We investigated the measurement error of primary stability at the time of implant placement using a resonance frequency analyzer. Ten implants were examined in four patients. Implant stability quotient (ISQ) values were obtained 16 times in each subject implant by doing four repetitions each on the implant from four directions (mesial, distal, buccal and lingual). Generalizability theory was used to estimate the measurement error of implant stability. Generalizability study (G study) was used to assess the relative contribution of identified error sources (direction of measurement and number of repetitions) to the total measurement error. The indices of dependability, standard error of measurement (SEM), and minimum detectable difference (MDD) for the ISQ values when the measurement conditions were changed were calculated using decision study (D study). In the G study, we found that the measurement direction and the interaction between direction of measurement and the implant contributed significantly to measurement errors. D study showed an index of dependability of 0.86 with four repetitions in one direction, and 0.96 with one repetition in each of four directions. SEMs and MDDs for averaging data from four different directions represented approximately half the value of those of multiple measurements in any one direction. We found that the measurement error for primary stability of the implants could best be decreased by averaging data from different directions rather than from only one direction.

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We evaluated how the interval of oral health check-ups affects oral health promotion in the workplace for 27 males and 132 females who received oral health check-ups for over 10 years. The findings from the initial and most recent check-ups were compared for each group. We found that the number of subjects whose check-up interval was less than two years showed an increase in CPI (Community Periodontal Index) code 0 compared with other groups, while they showed a decrease in codes 3 and 4. As the interval of the check-ups increased, the oral health was poorer. In particular, periodontal status worsened in the subjects whose checkup interval was greater than 5 years. On the other hand, there was no relationship between the DMFT index and check-up interval. Based on these results, we concluded that the interval between oral health check-ups for workers should not exceed 2 years in order to maintain good oral health.

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We examined the effect of hydration on the quantitative light-induced fluorescence of white-spot early carious lesions on the deciduous enamel surface. The surfaces of exfoliated deciduous teeth were cleaned with non-fluoride polishing gel, and a window 2.0mm×3.0mm was made with nail varnish. The specimens were subjected for 5 days to a pH-cycling model of demineralization for 6h and remineralization for 18h at 37℃, and then placed in a remineralizing solution for 2 days. Fluoride dentifrice treatment was performed for one minute twice each day for the first 5 days. Two types of quantitative light-induced fluorescence (QLF) images were performed as follows. A wet cotton ball was placed on the specimen for one minute. After removing the cotton, the first fluorescence images were acquired at 2 seconds intervals for 30 seconds. During image acquisition, the specimens were dehydrated with compressed air. In order to take the second QLF images, a wet cotton ball was again placed on the specimen for one minute, and a wet-specimen image was acquired as soon as the cotton was removed. Dryspecimen images were taken after drying the specimen with compressed air for 10 seconds. Image analysis was then performed to determine the ΔQ, ΔF, and area of the early carious lesions. Early carious lesions became clearly visible as the surface was dehydrated. However, changes in the appearance decreased after 10 seconds. Results of the QLF image analysis showed that dehydration produced a statistically significant change in all parameters for every group. This difference was greater in the controls than in the fluoride groups. These findings suggest that a controlled dehydration with QLF may be used to evaluate the activity of early carious lesions in deciduous teeth.

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We surveyed Japanese elementary school children to determine the frequency distribution of their oral health and developed theoretical distributions of caries prevalence for various age groups. We studied 3,222 elementary school children between 1995 and 2007, and used a study of 4,155 people done by the National survey of dental diseases in Japan for 2005. The frequency distribution of dental caries in the first and second grade elementary school children from 1995 to 2007 usually had a Poisson distribution, while the third to sixth grade children for the same period changed from a quasi-normal distribution to a Poisson distribution. Caries prevalence from the National survey of dental disease in Japan for 2005 had a Poisson distribution in 6, 7 and 10 year olds. The frequency distribution for those 11-29 years of age was not defined with a slant to the left, it was similar to the normal distribution for those 30-49 years of age, and it was not defined with a slant to the right for those 50-79 years of age. Calculation of the statistical significance for the decayed, missing and filled teeth (DMFTindex) of Japanese elementary school children were different when the Poisson distribution was used compared to use of the t-distribution. We found that the DMFT for Japanese children generally had a Poisson distribution. These results suggest that the Poisson distribution is good for analysis of dental caries prevalence in Japanese children.

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Previously we demonstrated up-regulated transcriptional levels of several stress response genes in biofilm-forming Prevotella intermedia (P. intermedia) using microarray analysis and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). To further investigate the biofilm formation-gene expression relay system in P. intermedia, we obtained a biofilm-non-forming mutant by exposing P. intermedia strain OD 1-16, a biofilm-forming clinical isolate to ethidium bromide (EtBr), and performed comparative genome analyses in OD 1-16 and a mutant by means of random amplified polymorphic DNA assay (RAPD). In this study, we obtained one mutant that lacked the ability to form biofilm from EtBr-treated OD 1-16 cultures and designated it as strain 171. RAPD revealed that strain 171 had a mutation in a gene encoding trpG type glutamine amidotransferase. The results indicated that this gene might be involved in the biofilm formation of this organism.

