When using post materials that are more rigid than teeth for abutment construction, tooth root fracture may be caused by stress concentration in the remaining part of the tooth root. Most of the tooth root fractures clinically observed in metal post abutment cases are longitudinal fractures, resulting in tooth extraction in many cases. In cases with sufficient coronal tooth substance, post-less abutment construction has recently been considered. Fiber posts have recently attracted attention as a post material for resin abutment construction due to their flexibility with elastic modulus similar to that of dentine. In Japan, although approval by the Ministry of Health, Labour and Welfare has recently been obtained, there have been few experimental studies and clinical reports on fiber posts. In this study, we performed a breakdown test and finite element analysis of fiber posts as in vitro studies, and reviewed overseas references on clinical results. Eexperimental results show that, the effects on preventing stress concentration are high in all abutment construction methods when sufficient ferrule in the remaining teeth is present, and stress may be concentrated in the cervical area in fiber post abutment cases. Clinical results obtained from references showed that, fiber posts are superior to cast posts and commercially available metal posts, in terms of fracture and dislodgment. However, since issues were revealed in previous clinical studies, further comparison studies are necessary to evaluate the superiority of fiber posts compared with metal posts.

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In the scientific meetings of the Japan Prosthodontic Society, many high-level research presenta-tions are given, and yet a large proportion of the presentations have not been published. Since 2002, the Japan Prosthodontic Society has published PRP (Prosthodontic Research & Practice), which is the official English journal of the Society, to introduce scientific data of research in the field of prosthodontics internationally. PRP will be published quarterly from 2006. The editorial committee of the Japan Prosthodontic Society tries to give advice to authors, and to publish the prepublication paper in the PRP journal not as a rejection but as a correction. In order to give members of the Japan Prosthodontic Society a better understanding of the PRP journal, we held a Skills Improvement Seminar for Submitting Articles to the PRP at the 114th scientific meeting (Niigata) and the local branch scientific meetings. This paper summarizes the first half of the seminar and describes the editing work of PRP.

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Over the last decade, research on prosthodontics has progressed and several academic associations and/or societies have been established. The number of journals published by the academic socie-ties hasincreased. Prosthodontic Research & Practice (PRP), an official journal of the Japan Prosthodontic Society, was launched in 2002 and will be published quarterly from 2006. Most of the presentations in the scientific meetings of the Japan Prosthodontic Society have been buried, although the scientific quality and/or clinical values of some of them are relatively high. On the other hand, the reviewers of the scientific journal tend to review critically and severely, to main-tam n the quality of the journal. There are few review systems to improve the quality of the articles. Hence, the editorial board tries to make comments to improve the quality of submitted articles. This paper summarizes ‘How to prepare scientific papers in English’ as presented in the ‘PRP Skills Improvement Seminar’ at the 114th Scientific Meeting of the Japan Prosthodontic Society (Niigata).

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Purpose: This in vitro study investigated the use of short posts for fiber post and composite resin core restorations.
Methods: A replica of a human maxillary central incisor was prepared from bovine teeth using the CELAY system (MIKRONA, Switzerland). Specimens consisted of three different post lengths (2, 5, 8mm) and three types of remaining coronal tooth structure (0, 0.5, 1mm). The failure load and failure mode in the fiber post and composite resin core and cast metal post and core restorations were compared.
Results: There was no significant difference in failure load between both post and core methods with 1mm of remaining coronal tooth structure. Therefore, shorter posts may be used in this condition. High failure loads were recorded with 5 and 8mm post lengths that had 0mm of remaining coronal tooth structure in cast metal post and core restorations. However, there was no significant difference in failure load with any post length in fiber post and composite resin core restoration. A high failure load was recorded with 5mm and 8mm post lengths that had 0.5mm of remaining coronal tooth structure. A long post may be required in cases with less coronal tooth structure. The failure mode was repairable for fiber posts with 0mm of remaining coronal tooth structure. However, the failure mode was impossible to repair in those that had 0.5mm, 1mm of remaining coronal tooth structure.
Conclusion: This in vitro study suggested that short post lengths would be adequate for fiber post and composite resin core restorations. However, the failure mode may be impossible to repair when using a fiber post.

