hybrid that consisted of a pharyngeal bulb and a palatal lift.
Interventions: Each patient was asked to produce each speech sample in both conditions of placement and removal of their respective appliances.
Main outcome measures: Smoothed EMG signals of the levator veli palatini muscle were recorded with and without the appliance during five repetitions of each speech sample. The average value of peak smoothed levator EMG was compared between placement and removal conditions for all subjects and between the two subject groups in each experimental condition.
Results: With a speech appliance in place, the range of levator activity was distributed in a portion lower than that in the removed condition for subjects in both appliance groups. In addition, the intervals were smaller in the placement condition than in the removed condition.
Conclusion: A speech appliance may prevent hypernasality, nasal emission of air, or both associated with VPI because of mechanical obturation of the velopharynx and an alteration in velopharyngeal function.