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We evaluated how the interval of oral health check-ups affects oral health promotion in the workplace. We studied 27 males and 132 females who received oral health check-ups for over 10 years. The findings from the initial and most recent check-ups were compared for each group. We found that the number of subjects whose check-up interval was less than two years showed an increase in CPI (Community Periodontal Index) code 0 compared with other groups, while they showed a decrease in codes 3 and 4. As the interval of the check-ups increased, the oral health was poorer. In particular, periodontal status worsened in the subjects whose check-up interval was greater than 5 years. On the other hand, there was no relationship between the DMFT index and check-up interval. Based on these results, we concluded that oral health check-ups are useful for promoting the oral health of workers.

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We surveyed the frequency distribution of dental caries prevalence in 796 elementary school children and found theoretical distributions adequate to analyze caries prevalence data in Japanese children. The frequency distributions of dental caries prevalence in the first- and the second-grade children usually had a Poisson distribution for the years 1995 to 2007, while third-, fourth-, fifth- and sixth-grade children changed from a quasi-normal distribution to a Poisson distribution between 1995 and 2007. The Survey of Dental Disease for 2005 had a frequency distribution of caries prevalence with a Poisson distribution in 6, 7 and 10 year-old children. These findings suggest that the Poisson distribution is appropriate as a theoretical distribution for analysis of dental caries prevalence data in Japanese children, and that it can be used as a basis for making decisions on oral health activities.

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We examined the effect of hydration on the quantitative light-induced fluorescence of white-spot early carious lesions on the deciduous enamel surface. Surfaces of exfoliated deciduous teeth were cleaned with non-fluoride polishing gel, and a window 2.0×3.0mm was made using nail varnish. The specimens were subjected for 5 days to a pH-cycling model (demineralization for 6h, remineralization for 18h) at 37℃ and then placed in a remineralizing solution for two days. Fluoride dentifrice treatment was performed for one minute twice each day. Quantitative light-induced fluorescence (QLF) images were produced as follows. A wet cotton ball was placed on the specimen for one minute and a wet-specimen image was acquired as soon as the cotton was removed. Dry-specimen images were taken after drying the specimen with compressed air for 10 seconds. Image analysis was then performed to determine the delta F, area and delta Q. Dehydration produced a statistically significant change in all parameters for every group (p<0.05). This difference was greater in the control group than in the fluoride group. These findings suggest that the method of controlled dehydration with QLF may be used to evaluate the activity of early carious lesions in deciduous teeth.

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Inflammation in dental pulp tissue is associated with tissue degradation. Matrix metalloproteinases (MMPs) are believed to participate in this destruction. In the inflamed pulp, many kinds of inflammatory cytokines such as tumor necrosis factor (TNF)-α, are released from the inflammatory tissue. In the present study, we examined the TNF-α to MMP-3 pathway and whether TNF-α affected the production of MMP-3 in dental pulp fibroblasts. TNF-α increased the expression of MMP-3 in a dose-dependent manner in dental pulp fibroblasts. U 1026, which are MAPK/ERK (MEK 1/2) inhibitors, inhibited the MMP-3 production induced by TNF-α in dental pulp fibroblasts. Moreover, in dental pulp fibroblasts cultured with TNF-α, extracellular-regulated kinase 1/2 (ERK 1/2) was phosphorylated in a timedependent manner with the maximum phosphorylation at 30min, and U 0126 abolished this phosphorylation of MEK 1/2 in TNF-α-stimulated dental pulp fibroblasts. These results suggest that TNF-α may enhance pulp tissue destruction during pulp inflammation in part by regulating MMP-3, and that the MEK 1/2-ERK 1/2 pathway is involved with MMP-3 production in dental pulp fibroblasts.

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There are many case reports on the clinical effect of maxillary prognathy. However, few reports compare relapse cases with those that result in stable occlusion. We compared a maxillary prognathy relapse case (case A) and one with stable occlusion (case B) three and a half years after completion of orthodontic treatment. Four reference lines (L1, L2, L3 and L4) and two reference points (A0, PM-A0) were established on the plaster models of the two cases. Case A with relapse showed no remarkable changes in the Mid-Curve except in the anterior region. However, the primary cause of the relapse was a large change in the width and depth of the PM Curve. There were no remarkable changes in the MM Curve. Case B showed no remarkable changes in the Mid-Curve of the anterior and premolar regions. However, there were considerable changes in the deep palate of the molar region at the Mid-Curve. This stable occlusion case showed remarkable changes in the depth at the MM Curve, but no significant changes at the PM Curve. Our findings based on three-dimensional models were highly accurate and reliable in distinguishing the differences between the relapse case and the one with stable occlusion.

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Previously we demonstrated up-regulated transcriptional levels of several stress response genes in biofilm-forming Prevotella intermedia (P. intermedia) using microarray analysis and quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR). To further investigate the biofilm formation-gene expression relay system in P. intermedia, we obtained a biofilm-non-forming mutant by exposing P. intermedia strain OD 1-16, a biofilm-forming clinical isolate to ethidium bromide (EtBr), and performed comparative genome analyses in OD 1-16 and a mutant by means of random amplified polymorphic DNA assay (RAPD). In this study, we obtained one mutant that lacked the ability to form biofilm from EtBr-treated OD 1-16 cultures and designated it as strain 171. RAPD revealed that strain 171 had a mutation in a gene encoding trpG type glutamine amidotransferase. The results indicated that this gene might be involved in the biofilm formation of this organism.

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