Trends in Primary Tooth Emergence Pattern and Associated Factors in Japanese Infants.

OBJECTIVE: The purposes of this study were to analyse trends in primary tooth emergence patterns and to identify physical factors potentially associated with them. METHODS: The participants were 27,454 infants who underwent routine 18-month-old health examinations in Ebetsu City, Japan, between 1980 and 2012. This study was conducted using data from infants' 18-month-old health examinations over a 33-year period. The mean number of emerged primary teeth was analysed by sex using a general linear model. For logistic regression analysis, the proportion of infants with 16 emerged teeth or more at 18 months old was used as a dependent variable. Examination year; birth order; birth weight; weight, height, and chest girth at 18 months old; number of fused teeth; and mother's age were used as independent variables. RESULTS: The mean number of emerged primary teeth decreased over the 33-year period. Birth weight and weight and height at 18 months old decreased, and the proportion of low-birth-weight (<2500 g) infants increased over the 33-year period. On general linear model analysis, the yearly change in the mean number of emerged primary teeth was -0.0188 for boys and -0.0181 for girls. Birth weight and weight and height at 18 months old were significantly associated with the presence of 16 emerged primary teeth or more, according to the logistic regression analysis. CONCLUSIONS: The results demonstrated that, over the 33-year period examined, the mean number of emerged primary teeth decreased and birth weight and weight and height at 18 months old were associated with the pattern of tooth emergence.

Correlations of noncarious cervical lesions and occlusal factors determined by using pressure-detecting sheet.

OBJECTIVES: The purpose of this clinical study was to examine the relationships of v-shaped noncarious cervical lesion (NCCL) formation with occlusal factors. METHODS: A total of 159 male self-defense force officials with a mean age of 36.2 years participated in this study. All present teeth were examined for the presence and type of NCCL using the Tooth Wear Index (TWI). The subjects were then interviewed about bruxing and toothbrushing habit. Finally, occlusal force, occlusal contact area and average pressure were measured using a pressure-detecting sheet. Subject-level logistic regression was carried out to assess the associations of factors with presence of v-shaped NCCL teeth. Subjects without v-shaped NCCL were designated as control subjects. RESULTS: Totally, 4518 teeth were examined. Seventy-eight subjects (49.1%) had one or more teeth with typical v-shaped NCCL (259 teeth). The number of teeth with v-shaped NCCL of grade 2 (defect less than 1mm in depth) was 195 (4.3%), and the number of teeth with v-shaped NCCL of grade 3 (defect 1-2mm in depth) was 54 (1.2%). The prevalence of teeth with v-shaped NCCL was significantly higher in the maxilla than in the mandible. Most of the NCCL teeth were premolars. There was no significant difference between teeth with NCCL on the right side and those on the left side. Subject-level logistic regression analysis revealed that age (OR=1.11), toothbrushing pressure (400g, OR=2.43) and occlusal contact area (>23.0mm(2), OR=4.15) were associated with the presence of NCCL teeth. CONCLUSIONS: It is concluded that aging, toothbrushing pressure and occlusal contact area are associated with the presence of NCCLs.

Prevalence of oral malodor and the relationship with habitual mouth breathing in children.

The prevalence of oral malodor and association of habitual mouth breathing with oral malodor were investigated in children residing in rural areas. One hundred and nineteen children participated in this study. A sulfide monitor and organoleptic method were used to evaluate oral malodor. About 8% of children had a sulfide level in mouth air above the socially acceptable limit (75 ppb). Habitual mouth breathing was a factor contributing to oral malodor. Oral malodor was not significantly correlated with plaque index, history of caries or frequency of toothbrushing.

A pilot study of a simple screening technique for estimation of salivary flow.

OBJECTIVES: The purpose of this study was to develop a simple screening technique for estimation of salivary flow and to test the usefulness of the method for determining decreased salivary flow. STUDY DESIGN: A novel assay system comprising 3 spots containing 30 microg starch and 49.6 microg potassium iodide per spot on filter paper and a coloring reagent, based on the color reaction of iodine-starch and theory of paper chromatography, was designed. We investigated the relationship between resting whole salivary rates and the number of colored spots on the filter produced by 41 hospitalized subjects. RESULTS: A significant negative correlation was observed between the number of colored spots and the resting salivary flow rate (n = 41; r = -0.803; P < .01). For all complaints of decreased salivary flow (n = 9) having cutoff values <100 microL/min for the salivary flow rate, 3 colored spots appeared on the paper, whereas for healthy subjects there was < or =1 colored spot. CONCLUSION: This novel assay system might be effective for estimation of salivary flow not only in healthy but also in bedridden and disabled elderly people.