Incisal relationships during speech.

The dimensions of movement of the mandible during the reading of a standard passage of text have been measured and enable a speech envelope to be described. The relationship between closest speaking space and the vertical overlap of the incisor teeth shows that there is a trend in this direction, but it is not as definitive a correlation as has been previously assumed. The relationship between the anterior speaking space and the horizontal overlap of the incisor teeth shows a similar trend but with a much reduced correlation. There was often a small space of approximately 0.2 mm between the mandibular incisor teeth and the palatal aspects of the maxillary incisor teeth that, although a common finding in this study, was by no means a constant feature for all subjects.