The frequency of ankyloglossia in Japan varies greatly depending on the report. The purpose of this study was to examine the frequency of expression by age, and the correlation between morphology and function. We conducted a survey of 2,886 children aged 4 to 6 years. The following results were obtained.

1. The length of the lingual frenulum and the shape of the tip of the tongue were abnormal in 10% of the children. In these children, the tongue had a heart-shaped tip and a lingual frenulum less than 1 cm long; in 3%, the tongue tip was thickened. The length, thickening of the lingual frenulum, and shape of the tongue tip did not differ among ages.

2. Children with functional problems, such as difficulty with anterior, lateral, and vertical movements of the tongue, had a similar proportion of morphologic abnormalities; approximately 30% of children could not produce popping sounds and had dysarthria. Functional impairments correlated with age, and the range of motion of the tongue increased with increasing age.

3. Morphology of the lingual frenulum correlated with its function, and the length and morphology of the tongue tip were highly associated with functional impairments, such as difficulty moving the tongue in the anterior, lateral, and vertical directions.

4. The association between mandibular midline diastema and interocclusion with functional problems was very small.

Antimicrobial resistance (AMR) has become a global problem. In Japan, the AMR Action Plan was enacted in 2016, under which medical institutions are required to monitor trends in the use of antimicrobial agents and promote their appropriate use. Although efforts to ensure proper use have been made in medical departments, in dentistry it has been pointed out that the situation and frequency of unnecessary use of antimicrobial agents have not been sufficiently investigated. In this study, we investigated the use of oral antimicrobials for outpatients in pediatric dental practice among dental colleges and university hospitals in Japan.

The subjects were patients aged between 1 and 16 years who visited the pediatric dental outpatient clinics of 18 hospitals and were prescribed oral antimicrobials from April 1, 2015 to March 31, 2018. The names of the antimicrobial agents, the procedures performed on the day of prescription, and the total number of patients under 16 years of age were counted. In addition, we asked the participating hospitals to voluntarily survey the details of the prescription (dosage and administration, name of disease). The number of days of therapy (DOT) was calculated from the number of days of use, and the reason for use was determined from the name of the disease.

The results of this study showed that the use of third-generation cephalosporin antibiotics has decreased, whereas the use of penicillin has increased in pediatric dental practice. However, the total amount of antimicrobials used has not decreased. In most cases, antimicrobial agents were used for the treatment of dental infections.

Impaction of primary teeth is much rarer than that of permanent teeth. Most cases of primary tooth impaction are observed in the primary second molar ; impaction of the lower primary first molar is rare. This report describes the treatment of a 4-year-old boy with delayed eruption of the mandibular primary first molar and malposition of the first premolar tooth germ due to the presence of an odontoma.

Treatment consisted of surgical removal of the odontoma and traction of the buried primary first molar. Two years after the treatment, the primary first molar reached the occlusal plane, and the first premolar tooth germ recovered its normal position. At age 9 years and 11 months, the first premolar erupted in a normal position, and at age 11 years and 10 months, the tooth almost reached the occlusal plane.

Although the frequency of impaction of primary teeth is very low, early treatment of impacted primary teeth is effective for the development of successor teeth. The present case shows that continued periodic examination after removal of odontoma is important for the development of normal permanent dentition.

We experienced a case in which the left maxillary canine tooth had an eruption disturbance due to odontoma. During a dental health examination for 3-year-olds, the patient was told that the left maxillary deciduous canine had not erupted, and so she visited a local dental clinic. At 4 years 0 months of age, she was referred to our department. A panoramic X-ray had been taken by a local dental clinic at 4 years 0 months of age. An impacted maxillary left deciduous canine and an opaque image near the cusp were observed. At 4 years 2 months of age, Specimen 1 (odontoma) and Specimen 2 (cyst) were removed under general anesthesia, and traction of the left maxillary canine was started. As a result of histopathological examination, Specimen 1 was diagnosed as a complex odontoma and Specimen 2 as a compound odontoma. A lingual arch with a hook and FM Super Thread^® were used for traction. Eleven months after the start of traction, the appliance was removed because guidance into the dentition was observed. After removal, follow-up was performed at 1-month intervals. At 5 years 4 months of age, external resorption of the maxillary left deciduous canine root due to premature contact was observed. An occlusal adjustment was made to prevent premature contact. After the occlusal adjustment, there was no rapid progression of external resorption, but it fell out at 7 years 4 months of age. At 9 years 1 month of age, the maxillary left canine began to erupt. The maxillary left canine erupted in the lower position on the labial side. It is considered necessary to continue occlusal guidance.

