Incompetent lip seal and nail biting as risk factors for malocclusion in Japanese preschool children aged 3-6 years.

BACKGROUND: Malocclusion is a multifactorial condition associated with genetic and environmental factors. The purpose of this study was to investigate the prevalence of occlusal traits, oral habits, and nose and throat conditions by age and to assess the association between malocclusion and its environmental factors in Japanese preschool children. METHODS: A total of 503 Japanese children (258 boys and 245 girls aged 3-6 years) were recruited. Occlusal traits were assessed visually to record sagittal, vertical, and transverse malocclusion, and space discrepancies. Lip seal was recorded by an examiner, and oral habits (finger sucking, lip sucking or lip biting, nail biting, chin resting on a hand) and nose and throat conditions (tendency for nasal obstruction, allergic rhinitis, palatine tonsil hypertrophy) were assessed by a questionnaire completed by the parents. The prevalence of each item was calculated, and binary logistic regression was used to examine the factors related to malocclusion. RESULTS: 62.0% of preschool children in the present study exhibited malocclusion, and 27.8% exhibited incompetent lip seal. Nail biting was the most frequent oral habit with a prevalence of 18.9%. Nasal obstruction was recorded in 30.4% of children. The results of binary logistic regression showed that incompetent lip seal was significantly related to malocclusion, and that nail biting was significantly negatively related. CONCLUSIONS: Incompetent lip seal is significantly associated with malocclusion, but nail biting may not necessarily be a deleterious habit for the occlusion in Japanese preschool children.

The number of erupted teeth as a risk factor for dental caries in eighteen-month-old children: a cross­sectional study.

BACKGROUND: Dental caries is one of the most common chronic diseases worldwide, affecting lifelong as well as children. Therefore, it is important to clarify factors related to early childhood caries (ECC) in a younger population in terms of caries prevention. However, the prevalence of ECC is low in developed countries in the twenty-first century and a large-scale survey is needed to clarify the risk factors. Furthermore, earlier tooth eruption is not taken into consideration in most studies of ECC, even though it may be a factor of ECC. The present study investigated the prevalence and risk factors of dental caries in children aged 18 months in a core city of Japan. METHODS: Findings from a total of 7351 children aged 18 months were analyzed. Anthropometric measurements of height and weight, as well as an oral examination and a microbiological caries-risk test, were performed. Additionally, a structured interview sheet was provided to the parents or guardians. Findings of dental caries at 18 months of age were evaluated using a logistic regression model. RESULTS: Of the enrolled children, 1.2% had experienced dental caries. Multivariable logistic regression analysis results indicated a significant association with dental caries at 18 months of age for the following factors: second child (OR = 1.78; 95% CI:1.08-2.93, P < 0.05), third and later child (OR = 2.08; 95% CI:1.12-3.89, P < 0.05), 12 or fewer erupted teeth (OR = 0.47; 95% CI:0.24-0.96, P < 0.05), 17 or more erupted teeth (OR = 4.37; 95% CI:1.63-11.7, P < 0.01), Cariostat score (+ + +) (OR = 3.99; 95% CI:1.29-12.31, P < 0.05), daily eating before bed (OR = 2.62; 95% CI: 1.55-4.45, P < 0.001), three or more snacks per day (OR = 2.03; 95% CI:1.15-3.58, P < 0.05), and breastfeeding (OR = 3.30; 95% CI:2.00-5.44, P < 0.001). CONCLUSIONS: These results suggest that the number of erupted teeth, as well as birth order, eating habits, and breastfeeding, are significant factors in dental caries occurrence at 18 months of age.

Clinical characteristics of children and guardians possessing CBP-positive Streptococcus mutans strains: a cross-sectional study.

Streptococcus mutans is a major etiological agent for dental caries. We previously demonstrated that S. mutans strains expressing collagen-binding proteins (CBPs) were related to the pathogenesis of systemic diseases. However, their acquisition and colonization remain unknown. Here, we investigated the detection rates of CBP-positive S. mutans strains in children and their guardians to clarify the background for the acquisition and colonization in children. Saliva samples were collected from children and their mothers, and detection of S. mutans and collagen-binding genes (cnm, cbm) was performed by PCR after DNA extraction. The oral status of each child was examined, and their mothers were asked to complete a questionnaire. The isolation rate of Cnm-positive S. mutans was significantly higher in mothers than in children. Notably, the possession rates of CBP-positive strains in children were significantly higher in children whose mothers had CBP-positive strains than in children whose mothers did not have these strains. Furthermore, children with CBP-positive strains had a significantly shorter breastfeeding period than children without these strains. The present results suggest that nutritional feeding habits in infancy are one of the factors involved in the acquisition and colonization of CBP-positive S. mutans strains.

