Mandibular incisor position for English consonant sounds

Area of Science:

• Speech Science
• Dental Phonetics
• Biomechanics of Speech

Background:

• Understanding the precise positioning of the mandible and incisors during speech is crucial for various applications, including speech synthesis, clinical diagnostics, and orthodontic treatment planning.
• Previous research has provided insights into articulatory movements, but detailed mapping of mandibular incisor positions across the full range of English consonants remains less explored.

Purpose of the Study:

• To systematically describe the vertical, anteroposterior, and lateral positions of the mandibular incisors for all 24 consonant sounds in the English language.
• To investigate whether these incisor positions are influenced by the consonant's placement within a word (initial vs. final).
• To determine if the incisor's position for a consonant sound is affected by its coarticulation with open or closed vowel sounds.

Main Methods:

• Utilized electrognathography, a non-invasive technique, to record mandibular movements.
• Collected data from 30 young adult subjects performing a series of speech tests involving various English consonant and vowel sounds.
• Analyzed the recorded data to determine mean incisor positions in three dimensions (vertical, anteroposterior, lateral) for each consonant sound.

Main Results:

• Vertical incisor displacement ranged from 2.5 mm (sibilants) to 11.7 mm (/H/) from the intercuspal position.
• Anteroposterior incisor displacement ranged from 1.4 mm anterior (sibilants) to 1.8 mm posterior (/M/) relative to the intercuspal position.
• Lateral incisor displacement was minimal (<1 mm). Word position did not affect incisor position, but vertical opening increased significantly for 8 consonants with open vowels; anteroposterior and lateral positions were unaffected by vowels.

Conclusions:

• Mandibular incisor position for English consonants is independent of word-initial or word-final placement.
• Coarticulation with open vowels significantly influences the vertical incisor position for certain consonant sounds.
• Sibilant consonant sounds consistently demonstrated superior and anterior incisor positions, falling within clinically acceptable ranges across subjects.