The author proposed a new definition of the root canal preparation as the intracanal procedure “to make the pathologic root canal ready for a sound periapical tissue”. Under this definition, “Root Canal Preparatology” discusses systematically all intracanal procedures, includung biomechanical preparation, irrigation, medication etc. These procedures are appreciated not only for what they can do in the root canal but more importantly for how they can contribute to the healing of the periapical tissue. The focus of root canal preparation should not only focused on 1/3 of the opex but also in the periapical tissues.

  In “Root Canal Preparatology”, diagnosis of the root canal configuration, intracanal conditions and periapical tissue healing are refered to as a key concept in guiding the operator to subsequent procedures of the preparation. These diagnostic procedures work before, during and after the preparation to check how the treatment is proceeding. They are based upon a solid knowledge of morphology, biochemistry, bacteriology, physiology and other related basic sciences. However, at present not enough emphasis is given on the importance of this kind of diagnostics. Further development of diagnostics for root canal preparation is needed in order to make root canal therapy more successful.

  Iontophoresis is a kind of electrosterilization.

  Electrolyte molecules are dissolved in water, dissociated and broken up into positive ions (cations) and negative ions (anions). When an electric current passes through a electrolyte solution, cations are attracted to the negative pole (cathode), while anions are attracted to the positive pole (anode).

  This phenomenon is referred to as electrophoresis.

  The resultant ions are destructive to microorganisms.

  The principle of iontophoresis for the treatment of infected root canal is based on this phenomenon.

  Iontophoresis has a long history of nearly one hundred years.

  In this article the history of development of apparatus and the studies on iontophoresis in Japan are described.

  For the purpose to evaluate the tissue reaction of root canal filling materials, the poly-tetraflourethylen tubes which were filled with 4 kinds of root canal filling materials were implanted into the rat subcutaneous tissue.

  The tissue reactions were studied for 12 weeks after the implant, and the results were compared and examined.

  The results obtained were as follows :

  1. The polytetraflourethylen cylinder as control, Opian Gutta and Canals were surrounded by fibrous connective tissue after 8 weeks.

  2. The invasion of granulation tissue continued into Sealpex with exudative changes, and many foreign body giant cells were observed in this tissue.

  3. After 8 weeks, granulation tissue decreased and fibrous connective tissue sorrounded GP Sealer, but also endocytosis by some macrophages was occured.

  The standard type reamers and gutta percha points on the market were measured according to the ISO standard and the conclusion reached as follows.

  1. The endodontic comparison gauge of each company was inaccurate in size, compared with the standard.

  2. As to the measurement of reamers, most of reamers' points d₁ were within the tolerance and remarkably deviated as their size goes larger. Most of d₂ were out of the tolerance at the size of high utilization and the number of inaccurate size increased according as the size becomes larger.

  3. As to the measurement of gutta percha points, the tips d₁ of points of the two companies were within the tolerance but that of the two other companies were out of the tolerance. Most of d₂ were the lower limit of the tolerance at the size of highly frequent use and the number of inaccurate size increased according as the size becomes larger.

  4. It is necessary to maintain accuracy of the reamers as the present state and especially to make d₂ more accuracy.

  5. It is necessary to enlarge the extent of tolerance and also to revise the standard of points' size.

  In order to be able to systematically carry out root canal treatment, the instruments and guttapercha-points used for treatment should be arranged based on the angle of the angle of the tip and taper regulated by the International Standardized Organization (ISO). But in reality, standardization of root canal instruments and guttapercha-points is difficult. Variations from the standard requirements can be observed between different manufacturers and even within a manufacturer. For the purpose of comfirming the above mentioned problems, we examined several files and reamers manufactured by six different manufactures (MANI, GC, Kerr etc) under the SEM.

  The tip and edges of each instrument were examined in detail before and after its use. As a result, four out of the thirty-six unused instruments were found not to be proper for the ISO. All H-files, however, were found to meet the acceptable standard requirements. We were also able to observe a variety of morphological changes on the tip and edges of used instruments. Especially when these instruments were used in strongly curved canals, the changes observed on the tip or edges in these instruments were severe and irreparable. Form the above findings, one must realize the importance of a careful and meticulous examination of every file and reamer prior its insertion in root canal, and this is especially critical when reusing old instruments.

  In November, 1981, nonsurgical endodontic treatment was performed on the mandibular left first molar of a 37-year-old male at the author's clinic. Two of the three canals of this tooth were underfilled 2mm because of the presence of obstructions.

  Eight years later, radiographs revealed a radiolucency with a diameter of approximately 12mm associated with the apex of the mesial root canal of the tooth. Apicectomy was carried out on the mesial root, with a histopathological diagnosis of the presence of a cyst.

  This case suggests that long-term and short-interval observation be made on underfilled roots due to the presence of obstruction.