Haruo Nakagaki

Micro-Sampling by Abrasion

An attempt has been made to develop a technique for the serial sampling of porous enamel, mesenchymal tissues, ectopic mineral deposits, developing tissues and other material not amenable to the estab

Five-Year Incidence of Periodontal Disease Is Related to Body Mass Index

Numerous cross-sectional epidemiological studies suggest that obesity is associated with periodontal disease. This longitudinal study tested whether body mass index (BMI) was related to the development of periodontal disease in a sample of employed Japanese participants. Data are from the statutory medical checkups routinely collected for employees in and around Nagoya, Japan. The authors tested the relationship between BMI at baseline and the 5-year incidence of periodontal disease in a sample of 2787 males and 803 females. The hazard ratios for developing periodontal disease after 5 years were 1.30 (P < .001) and 1.44 (P = .072) in men and 1.70 (P < .01) and 3.24 (P < .05) in women for those with BMIs of 25-30 and ≥ 30, respectively, compared to those with BMI < 22, after adjusting for age, smoking status, and clinical history of diabetes mellitus. These findings demonstrate a dose-response relationship between BMI and the development of periodontal disease in a population of Japanese individuals.

Effect of strontium in combination with fluoride on enamel remineralisation in vitro

Previous studies showed that strontium (Sr) as well as fluoride (F) can enhance enamel remineralization. The aim of this study was to evaluate the effects of Sr in combination with F on enamel remineralization in vitro. Sixty enamel specimens obtained from caries free human premolars were demineralised to produce caries-like lesions. Half of each lesion was covered with nail varnish as an untreated control. The specimens were then randomly divided into F and Sr+F treatment groups. The F group was exposed to remineralizing solutions (1.5mM CaCl(2), 0.9 mM KH(2)PO(4)) containing 1 ppm, 0.1 ppm or 0.05 ppm F. The Sr+F treatment group was exposed to the same solutions including 10 ppm Sr. After 2 weeks, lesion depth, mineral loss and percentage enamel remineralization were determined using transversal microradiography. There was a significant decrease in mineral loss in all groups (p<0.001). Lesion depth was significantly reduced for all groups (p<0.05) with the exception of group F. Remineralization was significantly affected by F concentration (p=0.000). The participation of Sr resulted in a significant enhancement of remineralization (p<0.001) with a synergistic effect of the Sr+F combination (p<0.01). It was concluded that while the remineralizing process was affected by the concentration of F, there was also an interaction between F and Sr when they were used in conjunction.

Distribution of fluoride across human dental enamel, dentine and cementum

This was determined across the entire width of sections from 20 mandibular premolars, containing enamel, coronal dentine, root dentine and cementum. An abrasive technique was used to sample all three dental tissues in a single experiment. In the profiles of fluoride distribution, fluoride concentration was thus precisely related to the position of the tissue sample. There was a marked increase in the fluoride content of coronal and root dentine, at least until the age of about 50 years. There had been uptake of fluoride by the root dentine and cementum throughout the life of the tooth. There was no evidence of any change in the fluoride content of enamel with age.

Relationship between Periodontal Status and Levels of Glycated Hemoglobin

The objective of this study was to assess whether there is a bi-directional relationship between periodontal status and diabetes. Study 1 included 5,856 people without periodontal pockets of ≥ 4 mm at baseline. Relative risk was estimated for the 5-year incidence of periodontal pockets of ≥ 4 mm (CPI scores 3 and 4, with the CPI probe), in individuals with glycated hemoglobin (HbA1c) levels of ≥ 6.5% at baseline. Study 2 included 6,125 people with HbA1c < 6.5% at baseline. The relative risk was assessed for elevation of HbA1c levels in 5 years, with baseline periodontal status, assessed by CPI. Relative risk of developing a periodontal pocket was 1.17 (p = 0.038) times greater in those with HbA1c of ≥ 6.5% at baseline, adjusted for body mass index (BMI), smoking status, sex, and age. Relative risks for having HbA1c ≥ 6.5% at 5-year follow-up in groups with periodontal pockets of 4 to 5 mm and ≥ 6 mm at baseline were 2.47 (p = 0.122) and 3.45 (p = 0.037), respectively, adjusted for BMI, alcohol consumption, smoking status, sex, and age. The risk of developing periodontal disease was associated with levels of HbA1c, and the risk of elevations of HbA1c was associated with developing periodontal pockets of more than 4 mm.

