Recently The laser has been applied to numerous dental clinical fields such for treatment of hard and soft tissue diseases. The mechanism of the laser action on dental hard tissues, however, is unclear. The aim of this study was to investigate alterations of the inorganic crystals of human deciduous enamel with CO₂ laser irradiation using a polarizing microscope and a Micro X-ray diffraction. Based on observation of the polarizing microscope, several half-circular layers were found around the central irradiated regions while the interference colors of the central regions and the several layers showed grey-white, dark brown, orange, yellow and blue, respectively. Based on analysis of the altered regions using Micro X-ray diffraction, it was found that the enamel crystals [HAP: Ca₁₀(PO₄)₆(OH)₂]were altered as follows. At the irradiated central regions, high temperature phases such as α-Ca₃(PO₄)₂ and semi-high temperature phases such as β-Ca₃(PO₄)₂, α-,β- and γ- Ca₂P₂O₇ were identifled. In the surrounding layers, there were gradual changes from high temperature phases to semi-high temperature phases, and to the normal HAP. It was confirmed also that the altered regions correspond to those observed using the polarizing microscope.

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From October in 2005 to September in 2006, among 1,110 for the first time pediatric patients visited our pediatric dentistry clinic in Chiba hospital,313 with clinical information forms or introduction letters from dental clinics or general hospitals were selected as subjects. The age of the patients at the time of the first visit, the type of treatment requested, medical condition, existence of developmental disability, location of medical institutions referring the patients and the places of residence of the patients were recorded and the following results were obtained.
1. The most common age group at the time of the first vis it for the 313 subjects was 3 to 7 years, accounting for more than half of them (173; 55.3%).
2. The most commonly requested treatment was caries treatment (139) followed by supernumerary teeth, traumatized teeth, retarded eruption, impacted teeth, malalignment and malocclusion.
3. Of requests for caries treatment,60% involved patients under 6 years of age. In the traumatized teeth group,40% of the patients were 1 to 2 years of age. Based on these results, it was assumed that medical institutions referring those patients had difficulty in treating young children.
4. The number of patients with a medical history of developmental disability was 44 (14.1%). They involved predominantly mental retardation, cardiac disease, asthma and autism.
5. Patients referred from medical departments (MD) amounted to 7 (2.2%). They involved pediatrics (4) plastic surgery (1), psychiatry (1), and obstetrics and gynecology (1).
6. Patients from Chiba were predominant in terms of both the locations of the medical institutions and their places of residence.
7. By active cooperation between hospital and clinic, the number of pediatric patients with letter of introduction from medical institutions in the community was on the increase in our pediatric clinic in Chiba Hospital.

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Objective: As part of a caries prevention program, a baseline survey determined caries risk, and examined its relationship to diet and smoking history in a sample of Japanese pregnant women. Subjects and methods: All of the 400 Japanese pregnant women aged 19-43 years (mean: 29.2 y, SD=4.2,3^rd-6^th month of pregnancy), who visited Miyake OBGYN Clinic, Okayama, were surveyed in the clinic which is the largest in Okayama-city. A three-page,50 item questionnaire covering diet, use of chewing gum/tablet/toothpaste/mouthwash, daily use of xylitol chewing gum, smoking history, and demographics was designed and was used. The survey on diet was a modification of an earlier validated work adapted for Japanese. Salivary mutans streptococci level, an indicator of caries risk, was determined (Dentocult SM®, Orion Diagnostica, Finland). The frequency score of each food item consumed during the last month (0=never,1=rarely,2=1 time per week,3=2-3 times per week,4=1 time per day,5=2-3 times per day,6=4+times per day) and smoking history (yes/no)were compared among Dentocult SM score (SM) groups.
Results: The proportion of each score was 8.5% (SM=0),35.3% (SM= 1 ),38.0% (SM=2), and 18.3% (SM = 3). More than half of the Japanese pregnant women were at a high caries risk (56.3%; SM=2 or 3), and less than one out of ten high risk women had visited dental practices (7.8%). Less than one out of ten (8.8%) pregnant women had smoked. No significant difference but trend was found on the presence of smoking among SM groups (p=0.08). The highest food frequencies were rice (mean=4.59), milk (3.07), bread (2.98), sugared yoghurt (1.56), ice cream/sorbet (1.47), cold drink (1.41), banana (1.36), cheese (1.29), sugar or honey in coffee or tea (1.26), lactic acid drinks (1.19), candy (1.16), chocolate (1.06) and plain yogurt (1.01) were rated as the most frequently consumed by the pregnant women. Significant differences were found on the frequency scores of 8 food items between the risk groups. Almost one out of 20 (5.3%) had chewed gum including xylitol everyday. Almost of the half (48.6%) of the pregnant women had chewed gum,9.2% had eaten tablet or mints, while 99.4% had used toothpaste, and 8.3% had used mouthwash during the last month.
Conclusions: These results suggested that the considerable effort will be required by the oral health profession to intervene or give oral health instruction into this population.

