Prevotella melaninogenica is a gram-negative anaerobic commensal bacterium present in the human oral cavity and has been isolated as a pathogen from suppurative diseases inside and outside the oral cavity. However, little is known about the virulence factors of P. melaninogenica. Periodontal pathogens, Porphyromonas gingivalis and Tanerella forsythia, secrete virulence factors such as proteases and bacterial cell surface proteins via the type IX secretion system (T9SS) involved in virulence. P. melaninogenica also possesses all known orthologs of T9SS. In this study, P. melaninogenica GAI 07411 mutant was con structed that lacked the ortholog of porK, the gene encoding a major component of T9SS. The porK mutant has reduced hemagglutination and biofilm formation. In addition, after growth on medium containing skim milk, the diameter of the halo surrounding the porK mutant was smaller than that of the wild-type strain, suggesting a reduction in extracellular protease secretion. To investigate this in detail, the culture supernatants of the wild-type strain and the porK mutant strain were purified and compared by two-dimen sional electrophoresis. In the mutant, the number of spots detected was low, indicating a decrease in the number of secreted proteins. In infection experiments, the mortality rate of mice inoculated with the porK mutant was statistically significantly reduced compared to the wild-type strain. These results suggested that P. melaninogenica secretes potent virulence factors via T9SS, which contributes to the pathogenesis of this bacterium.

The purpose of this study was to examine the relationship between oral function and morphology using measured values of lip closing force and tongue pressure in early adulthood and three-dimensional scan data of a dentition model, and to assess the evaluation method.

The subjects comprised 102 adults (62 males, 26.2±3.3 years old; 40 females, 24.4±3.6 years old) with healthy dentition, all of whom gave informed written consent. Lip closing force and tongue pressure were measured, and upper and lower jaw dentition models were obtained. Three-dimensional morphometric measurements of the models were performed, and correlations among lip closing force and tongue pressure and the measured values of each model based on the obtained 3-D data were determined, along with any gender difference between the measured values, and the measured values of the model.

There was a positive correlation between lip closing force and tongue pressure, and in men, there was a significant correlation between tongue pressure and distance between the bimaxillary first molar cusps and the distance between the palatal teeth and neck.

All of tongue pressure, lip closing force, maxillary first premolar palatal distance, second molar interdental distance, first molar interdental distance, palatal depth, palatal volume, and palatal surface area differed significantly by subject gender.

The 3-D data of the dentition model enabled detailed measurements including palatal volume in early adulthood when growth was completed and dentition occlusion was stable. In the future, we plan to continue research in young people.

Recently, the daily environment for children in Japan has been changing because of the significantly declining birthrate. The purpose of this study was to investigate the actual conditions of new child patients visiting the pediatric dentistry department of two different college hospitals as well as regional differences. The subjects were children under 16 years old who visited the Pediatric Dentistry Department of Tokyo Dental College Suidobashi Hospital (hereafter “Suidobashi”) or the Chiba Dental Center (hereafter “Chiba”) from 2016 to 2018. The number of new patients, age at first consultation, chief complaint and status of dental caries were determined, with the following results.

1.The number of new patients under 16 years old was 2,538 at Suidobashi, and 2,850 at Chiba. The number has been increasing annually at Suidobashi, while it has been decreasing at Chiba.

2.At both hospitals, dental caries was the most common chief complaint of new patients (Suidobashi: 40.0%, Chiba: 39.6%), followed by malocclusion (Suidobashi: 19.3%, Chiba: 18.3%). When divided by age, the maximum number of patients primarily affected by dental caries was found in the 2-year-old group at Suidobashi and in the 4-year-old group at Chiba.

3.The highest caries prevalence rate in deciduous dentition was shown in 4-year-old patients (70.2%) at Suidobashi, and 3-year-old patients (56.6%) at Chiba.

4.As for df index, the highest values at both hospitals were seen in patients aged 4 years (Suidobashi: 40.7%, Chiba: 43.5%).