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Purpose: This study investigated the effect of the position of reinforcement wires, differences in artificial teeth, and framework designs on the breaking strength of overdentures.
Methods: The basal surfaces of composite resin teeth and acrylic resin teeth were removed using a carbide bur. A reinforcement wire or a wrought palatal bar was embedded near the occlusal surface or basal surface. Four types of framework structures were designed: conventional skeleton (skeleton), housing with skeleton (housing), housing plus short metal backing (metal backing), and housing plus long metal backing (double structure). After the wires, bars, and frameworks were sand-blasted with 50μm Al₂0₃ powder, they were primed with a metal primer and embedded in a heat-polymerized denture base resin. The breaking strengths (N) and maximum stiffness (N/mm) of two-week aged (37deg;C) specimens were measured using a bending test (n=8). All data obtained at a crosshead speed of 2.0mm/min were analyzed by ANOVA/Tukey's test (α=0.01).
Results: There were no statistical differences between the two kinds of artificial teeth (p>0.01). The wrought palatal bar had significantly higher strength than the reinforcement wire (p<0.01). Greater strengths were found for specimens with frameworks than those without frameworks (p<0.01). The breaking strength of the wrought palatal bar embedded near the occlusal surface was higher than that on the basal surface (p>0.01). The breaking strength and maximum stiffness of the double structure framework were significantly greater (p<0.01) than those of the conventional frameworks.
Conclusion: The breaking strengths of overdentures were influenced by the size and position of the reinforcement wires. Double structure frameworks are recommended for overdentures to promote a longterm prognosis without denture breakage.

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Purpose: To consider changes in the physical properties of mouthguard materials with the change of temperature, shock-absorbing examination and Shore hardness measurement of existing MG materials and other elastic materials were carried out.
Methods: Both examinations were done under two temperature conditions: at room temperature (25deg;C) and simulated intraoral temperature (37deg;C). In addition, a comparative study of the relation between Shore hardness and shock absorption of the materials was made. A self-made drop impact machine was used for the shock-absorbing examination. The thickness of a sample was assumed to be 3mm. The loading was applied by dropping 3 kinds of steel ball, ∅ 10mm (4.0g), ∅ 15mm (13.7g), and ∅ 20mm (32.6g) from a height of 60cm. The shock absorption of all materials was compared by the maximum impact force. Shore hardness was measured based on the JIS standard.
Results: The shock absorption of each material showed a different tendency depending on the loading condition. Furthermore, the shock absorption of the same material showed different results depending on the temperature condition. Shore hardness measurements tended to show low values with the condition of 37deg;C for all materials.
Conclusion: From the relation between shock absorption and Shore hardness, it was confirmed that there is a correlation between hardness and the maximum impact force in the materials that showed shock absorption by elastic deformation. Some materials showed high shock absorption compared with existing MG materials.

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Purpose: A jaw motion tracking device that measures six degrees of freedom has recently been developed. Understanding jaw motion is useful, but previous measurement methods were impractical for use in dental clinics. The overall aim of this study was to demonstrate the simple operation, low cost, and high precision of a recently developed jaw tracking device. In addition, this study explored its potential clinical applications.
Methods: In this study, we compared two jaw motion tracking devices: a digital system type of device and an optical type of device. First we established a baseline occlusal plane from which to measure jaw motion in the same subject with both devices. The jaw motion signals were sampled at a frequency of 100 Hz. The subjects were three healthy women (mean age ± SD = 26.3 ± 1.2 years) who were recruited from among the crown-and-bridge faculty of Tsurumi University of Dentistry. The jaw motions measured were open-close movement, sagittal border movement, and frontal border movement. In addition, the kinematic axis point was calculated from the sagittal border movement. Data from the digital system type of device and data from the optical device were compared. The data were selected to measure rotation and translocation, i.e. jaw position about protrusion, both laterotrusion and maximal opening of the mouth.
Results: The root mean square (RMS) error of position measurement was 0.163 mm with MM-JI-E and 0.178 mm with the optical type of device. The RMS error of jaw motion measurement with the optical type of device was maximum at 0.8mm and minimum at 0.1mm. This was similar to that with digital system type of jaw motion tracking device.
Conclusion: This study showed the possibility of developing clinical applications for this jaw motion device.

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Purpose: Various methods of evaluating the ability of mastication have been reported, most of which involve evaluating of the ability to comminute foods. In this study, a new method of evaluating the ability of mastication focusing on bolus formation was applied to denture wearers.
Methods: One hundred and twenty-five subjects (71 males and 54 females) using removable dentures and receiving follow-up in the Niigata University Hospital were selected. This group was categorized by Eichner's classification, and investigated for the effect of prosthetic treatment by counting the number of chewing strokes until the first swallow of rice crackers.
Results: It was clarified that the number of chewing strokes until the first swallow counted by visual observation agreed well with the number of chewing strokes counted by electromyogram wave of masseter muscle, laryngeal motion, and swallowing sound, as a preparatory experiment. Using the method of counting chewing strokes by visual observation, the effect of prosthetic treatment was evaluated, and the results were as follows. 1) There is a significant difference in the number of chewing strokes without dentures between the Eichner A group, B group, and C group. 2) There was no significant difference in the number of chewing strokes with dentures among the three groups. 3) A significant decrease in the number of chewing strokes was proven by the use of removable dentures. 4) Both the improvement rate of chewing strokes (the ratio of the number of chewing strokes with dentures until the first swallow to that without dentures) and the difference of chewing strokes increased significantly in the order of Eichner A, B, and C.
Conclusion: It was clarified that the effect of prosthetic treatment can be quantitatively evaluated by counting the chewing strokes of rice cracker. Moreover, it was suggested that the condition of prosthetic treatment can be evaluated by analyzing the improvement rate of chewing strokes.

