Jiro Nakamura

Calcium Concentration and pH of the Periapical Environment after Applying Calcium Hydroxide into Root Canals In Vitro

The purpose of the present study was to determine both calcium concentration and pH in the periapical region after application of 1 of 4 different calcium hydroxide preparations into experimental root canals. Fifty root canal models were divided into five groups: group 1--calcium hydroxide was mixed with distilled water at a powder/water weight ratio of 38%; group 2--calcium hydroxide was mixed with distilled water at 44%; group 3--calcium hydroxide was mixed with distilled water at 50%; group 4--calcium hydroxide powder only was used; and group 5-the control group, in which nothing was applied to the canals. All samples were immersed in distilled water maintained at 37 degrees C. Calcium concentration and pH of the distilled water were measured after 3 days, 7 days, and then at weekly intervals up to 15 wk, during which time the storage medium was renewed after each measurement. Calcium concentration and the change in pH of the distilled water were statistically quicker and greater in groups 1 to 3 (mixture groups) than group 4 (powder only) (p < 0.05). The highest calcium concentration (peak Ca2+ release) was observed after 3 days for the mixture groups, whereas that for the powder only group was found at 7 days. Peak pH change was found after 14 days for the mixture groups, whereas that for the powder only group was found at 49 days. After peaking, all groups showed a decline of the pH over time. These results suggest that the time required for optimum intracanal activity when using calcium hydroxide mixtures is at least 2 wk.

Effect of Canal Drying Methods on the Apical Seal

The purpose of this study was to observe the seal obtained in human root canals under different in vitro treatment conditions. Root canals of freshly extracted human maxillary incisors received traditional biomechanical preparation and irrigation with 10% NaClO, followed by a final rinse of distilled water. Teeth were divided into four groups. In group 1, each root canal was dried with one paper point. In group 2, each root canal was dried with four paper points. Group 3 was dried with four paper points, followed by a gentle burst of warm air. Group 4 was dried using four paper points, followed by an internal 200 degrees C heat probe. Twenty canals in each group were filled with a gutta-percha cone and a zinc oxide-eugenol sealer, whereas 20 were filled with a glass ionomer sealer. All teeth were immediately immersed in India ink for 1 or 4 wk. The teeth were cleared, and the dye penetration-leakage measured with an accuracy of +/- 0.01 mm. Optimum sealing conditions were observed when the canal was dried with paper points and a 200 degrees C probe. There were no significant differences between 1 and 4 wk immersion. Glass ionomer sealer appeared more susceptible to the wet condition of the root canal walls than zinc oxide-eugenol sealer. An additional 40 teeth were prepared in the same manner as the dye penetration tests to observe the drying conditions of the root canal walls, and the moisture inside the canals was measured to an accuracy of 0.0001 g. The highest degree of internal canal wall dryness was found in group 4.

Cataract surgery training using pig eyes filled with chestnuts of various hardness

This method uses pig eyes filled with cooked chestnuts serving as pseudonuclei with the goal of teaching dividing techniques of phacoemulsification and aspiration. The pseudonuclei simulate the various degrees of human lens nuclear sclerosis. The chestnuts are trimmed to lens size. After lens extraction through a self-sealing straight incision from the pig eyes, the chestnuts are inserted in the capsular bag through the incision, which is then sutured. These preparatory procedures were initially performed by experienced surgeons but after practicing phacoemulsification technique several times, inexperienced surgeons were able to complete the entire procedure, allowing them to practice phaco chop, divide and conquer, and nondividing phacoemulsification.

Nd:YAG laser irradiation of the human dental pulp: implications as a predictor of pulp hemodynamics.

The aim of study this was to evaluate in vivo the pulpal blood flow rate, pulpal responsiveness, systemic blood pressure, and pulse rate during Nd:YAG laser irradiation of an isolated tooth.

Expression of protein gene product 9.5 in the anterior lens epithelial cells of atopic cataracts

Purpose: To investigate the mechanisms of atopic cataract by immunohistochemically observing protein gene product 9.5 in lens epithelial cells (LECs) of atopic cataracts. Setting: Departments of Ophthalmology and Anatomy, Shiga University of Medical Science, Shiga, Japan. Methods: Specimens of anterior capsule obtained from 6 patients with atopic cataract and 8 patients with senile cataract were stained immunohistochemically and examined by light, electron, and confocal microscopy. Results: In the LECs of the atopic cataracts, the arrangement and cell shape were varied. Immunohistochemistry for protein gene product 9.5 demonstrated selective localization, unlike with senile cataracts. This was especially prevalent in the spindle‐shaped cells around the central opaque lesion. Protein gene product 9.5 positive cells overlapped with major basic protein positive cells in the atopic cataracts. Conclusions: The results indicate that the properties of LECs of atopic cataracts are different from those of senile cataracts. Protein gene product 9.5 and major basic protein seem to be concentrated in atopic cataracts.

