Streptococcus gordonii, an early colonizer of dental plaque biofilm, expresses the surface protein adhesin SspA/B, by which the bacterium binds to salivary agglutinin (gp340). SspA/B has an exten sive homology with PAc, a surface adhesin of Streptococcus mutans, thus S.gordonii competes with S.mutans for the same niche environment in salivary pellicles. The aim of this study was to develop an anti-adherence agent that enables control of cariogenic S. mutans biofilm, for which we used the streptococcal SspA/B peptide analog Ssp(A4K-A11K). Our results showed that Ssp(A4K-A11K) significantly bound to saliva and inhibited adhesion of S.mutans to saliva-coated surfaces. Pretreatment with Ssp(A4K-A11K) significantly attenuated biofilm formation via an antagonistic mechanism, while the analog was less effective on adherence and biofilm formation of commensal streptococci. Notably,Ssp(A4K-A11K) treatment delayed a drop in pH in culture medium to a critical level. These findings will contribute to development of techniques to control cariogenic biofilm.

Glucan-binding proteins (Gbps) of Streptococcus mutans, a major pathogen of dental caries, mediate binding of glucans synthesized from sucrose by the action of glucosyltransferases (GTFs) encoded by gtfB, gtfC, and gtfD. Several stress proteins, including DnaK and GroEL, encoded by dnaK and groEL, respectively, are related to environmental stress tolerance. The contribution of Gbp expression to biofilm formation was analyzed by focusing on expression levels of genes encoding GTFs and stress proteins. Biofilm-forming assays were performed using GbpA-, GbpB-, and GbpC-deficient mutant strains as well as the parental strain MT8148. Expression levels of gtfB, gtfC, gtfD, dnaK, and groEL were evaluated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assays. Furthermore, the structure of biofilms formed by these Gbp-deficient mutant strains was observed with confocal laser scanning microscopy (CLSM). Biofilm-forming assay findings demonstrated that the amount formed by the GbpA-deficient mutant strain (AD1) was nearly the same as that by the parental strain, while the GbpB- and GbpC-deficient mutant strains produced amounts lower than MT8148. Furthermore, RT-qPCR assay results showed that the expressions of gtfB, dnaK,and groEL in AD1 were elevated as compared with MT8148. CLSM also revealed that the structure of biofilm formed by AD1 was prominently different as compared with that formed by the parental strain. These results suggest that a defect in GbpA influences expression of genes controlling biofilm formation, indicating its importance as a protein for firm and stable biofilm formation.

Streptococcus mutans is a major pathogen of dental caries and also considered to be one of the causative agents of infective endocarditis (IE). Recent studies have noted frequent detection of bacterial DNA encoding 120-kDa cell surface collagen-binding proteins (CBPs) in samples obtained from S. mutans-positive IE patients. In addition, some CBP-positive S. mutans strains have been found to lack the 190-kDa protein antigen (PA), and that absence strengthened bacterial adhesion to and invasion of endothelial cells. Interaction of pathogenic bacteria with serum or plasma is considered to be an important virulence factor for systemic disease development. In the present study, the pathogenesis of IE induced by S. mutans strains was examined based on different CBP and PA expression patterns,with focus on interactions with serum and plasma. CBP＋/PA－strains showed prominent aggregation in the presence of human serum or plasma, which was significantly greater than that of the examined CBP＋/PA＋and CBP－/PA＋strains. Aggregation of CBP＋/PA－strains was also observed in the presence of a high concentration of type IV collagen, a major extracellular matrix protein in serum, while that was drastically reduced when the serum complement was inactivated. Furthermore, findings from an ex vivo adherence model and in vivo rat model of IE showed that extirpated heart valves infected with CBP＋/PA－strains had prominent bacterial mass formation, which was not observed following infection with CBP＋/PA＋or CBP－/PA＋strains. These results suggest that CBP＋/PA－S. mutans strains utilize serum to contribute to the pathogenicity of IE.

The aim of this investigation was to examine the relationship between dental clinic visit behavior and caries experience of physically disabled children. We analyzed the school dental health examination records of students attending 3 different special needs schools, as well as results of a questionnaire survey given to the students and their parents in 2016.

1.The survey responses showed that 87.1% of the children had chosen a family dental clinic and 72.7% regularly visited there at least once a year.

2.The types of dental care institutions who provided care for the children included university hospital dental clinics (n＝68 respondents), clinics for general / pediatric dentistry (n＝55), dental clinics attached to a facility for disabled individuals (n＝23), dental clinics in a general hospital (n＝15),and dental centers for disabled individuals (12).

3.There were no significant differences regarding the prevalence rate of decayed / filled permanent teeth among the children regardless of type of dental care institution that provided care.

4.Beginning periodic dental visits before the age of 6 years was significantly associated with reduced prevalence of caries and average number of decayed / filled permanent teeth.

These results indicate that disabled special needs children tend to receive dental care from a specialized institution. Furthermore, periodic dental clinic visits, regardless of type of institution, should be recommended for such children to prevent dental caries occurrence.