Evaluation of the collagen-binding properties and virulence of killed Streptococcus mutans in a silkworm model.

Streptococcus mutans, a major pathogen of dental caries, is also known as a causative agent of cardiovascular disease. A 120 kDa collagen-binding protein (Cnm) of S. mutans is an important contributor to the pathogenicity of cardiovascular disease. Although dead bacteria have been detected in cardiovascular specimens by molecular biological methods, the pathogenicity of the bacteria remains unknown. Here, we analyzed the pathogenicity of killed S. mutans by focusing on collagen-binding ability and the effects on silkworms. In live S. mutans, Cnm-positive S. mutans had high collagen-binding activity, while Cnm-negative S. mutans had no such activity. After treatment with killed Cnm-positive S. mutans, amoxicillin-treated bacteria still had collagen-binding ability, while lysozyme-treated bacteria lost this ability. When live and amoxicillin-treated S. mutans strains were administered to silkworms, the survival rates of the silkworms were reduced; this reduction was more pronounced in Cnm-positive S. mutans infection than in Cnm-negative S. mutans infection. However, the administration of any of the lysozyme-treated bacteria did not reduce the survival rate of the silkworms. These results suggest that amoxicillin-killed Cnm-positive S. mutans strains maintain collagen-binding properties and pathogenicity in the silkworm model, and are possibly associated with pathogenicity in cardiovascular diseases.

Relationship between Dental Occlusion and Maximum Tongue Pressure in Preschool Children Aged 4-6 Years.

Tongue function is regarded as a primary factor in the etiology of malocclusion, but details of the relationship remain unknown. The purpose of the present study was to investigate maximum tongue pressure, in preschool children to examine its relationship with dental occlusion. A total of 477 healthy children (248 boys, 229 girls, aged 4-6 years) were recruited. Dental occlusion was assessed visually to record sagittal, vertical, and transverse malocclusion, and space discrepancies. Maximum tongue pressure was measured using a balloon-based tongue pressure measurement device. Additionally, 72 children (37 boys, 35 girls, aged 4-5 years) were recruited for a 1-year follow-up study. Approximately half of the children (53.5%) showed some type of malocclusion in the present study. Maximum tongue pressure was highest in the 6-year-old children. The results of a two-way ANCOVA show that the effect of age was significant (p < 0.001); however, the effects of sex and dental occlusion, or the interactions among these variables, did not reach significance. Additionally, maximum tongue pressure increased significantly in the 1-year follow-up study (p < 0.001), especially in the normal occlusion group. Maximum tongue pressure increases markedly with growth in the preschool years and can be associated with some types of malocclusion in preschool children.

Inhibitory effects of flavedo, albedo, fruits, and leaves of Citrus unshiu extracts on Streptococcus mutans.

OBJECTVES: Citrus unshiu has been shown to exhibit antimicrobial effects against citrus diseases. In the present study, C. unshiu was divided into flavedo, albedo, fruits, and leaves; the inhibitory effects of these extracts on Streptococcus mutans, a major pathogen of dental caries, were investigated. DESIGN: C. unshiu specimens were separated into flavedo, albedo, fruits, and leaves. First, pH values and polyphenol amounts in Citrus extracts were measured. In addition, Citrus extract was added to the bacterial suspensions of S. mutans MT8148, and inhibitory effects of C. unshiu extracts on MT8148 for antimicrobial activity, bacterial growth, and biofilm formation were analyzed. These assays were also performed using C. sinensis extracts. RESULTS: Among these extracts, albedo exhibited a pH value closest to neutral, while the fruits exhibited the most acidic pH value; the pH values significantly differed between these extracts (P < 0.05). In addition, the amounts of polyphenols were significantly higher in albedo than in other extracts (P < 0.001). All extracts showed inhibitory effects on MT8148 for antimicrobial activity, bacterial growth and biofilm formation. These inhibitory effects were significantly stronger in flavedo, albedo, and fruits, compared with leaves (P < 0.05). Furthermore, extracts of Citrus sinensis also showed inhibitory effects on S. mutans, although these effects were weaker than the effects of C. unshiu. CONCLUSION: These results suggest that extracts from C. unshiu fruits exhibit inhibitory effects on S. mutans, among which albedo may be especially useful for dental caries prevention due to its neutral pH and abundant polyphenols, in addition to its inhibitory effects.

Oral management with mouthguards during the mixed dentition period: A case report.