Two cases of optic neuritis in which relative afferent pupillary defect and decreased critical flicker fusion frequency could be detected before visual acuity worsened

RAPD (relative afferent pupillary defect) for light reflex and decreased CFF (critical flicker fusion frequency) are sensitive indicators of unilateral optic neuritis. Previous studies have shown that light reflex and CFF usually improve more slowly than visual acuity during the recovery period of optic neuritis. However, there are few chances to observe the relationship between visual acuity and light reflex or between visual acuity and CFF during the early onset of optic neuritis. This paper describes two cases of unilateral optic neuritis in which RAPD and decreased CFF could be detected during early onset before visual acuity worsened. The cases show that a dissociation between visual acuity and light reflex or between visual acuity and CFF may also occur during the early onset of optic neuritis, as it can during the recovery or remission period. That is, light reflex and CFF are affected more rapidly and recover more slowly in optic neuritis. Therefore, when patients with normal visual acuity complain of visual symptoms of unknown origin, investigators must keep the possibility of optic neuritis in mind while observing light reflex and measuring both visual acuity and CFF.

Studies on the effect of different kinds of toothbrushes on plaque removal and toothbrushing pressure in scrubbing method of toothbrushing. (Report 4). For toothbrushes of nylon bristles arranged in different flexibility of handles and diameter of bristles.

スクラッビング法に適した歯ブラシについて, 第4報として柄の弾力性と毛の直径の違いがブラッシング圧とプラーク除去効果に与える影響について比較検討した。今回は, 第1報から第3報の結果を考慮して, 毛の材質はナイロン毛, 先端形態はラウンドカット, 毛の長さ10 mm, 植毛部の長さ25mm, 毛束配列3列26毛束, 柄の形態はストレートに統一し, 柄の弾力性 (ポリエチレン樹脂: 弾性率4, 500kgf/cm2, ポリプロピレン樹脂: 弾性率9, 400kgf/cm2, アクリロニトリルースチレン樹脂: 弾性率38, 000kgf/cm2) と毛の直径 (0.15mm, 0.20mm, 0.25mm) の異なる9種類の歯ブラシを試作した。被験者9名にスクラッビング法によるブラッシングを行わせ, 前後のプラークのスコアーを測定し, プラーク除去率を算出した。ブラッシング圧は渡辺のブラッシング圧測定装置を用い測定した。その結果, ブラッシング圧は, 歯ブラシの毛の直径が太くなるに従い高くなり, 0.15mmと0.25mm, 0.20mmと0.25mmとの間に有意差 (p<0.01) を認めたが, 3種類の柄の間では有意差は認められなかった。プラーク除去率は, 3種の毛の直径および3種の柄の間には有意差は認められなかった。

A Histological Study on Hybrid Materials Compounded with Porous Hydroxyapatite and Periodontal Ligament Cells in vivo.

We produced a hybrid material compounded with periodontal ligament cells, which may differentiate into osteoblasts and/or cementblasts, and porous hydroxyapatite granules. Hybrid materials were implanted in the jaws of rabbits from which periodontal ligament cells has been obtained. Periodontal ligament cells were obtained from the incisor roots of the rabbits and cultured at 37•Ž in ƒ¿ -MEM supplemented with 10% fetal calf serum and

Effects of Posterior Tooth Occlusion on the Reflex Response of the Human Masseter Muscle.

本研究では, 3種の刺激方法 (a. 上顎右側中切歯へのtapping刺激, b. 上顎右側中切歯唇側歯肉への電気刺激, c. オトガイ部へのtapping刺激) で咬筋に誘発された反射性筋活動が, 臼歯部咬合によって抑制されるか否かを検討した。その結果, 3種の刺激で咬筋に誘発された反射性筋活動は, 臼歯部咬合によっていずれも明らかに抑制された。また, この臼歯部咬合による咬筋筋活動の抑制は, 咬合している上下顎臼歯歯肉の浸潤麻酔後には完全に消失した。したがって, この臼歯部咬合による咬筋筋活動の抑制は, 咬合している臼歯部歯根膜中に存在する機械的受容器からの求心性信号によって生じたことが示唆された。

Study on hybrid materials compounded with porous hydroxyapatite and culture cells. 1. Attachment and the invasion of cultured cells to porous hydroxyapatite

The purpose of this study was to investigate the effects of hybrid material compounded with periodontal ligament cells on human teeth and porous hydroxyapatite. As the first step, we tried to produce hybrid materials compounded with periodontal ligament cells and porous hydroxyapatite, and to observe the attachment and invasion of periodontal ligament cells porous hydroxyapatite. Human periodontal ligament cells which had been scraped off the root with a disposable blade were cultured at 37 degrees C in alpha-MEM plus 10% fetal calf serum. The culture cells were attached to the porous hydroxyapatite in vitro. After 3 and 14 days of incubation, the specimens were fixed in gluteraldehyde and examined using SEM. Other specimens were embedded in paraffin and successive specimens were prepared for to remodelling of the attachment and invasion. Many cells attached to the P-HAP granules, and some cells invaded the P-HAP granules. The results suggest that when these hybrid materials are implanted in bone defects, the cells remain in the defect for a certain period, and exhibit the functions and characteristics of itself.