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Objectives: Leptin has recently been shown to have an effect on bone formation, though the relationship between leptin deficiency and mandibular bone mass has not been fully elucidated. In the present study, we investigated the effects of leptin deficiency on mandibular bone structure.
Materials and Methods: Fifteen 5-week-old ob/ob mice and fifteen 5-week-old lean mice were used in the present study. Five from each group were euthanized at 6,9, and 12 weeks of age, after which the mandibles and femurs were extracted. The specimens were analyzed by means of cephalometry, and subjected to three-dimensional measurements of bone density and bone strength using peripheral quantitative computed tomography (pQCT).
Results: The mean body weight of the ob/ob mice increased significantly compared to that of the lean mice. Cephalometry findings showed that the mean length of the femur in ob/ob mice was significantly shorter than that in the lean mice. In the cephalometry of the mandibles, numerous parameters of length in the anterior-posterior direction in lean mice were significantly higher than those in ob /ob mice at each age. In contrast, parameters of height in the superior-inferior direction (Al' -Me) in ob/ob mice were significantly higher than that in lean mice at each age. pQCT analyses of bone density and bone strength showed that all parameters for the mandibles, except for trabecular bone mineral content and cross-sectional area, in ob/ob mice were significantly greater than those in lean mice. In contrast, the diaphysis of the femurs in ob/ob mice was significantly smaller.
Conclusions: Mandibles and femurs in ob/ob mice showed different architectural characteristics compared to those of lean mice.

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The purpose of this study was to examine vickers hardness, changes in the ability of acid resistance and changes in crystallography using X-ray diffraction of enamel after Nd: YAG laser irradiation.
The following results were obtained:
1. The Vickers hardness of enamel after Nd: YAG laser irradiation at 100 mJ output increased significantly.
2. The Vickers hardness of dentin after Nd: YAG laser irradiation at 100 mJ output increased significantly just as in the enamel.
3. The results of acid resistance examined using QLF showed a statistically significant difference between the two groups. The non-laser irradiation group ofΔF(average of depth of demineralization)was-9.68±1.90, while the laser irradiation group was -7.75±1.31.
4. The SEM image showed a smooth surface structure, while numerous irregular micro cracks, large or small numerous micro holes were observed.
5. The results of X-rd diffraction Showed decomposition and created β-TCP in at some of the enamel after Nd: YAG laser irradiation.

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The purpose of this study was to investigate the changes in the status of caries in schoolchildren who lived in Changchun City, China, by comparing the results of surveys in 2001 and 2005. In both years, the subjects were children aged 6-12 years. A total of 194 children (97 males and 97 females)was evaluated in 2001 and 214 children (101 males and 113 females) in 2005.
The percentage of caries children with caries, the dft index, the DFT index, the ratio of dft and the ratio of DFT were higher in 2005 than in 2001. The percentage of the teeth with caries,52.3%, could be classified as severe, and 68.9% were secondary.
As the results, the dental health of sch oolchildren in Changchun City, China has deteriorated.

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EL/Sea (EL) mice have a 100% incidence of defect of the third molars (M3) and are used as animal specimens for the study of tooth loss.
Previous studies reported that a reg ion flanked by 61.8 cM and 66.2 cM in chromosome 3 was involved in the defect of M3 of EL, and named this gene absence of the third molars (am3).
In the meantime, it was also found that EL mice are animal specimens for the stu dy of fused roots of the upper first molar and epilepsy.
The purpose of the present study was to find whether there was a difference in the incidence of the defects of M3 between the upper and lower jaw, and whether the appearance of fused roots of the upper first molar and epilepsy are controlled by am3.
Although the number of M3 in EL congeni c mice did not show any differences between right and left in the jaw, the upper M3 rather than the lower one was more strongly visible in EL congenic mice.
This result suggests that am3 strongly affects the loss of upper M3 though am3 affects both the upper and lower by the M3.
EL congenic mice ha d the same frequency of fused roots of the upper first molar and epilepsy as EL mice.
These results suggest that am3 is not related to the appearance of fused roots of the upper first molar and epilepsy.

