2024 Volume 62 Issue 1 Pages 1-8
In order to evaluate articulatory function to establish a diagnosis in patients with developmental insufficiency of oral function, it is necessary to examine not only speech sounds but also occlusion, and lip and tongue morphology, as well as their functions for articulation maneuvers. However, no effective evaluation method has yet been established.
In the present study, the functions of the lips as an organ for articulation were observed in children who made a labiodental sound when attempting to articulate a bilabial sound that requires closure (contact) of the upper and lower lips. From those observations, causative factors of dental-labial sounds were investigated. One hundred forty-six boys and girls aged 4 to 12 years old were asked to articulate words containing bilabial sounds, and their lip movements were recorded. Based on findings of contact of the upper and lower lips during bilabial articulation, they were divided into those who did (contact group) or did not (non-contact group) show lip contact, then compared for lip-closing force and anterior occlusion including overbite and overjet (OJ).
For subjects in the deciduous and incisor replacement phases, there were no significant differences between the contact and non-contact groups in regard to lip-closing force or anterior occlusion. In contrast, for those in the lateral tooth replacement period, the non-contact group showed significantly greater OJ and significantly lower lip-closing force. Additionally, logistic regression analysis showed that lip-closing force and OJ had clear effects on lack of lip contact.
Analysis of contact between the upper and lower lips during bilabial articulation was found to be useful for confirming oral functions such as development of lip-closing force or anterior occlusion. It is considered that the present diagnostic method may be useful for evaluating developmental insufficiency of oral function.
