Masashi Yakushiji

Colonization pattern of periodontal bacteria in Japanese children and their mothers

BACKGROUND AND OBJECTIVE The purpose of this study was to determine the time of infection by anaerobic gram-negative rods associated with periodontal disease, and to clarify their transmission from mother to child. MATERIAL AND METHODS Seventy-eight Japanese children (including 10 siblings), aged from 3 to 9 years, and 68 mothers, were enrolled in this study. Colonization by 11 periodontal bacterial species was determined using polymerase chain reaction amplification of samples of subgingival plaque obtained from the children and their mothers. RESULTS The detection rates of Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola increased in children after the age of 6 years. We found a high consistency in colonization by P. gingivalis, T. denticola, Prevotella intermedia and Prevotella nigrescens in 9 of the 10 siblings. The average number of bacterial species in plaque samples harboring Fusobacterium nucleatum and/or Fusobacterium periodonticum was significantly greater than in those without, in both children and mothers. Kappa statistical analysis revealed that the detection of Capnocytophaga gingivalis, Capnocytophaga ochracea, Campylobacter rectus and T. denticola in children was consistent with that in the mother. CONCLUSION Periodontal bacterial colonization in Japanese children increased with age and was associated with F. nucleatum and/or periodonticum, and the bacterial flora in children was similar to that in their mothers.

Analysis of matrix metalloproteinase (MMP-8 and MMP-2) activity in gingival crevicular fluid from children with Down’s syndrome

BACKGROUND AND OBJECTIVE High levels of colonization by periodontopathic bacteria and a high prevalence of chronic inflammatory periodontal disease have been reported in children with Downs syndrome. Matrix metalloproteinases (MMPs) are mediators of extracellular matrix degradation and remodelling, and are deeply involved in the course of periodontal disease. To clarify the relationship between Downs syndrome and periodontitis, we investigated levels of MMP-2 and MMP-8 in gingival crevicular fluid (GCF) and detection of periodontopathic bacteria from subgingival plaque. MATERIAL AND METHODS Samples of GCF and plaque were isolated from central incisors. Levels of MMPs were evaluated by enzyme-linked immunosorbent assay, and periodontopathic bacteria were detected by polymerase chain reaction. RESULTS Levels of MMP-2 and MMP-8 in Downs syndrome patients were higher than those in healthy control subjects. In the Downs syndrome group, increases in these MMPs were observed in GCF from patients with an oral hygiene index score of < 2 and in GCF from sites that were negative for bleeding on probing. The detection rate of periodontopathic bacteria in Downs syndrome patients was higher than that in the control subjects. Matrix metalloproteinase-2 levels in sites harbouring Porphyromonas gingivalis or Aggregatibacter (Actinobacillus) actinomycetemcomitans were lower than in those without these microorganisms. CONCLUSION These results suggest an increase in MMP-2 and MMP-8 in Downs syndrome patients, regardless of whether inflammation of periodontal tissue is present or not.

Transmigration of impacted mandibular canine to opposite side

Abstract Case Report A boy visited a local dentist for the treatment of other teeth at the age of 12 years, and the same dentist at the age of 17 years and 6 months. Comparison of panoramic X-rays taken at the age of 17 years and 12 years revealed that the impacted left mandibular canine had transmigrated to the right side, and so the patient was referred to our department for a more detailed examination. The panoramic X-ray obtained at the age of 12 years showed that the left mandibular canine was horizontally impacted almost in the center of the mandibular bone, with its tooth crown oriented toward the right. The panoramic X-ray taken at the age of 17 years and 6 months showed that the apex of the impacted left mandibular canine had horizontally migrated to the tooth root apical area of the right mandibular first molar. Conclusion Transmigration of the mandibular canine across the mandible midline is an uncommon phenomenon. When delayed eruption of primary teeth occurs, it is necessary to confirm the position of permanent tooth germs using panoramic X-rays.

