The Role of Genetic Factors in the Outbreak Mechanism of Dental Caries.

OBJECTIVE: The aim of the present study was to investigate the relationships between cariogenic bacterial infection and single nucleotide polymorphisms (SNPs) in candidate genes associated with dental caries, and to explore the factors related to caries in children. STUDY DESIGN: Children aged 3 to 11 years were selected. Detection of cariogenic bacteria (Streptococcus mutans, Streptococcus oralis, Streptococcus sobrinus and Lactobacillus) from the plaque of each patient, and SNP analyses of five candidate genes (MBL2, TAS2R38, GLUT2, MMP13 and CA6) were performed using DNA isolated from buccal mucosal cells. The dental caries experience in primary and permanent teeth was determined using the decayed, missing and filled teeth (DMFT) index, and the effects of the observed factors on the DMFT value were analyzed by multiple regression analysis. RESULTS: The results of the multiple regression analysis showed that the DMFT value significantly increased in the presence of S. mutans or S. sobrinus (p < 0.001), while the dmft/DMFT value decreased in the presence of nucleobase C in MBL2 (p < 0.05). CONCLUSION: These results suggest that the MBL2 gene is related to the pathogenesis of dental caries.

Characterization of a PTH1R missense mutation responsible for Jansen type metaphyseal chondrodysplasia.

Parathyroid hormone and parathyroid hormone-related peptide (PTHrP), and its receptor (PTH1R) play an important role in differentiation of bone and cartilage in the developing stages. Constitutive dimers of PTH1R are believed to be dissociated by ligand binding, and monomeric PTH1R is capable of activating G protein. Jansen type metaphyseal chondrodysplasia is caused by missense mutations in PTH1R, which are constitutively active even without the presence of the ligands. However, the underlying pathomechanisms remained largely unknown. In this study, we have attempted to further characterize a PTH1R missense mutation H223R responsible for Jansen type metaphyseal chondrodysplasia. cDNAs encoding wild-type (Wt)- and H223R mutant (Mut)-PTH1R were transfected into HEK293T cells, and as a consequence of western blots, both the Wt- and Mut-PTH1R proteins showed several fragments between 55 and 65 kDa in size, while the patterns of N-glycosylation were distinct between them. Then we hypothesized that the Mut-PTH1R might physically interact with the Wt-PTH1R, leading to affect the downstream cAMP accumulation. Co-immunoprecipitation assays clearly showed that interaction occurred not only between the Wt-PTH1R themselves, but also between the Wt- and Mut-PTH1R. Furthermore, we performed CRE reporter assays to investigate cAMP accumulation. Constitutive, ligand-independent cAMP accumulation was observed in HEK293T cells expressing the Mut-PTH1R. Interestingly, there was a statistically lower constitutive activity in HEK293T cells co-expressing the Wt- and Mut-PTH1R proteins. Summarizing, it seems likely that Mut-PTH1R may be, at least in part, co-localized with Wt-PTH1R by forming a heterodimer, leading to affect the function to each other.

Symmetrical agenesis of the mandibular third molars and agenesis of other teeth in a Japanese orthodontic population.

This study was conducted to investigate the association between symmetrical agenesis of the mandibular third molars and agenesis of other teeth in Japanese orthodontic patients. A sample of 64 patients with symmetrical agenesis of the mandibular third molars and without agenesis of the maxillary third molars was selected as the third molar agenesis group. In addition, 585 patients with all 4 third molars were selected as controls. The main materials examined for diagnosis of tooth agenesis were panoramic radiographs. The prevalence rate of tooth agenesis was compared between the groups using the chi-squared or Fisher's test, and the odds ratio. Significantly increased occurrence of overall agenesis of the maxillary lateral incisors, and overall and symmetrical agenesis of other teeth including the maxillary and mandibular second premolars and mandibular first molars were observed in the patients with symmetrical agenesis of the mandibular third molars and without agenesis of the maxillary third molars. Irrespective of the presence or absence of symmetrical agenesis of the mandibular third molars, no significant differences in the prevalence rates of overall or symmetrical agenesis of other teeth and specific teeth were noted between the sexes or between the right and left sides of the jaws in the patients without maxillary third molar agenesis. (J Oral Sci 58, 171-176, 2016).

Patterns of bilateral agenesis of maxillary third molars and agenesis of other teeth.

