This review is to introduce the recent studies of the neurotrophic effect which were reported by us and other researchers. Differentiation of the myoepithelial cells and acinar cells of the sublingual gland and lingual fungiform papillae is suppressed by neurectomy of the chorda tympani-lingual nerve of the newborn rats. Parasympathectomy within 48 hours after birth totally inhibit the development of myoepithelial cells. The effect of denervation is maximum at this time of operation and diminish gradually there after. Denervation at the 30th postnatal day cause no detectable change. In the sublingual glands parasympathectomized at 24 hours after birth, unusual serous acini consisted of several serous secretory cells are observed. The serous secretory cells which form an unusual acini are similar to serous demilunar cells of the normal mixed acini. Morphological changes of the fungiform papilla due to denervation first start with an atrophic state, and then progress to forms close to filiform papillae. When immature fungiform papilla is denervated, it change eventually to a complete filiform papilla which is the same as ordinary filiform papilla. These findings indicate that the chorda tympani and/or lingual nerve are required for the normal differentiation of myoepithelial cell, acinar cell and fungiform papilla, and also suggest that the trophic activity may be universal function of neurons.

　A pathologist's view on superantigens is presented. Recent findings on exogenous and endogenous superantigens are reviewed. The author's own work on discovery of nonspecific mitogens in streptococcal culture filtrate, erythrogenic toxins as superantigens, antimitogen assay of human sera, and its application to study on the etiology of Kawasaki disease are briefly described. Superantigens seem to be a counterat tack by unicellular microorganisms against the immune system that has been evolved by multicellular organisms including men. Such an interpretation of meaning may provide a clue to further progress of research if presented as testable.

　The purpose of this study was to measure the changes of temperature in the tooth structures when smoked stopping and pulpr (CCI₂F₂) were applied on the surface of extracted human teeth.

　Twenty extracted human permanent teeth were used for this research. They were clinically intact. A thermography (Agema) and a thermocouple (Hioki) were used and compared in respect of measuing the temperature of the teeth.

　The changes of temperature were as follows. Smoked stopping ; 2. 2℃, pulper : 1. 4℃ by thermocouple. Smoked stopping : 3. 2℃, pulper : 2. 9℃ by thermography.

　From the above results, at first it could be concluded that the thermography was more useful to know the time-depending thermal conduction on the sectioned tooth surface, and it was more accurate than the thermocouple about the temperature on the surface. And secondly the thermal pulp testing with either smoked stopping or pulper seemed to be not harmful to the dental pulp as long as the tooth was intact.

　While we carry out oral management annually in treating pediatric patients, we may frequently encounter unexpected events. One of them is the case in which the dental pulp becomes inflamed for some reason, leading to early abnormal root resorption. In the deciduous molars particularly, despite the long time needed for the period of changing dentition, only one root may show almost completely root resorption while the other roots are healthy. According to the routine method, such a case should be treated by tooth extraction and the use of a space maintainer. However, there may frequently be some cases in which we hesitate to use such treatment. If a tooth under this condition is preserved, it will be very difficult to fill a root canal using a paste-type root canal filling material and to maintain the tooth until the dedentition, because of obliteration of the root canal. I performed root canal filling using Obturation Gutta for the root with abnormal resorption and a paste-type root canal filling material (Sealapex) for the other roots without resorption. I have been obtaining good results by using Obstration Gutta that enabled preservation of the teeth which have been considered difficult to preserve and their maintenance until the period of changing dentition, owing to the only slight biostimulation and the dense obliteration of the root canal by the material.

　Interaction between 4-META/MMA-TBB resin and dental pulp was investigated in vivo and in vitro. ① A cavity was prepared and the pulp was exposed in the occlusal surface of the tooth and filled with 4-META/MMA-TBB resin. Newly formed dentin was recognized just below the agent. During the healing stage, no inflammatory cell was observed but macrophages were detected close to the newly formed dentin, where tunnnel defects were appeared. ② 4-META/MMA-TBB resin was applied on the surface of pulp and 0.5% agar in vitro to investigate the surface structure on the resin after polymerization. When polymerization occured on the pulp, the surface of the resin revealed rods in shape. On the other hand, abundant cavities were found at the resin surface on the 0.5% agar.