Effects of prolonged breast- and bottle-feeding on occlusal characteristics in the primary dentition

The purpose of this study was to assess the effects of prolonged breast- and bottle-feeding on the growing primary dentition. This longitudinal study was conducted through a survey questionnaire and clinical examination of 592 children from 18 months to 36 months of age. Selected occlusal characteristics were compared among groups of children with different durations of breast- or bottle-feeding. The prevalence of breast-feeding at 18 months, 24 months and 36 months of age was 9.3%, 3.2% and 0.2% respectively. Prevalence of bottle-feeding was 14.4%, 2.9% and 0.7% respectively. Deepbite showed tendencies towards increasing prevalence with increased bottle-feeding duration. One third of the children who continued bottle-feeding at 24 months of age exhibited deepbite. Anterior crossbite were significantly more prevalent among those with continued breast-feeding at 18 months but ceased by 24 months (28.0%) than for that in the habit-free group (11.7%). However, anterior crossbite showed tendencies towards decreasing prevalence with increased breast-feeding duration. The prevalence of anterior crossbite was 6.7% in the children who continued breast-feeding at 24 months of age. However, the study suggests that spontaneous change in the occlusion following feeding discontinuation, although longer-term longitudinal studies are needed to demonstrate such changes directly.

Tuned-Aperture Computed Tomography (TACT®) to assess impacted teeth using 2D slices and 3D pseudo-holograms

The purpose of this clinical study was to compare the diagnostic information yield of interactive TACT 3D pseudo-holograms, 2D TACT slices and conventional dento-alveolar images for the imaging and localization of impacted maxillary incisor teeth.

Influence of Lifestyle Factors on Risk of Dental Caries among Children Living in Urban China

The prevalence of dental caries has been decreasing among kindergarten children in Shanghai, China, over recent years, although it still remains at an unacceptably high level. The purpose of this study was to identify which factors were important in providing oral health guidance and achieving further improvement in the oral health status of kindergarten children in urban China. A survey was conducted on dental caries in 128 Japanese and 368 Chinese kindergarten children and a questionnaire given to their parents/guardians on each childs lifestyle and dietary habits from birth to the present. Correlations between responses to each questionnaire item and the status of dental caries were statistically analyzed. The dft index score (p=0.0016), prevalence of dental caries (p=0.0002), and percentages of children with decayed (untreated caries-affected) teeth (p<0.0001) were significantly higher in the Chinese than in the Japanese children. Many differences were observed in lifestyle factors between the two groups. The percentage of parents failing to control the childs snacking habits between meals was higher in China, and weaning was significantly delayed in China compared with in Japan. These lifestyle factors were considered to be associated closely with the high risk of dental caries in Chinese kindergarten children. These findings indicate that oral health guidance for kindergarten children in Shanghai, China, should focus on control of dietary habits, including control of inter-meal snacking, and breastfeeding practices. The results of this study may help improve the status of dental caries among Chinese children.

Morphological characteristics on the mandibular fused deciduous anterior teeth with Micro-CT

Abstract This study aimed to clarify the morphological characteristics of the fused portion in the mandibular fused deciduous anterior teeth using microfocus x-ray computerized tomography, a method which allows nondestructive three-dimensional observation at high resolution in any direction. The specimens consisted of five mandibular deciduous central/lateral incisor fused teeth, and four lateral incisor/canine fused teeth. These specimens were scanned using x-ray micro-CT and three-dimensional images of anatomical features of the crowns were reconstructed. Two-dimensional sliced images were created and then, the morphology of the fused portions were examined by measuring angle of the fused portion, enamel and dentin thickness at the fused portion. Angles of lingual fused portion in deciduous central/lateral incisor fused teeth, and labial fused portion in deciduous lateral incisor/canine fused teeth are significantly smaller, and the enamel thickness at these fused portions are also thinner. The values of the dentin thickness in deciduous central/lateral incisors tended to be thinner than those of deciduous canine, which means dentin thickness of the deciduous central/lateral incisors are thinner than that of canine. The fused portions in the fused deciduous anterior teeth have the similar morphological features to those of pit and fissure of the occlusal surface in molars and are likely to be the initiation and predilection sites of dental caries. Therefore, it is considered to be preferable to apply pit and fissure sealant into the fused portions at an early time point of the treatment.