We conducted a questionnaire survey of parents regarding oral cleaning and use of dental floss by their elementary school-age children to determine the rate of dental floss usage in childhood. The following results were obtained.

1.In terms of daily toothbrushing, the proportion of positive responses to “My child brushes his / her teeth without any help” tended to increase as school grade increased. In line with this, responses to “I brush my child's teeth for him / her” tended to decrease with increasing grade.

2.The percentage of children using dental floss regularly (every day or frequently) was 18.4%, with no significant difference related to school grade.

3.In terms of dental floss usage, the proportion of children in earlier grades using dental floss with parental assistance was greater than 50%. Moreover, the proportion of children flossing by them selves tended to increase as the school grade increased.

4.Reasons for flossing were “Dentist's or dental hygienist's recommendation”, followed by “My family or I (respondent) use (or have used) dental floss.”

5.More than 65% indicated that their children visit a dental clinic “Regularly,” and the response “When he / she gets a cavity” tended to increase as grade increased.

The present findings suggest that elementary school age is an important time to increase awareness of the importance of good oral hygiene practices for later life. To help them familiarize themselves with the habit of flossing in early childhood under parental supervision, it is important to teach not only children but also their parents and other family members how to properly use dental floss.

In infants with a cleft lip and alveolus with / without a cleft palate, treatment with a presurgical naso­alveolar molding (PNAM) technique has an important role in growth guidance of the noso­ alveolus and palatal morphogenesis, as well as nursing. The structure of the device used and planning differ among institutions and hospitals. At our institution, we utilize hard resin as the base palate and a nasal stent. Furthermore, in addition to daily maintenance of the device, a visit to the clinic every few weeks for adjustment of the appliance for a relatively long period (average 6 to 8 months) is needed until the time of plastic surgery. Thus, parental cooperation is essential, and stress experienced by both parents and their infants must be considered. The purpose of this study was to evaluate our PNAM treatment for cleft infants by surveying their parents. A questionnaire regarding PNAM treat­ ment was given to the parents of 62 children who underwent plastic surgery following PNAM treat­ ment at the Department of Dentistry of our medical center for cleft lip and alveolus with / without cleft palate between April 2011 and December 2017. The questionnaire was returned by the parents of 60 (96.8%) patients and the following findings were obtained.

1.PNAM treatment was introduced for affected infants during the relatively long period prior to per­ formance of a cheiloplasty.

2.Some parents (43.3%) wanted to stop the PNAM treatment, though there was no clear relation of the desire with troubles seen following treatment.

3.A majority of the patients (88.3%) experienced troubles following PNAM treatment, including skin trables caused by use of medical­paper­tape (71.7%).

4.Most of the parents (96.7%) were satisfied with the results of PNAM treatment, shown by an an­ swer of “satisfied” or “moderately satisfied”.

The present findings indicate that PNAM treatment is generally acceptable by parents of infants with a cleft palate. Nevertheless, there is room for improvement of preventive methods in order to avoid troubles caused by that treatment. We intend to develop a readily available support system for such problems.

We performed a cross-sectional national investigation of deciduous tooth eruption timing and sequence in 8724 children in Japan between the ages of 3 months and 3 years 11 months in order to assess changes in deciduous tooth emergence. The following results were obtained.

1.Tooth emergence in boys occurred as follows. A emergence occurred between 5 and 9 months of age, A between 7 and 11 months, B between 9 months and 1 year 2 months, B between 9 months and 1 year 3 months, D between 1 year 1 month and 1 year 6 months, D between 1 year 1 months and 1 year 7 months, C between 1 year 2 months and 1 year 8 months, C between 1 year 2 months and 1 year 9 months, E between 1 year 11 months and 2 years 7 months, and E between 2 years and 2 years 11 months. There was no significant difference in regard to eruption timing between B and B, D and D, C and C, D and C, and D and C.

2.Tooth emergence in girls occurred as follows. A emergence occurred between 6 and 9 months of age, A between 7 and 11 months, B between 9 months and 1 year 1 month, B between 9 months and 1 year 2 months, D between 1 year 1 month and 1 year 7 months, D between 1 year 1 months and 1 year 7 months, C between 1 year 3 month and 1 year 9 months, C between 1 year 4 months and 1 year 9 months, E between 1 year 11 months and 2 years 7 months, and E between 2 years 1 month and 2 years 10 months. There was no significant difference in eruption timing between A and A, A and B, B and B, D and D, and C and C.

3.A comparison between boys and girls showed no significant difference in eruption timing, except for C and C, as that occurred 1 month earlier in boys.

4.As compared to a previous report presented in Japan in 1988, eruption timing was significantly earlier for A, A, C, and D in boys, and for A and D in girls.

The purpose of the present study was to compare the retention rate and caries preventive effect of a sealant containing S-PRG filler (Beautisealant) with those of a resin-based fluoride releasing sealant (Teethmate F1) using a split-mouth protocol. Sealant retention rate and caries presence were evaluated after 6 months, and then again after 1, 2, and 3 years. Our results revealed the following.