A Method for the Quantitative Site-Specific Study of the Biochemistry within Dental Plaque Biofilms Formed in vivo

The study of plaque biofilms in the oral cavity is difficult as plaque removal inevitably disrupts biofilm integrity precluding kinetic studies involving the penetration of components and metabolism of substrates in situ. A method is described here in which plaque is formed in vivo under normal (or experimental) conditions using a collection device which can be removed from the mouth after a specified time without physical disturbance to the plaque biofilm, permitting site-specific analysis or exposure of the undisturbed plaque to experimental conditions in vitro. Microbiological analysis revealed plaque flora which was similar to that reported from many natural sources. Analytical data can be related to plaque volume rather than weight. Using this device, plaque fluoride concentrations have been shown to vary with plaque depth and in vitro short-term exposure to radiolabelled components may be carried out, permitting important conclusions to be drawn regarding the site-specific composition and dynamics of dental plaque.

Distribution of fluoride concentration in the rat's bone.

SummaryThe present study was undertaken to determine the fluoride distribution profile in the rat femur. Male Wistar rats were divided into four groups and given water containing 0, 25, 50, and 100 ppm of fluoride, respectively, for 10 weeks. The fluoride distribution from the periosteum to the endosteum was determined in each specimen after sampling using the abrasive microsampling technique [5]. In the outer circumferential lamellae, the concentration of fluoride was relatively high in the periosteal layer and then decreased gradually towards its interior. In the haversian and interstitial lamelae, it was lower and roughly constant through the tissue. In the inner circumferential lamellae, it rose again to reach the highest level towards the endosteal surface. Fluoride concentration throughout the cortex increased significantly with increasing intake of fluoride. These increases were especially marked at periosteal and endosteal surfaces.

Tooth loss and intakes of nutrients and foods: a nationwide survey of Japanese dentists.

OBJECTIVES To clarify the association of tooth loss with dietary intakes among dentists, for whom sufficient dental care is available. METHODS We analyzed the data from 20 366 Japanese dentists (mean age +/- SD, 52.2 +/- 12.1 years; women 8.0%) who participated in a nationwide cohort study from 2001 to 2006. The baseline questionnaire included a validated food-frequency questionnaire to estimate intakes of foods and nutrients. We computed the geometric means of daily intakes by the number of teeth, adjusting for age, sex, smoking, physical activity, and history of diabetes. RESULTS The mean intakes of some key nutrients and food groups, such as carotene, vitamins A and C, milk and dairy products, and vegetables including green-yellow vegetables, decreased with the increasing number of teeth lost (P for trend <0.05). On the contrary, mean intakes of carbohydrate, rice, and confectioneries were increased among those with fewer teeth (P for trend <0.05). The difference in the geometric mean (%) between totally edentulous subjects and those with > or =25 teeth, that is [(Geometric mean for > or =25 teeth) - (Geometric mean for 0 teeth)]/(Geometric mean for > or =25 teeth) x 100, was 14.3%, 8.6%, 6.1%, and -6.1% for carotene, vitamin C, vitamin A, and carbohydrate, respectively. For food groups, it was 26.3%, 11.9%, 5.6%, -9.5%, and -29.6% for milk and dairy products, green-yellow vegetables, total vegetables, rice, and confectioneries, respectively. CONCLUSIONS Tooth loss was linked with poorer nutrition even among dentists.

Distribution of fluoride in cortical bone of human rib

SummaryWe describe a detailed study of fluoride distribution with age in the human cortical rib bone. Human ribs were obtained from 110 subjects (M:68,F;42) aged 20–93 years. The fluoride distribution from the periosteal to endosteal surfaces of the ribs was determined by sampling each specimen using an abrasive micro-sampling technique, and the samples were analyzed using the fluoride electrode, as described by Weatherell et al. [1]. The concentration of fluoride was highest in the periosteal region, decreased gradually towards the interior of the tissue where the concentration of fluoride tended toward the plateau, and then rose again towards the endosteal surface. Patterns of fluoride distribution changed with age, and the difference between periosteal and endosteal fluoride levels increased with age. Although average fluoride concentrations increased with age in both sexes, there was a significant difference between males and females at the age of about 55 years (P<0.05).

Distribution of fluoride in human cementum

Fluoride and phosphorus concentrations were determined in layers of cementum and dentine serially-abraded from the root surface, passing through the cementum-dentine junction and into the underlying dentine, using silicon carbide-impregnated film. The concentrations of F in the cementum mineral were variable but consistently maximal at or near to the external surface of the root and tending to fall towards the interior and across the cementum-dentine junction into the underlying dentine. The F content in the cementum tended to increase with age.