Custom-made mouthguards are widely used by athletes during training and sporting events for the prevention of oral injuries. However, even though the prevalence of dental injuries in children in the primary or mixed dentition stages is high, few reports have focused on mouthguard use for such cases due to the difficulties associated with adapting them as teeth are lost and replaced. This report presents a case of a Japanese boy in the mixed dentition stage with a custom-made mouthguard. For fabrication, self-curing acrylic resin was used to fill portions of a working model to keep space for the later eruption of permanent teeth. However, adjustment was necessary when gingival swelling occurred in association with maxillary canine eruption, after which refabrication was necessary. Regular management of a custom-made mouthguard by the attending dentist is important for children in the mixed dentition period, especially during maxillary canine eruption, which causes drastic dentition changes. In the present case, custom-made mouthguards were fully effective based on the prediction of changes in the dentition and with regular dental management.

Potential involvement of Streptococcus mutans possessing collagen binding protein Cnm in infective endocarditis.

Streptococcus mutans, a significant contributor to dental caries, is occasionally isolated from the blood of patients with infective endocarditis. We previously showed that S. mutans strains expressing collagen-binding protein (Cnm) are present in the oral cavity of approximately 10-20% of humans and that they can effectively invade human umbilical vein endothelial cells (HUVECs). Here, we investigated the potential molecular mechanisms of HUVEC invasion by Cnm-positive S. mutans. The ability of Cnm-positive S. mutans to invade HUVECs was significantly increased by the presence of serum, purified type IV collagen, and fibrinogen (p < 0.001). Microarray analyses of HUVECs infected by Cnm-positive or -negative S. mutans strains identified several transcripts that were differentially upregulated during invasion, including those encoding the small G protein regulatory proteins ARHGEF38 and ARHGAP9. Upregulation of these proteins occurred during invasion only in the presence of serum. Knockdown of ARHGEF38 strongly reduced HUVEC invasion by Cnm-positive S. mutans. In a rat model of infective endocarditis, cardiac endothelial cell damage was more prominent following infection with a Cnm-positive strain compared with a Cnm-negative strain. These results suggest that the type IV collagen-Cnm-ARHGEF38 pathway may play a crucial role in the pathogenesis of infective endocarditis.

Contribution of Severe Dental Caries Induced by Streptococcus mutans to the Pathogenicity of Infective Endocarditis.

Streptococcus mutans, a major pathogen of dental caries, is regarded as a causative agent of infective endocarditis (IE), which mainly occurs in patients with underlying heart disease. However, it remains unknown whether severe dental caries that extend to pulp space represent a possible route of infection. In the present study, we evaluated the virulence of S. mutans for IE development using rats with concurrent severe dental caries and heart valve injury. Dental caries was induced in rats through the combination of a caries-inducing diet and the administration of S. mutans into the oral cavity. Then, the heart valves of a subset of rats were injured using a sterile catheter and wire under general anesthesia. The rats were euthanized at various times with various stages of dental caries. The number of teeth affected by dental caries with pulp exposure was increased in the rats in a time-dependent manner. S. mutans was recovered from injured heart tissue, which was mainly observed in rats with higher number of S. mutans bacteria in mandibular bone and a larger number of teeth in which caries extended to pulp. Dental caries was more severe in rats with heart injury than in rats without heart injury. Sequencing analysis targeting 16S rRNA revealed that specific oral bacteria appeared only in rats with heart injury, which may be related to the development of dental caries. Our findings suggest that dental caries caused by the combination of S. mutans infection and sucrose intake may contribute to S. mutans colonization in injured heart tissue.

Specific strains of Streptococcus mutans, a pathogen of dental caries, in the tonsils, are associated with IgA nephropathy.

Streptococcus mutans is known to be a major causative agent of dental caries, and strains expressing the cell surface collagen-binding Cnm protein contribute to the development of several systemic diseases. A relationship between tonsillar immunity and glomerulonephritis has been recognized in IgA nephropathy (IgAN), and specific pathogens may have effects on tonsillar immunity (mucosal immunity). Here, we present findings showing a relationship between the presence of Cnm-positive S. mutans strains in the tonsils of IgAN patients and IgAN condition/pathogenesis. Analyses of tonsillar specimens obtained from patients with IgAN (n = 61) and chronic tonsillitis (controls; n = 40) showed that the Cnm protein-positive rate was significantly higher in IgAN patients. Among IgAN patients, the tonsillar Cnm-positive group (n = 15) had a significantly higher proportion of patients with high urinary protein (>1.5 g/gCr) and lower serum albumin level than the Cnm-negative group (n = 46). Additionally, Cnm protein and CD68, a common human macrophage marker, were shown to be merged in the tonsils of IgAN patients. These findings suggest that Cnm-positive S. mutans strains in the tonsils may be associated with severe IgAN.