The purpose of this study was to investigate the patterns of bilateral agenesis of maxillary third molars and other tooth agenesis in Japanese orthodontic patients. A group of 262 subjects with bilateral agenesis of maxillary third molars (group A) was divided into three subgroups: group 1A consisting of 114 subjects without agenesis of mandibular third molars; group 2A, 31 subjects with unilateral agenesis of mandibular third molars; and group 3A, 117 subjects with agenesis of all third molars. As controls, 926 other subjects without third molar agenesis were selected (group C). Panoramic radiographs were mainly used to examine for tooth agenesis. The Chi square test and odds ratio were used to make statistical comparisons. The prevalence rates of agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, and bilateral agenesis of maxillary lateral incisors and second premolars were significantly higher in any one of the third molar agenesis groups than in the control group. Characteristically, no significant increase in occurrence of bilateral agenesis of mandibular second premolars was demonstrated by the subjects with bilateral agenesis of maxillary third molars. Irrespective of whether unilateral or bilateral agenesis of mandibular third molars is present or not, the Japanese orthodontic patients with bilateral agenesis of maxillary third molars exhibited a significantly increased occurrence of unilateral or bilateral agenesis of maxillary lateral incisors, mandibular incisors and maxillary and mandibular second premolars, except for bilateral agenesis of mandibular incisors and second premolars.

Emotional intelligence score and performance of dental undergraduates.

The purpose of this study was to investigate the relationship between emotional intelligence (EI) and undergraduate dental students' ability to deal with different situations of communication in a clinical dentistry practical training course of communication skills. Fourth-year students in 2012 and in 2013 at the Nippon Dental University School of Life Dentistry at Niigata participated in the survey. The total number of participating students was 129 (88 males and 41 females). The students were asked to complete the Japanese version of the Mayer-Salovey-Caruso Emotional Intelligence Test in communication skills. Female students tended to have significantly higher EI score than males. The EI score in the group with high-grade academic performers was higher than in the low-grade group. The influence of EI on academic performance appeared to be mainly due to the students' ability to accurately perceiving emotions and to their ability to understand emotional issues. The importance of EI may also lie in its ability to parse out personality factors from more changeable aspects of a person's behavior. Although further studies are required, we believe that dental educators need to assume the responsibility to help students develop their emotional competencies that they will need to prosper in their chosen careers. In our conclusion, dental educators should support low achievers to increase their levels of self-confidence instead of concentrating mainly on improving their technical skill and academic performance. This may lead to upgrading their skills for managing emotions and to changing their learning approach.

Effects of long-term repeated topical fluoride applications and adhesion promoter on shear bond strengths of orthodontic brackets.

OBJECTIVE: The purpose of this study was to assess the effects of long-term repeated topical application of fluoride before bonding and an adhesion promoter on the bond strength of orthodontic brackets. MATERIALS AND METHODS: A total of 76 bovine incisors were collected and divided equally into four groups. In group 1, the brackets were bonded without topical fluoride application or adhesion promoter. In group 2, before bonding, the adhesion promoter was applied to nonfluoridated enamel. In group 3, the brackets were bonded without the application of the adhesion promoter to enamel, which had undergone long-term repeated topical fluoride treatments. Teeth in group 4 received the long-term repeated topical applications of fluoride, and the brackets were bonded using the adhesion promoter. All the brackets were bonded using BeautyOrtho Bond self-etching adhesive. The shear bond strength was measured and the bond failure modes were evaluated with the use of the adhesive remnant index (ARI) after debonding. RESULTS: The mean shear bond strength was significantly lower in group 3 than in groups 1, 2, and 4, and there were no significant differences between the groups except for group 3. There were significant differences in the distribution of ARI scores between groups 2 and 3, and between groups 3 and 4. CONCLUSIONS: The adhesion promoter can recover the bond strength reduced by the long-term repeated topical applications of fluoride to the prefluoridation level and had a significantly great amount of adhesives left on either fluoridated or nonfluoridated enamel.

Cross-cultural comparison of the attitudes of dental students in three countries.

The aim of this study was to identify and compare the attitudes of dental students toward their career choice and dental education in three different countries. Three hundred thirty-six dental students from the University of British Columbia, Canada; Mahidol University and Chiang Mai University, Thailand; and Nippon Dental University, Japan, participated in this study. Information was derived from a questionnaire consisting of career choice items and dental education items. Significant differences in the responses of the participants from each of the three countries were detected for each of the questionnaire items (P<0.001). Regarding factors that may have served as motivations for career choice, the majority of dental students from each country indicated positive reasons such as interpersonal motives, caring for other people, and academic interest. For future career options, the majority of Japanese and Canadian students planned to work as general dentists. Thai students were more likely than Japanese or Canadian to prefer specialization than practicing general dentistry. Nearly three-quarters of the Canadian and Thai students were satisfied with the teaching faculty of their schools, while only a quarter of the Japanese students indicated satisfaction. The findings from this study enhance our understanding of differences and/or similarities among dental students in three nations; this information may help to define strategies to improve the quality of international student exchange programs.