It is especially important to have a sufficient and exact knowledge of the morphology of apical foramina and the area of root apices for endodontic practice.

  Many microscopic studies on this area were carried out in the past. Recently, SEM was introduced to the researches in the field of dentistry. And now, the structural details of hard tissues of the tooth are becoming much more apparent.

  In this article, several principle SEM studies concerning the morphology of root apices reported up to date were introduced and the main points of these studies were mentioned and discussed.

  A comparison of the cytotoxic effects of a cultured rat bone cells and dental pulp cells between newly-developed root canal sealers and commercially available sealers were done in this study. Various root canal sealers were applied to cultured bone cells and pulp cells by the enzyme digestion method. Measurement of [³H]-thymidine incorporation, alkaline phosphatase activity, and calcium release were performed.

  No significant difference was found in cellular DNA synthesis to New B-1, New B-5 and controls. Those cells (in close proximity with) Tubliseal, Diaket and AH-26 demonstrated a significant difference from controls in DNA synthesis and alkaline phosphatase activity. Calcium release at 24 hours was significantly different in the cells treated with New B-1 and New B-5 compared to controls. On the other hand, no appreciable difference was found between New B-6, Sealapex and controls. At 48 hours, cells treated with New B-1, New B-5 and New B-6 showed a significant difference from controls, but the cells exposed to Sealapex did not.

  Newly-developed root canal sealers have lower toxicity in vitro than commercially available root canal sealers.

  The ultrasonic endodontic system is recommended to prepare root canals more effectively and with less fatigue to the operator. The intracanal instruments, which resemble standard K-type files without a handle, are ultrafast vibratory motion and are in contact with dentin walls. Our concern is the effect of the ultrasonic vibration on the integrity of these files and on the rate of wear or deterioration and fracture. Therefore, it is necessary to determine the effect with time.

  The purpose of this study was to examine the wear or deterioration of files and to clarity the fracture mechanism.

  Ultrasonic instruments are K-type files without a handle (＃10～40, MANI) soldered with No.1 tip (Satelec). The ultrasonic machine Suprasson Piezomatic P 2 (Satelec) was designed for either ultrasonic scaling or endodontic instrumentation.

  The settings on the machine were as recommened by manufacturer, i.e. power at 0.1 (0.7w) and water coolant.

  Ultrasonic files were applied to canal treatment, and then observed under scanning microscope and X-ray microanalyzer (wave dispersive type and energy dispersive type), after 0 (unused controls), 1, 3, 5, 7, 10 and 15min.

  The results were as follows ;

  1. Surface of unused ultrasonic files showed shavings, pores, lengthwise cracks, and inclusions.

  2. Surface of used ultrasonic files showed pressed and lost shavings, attrition of edges, scrach like tire track, and enlargment of length with cracks.

  3. Attrition of ultrasonic files' edges could be seen with usage and increased rappidly after 7min.

  4. The image of fracture of the soldered parts were looked different from that of the tip of files.

  5. Surface and fractured face showed enclusures which originated from slug and were made from aluminium, magnesium, niobium, titanium, silicon, sulfur, barium, kalium, zinc, phosphorus, chlorine, calcium, and oxygen.

  6. These inclusions were thought to be one cause of ultrasonic files' fracture.

  Various endodontic techniques have been used to obtain a three-dimensional obturation of the root canal. One method is to use solvents of gutta-percha to obtain better fitting of the gutta-percha primary cone to the root canal wall. This procedure has the disadvantage of the dimensional changes that occur when the solvent evaporates.

  GP-solvent is a newly developed root canal filling material solvent that contains d-limonene as its principal component. In the preliminary and clinical studies GP-solvent showed less side effects than chloroform.

  The purpose of this study was to compare the sealing ability of different obturation techniques : 1) lateral condensation of gutta-percha with no solvent softening (standardized lateral condensation), 2) lateral condensation of gutta-percha with softened GP-solvent primary cone, 3) 2)＋ultrasonic condensation, 4) lateral condensation of gutta-percha with softened chloroform primary cone, and 5) 4)＋ultrasonic condensation.

  The obturated 82 single-root incisors were immersed in indian ink, decalcified and cleared.

  The results showed that :

  1. Reappearance of inner surface of root and apical seat could not take place when the gutta-percha point had been softened in GP-solvent for an hour.

  2. Although all of root canal obturation techniques showed some amount of apical leakage in vitro, the GP-solvent softened primary cone obturation technique showed considerably more leakage than others.

  3. The sealing ability of the chloroform-softened cone obturation technique was increased with ultrasonic condensation. On the other hand, that of GP-solvent softened cone did not increased.

  4. A two-way analysis showed that no periapical sealing was obtained with the GP-solvent softened primary cone obturation technique (P<0.05).

  Finally, this GP-solvent softened primary cone obturation technique for apical seals did not prove efficient.

  We edited a collection of original music, for patients undergoing dental procedures to listen to for the reduction of uneasiness and the pain perception. The pain perception during the dental treatment was evaluated by computer mapping EEG. We compared the pain perception of patients undergoing treatment with and without the music stimuli, from the point of electrophysiology and by analyzing blood pressure and pulse. As a electrophysiological monitor, EEG was analyzed two dimentionally by computer mapping EEG (CME) using SAN-EI Signal Prosessor 7T18. The effects of music on the pain perception and uneasiness were analyzed by the changes of α waves area in CME.

  Conclusion

  1. No differences of pulse nor blood pressure were recognized following music stimuli.

  2. The increased α waves were observed following music stimuli.

  3. The α waves were almost diminished when the pain stimuli were given. And then the α waves appeared again and increased when the music was given under the painful stimuli.

  4. The α waves which were decreased following the sound stimuli of turbine or reaming and filing, were increased when the music was given under these sound stimuli. The decreased α waves exsisted following the stimuli of a child crying, were further decreased when the music was given under this situation.

  This report identifies the objective estimation about the effect on sensitive perception by music.

  We know that when patients need surgical treatment it is essential to make a blood test to know their blood types and the presence of contagious disease. But, in dental practice, patients are treated without a blood test and dentist is in direct contact with patients' saliva and or blood, so we are exposed to contamination of hepatitis, syphilis and many other germs. Contamination could be caused by using infected instruments too.

  Certainly, sterilization and disinfection in a dental office can not be the same these of as hospitals, but we must find the way to protect our health and our patients' health during dental treatments.

  A method of daily sterilization and disinfection of metalic instruments, plastic accesories, and non soaking equipments ; hygiene ; and cloth in a dental office are mentioned in this study.