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.

Supernumerary teeth are usually asymptomatic, and their presence is detected incidentally on radiographs. The most common type of supernumerary teeth is maxillary incisors followed by maxillary molars. There is usually one supernumerary tooth; cases with multiple such teeth are rare. We report a rare case of a patient who presented with four supernumerary teeth in the bilateral mandibular premolar lingual space. In this case, the mandibular second premolar had a morphological abnormality, and it was difficult to diagnose the supernumerary teeth.

We experienced two cases of soft tissue damage caused by a 30-cm long ballpoint pen with a mascot attached. In case 1, two large lacerations were found in the soft palate, and 21 sutures were placed under general anesthesia. In case 2, a slight laceration was found in the upper labial frenum, and the patient was followed up. Even with daily necessities such as ballpoint pens that are not normally used in the oral cavity, infants play with them in their mouths, so it is necessary to alert parents to the danger of infants playing with things in the oral cavity.