Ryuji Sasa

Morphological and Microleakage Studies of the Cavities Prepared by Er:YAG Laser Irradiation in Primary Teeth

OBJECTIVE The purposes of this study were to investigate cavity surfaces morphologically, and compare microleakage at cavities prepared by Er:YAG laser after composite resin restoration versus conventional mechanical treatment in human primary teeth in vitro. BACKGROUND DATA There have been few reports on microleakage at cavities prepared by Er:YAG laser irradiation. MATERIALS AND METHODS A total of 30 cavities (class V) in human primary teeth were used. Half of the cavities were prepared by an Er:YAG laser system at 300 mJ pulse energy and 4 Hz, and the other half were prepared with a high-speed diamond bur. Five cavities from each group were investigated by scanning electron microscopy (SEM) and histopathological examination. Remaining cavities were filled with a composite resin without an acid-etching technique and then subjected to microleakage test in 0.6% rhodamine B solution under thermocycling. RESULTS Microleakage (score: 2.45 +/- 1.07) at cavities prepared by laser was significantly less than that by bur (score: 1.30 +/- 0.95; p < 0.05). SEM observation showed that, compared with the relatively flat appearance of cavities prepared by bur, cavity margins prepared by laser were irregular but there was almost no smear layer at the cavity walls. CONCLUSION It can be concluded that cavity surfaces prepared by Er:YAG laser are irregular, but microleakage at cavities prepared by the laser after filling with composite resin is better than that by mechanical bur using the dye penetration method.

Defects in mandibular bone area, enamel iron content and dentine formation following gastrectomy in rats

Fourteen 5-week-old male Sprague-Dawley rats were equally divided into two groups, sham-operated and gastrectomized. Tetracycline and calcein were given to label dentine. Four weeks after surgery, blood was collected for measurement of serum iron, calcium and parathyroid hormone (PTH) and the mandibles and maxillae were then removed. Sagittal sections of the maxilla or cross-sections of the mandible were prepared and examined. Backscattered electron images of the maxilla were taken and the iron content at the neck of incisors was measured by energy-dispersive X-ray. The dentine apposition rate in maxillary incisors was measured by fluorescence microscopy. Serum iron was significantly decreased, while PTH was significantly elevated without any change in the serum calcium in gastrectomized rats. Gastrectomy caused a gross loss of iron content in superficial enamel. The dentine apposition rate was significantly reduced by 30%. Both cortical and cancellous bone in the mandibula were significantly reduced. However, the total bone area in gastrectomized rats was similar to that in sham-operated rats. These results suggest that bone resorption was enhanced and dentine formation was reduced after gastrectomy.

Fructooligosaccharides prevent disorders of the femoral neck following gastrectomy in growing rats

Gastrectomy-evoked osteopenia in the femoral metaphysis of rats can be prevented by the consumption of fructooligosaccharides (FOS). We examined the effect of FOS on the femoral neck. Twenty-eight 5-week-old male Sprague-Dawley rats were divided into two groups, sham-operated (SH) and gastrectomized (GX). One week after each operation, the rats were fed diets containing 0.5% calcium with or without 7.5% FOS for 4 weeks. After dietary treatment, the middle of the femoral neck was cross sectioned. Backscattered electron images of the sections were then taken to calculate the following morphometric parameters: (1) percent trabecular bone volume (%TBV), (2) percent cortical bone volume (%CBV), and (3) percent bone marrow cavity (%MV); all were determined relative to the entire scan area (SC). Calcium, phosphorus, and magnesium (weight percent) were then measured on the cortical bone by energy-dispersive X-ray analysis. Total bone volume (%BV = %TBV + %CBV) and %CBV were almost identical among the groups, except in GX rats. In GX rats, these variables were significantly (approximately 20% and 30%, respectively; P ≪ 0.01) less than those in SH rats, whereas there were no changes in the other groups over the entire scan area. The calcium concentration close to the periosteal surface of cortical bone was markedly reduced by gastrectomy. This reduction was completely prevented by FOS consumption. These results suggest that FOS consumption prevents gastrectomy-evoked osteopenia regarding both volume and calcium concentration of the femoral neck.

Identification of Streptococcus salivarius by PCR and DNA probe

Aims: To establish species‐specific PCR and DNA probe methods for Streptococcus salivarius and to clarify the distribution of dextranase in oral isolates of Strep. salivarius.

Species-specific PCR method for identification of Streptococcus downei

Aims:  To establish a rapid method to differentiate Streptococcus downei and S. sobrinus by multiplex PCR.

The characteristics of the deciduous dental arch form of children in Changchum-city, China

Abstract It is important to know racial differences in the characteristics of the dental arch form from the view point not only of dental interests but also of anthropology. We got an opportunity to investigate the status of oral condition of children living in the Changchum-city, Jilin Province in China. The size and the form of the deciduous dental arch were measured using plaster casts prepared from the impressions taken at the time of oral examination. The same measurement was conducted using the dental plaster cast of the Japanese children and the size and shape of the dental arch were compared between the Japanese and the Chinese children. The subjects were the Chinese children who had the Hellman IIA dentition lining in Changchum-city. The average age of the Chinese children was 9 years and 4 months and that of the Japanese children was 4 years and 1 month. The measurement results showed that the Chinese children were bigger than Japanese children in every measurement items. As for the dental arch form, Japanese children had a U-shaped arch form with wider width in the front part of the dental arch. On the other hand, the Chinese children had a half-circle-shape arch form that the front arch width was not so wide but that of the back was wide.