Contribution of Streptococcus mutans Strains with Collagen-Binding Proteins in the Presence of Serum to the Pathogenesis of Infective Endocarditis.

Streptococcus mutans, a major pathogen of dental caries, is considered one of the causative agents of infective endocarditis (IE). Recently, bacterial DNA encoding 120-kDa cell surface collagen-binding proteins (CBPs) has frequently been detected from S. mutans-positive IE patients. In addition, some of the CBP-positive S. mutans strains lacked a 190-kDa protein antigen (PA), whose absence strengthened the adhesion to and invasion of endothelial cells. The interaction between pathogenic bacteria and serum or plasma is considered an important virulence factor in developing systemic diseases; thus, we decided to analyze the pathogenesis of IE induced by S. mutans strains with different patterns of CBP and PA expression by focusing on the interaction with serum or plasma. CBP-positive (CBP+)/PA-negative (PA-) strains showed prominent aggregation in the presence of human serum or plasma, which was significantly greater than that with CBP+/PA-positive (PA+) and CBP-negative (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. In addition, aggregation of CBP+/PA- strains was drastically reduced when serum complement was inactivated. Furthermore, an ex vivo adherence model and an in vivo rat model of IE showed that extirpated heart valves infected with CBP+/PA- strains displayed prominent bacterial mass formation, which was not observed following infection with CBP+/PA+ and CBP-/PA+ strains. These results suggest that CBP+/PA-S. mutans strains utilize serum to contribute to their pathogenicity in IE.

The in vivo Inhibition of Oral Biofilm Accumulation and Streptococcus mutans by Ceramic Water.

Combustion-synthesized titanium carbide ceramics uniformly disperse silver, producing silver ions and hydroxyl radicals in water. This generates antimicrobial activity against various bacteria. One such bacterium is Streptococcus mutans, a gram-positive anaerobic bacterium known as a major pathogen of dental caries. In this study, we analyzed the inhibition of oral biofilms and S. mutans by ceramic water in in vitro and human studies. S. mutans strains showed significantly lower antimicrobial and sucrose-dependent adhesion activity in the presence of ceramic powder compared with untreated culture medium. Confocal microscopy revealed that S. mutans biofilm structures with ceramic powder were thin and coarse. Twenty-seven volunteers (13 males, 14 females; 18-37 years old, mean 25.2 years) were enrolled for subsequent studies. After each meal, one group was asked to rinse with ceramic water while the other rinsed with untreated water for 1 week. After 1 week, the rinsing contents were switched between the groups and the same protocol was followed for an additional week. After rinsing with ceramic water, the average plaque score was 43.0 ± 3.7, which was significantly lower than the baseline value (74.1 ± 5.7, p < 0.001). However, no significant difference was observed when rinsing with untreated water. In addition, the total number of S. mutans in saliva was significantly reduced after rinsing with ceramic water compared with untreated water (p < 0.05). These results suggest that ceramic water possesses antimicrobial activity against S. mutans and inhibits biofilm formation. Rinsing with ceramic water can also inhibit dental plaque formation and S. mutans colonization in humans.

Contribution of the interaction of Streptococcus mutans serotype k strains with fibrinogen to the pathogenicity of infective endocarditis.

Streptococcus mutans, a pathogen responsible for dental caries, is occasionally isolated from the blood of patients with bacteremia and infective endocarditis (IE). Our previous study demonstrated that serotype k-specific bacterial DNA is frequently detected in S. mutans-positive heart valve specimens extirpated from IE patients. However, the reason for this frequent detection remains unknown. In the present study, we analyzed the virulence of IE from S. mutans strains, focusing on the characterization of serotype k strains, most of which are positive for the 120-kDa cell surface collagen-binding protein Cbm and negative for the 190-kDa protein antigen (PA) known as SpaP, P1, antigen I/II, and other designations. Fibrinogen-binding assays were performed with 85 clinical strains classified by Cbm and PA expression levels. The Cbm(+)/PA(-) group strains had significantly higher fibrinogen-binding rates than the other groups. Analysis of platelet aggregation revealed that SA31, a Cbm(+)/PA(-) strain, induced an increased level of aggregation in the presence of fibrinogen, while negligible aggregation was induced by the Cbm-defective isogenic mutant SA31CBD. A rat IE model with an artificial impairment of the aortic valve created using a catheter showed that extirpated heart valves in the SA31 group displayed a prominent vegetation mass not seen in those in the SA31CBD group. These findings could explain why Cbm(+)/PA(-) strains are highly virulent and are related to the development of IE, and the findings could also explain the frequent detection of serotype k DNA in S. mutans-positive heart valve clinical specimens.