Abstract : Every things can not stay in the same conditions. In order to foresee the immediate or long future, it is the best way to examine the past things in detail like the time of writing academic papers. However, my speciality is endodontics and laser treatment. So, the subject about the problems in the present dentistry and future outlook was very difficult for me to write for a short time. First of all, I tried to strictly express my opinion about past and present of social, education, researches, treatments and then the outlook was discussed in short. In addition to the above matters as concerns our dental association, although I think a little bit to say too much, I said my opinion about the Japan Dental Association, the government health insurance system, dental hygienists, technicians, and companies. Finally, I like to express that there was no enough time and pages to write the full paper about this very wide and complicated problems in dentistry. I ask you to review about these matters in detail by yourself looking into and criticizing my paper. I think that there is a no problem because my country is managed under the democratic rules.

Abstract : Many mechanical preparation systems have been developed for greater speed and efficiency of treatment. However, in engine driven mechanical preparation, the operator loses most of his tactile sense, and it is hard to know the exact location of the file tip during the preparation procedures. As a result, precise preparation of the apical portion of the canal has been difficult, and the danger of the destruction of the apical constriction has always been present.

 Recently developed nickel-titanium files have been reported as being safe to use with a rotary motion because of their superelastic property. However, nickel-titanium files seem to be easily broken when they are used with an engine driven rotary motion.

 To avoid these disadvantages of engine-driven preparation and nickel-titanium files, we have developed a new handpiece (the TriAuto ZX, J. Morita MFG. Co., Kyoto) which electronically monitors the location of the file tip and the torque applied to the file during all instrumentation procedures.

 The TriAuto ZX has three automatic mechanisms.

1. Auto-start-stop mechanism

 The file starts to rotate when it is inserted in the canal. Without this mechanism, the operator has to push the main switch to start the rotation for each file change.

 The file stops rotating when it is removed from the canal. This function facilitates changing files and reduces battery consumption.

2. Auto-torque-reverse mechanism

 If there is too much torque, the file reverses its rotation. This mechanism has been developed to reduce file breakage. It also prevents tight locking of the file to the root canal.

3. Auto-apical-reverse mechanism

 When a file tip reaches the immediate vicinity of the apical constriction, the file reverses its rotation. This mechanism has been developed to avoid overinstrumentation.

 Appropriate techniques should be developed to minimize the danger of nickel-titanium file breakage when using our handpiece. Those are ; how to move the handpiece, how to advance a file down the canal, how much force we should load apically, what kind of file sequences (size and taper) we should take, etc.

 Also, it might not be correct to claim that all the instrumentation procedures should be prepared with our handpiece. Simultaneous use of a hand instrumentation depending upon the morphology and the difficulty of the root canal may be a better way to get a good result.

Abstract : Sterilization of turbines and engine handpieces is very important for infection control in a dental office, but when sterilization is performed by an autoclave, they become useless for our work, because when we use them in the mouth, particles of the scraped teeth, saliva and blood stick to the ball bearing of the turbines or the engine handpieces which become hard when heated in an autoclave, hindering their good functions. That is why we must take all the necessary steps before and after the dental cutting apparatus are sterilized by autoclave. 1. Temperature 2. Cleansing 3. Lubricant 4. Wrapping, these steps followed correctly will keep out dental cutting apparatus in good function for the long.

Abstract : In this study, the morphological changes of the hard tissue structure after Hol : YAG laser ablation were investigated by a macroscope and an electron scanning microscope. The apices of extracted human teeth were resected by the way of apicoectomy. The holes for examining the effectiveness to the bone tissue were made on the buccal surface of the rabbit’s mandibula using Hol : YAG laser. The average setting conditions of the laser were approximately 1.0 J and 10 pulse/sec. Under the copious water flow, this experiment was carried out. Consequently, macroscopic and scanning electron microscopic inspection showed some degree of thermal damage after Hol : YAG laser ablation. Although Hol : YAG laser ablation produced some signs of thermal damage, we think that the characteristics of this laser system provide certain advantages for special clinical indications (e. g. arthroscopic surgery) because of its fine fibers.

Abstract : The effects of argon laser irradiation on the permeability and structural changes of the root canal walls were investigated in vitro. Thirty extracted human single-rooted teeth were randomly assigned to three groups. Group 1 teeth were prepared conventionally but not lased. Group 2 teeth after conventional preparation, received four 15s duration laser exposures for total exposure of 60s/canal. Group 3 specimens, after conventional preparation, the root canal walls were treated by 38% Ag(NH₃)₂F for 10s, and then lased as the group 2 teeth. Laser parameters were set at 1 w, 5 Hz ; using simultaneous water coolant spray. The external surfaces of the teeth were sealed with nail vanish, and placed in 0.6% Rhodamin B solution for 48 hr. The teeth were then sectioned for study by stereomicroscope and SEM. Statistical analysis showed there was no significant difference of dye penetration between the groups (P<0.05). SEM examination showed that the argon laser-treated root surfaces (group 2) were partially recrystallized with open dentinal tubules and minor debris. The root canal surfaces of argon laser irradiation with 38% Ag(NH₃)₂F (group 3) revealed fusion and melting, numerous small particles, and generally free of smear layer ; open dentinal tubules in some melted parts were also visible.

Abstract : The effective shaping of root canal wall with following the tortuous canal is very important. Therefore, many new instruments and machines have been developed up to now.

