To contribute to decision-making regarding resection of the upper labial frenum, we conducted a oneyear follow-up study on 197 children aged three to five years who attended kindergarten or nursery school to observe the changes in the morphology and the position of attachment of the upper labial frenum. The following results were obtained.

1. Regarding the incidence of transition from Type I to other types of the upper labial frenum depending on the age at the beginning of the study, the incidence of the transition from Types-disease to Type I was significantly higher in the period from five to six years of age.

2. Among the children experiencing the transition from Type I to Types-disease, the proportion of those experiencing the transition to Type II was the highest (73.3%), followed by the transition to Type III (20%). No transition to Type V or VI was observed.

3. Among the children experiencing the transition from Types-disease to Type I, the proportion of those experiencing the transition from Type III was the highest (41.7%), followed by the transition from Type II (37.5%) in all age groups. No transition from Type VI was observed.

The presence or absence of transition from Type I to Types-disease and the details of transition suggest that a transition stage exists during the period from five to six years of age. Moreover, mutual transition among Types I, II, and III occurred relatively frequently, whereas the transition from Type I to Types V and VI was rarely observed. Because Types V and VI during the deciduous dentition period can be the cause of median diastema and other disorders at the time of permanent anterior tooth eruption, it is important to provide treatment while taking into consideration the possibility of the effects of these abnormalities on the development of oral functions.

With recent progress in technology, IoT devices that connect objects to the Internet have proliferated rapidly, facilitating daily routines in various ways.

We conducted a questionnaire survey on how the continuous use of IoT toothbrushes for children changes their behavior and skills, as well as parentsʼ concerns about their childrenʼs tooth-brushing behavior. The following results were obtained.

1. Regarding childrenʼs tooth-brushing skills from the parentsʼ point of view, more than 90% of the children answered that they could move their toothbrushes in their entire oral cavity through continuous parent-child tooth-brushing.

2. Regarding childrenʼs tooth-brushing behavior, approximately 70% of children utilizing the test product, which consisted of a device attached to the toothbrush and a smartphone app for the device with visual and auditory tooth-brushing guidance, reported that they started brushing by themselves.

3. Regarding parentsʼ concerns related to tooth-brushing, approximately 90% of the parents whose children used the test product suggested that their anxiety reduced with its continued usage.

These results suggest that IoT toothbrushes may motivate children to initiate tooth-brushing by themselves and improve their tooth-brushing skills, which may reduce parentsʼ concerns.

With the aim of understanding the actual status of dentistry for children and disabled persons at Hokkaido University Hospital as an advanced treatment hospital, and the changes that have occurred over time, we investigated the actual status of new patients visiting our clinic over a five-year period from 2016 to 2020 and reached the following conclusions.

The average number of new patients per year was 338, with slight differences observed from year to year. Male and female patients accounted for 57.1％ and 42.9％ of the total, respectively, showing a gender difference. The age at the first visit peaked between 4 and 7 years old. The most common chief complaint was tooth decay and toothache (46.8％), with a wide range of other complaints. The total number of new patients living in Sapporo City accounted for 74.2％, but some came from neighboring areas and some from more than 100 km away. The patients with pre-existing medical conditions accounted for 41.1 ％ of the total. The most common diseases were mental and behavioral disorders, but there was a wide range of other diseases as well. The patients treated as usual were 71.9％; the rest required restraints or general anesthesia. Referred patients accounted for 80.3％ of the total. Most patients were referred from dental clinics, but there were also referrals from medical departments and other medical facilities.

The results suggest the necessity of having specialized knowledge and skills to deal with various cases, as well as to respond to the changing medical systems and needs of pediatric and disabled dentistry over time, in dentistry for children and disabled patients in higher medical institutions.

We describe the case of an 8-year-10-month-old boy who presented with a supernumerary tooth displaying incisor-like crown morphology in the right deciduous mandibular first molar. At the time of the initial examination, the patient was in Hellman dental developmental stage IIIA. An abnormal crown morphology was observed in the right deciduous mandibular first molar. The crown of the tooth with abnormal crown morphology showed a mandibular incisor-like morphology, and 3/4 of the tooth had erupted. The color of the crown was similar to that of the mandibular central incisor. Dental and panoramic X-rays confirmed that it was a single-rooted supernumerary tooth, and the crown of the first premolar was visible immediately below the tooth. There were no other abnormalities including the number of teeth. Cone-beam CT showed that the root of the supernumerary tooth was fully mature and the root apex of the tooth was oriented proximally to the first premolar. The supernumerary tooth was extracted since the crown of the right first premolar was fully mature and the supernumerary tooth was causing the eruption of the right first premolar. Postoperatively, the patient is being followed up with dental caries prevention measures.