　Taken all together, the surface structure of polymerized 4-META/MMA-TBB may cause macrophage migration around the interface between pulp and resin.

　It has been 35 years since Sunada first introduced an electronic method of measuring the length of the root canal in 1958. Since then, although various electronic devices has been developed, the principle of those devices did not have so much differences from that of Sunada's.

　The most important advantage of the electronic method is that it can measure the length of the canal to the apical foramen, not to the anatomical apex which the roentogenographic method can usually recognize. On the other hand the most striking disadvantage of the electronic method is that, if there are strong electrolytes in the canal, the meter shows a reading which is too short or sometimes the measurement itself becomes impossible. Therefore, especially in U.S. and Europe, the electronic method was recognized as a rather simplified method which could not replace the roentogenographic method.

　Recently, the new devices (the Root ZX and the Apit) has been developed which simultaneously measures 2 impedances of the canal using current sources with 2 different frequencies. These devices can make an accurate measurement of the root canal length even if a strong electrolyte is in the canal.

　The apit, by taking a difference between 2 impedances, can minimize the influence of the electric variables of the canal. Although, the device's meter only moves when the file gets to within 1 or 2 mm of the apical foramen, and it must be separately calibrated for each individual canal.

　The Root ZX needs no calibration, because it can minimize the influence of the electric variables by taking a quotient between 2 impedances. The microprocessor of the device corrects the calculated quotient so that the position of the file tip and the meter reading are directly related. This means that root canal enlargement can easily be performed while simultaneously monitoring the length of the canal.

　With an employment of the new electronic device, the more precise enlargement of the apical portion of the canal has become possible, than with a roentogenographic method.

　The mandibular second bicuspid is sometimes missing. Next to the third molar, this tooth is most frequently missing in the human dentition.

　The patient was a 3 years 11 months old male at the first visit. The chief complaint was the caries treatment. All the cavities were treated and the patient was sent to recall system at our department.

　The rootcanal of the right lower primary molar was infected due to caries after 3 years. The mandibular second bicuspid was missing according to radiographic examination. This tooth needed to be treated endodontically. The endodontic treatment was successful.

　The patient came to our department suddenly after 9 years and 5 months, because this tooth moved extremely. Radiographic examination revealed the development of second bicuspid crown.

　This paper deals with the difficulty of the diagnosis in the patient whose mandibular second bicuspid was considered to be missing.

　Today people expect many things from a dentist. Patients demand a clean dental practice based on clean (clear) planning, clean treatment, and a clean (fair) fee.

　In this essay I stated my opinion about clean treatments, particularly on clean endodontics. I have also given some examples relating to clean endodontics from my own clinic.

　Endodontics, like jaw surgery, involves cutting into the bone. Therefore, special care is required to prevent the area from becoming infected. This treatment is accompanied by bleeding so it is especially important that any instruments used are thoroughly cleaned.

　We must remember that micro biological safety is not our only concern. The atmosphere and environment in our practice are also factors in helping our patients and co-workers feel comfortable. Dentists and assistants must be as concerned about their own cleanliness as they are about their patients cleanliness.

　It is important that it is practical for the general dental practitioner to implement these cleaning systems continuously.

　The gutta percha points were recognized at the Devisional Council on Medical and Safety Facilities of the Japanese Industrial Standards Committee on October, 27, 1992 and have been established as the Japanese Industrial Standard (JIS T-6515 1993) this time and it is arranged to publish in the Official Gazette at an early date.

　It is supposed to be revised in some details, but all the standard which is recognized at the Divisional Council is published here. Further, the standard is characterized remarkably in that the method of disinfection is decided not by the dentist but by the manufacturer.