 The purpose of this study was to observe the morphological changes of the canal wall after instrumentation with conventional stainless steel files and nickel-titanium files that come to be used recently and furthermore to investigate the possibility of the enlargement with Argon Laser irradiation. 44 extracted maxillary molars were instrumented by Mac File (NiTi Co.) and K File (Kerr Co.) with alternative irrigation of 8% NaOCl and 3% H₂O₂. Argon Laser (λ=514 nm, 1W or 2W, CW : HGM Co.) was irradiated on the root canal wall with fiber. The morphological changes of the canal wall was observed by a stereomicroscope and a scanning electric microscope after making the vertical slice. The scores of debris were statistically evaluated using the Mann-Whitney U test.

 We observed that there was no remarkable difference between the morphological changes of the canal wall after instrumented with NiTi files and those of SS files. However, NiTi files removed more efficiently intracanal debris than SS files. And Argon Laser irradiation accelerated to remove intracanal debris effectively.

Abstract : Not only from such modern sciences and technologies as myophysiological dynamics, geophysics, environmental science, energy-saving technology and Human Factor’s Engineering viewpoints, but also from our traditional art and cultural heritage point of view, an ultimate Reaming Maneuver was sought out and discussed by this second article in this series.

 Attempts were made to clarify following topics :

 1) Hand Reamer’s Grips were classified into three main types and two of which were further subclassified, and short but suitable nomenclatures were tentatively given to each type for the convenience of the readers to make more accurate and precise explanations and discussions possible in this series hereinafter.

 2) The root and origin of the Hand Reamer was hunted after among our traditional hand tools and instruments which are still in popular use today. Simple, natural, and routine usage of the original tool offers a good hint to deduce the most natural and rational Reamer’s Grip and the most logical and efficient Reaming Maneuver to the treatment region concerned

 3) (a) The operator’s (Endodontist’s) best Home Position

   (b) The least stress affected and the best balanced and the stablest patient’s posture during treatment

   (c) The most rational posture-position interrelationships between operator (Endodontist) vs patient during treatment

   Those three important topics (a), (b), (c) were clearly commented and courteously discussed by Dr. Daryl R. Beach’s excellent logical F₁, F₂, F₃ concept.

 4) The above mentioned topics 1), 2), 3) and how to perform an ideal Reaming Maneuver into the Maxillary Anterior Teeth Root Canals with the best Reamer’s Grip under the most logical and rational F₁-F₂-F₃ interrelationships were displayed by fifteen clear, concrete and didactic Illustrations.

 Before closing, a New Vogue Phrase “Reaming Manner” made her first debut in the Endodontic Society. Hope she may add a decent flaver and exquisiteness to the Society !

Abstract : The purposes of this study were to observe the morphological changes after Er : YAG laser irradiation and to evaluate the possibility of clinical application by this laser. Twenty-eight extracted humam straight canal and single-rooted teeth showing no clinical sign of caries, were used for this research. All teeth were accessed coronally and instrumented up to #50 K-file using conventional methods. The specimens were bisected longitudinally and irradiated with Er : YAG laser at the following parameters ; a pulse energy of 400 mJ, a repetition rate of 6 Hz, and irradiation times of 1, 2, and 4 sec. Samples were observed using stereomicroscope, light microscope, and scanning electron microscope. No carbonization and crack were observed in any samples regardless of irradiation time using stereomicroscope. In light microscope evaluation, root canal preparation with Er : YAG laser could be observed. Multi-layer structure was visible on laser irradiation site in scanning electron micrograph. These results suggest that Er : YAG laser is applicable to root canal treatment.

Abstract : This study was performed to observe radiographically the condition of the root canal filling, the resorption of the deciduous tooth root and two filling materials, and the eruption of the permanent tooth during the period from 2 weeks to 10 weeks after treatment.

 The teeth used in this study were deciduous molars (12 teeth, 24 root canals) of 3 infant dogs (Siberian hasky). The experimental teeth (6 teeth, 12 root canals) were examined after immediate root canal filling. The healthy teeth of the opposite side (6 teeth, 12 root canals) were used as the controls.

 The root canal filling materials used in this study were Canals N and GPsealer. The results were summarized as follows. There were no significant differences between the conditions of two root canal fillings in radiographs taken immediately after root canal filling.

 The root tissues was slightly resorbed on the entire root surface, but the root filling materials were slightly resorbed at the apical protion. The resorption of root tissues was observed at both the tooth germ side and the opposite side. The eruption of permanent successors was slightly delayed in experimental side as compared with control side.

 It was found the periapical lesions around root apex from 2 weeks after over-filling with Canals N. And, buccal fistura were observed in the teeth filled with GPsealer, from 6 weeks after root filling.

Abstract : The root canal filling is performed as the terminal treatment in the endodontics and the root canal filling material must be X-ray opaque. The reason is that the precise packing of the root canal material in the root canal is comfirmed by the film of the X-ray photograph.

 Therefore, it is prescribed that the opaqueness of the root canal filling material to the X-ray to measure by the photographic densitometer in the ISO-6877 (First edition 1995-06-01) standard.

 Then, the authors have measured the root canal filling material on the market according to the standard and the results will be reported.

Abstract : In dental treatment, tooth particles, microbes, saliva and blood expelled during tooth cutting procedures can cause the hazards of infection to patients and to members of the medical staff. An extraoral dental suction system is often used as a method of eliminating sources of infection during tooth cutting.

 In order to investigate the effectiveness of the extraoral dental suction system in reducing the risk of infection, we implemented the system during treatment in a clean booth ; i. e. we treated some patients requiring tooth cutting with the extraoral dental suction system, thus employing the microbe and ground particles removing capabilities in the patient’s oral cavity ; Bacillus sibtilis spores were sprayed experimentally with an atomizer in the same clean booth.

 Excellent particle and microbe removing capabilities were observed in the experiment, thus verifying the effectiveness of the system to reduce the hazards of infection.