Initial acquisition and transmission of Streptococcus mutans from Japanese mothers to children

Abstract The purpose of this study was to determine the time-window of infection for Streptococcus mutans between mother and child in Japan and which factors affected colonization by this microorganism. After obtaining informed consent, saliva was collected from the mothers and their children. These samples were serially diluted and inoculated onto Mitis-Salivarius agar and Mitis-Salivarius bacitracin plates, and then cultured under anaerobic conditions at 37°C for 5 days. Isolated mutans streptococci were identified by conventional biochemical characteristics and species-specific polymerase chain reaction based on the dextranase gene. No mutans streptococci groups were isolated from 0–5-month-old children with no erupted teeth. No statistically significant difference was found in detection rates in S. mutans among mothers milk, bottled milk or mixture. Cross-sectional study revealed that detection rates of S. mutans in the saliva samples increased with number of erupted teeth. Pulse-field gel-electrophoresis patterns obtained from isolated S. mutans using SmaI from the mothers and their children indicated that colonization by S. mutans in some Japanese children resulted from vertical transmission. In strains in which vertical transmission was observed, the mutacin IV and Smb A and B genes were detected from 8 out of 12 isolates. These results suggest that the window of infection for S. mutans is at around 6–23 months, and that colonization by this microorganism is mainly affected by number of erupted teeth.

Three dimensional observation of the occlusal grooves in the maxillary first and second deciduous molars with micro-CT

Abstract The purpose of this study was clarify the morphological condition of occlusal grooves in the maxillary first and second deciduous molars with micro-CT. We took photographs of the maxillary deciduous molars using a micro-CT device and reconstructed the three-dimensional image of the anatomical crown using a three-dimensional visualization and measurement software. For observation and measurement of the occlusal grooves, twodimensional sliced images were generated 10 images at each groove. On the generated two-dimensional sliced images, we measured the occlusal angle, the depth of the occlusal groove and the enamel thickness at its bottom. The sites which showed smallest angle were distal portions of the central groove in maxillary first deciduous molar, and lingual groove in maxillary second deciduous molar. The occlusal groove in maxillary second deciduous molar was deeper than that of maxillary first deciduous molar in all sites examined, except for distal portion of the central groove. The enamel thickness in maxillary second deciduous molars tended to have thicker enamel than that of first deciduous molars. In maxillary first deciduous molars, most of the occlusal grooves exhibited the shape classified into type P. Whereas in maxillary second deciduous molars, the ratio of type P was relatively low, especially, lingual grooves consisted of type V, whose angle was less than 90 degree, type U and type I, which had the shape looked like a stick. Distal portion of the central groove of maxillary first deciduous molar, and lingual groove of maxillary second deciduous molar tend to be the initiation and predilection sites of dental caries due to the anatomical features of their occlusal fissures. Moreover, it is preferable to apply pit and fissure sealant into the occlusal fissures containing this region at an early point of the treatment.

Effect of three fluoride agents on remineralization and fluoride uptake on enamel lesion

Abstract This study is to compare the fluoride uptake of three fluoride agents and the effect of remineralization on artificial enamel lesions. Eight human third molars were all divided into four slabs. The slabs were randomly assigned to the following four groups: group A (9,040ppm F, APF gel), group B (968ppm F, SnF 2 home gel), group C (22,600ppm F, fluoride varnish, FV) and a control group. After 72-hour demineralizing and 10-day pH-cycling period with the application of corresponding fluorides. The distribution of fluoride and mineral change was analyzed with EPMA and CMR respectively. There was a significant increase in the amount of F uptake after the application of the three fluoride agents compared to the control group. Group A showed an extremely greater F uptake compared to group C and B. The amount of F uptake from group C was greater than that of group B. The three tested groups showed signs of significantly greater amounts of remineralization as compared to the control group. Remineralization of group C was detected to be the greatest, followed by group A and group B, but there was no significant difference in them under statistical analysis. It can be concluded that all of the tested agents were effective in regaining mineral loss. FV may be recommended as a professional topical fluoride. It is as effective, if not more so, as traditionally used APF gel. Also 0.4% SnF 2 home gel is an efficient self-applied topical fluoride for daily use.