In this report, we describe a case of impaction of the lower left primary second molar of a 6-year-old boy. According to the panoramic radiography and dental cone-beam computed tomography (CBCT) examination, an odontogenic tumor-like structure including enamel component was observed and located near the crown region of the lower left primary second molar impacted with distal inclination. However, this tumor-like structure was independent, not included in the dental sac of the primary second molar. The lower left second premolar was congenitally absent. We diagnosed it as odontoma and removed it. We also performed a biopsy of the surrounding tissue of the odontoma for pathological examination. After removing the odontoma, the impacted primary second molar spontaneously improved its axis. After orthodontic treatment, the primary second molar was aligned in the mandibular arch.

We report the course of treatment of this case for more than 4 years and the consideration of histopathological diagnosis as odontoma.

The purpose of this study was to develop a non-invasive, non-contact lip closure test. The orbicularis oris muscle, which acts on lip closure, is a facial muscle that is distributed on the facial skin. It is also called skin muscle. Therefore, it may be possible to quantitatively evaluate lip closure from the facial skin while the mouth is pursed. We devised a new method of taking a three-dimensional facial photograph during lip-pursing. A portable three-dimensional image capture device (VECTRA H1, Canfield, USA) was used for photography. Images were taken continuously from three directions : 45 degrees on the left side, 45 degrees on the front side, and 45 degrees on the right side, during both resting and lip-pursing. These images were combined into one three-dimensional facial image by software (VECTRA VAM ver. 6.5.4, Canfield, USA). Then, the superimposed images were analyzed by dividing them into two selected areas, the facial area and the lip area. As a result, in the facial area, the difference in surface area was 0.6 mm, the distance between images was －0.1 mm, and the sum of volumes was 1.5 cm³. In the lip region, the difference in surface area was 3.3 mm, the distance between images was 2.3 mm, and the sum of volumes was 3.4 cm³. In both cases, the lip area was larger than the facial area. We were able to quantify lip-pursing due to the activity of the orbicularis oris muscle, which is dominant in the lip area.

Hemangiomas are one of the common neoplastic lesions seen in the oral and maxillofacial areas of children. However, since the clinical course and findings vary and differ from those seen in adult patients, testing and diagnosis become difficult. Here,we report the case of a 3-year-old child with a history of trauma to the deciduous teeth. The child was diagnosed with Masson's intravascular hemangioma (MIH) over the course of observation without a definitive diagnosis, despite exhibiting abnormal hemangiomatous findings.

The patient was brought to our department with the primary complaint of crown discoloration after trauma to the maxillary anterior deciduous teeth and gingival swelling in the left maxillary deciduous molar region. The deciduous teeth around the gingival swelling area were sound based on the radiographs taken; however, the cause was unknown. Despite follow-up, the patient had the problematic tooth extracted during an outpatient visit due to enlargement of the swollen area and for esthetic reasons. The patient was finally diagnosed with MIH following a histopathological examination. The patient followed a favorable clinical course after tumor extraction and has shown no signs of recurrence to date. We identified vital reactions in the dental pulp for the deciduous tooth adjacent to the area of gingival swelling and restored both the functional and esthetic aspects of the tooth.

For children in the growth and development phase, it is necessary to consider the frequency of radiological examinations and the effects on the pediatric patient when choosing the timing of intervention. Going forward, we plan to monitor the patient to check for neoplastic recurrence until the completion of permanent tooth eruption.

In recent years, the number of children visiting pediatric dental clinics complaining of physical dental trauma has been increasing. In fact, our clinic has treated many children with such complaints. In this article, we report a case of lockjaw by penetration of the mandibular deciduous incisors and maxillary deciduous canines into the lower lip.

The patient was a 3-year-old boy who was referred to our department for a more detailed examination for lockjaw caused by physical trauma. He had been unable to open his mouth for a week after the injury, making it difficult to eat. Penetration of the mandibular deciduous incisors and maxillary deciduous canines into the lower lip and root fracture of the mandibular left deciduous central incisor were confirmed by a simple CT scan of the head and neck. When an attempt was made to open the mouth under intravenous sedation, the deciduous canines on both sides of the maxilla came off from the lower lip, and an opening of about one finger width became possible. Therefore, the lower lip was debrided and lockjaw was released. Upon follow-up observation, the patient's lower lip wounds had healed, the lockjaw improved, and he was able to consume food.

Most cases of lockjaw caused by physical trauma are due to damage to hard tissue; however, as this case indicated, lockjaw can also be caused by damage to soft tissue.