要 約 : 根管象牙質に対しCO₂レーザーおよびNd : YAGレーザーを照射した場合の形態的変化を検索するために, 臨床的に抜歯の適応と診断された5本のヒト健全歯 (切歯および犬歯) を用いた.

 5.0 WのCO₂レーザー, または, 2.0 WのNd : YAGレーザーを1～4秒間, 被験歯に照射し, 走査型電子顕微鏡で観察した. その結果, どちらのレーザー照射も直径300～400 μmの円形の陥凹を生じることが明らかとなった.

 CO₂レーザーを照射した試料では, 陥凹の辺縁に, 幅約30 μmにわたり, ガラス状を呈する溶解面が観察された. 陥凹の内部では, 象牙細管やクラックが明瞭に観察された. Nd : YAGレーザーを照射した試料では, 円形の陥凹の内部は溶解融合していた. ガラス状を呈する面もCO₂レーザーの場合より広く, その表層には, 数個の細孔の散在, また多数の細孔の集合が, ガラス状の部分に混在して観察された.

要 約 : この研究の目的は, 3種類の根管充塡法の根尖封鎖性とガッタパーチャの根尖孔からの溢出傾向を比較することである. 真っ直な根管を有するヒト単根抜去歯38本を根管拡大し, 各10本ずつの3つの実験群と各4本ずつのポジティブ・ネガティブの両対照群に無作為に分けた. 被験歯は, シーラーとしてCanals Nを用い, グループⅠはUltrafil injection法, グループⅡは改良型Trifecta法, グループⅢは側方加圧法によって, それぞれ根管充塡された. 37℃の生食水中に7日間保管した後, 歯根表面にマニキュアを塗布した. 被験歯は, 37℃の1.56%メチレンブルー溶液中に7日間浸漬した. 歯根を横断し, 根尖部の色素浸透距離が計測された. 浸透距離の平均は, グループⅠで2.70 mm, グループⅡでは3.20 mm, グループⅢでは2.24 mmであった. 3種類の根管充塡法の間にはメチレンブルー色素の浸透に関して統計学的有意差はなかった. Ultrafil injection法では, 10本中8本 (80%) にガッタパーチャの溢出が生じた. 改良型Trifecta法と側方加圧法では, ガッタパーチャが根尖孔から溢出した例はなかった. この結果, 改良型Trifecta法は根尖封鎖性とガッタパーチャ溢出抑制の点で効果的であることが示唆された.

Abstract : Recently, calcium hydroxide has been generally used as an intracanal dressing. However, the placement of calcium hydroxide into the root canal has some difficulties. This study was carried out to compared the four placement techniques of calcium hydroxide as well as its removal from the root canal.

 Extracted single-rooted human teeth, which were instrumented up to #40 K-file, were used in this study. Barium sulfate was used in place of calcium hydroxide for assessment with X-ray. The powder mixed with saline was introduced into the root canal with one of the following techniques : a lentulo spiral, a counterclockwise-rotating K-file and a cotton broach, as well as an apical plugger in cases of powder dressing. After the X-ray examination, the dressings were removed by alternative irrigation with 8% NaOCl and 3% H₂O₂, with the aid of ultrasonics when necessary. The assessment of placement and removal was performed by dental X-ray examination.

 Satisfactory placement of the dressing on the apical portion was observed with the technique of a lentulo spiral, but it was poor with a cotton broach and apical plugger. Removal of the dreesing was acceptable in 60% of cases when both irrigation and ultrasonics were used. In some cases, a small amount of dressing remained near the apical seat.

Abstract : The purpose of this study was to evaluate the effect of Nd : YAG laser irradiation to accelerate the healling of the periapical lesion of the infected root canal in one-visit treatment, through animal and clinical experiments.

 To find the parameters of effective and safe irradiation, a histopathological examination was performed using 15 dogs with artificially-induced periapical lesion (340 roots). The root canals were instrumented up to #40 file with alternative irrigation of H₂O₂ and NaOCl. After drying the canal, the fiber tip of Nd : YAG laser was inserted to the apical seat. Then the canal was irradiated with different powers and timds in each laser group, but it was not irradiated in control groups. In the laser groups, Indian ink was applied on the apical canal wall of half of the moots before irradiation. Root canal obturation was immediately performed in both groups with gutta-percha and sealer. After2, 4 and 8weeks, the animals were sacrificed and prepared for histopathological examination. The results were as follows :

 1. Removal of debris from the root canal was noticed in the laser groups irrespective of the use of Indian ink.

 2. Transpiration of root canal wall was observed undes the condition of lW・1s with India ink, however, it was not observed under the condition of less than 2W・2s and 3W・1s without India ink.

 3. Periapical healing was significant after 4 weeks in the laser groups.

 From the above results, laser parameters for clinical application was determined to be 1W・1sec irradiation without India ink.

 For the clinical experiment, 70 cases of 38 volunteers which were diagnosed as asymptomatic pulp necrosis with periapical lesion were chosen. They were randomly divided into the laser group and the control group.

