This study was carried out to examine the influence of mouthguards on speech intelligibility. Nine male rugby football players with normal personal occlusion and normal speech served as subjects. All players took the speech intelligibility test while wearing self-adapted mouthguards, custom-made mouthguards and without wearing mouthguards.
The ratio of correct judgments for speech intelligibility wearing self-adapted mouthguards was significantly lower than that of wearing custom-made ones or of not wearing one. When misjudged syllables were evaluated by using the manner of production for articulation, plosives had a tendency to be misjudged as flapped sounds or as other plosives while subjects were wearing self-adapted and custom-made mouthguards. When misjudged syllables were evaluated by the points of production for articulation, bilabials and velars had a tendency to be misjudged as alveolar sounds while subjects were wearing self-adapted and custom-made mouthguards, and alveolar sounds had a tendency to be misjudged as various sounds while subjects were wearing self-adapted ones.
The findings showed that speech intelligibility with custom-made mouthguards was better than with self-adapted ones. Speech intelligibility may be better with mouthguards with reduced palatal thickness than with the current ones because points of prodution for alveolars and velars approach the normal points.