Fructooligosaccharides consumption inhibits the loss of iron from the incisor enamel surface in gastrectomized rat

We examine the effects of fructooligosaccharides (FOS) on the reduction in the incisor iron content in gastrectomized rat. Twenty-eight 5-wk-old male Sprague-Dawley rats were divided into two groups: sham operated (bSH) and gastrectomized (bGX). After 4 wk each group was divided into two subgroups according to the presence or absence of 7.5% FOS in the synthetic diet (SH, SH+FOS, GX, and GX+FOS). At 10 wk wafter surgery, the maxilla was prepared to examine the iron content of the incisor enamel surface at four points. These points corresponded to the iron content at 6,7,8, and 10 wk, respectively. Blood was collected to determine serum iron levels at 4 and 10 wk. The serum iron level significantly decreased at 4 and 10 wk the GX group. At 10 wk, the level in the GX+FOS group significantly increased but did not reaach that in the SH group. The iron content of the enamel surface time-dependently increased and no significant differences were seen between SH and GX+FOS at 8 and 10 wk. These results suggest that FOS consumption impaired the loss of enamel content following gastrectomy, and this effect preceded the effect on the serum iron level.

A study of prevalence of caries and oral health behavior in Japanese children with cleft lip and palate

Abstract The aims of this study were to investigate the condition of dental caries in 1–4 years old Japanese children with cleft lip and/or palate, and also to examine the relationships between age, location of the cleft, oral health behavior of cleft children and the incidence of dental caries. The study was carried out through a dental examination of a sample of children and a questionnaire to their parents which included questions about infant feeding practices, frequency of consumption of specific drinks and childrens frequency of tooth brushing. A sample of 116, 1–4 years old Japanese children (58 boys and 58 girls) with oral clefts referred to the Department of Pediatric Dentistry Clinic, Showa University, after receiving surgical treatment, participated in this study. Results indicated that the prevalence of caries in cleft children was related to patient age, location of clefts and oral health behavior. A higher level of dental caries was recognized in children with cleft lip and alveolus/palate than in those with cleft lip alone. Incidence of caries increased with patient age. Children who had been fed in a determined time were less affected than those who had been fed at will. Incidence of caries was also high in the children who ingested drinks with sugar than in those who did not. The results of this study suggest that it is important to improve the oral health behavior of cleft children to minimize the risk of caries. Moreover, children with clefts and their parents should as early as possible undergo a preventive program to ensure preservation of primary dentition.

Streptococcus mutans sortase catalyzes cell wall anchoring of WapA and FruA

Abstract Previous studies using a sortase-deficient mutant (SrtA − mutant-) of Streptococcus mutans have demonstrated that the sortase (SrtA) catalyzes cell wall anchoring of the surface protein antigen PAc, a dextranase and a glucan-binding protein C. In this study, cell wall anchoring of a wall-associated protein antigen A (WapA) and an exo- β -D-fructosidase (FruA) in S. mutans was examined by Western blot analysis with a specific antiserum. In the SrtA − mutant, FruA and WapA were not bound to the cell wall but were secreted into the culture supernatant. In contrast, in the wild type, both proteins were associated with the cell wall of S. mutans . Biological properties of the SrtA − mutant were examined by determination of fructan fermentation and adherence to a smooth surface. Both the SrtA − mutant and the wild type retained the ability to ferment levan. In addition, adherence to a smooth surface of the SrtA − mutant was as extensive as that of the wild-type 109c when sucrose was present. However, in the absence of sucrose, the adhesion of the SrtA − mutant remarkably decreased as compared with that of the wild type. These results suggest that SrtA catalyzes anchoring of WapA and FruA to the cell wall in S. mutans and that surface proteins anchored by SrtA are involved in the initial adhesion of S. mutans to smooth surface. In addition, it was shown that both cell wall-anchored and extracellular FruA are related to the degradation of extracellular fructan as a nutrient source.

Evaluation of the Effectiveness of Screening for Periodontal Disease by Questionnaire.

アンケート調査によって調べた自覚症状と臨床所見との関連性を分析し, アンケート調査による歯周病のスクリーニングの有効性について統計学的検討を行った。中国承徳市近郊の歯科医療低普及地域の住民486人 (14～44歳, 男性211名, 女性275名) について調査を行った。歯肉出血 (GI), ポケット (PD), アタッチメントレベル (AL) などの臨床診査, パノラマX線写真撮影及び, 歯肉出血, 歯の動揺など歯周病に関連すると思われる自覚症状18項目について聞き取り調査を行った。その結果, 個人別に見ると, 最低0, 最高16項目, 平均約5項目の自覚症状を有していた。自覚症状の数と年齢, および臨床診査における各個人別平均値との間に有意な相関が認められた。なかでも, ALとの相関が高くr=0.52), GIとの相関が最も低かった (r=0.17) 。CPITNを基準としてスクリーニングを試みた結果, 自覚症 (状の数が6項目以上の者を重症とした場合, 感度0.68, 特異度0.67であった。さらに, ALと関連のある項目を選択することで, より良好な感度が得られた。