1.The cumulative survival rate of completely retained Teethmate F1 at 3 years after occlusion of the first molar and premolars was significantly higher than that of Beautisealant (p＜0.05). The reten tion rate for both sealants with premolars was higher than that with the first molar during the observation period.

2.There was a significant difference regarding retention between Beautisealant and Teethmate F1 in the low-risk group, whereas the high-risk group showed no such difference.

These results suggest that Beautisealant and Teethmate F1 sealants have similar caries preventive effects in children at high risk for caries.

Third molars are the most posterior tooth in the jaw and often associated with various clinical problems, such as caries, periodontal disease, and malocclusion. However, no definitive guidelines for treatment of the third molar have been presented in Japan. We investigated radiographic evaluations of third molar development using panoramic X-ray images of patients treated at our dental clinic and analyzed the timing of therapeutic intervention. The average age for appearance of a radiolucent bud with no calcification was 9.4 years. Crown completion was found in patients aged 13-15 years, while root formation started at around 16 to 17 years old and was completed at around 18 to 23 years of age. Findings of a survey of patients aged 18 years and older showed that 94.8% had a third molar and all 4 teeth existed in 60.7% of those cases, while 97.3% of the third molar teeth, including cases of non-eruption in the oral cavity, erupted from the jawbone. Thus, many of the impacted third molars were erupted from the jawbone, but existed under the submucous membrane. In addition, a patient consciousness survey showed recognition of the third molar in approximately 80% of the respondents, with more than 60% answering “the third molar is an unnecessary tooth”. Based on our findings, we consider that third molar management should start at around 9 years of age, with the appearance of a radiolucent bud. Furthermore, for junior and senior high school students, dentists should be careful that the third molar does not have effects on the surrounding teeth or dentition caused by its root formation. If problems are noted, it will be necessary to determine whether extraction of the third molar at this stage is necessary. Also, panoramic X-ray imaging was shown effective for screening. Finally, we propose that a flowchart based on symptoms be used to make objective judgments.

To determine changes in the prevalence of dental caries and tooth surfaces because of frequent developments aimed at promoting the prevention of deciduous tooth caries, 3-year-old first-visit patients to a dental clinic in the Tokyo metropolitan area were surveyed regarding dental caries prevalence approximately every 10 years, from the 1970s to 2010s.

1.The prevalence of dental caries and mean number of decayed teeth per child tended to decrease throughout the study period, with the decrease from the 1990s to 2000s particularly marked.

2.When divided by tooth surface, caries prevalence for the occlusal surface of the lower second primary molar or distal surface of the lower first primary molar was highest in the period from 1970 to 1990. In contrast, in the 2000 and 2010 surveys, caries prevalence for the mesial surface of the upper deciduous central incisor was higher as compared to the occlusal / proximal surface of the lower primary molars, indicating that the region with most frequent development of dental caries changed from the occlusal surface of the lower second primary molar to the mesial surface of the upper deciduous central incisor after 2000.

3.Caries prevalence for the lower deciduous incisor was lower than that for other tooth types from the 1970s to 2000. No caries were observed in that location after 2000.

4.The reduction of dental caries from the 1990s and after 2000 may have been due to introduction of medical check-ups from a young age sponsored by local government agencies as well as an in crease in regular topical application of fluoride to tooth surfaces.

5.Our results indicated that the region with most frequent development of dental caries in 3-year-old children was the mesial surface of the upper deciduous central incisor. To prevent caries in this re gion, self-care corresponding to the individual oral health condition, such as use of dental floss,from an early age and regular professional care at a clinic are important factors.

We examined the records of patients who visited the Department of Pediatric Dentistry of Hiroshima University Hospital for the first time between 2011 and 2015.

1.The number of first-time visitors during the study period was 2500, with no significant difference among the years analyzed.

2.The number of new patients aged 3-6 years showed an increase, while that of those aged 6-9 years was decreased.

3.Among the new patients, 75% lived in Hiroshima City and that proportion was not significantly changed throughout the study period.

4.From 2011 to 2015, the proportion of new patients coming for “caries treatment” or “intraoral screening” was increased, while that of those coming for “cavity prevention” or “malalignment” was decreased.

5.From 2011 to 2015, the number of new patients referred by other hospitals or clinics was increased. This was especially noted after relocation of the department to a newly built outpatient clinical facility in 2013, after which 90% of the transferred patients were referral cases. In addition, since the new pediatric dentistry department was established in closer proximity to the pediatric department, inter-departmental collaboration was strengthened. We considered that relocation was one of the main factors responsible for the increase in number of new pediatric patients referred by the Medical Division of our hospital.

6.We also investigated systemic diseases presented by the new pediatric patients referred to our department by the Medical Division and noted that the numbers of those with a “solid tumor”, a “he matopoiesis tumor”, “non-neoplastic hematologic disease”, and “neurological disease” were increased after relocation of the department.

The present findings confirm that our Pediatric Dentistry unit functions well as part of a tertiary medical care institution and also highlight the importance of community-based health care, which we will continue to pursue.