5.Among younger children, there were more patients with severe dental caries at Suidobashi than at Chiba.

Among surgical procedures in the Pediatric Dentistry Clinic at Nihon University Dental Hospital, extraction of supernumerary teeth has been carried out the most frequently. In this study, we examined the dental records of children who visited our clinic from January 2010 to December 2018, and the records of 630 children who had supernumerary teeth were selected for this survey of children's management during extraction.

The male to female ratio was 2.5 : 1, and most of the children had one supernumerary tooth in the maxillary anterior region. Extraction of an erupted supernumerary tooth was carried out at around 6 years of age in many cases, while extraction of an impacted supernumerary tooth was most often performed at around 6–8 years. As for the method of managing children during extraction of the supernumerary tooth, 41% of the children were treated by the usual method, 34% under general anesthesia, and 25% under intravenous sedation. Among them, extraction of the impacted supernumerary tooth was carried out under general anesthesia in 49%, by the usual method in 37%, and under intravenous sedation in 14% of the affected children.

Binominal logistic regression analysis was carried out to examine the relationship between the degree of cooperation by children (n = 381) and the type of management during extraction, and we found that there was a significant relationship (p＜0.001) between them, indicating that a majority of cooperative children were treated by the usual method while a majority of uncooperative children were not. In contrast, there was no relation between the depth of the supernumerary tooth and the type of management during extraction in 183 children examined.

In conclusion, although both the degree of cooperation and the depth of the supernumerary tooth in children should be considered in determining management methods during extraction, the degree of cooperation by children was revealed to be a chief determinant of this matter in our clinic.

The Matsubara City Dental Association (Osaka) has established a patient referral network for members for difficult-to-treat children and disabled people. We analyzed how this system became widely known among members of the association and what kind of pediatric patients (under 18 years old) were referred, and obtained the following results.

1.From October 2013 to December 2019, the number of clinics that have used this network reached 14, or 24% of the member clinics of the association in the city.

2.Although the patients mainly complained about pain due to dental caries at the clinic of origin, the clinics seemed to have had difficulties because they were unable to properly treat those patients who were too young, disabled, or had fear due to their past dental treatment.

3.The majority of pediatric patients were younger than 6 years old, and the most common reason for referral was uncooperative children. Occasionally, about 10% of cases were newly classified as having intellectual disability, autism, ADHD, etc.

4.The median time from referral to visit was 5 days, and more than half of the pediatric patients with caries and pain who needed prompt treatment had consulted a pediatric dentist within one week since visiting the previous dentist.

5.There were four urgent cases for whom we used restraints for uncooperative children, but in other cases, in addition to tell-show-do and voice control, control by a hygienist was sufficient, and in some cases, no control was required at all.

The pediatric patient referral network of the district dental association has been promoting pediatric patient referrals and enriching dental care for local pediatric patients.

There are many types of soft tissue diseases that affect children, one of which is foreign bodies entering the soft tissue. Calcium hydroxide root canal material is used as a root canal filling agent for deciduous teeth, but due to its property, leakage of the root canal filling paste from the root apex can accidentally occur during dental treatment. We report a case of a white spot that occurred in the gingiva after root canal filling treatment for the maxillary left deciduous central incisor which did not disappear for 4 years. The patient visited a hospital complaining of aesthetic disorders.

From the current medical history and laboratory findings, the white spot was diagnosed to be an extraneous foreign body and was removed. A histopathological examination showed that the removed foreign material may have been residual root canal filling material. As a result of analyzing the components of the foreign matter, elements such as barium, sulfur, titanium, silicon, aluminum and sodium were detected. We also analyzed several root canal treatment materials. The components of the white spot were consistent with many components of CalcipexⅡ^®.

When calcium hydroxide is filled into the root of a deciduous tooth, it is absorbed together when the permanent tooth erupts. The root canal filling paste that leaks from the apex is also absorbed with time. However, components other than calcium hydroxide may remain. Dentists need to pay attention to the pressure at the time of root canal treatment, and to follow up after treatment.