 1. Postoperative pain was significantly less in the laser group.

 2. Periapical healing, determined by X-ray analysis after 3 and 6 months, was significantly better and earlier in the laser group.

 It was concluded that Nd : YAG laser irradiation of infected root canals was useful for one-visit treatment of asymptomatic pulp necrosis with periapical lesion.

Abstract : The present study was performed to evaluate the influence of vent made in the root canal during root canal obturation using Ultrafil. For the experiment, a root canal model made of polyester resin was used, in which the root canal taper was varied according to the size corresponding to No. 40 of the ISO specification. A 30-gauge injection needle was used as the vent for the root canal, and Ultrafil Regular set was employed as root canal obturation gutta-percha. The obturation status of the root canal was determined by evaluation using x-ray, observation of the continuous cutting surface from 0.5 mm to 6.5 mm of root canal tip every 1 mm, and measurement of the proportion of the gutta-percha area in the cross-sectional area of the root canal (gutta-percha condensing ratio). The conclusions were as follows :

 1. In case root canal obturation was performed without a vent in the root canal, to which injection nozzle can not be inserted up to the tip of the root canal, gutta-percha was not injected up to the tip of the root canal.

 2. In case root canal obturation was performed by making a vent in the root canal, to which injection nozzle can not be inserted up to the tip of the root canal, the vent served effectively as the discharge route for the air or the excessive amount of sealer.

 3. In the root canal model, in which a vent was made in the root canal and obturation was performed, gutta-percha was condensed satisfactorily at all cutting positions of the root canal.

 4. In the root canal model, in which a vent was made and obturation was performed, there was no influence of the difference of the root canal taper on obturation status, and no difference in gutta-percha the condensing ratio was noted.

Abstract : The purpose of this study was to evaluate the effects of a light-activated calcium hydroxide on the new hard tissue formation at the orifice and the pulpal stimulation after pulpotomy.

 Twenty teeth of two adult beagle dogs were used. The coronal pulp was mechanically removed with #3 round bar, after which the orifice was dressed with a calcium hydroxide pastes containing saline, or light-activated calcium hydroxide (Ultrablend). The animals were sacrificed one week, one month and three months after operation, and histopathologically evaluated.

 The result were as follows :

 The formation of new hard tissue in light-activated calcium hydrtxide was less than that in the calcium hydroxide paste. Beside in the three-month cases of light-activated calcium hydroxid, inflamation remained in pulp.

Abstract : The localization and origin of immunoglobulins in dentinal tubules of 10 vital and 10 nonvital human third molars having dentinal caries were investigated. The extracted teeth were prepared by Brown-Brenn staining for detection of bacterial invasion and immunohistochemical staining to determine the rate of various classes of immunoglobulins penetration into dentinal tubules. In vital teeth, all classes of immunoglobulins, excluding sIgA, penetrated into the dentinal tubules together with bacterial invasion. In contrast, their penetration rate in nonvital teeth was lower than that of bacterial invasion. These results suggest that the vital pulp tissue supplies the intratubular immunoglobulins. However, saliva may also contribute a large amount of immunoglobulins.

Abstract : The electric measurement of the canal length has established firm support among Japanese endodontists. Many types of devices are now commercially available. By this method, it is easy to determine the canal length without exposing patients to the X-ray. However, the results obtained are affected by various factors that modulate the electric conditions of the canal. Among these, we focused on the amount of 3% hydrogen peroxide in the canal and the size of the reamer used as the electrode.

 Widely-enlarged canals were investigated in this study using 3 kinds of apical locators, i. e. Endodontic Meter-SⅡ (EM), Root ZX (ZX) and Justy (JS). The EM uses 400Hz, while both ZX and JS adopt combinations of high and low frequencies. The experiment was conducted on 7 extracted human teeth. As the results, the indicated canal length was longer when the canal was filled with 3% hydrogen peroxide. When a #25 reamer was used, the impedance seemed to be higher than that with a #15 reamer, thus the size of the reamer affected the meter readings. The changes in meter readings brought by these factors were similar in all 3 apparatus.

Abstract : Preservation of the occlusal pressure and stimulusfree treatment were attempted for the infected root apex of an immature lower left second premolar. For this purpose, pumping irrigation with an engine reamer was carried out for a region from the root apex to a point 1 mm acove the apex. At the same time, a piece of plaster containing calcium hydroxide was applied to the affected tooth, and it was reapplied 15 timds during the 2-month period. This therapy resulted in improvement of the symptoms.

 When symptoms had disappeared completely and the lesion had improved, temporary root canal filling was performed. Four months later, the state of the affected area was examined, and root canal filling was carried out using a calcium hydroxide preparation and a gutta-percha point.

 Two years after the start of treatment (one year after root canal treatment), the lesion in the apex had disappeared, and apical hard tissue had formed. Thus, the infected immature tooth was successfully treated by a combination of occlusal pressure preservation, nonpressure irrigation and the use of calcium hydroxide.