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The purpose of this study was to understand the present situation of children with systemic diseases in a university pediatric dentistry clinic. Characteristics of the patients referred with systemic diseases who visited the Pediatric Dentistry Clinic of Hokkaido University Hospital for the first time during a seven-year period, from January 2000 to December 2006, were investigated. The following results were obtained:
1. In each year of the survey period, about 10% of the patients visiting our clinic for the first time were patients referred with systemic diseases. The ages of these patients were distributed most commonly between 1-3 years of age.
2. Sixty seven point four percent of the patients with systemic diseases visiting our clinic for the first time were referred by the Medical Clinical Division of Hokkaido University Hospital.
3. The largest percentage of patients involved the patients with blood disease (23.0%), and the next the patients with heart disease (20.4%).
4. The def and DMF numbers showed a higher score than that of the average Japanese children surveyed by the Ministry of Health, Labor and Welfare.
5. The ratio of the patients with untreated dental caries was 36.5%.
6. There was no difference between before and after the dental hospital merged with the medical hospital.
These results show that the patients with systemic diseases did not have a good oral condition. It was therefore suggested that we must continue appropriate oral treatment and management with enough understanding of the systemic diseases and the general condition of the patients through close communication with the medical doctors.

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At the Department of Pediatric Dentistry in MDU have been undertaking the dental check-ups of kindergarten children it in various parts of China since 1989. The results of the dental examinations of the same kindergarten in Shijiazhuang city undertaken in 1991 and 2006 are compared, and, in addition, the welfare Work Ministry had investigated children of same age in Japan and then discussed.
The subjects on the dental examination the situation were malocclusion, tooth abnormali ty, inflammation of the gum, and caries status for a total of 174 children (55 boys,119 girls) four or five years of age at Kindergarten in Shijiazhuang city.
The increasing trend toward maloccl usion and tooth abnormality was noted, and as for the inflammation of gum, a increasing trend was noted compared with 15 years ago.
There is a tendency toward a decrease in the mobility of caries, the ratio of caries contraction, and the number of average caries person which were compared with the previous time, and each item has the same ratio as in Japan. The caries treatment rate was remarkably low was the ratio 15 years ago. The ratio of non-treatment according to the caries grade was the same degree as the ratio 15 years ago. Moreover, in four year old children, mild caries showed a larger ratio and severe ones show smaller ratio compared with same ages in Japan. In the five year old, children this is reversed. This findings were compared with the findings 15 years ago, and prevalence of the inflammation of the gum showed an increasing trend. The caries treatment ratio is still low. A remarkable a trend toward an increase was the decrease in caries prevalence ratio of the primary teeth was noted. Mild caries of young children showed a tendency not to be treated based on the ratio of non-treatment according to the caries grade though there is a difference in the number of subjects of this investigations.
The unestablishment of the oral health improvement system including caries prevention programs and the deficiencies of the number of dentists is thought as a factor behind this.

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Young children possess a tendency to put various things that they see into their mouths.
This report describes a case where by it was thought that a foreign body in the form of a straw had impacted into a primary anterior tooth of a girl two years old 11 months for a long period time after which she came to our department in MDU hospital.
The case involved a girl aged two years eleven months, who had not been seeing dentists for about two years, though a trauma by a fall would be owed to the primary anterior teeth in about nine to ten months after her birth, and had been recognized as malformation of an anterior primary central incisor since then.
Afterwards, when she was two years eleven months old, she came to our department with sorenesses of the teeth as her chief complaint.
She was diagnosed as having a milk-white foreign body was recognized in the anterior primary central incisor according to our dental examination a foreign body impact and it was removed. The periodontal bone around it caused the absorption of a shape corresponding to the foreign body to a high degree. The object removed was a drinking-straw-like foreign body colored milk-white, and it turned out to be the contents of the pillow that had been used previously. A tendency of the periodontal bone was slightly recognized from the mesiodistal direction six months after the removal of foreign body.
It is necessary to do a careful removal of a foreign body after prompt and unerring diagnosis, and is preferable to do the medical examination to the restitution tendency to the periodontal tissues after the removal of foreign body.
Moreover, it is necessary to advance the spread of knowledge concerning the harm caused when children put foreign bodies into their mouth the guardian and the people involved to the child care.

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