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Purpose: This study was designed to establish the optimum grinding condition of barrel finishing for cobalt-chromium alloy. Smoothing of the mucosal surface, reduction of labor, and improvement of the working environment were estimated by the application of barrel finishing to cobalt-chromium alloy.
Methods: Tabular test pieces cast in cobalt-chromium alloy whose surface was standardized by waterproof abrasive papers were used in this study with a centrifugal flow barrel finishing machine. The abrasive that was most suitable for the primary polishing was selected, and proper polishing time was then decided by measuring the surface roughness of the test pieces. The abrasive and polishing time for the secondary polishing were decided in the same manner. Finally, the surface texture of the test pieces, which were finished in this condition by the manufacturer's instruction or by the electrolytic polishing method, were compared. Statistic analysis was performed by one-way analysis of variance and the multiple comparison test.
Results: A triangular prism-shape abrasive made of Al₂O₃ and SiO₂ whose one side or height was 6mm was selected for the primary polishing, and the same kind of abrasive with one side or height of 4mm was chosen for the secondary one. The optimum polishing time for the primary polishing and the secondary polishing were 60 minutes and 40 minutes, respectively. The surface roughness of the test pieces that were finished in this condition was significantly smaller than that finished following the manufacturer's indication or that finished by the electrolytic polishing method.
Conclusion: The optimum polishing condition of barrel finishing for cobalt-chromium alloy was established in this study. For the polished surface of cast dentures, polishing by a rotary cutting instrument after barrel finishing in this condition would be needed, as no luster was observed on the finished surface.

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Purpose: The record block for maxillomandibular registration of the denture is absolutely necessary in order to decide the mandibular position. This record block must provide sufficient strength so as not to cause deformation in the oral cavity. It must also fit the alveolar ridge well in order to keep accurate registration. Since most of the conventional materials for this purpose are not sufficient, a new specific light-polymerized resin was experimentally developed for the record base.
Methods: The mechanical strength and suitability of the new material were examined in comparison with a conventional autopolymerizing resin.
Results: 1) The transverse strength was equivalent to that of the autopolymerizing resin. 2) Although the shear bond strength was equivalent to the autopolymerizing resin, the intensity was drastically improved by the application of composite primer. 3) The light-polymerized resin and the autopolymerizing resin did not show any difference in suitability, and it was a clinical value without problem.
Conclusions: From these findings, it was confirmed that the new light-polymerized resin had the physical property for clinical application as a material for the record base.

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Purpose: When patients have their teeth taken care of, oneof their biggest concerns is how long the solution will last. Studies on the longevity or prognosis of bridges published so far have mainly reported on the evaluation of the survival rate for each kind of bridge. We believe that abutments need to be researched more carefully and clinically in the future.
Study selection: A Medline search was conducted, as well as manual searching of bibliographies from relevant articles. Studies reporting the survival rate were selected from the reports mentioning the prognosis of bridges. We mainly reviewed 1) the conditions of abutments before treatments and 2) applicable parameters in each case.
Results: We found no study that mentioned the detailed conditions of abutments before treatment using systematic evaluation parameters. Most parameters concerned the prosthodontics itself and bacteria. Only 21.2% described objective parameters.
Conclusion: This review indicates the necessity for establishing a classification of abutments based on some evidence so that the after-treatment conditions can be predicted from the pre-treatment conditions. It also indicates that we have to consider objective parameters carefully when conducting prospective research on the prognosis of fixed partial dentures or when establishing a new clinical evaluation system.

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Patient: A 70-year-old male patient visited our clinic withthe chief complaint of masticatory dysfunction due to ill-fitting upper and lower partial dentures. Serious periodontal disease was observed around the remaining teeth. The occlusal condition was crossbite due to mandibular protrusion, and the occlusal supporting area was classified as Eichner's B-3. A Konus telescopic denture was selected as a prosthesis.
Discussion: Dealing with the increase in occlusal force, the sagittal and lateral imbalances found using the Dental Prescale Occluzer system allowed us to minimize the damage to the prosthesis and effects on abutment teeth and periodontal tissue.
Conclusion: It is vital to identify and remove early pathological factors of force in postoperative manageme

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Patient: The patient was a 44-year-old woman who presented with masticatory and esthetic problems. She had discoloration of CR filling of a maxillary anterior tooth, marginal discoloration, anterior protrusion, median diastema, and closed bite where the mandibular anterior tooth region occluded with the maxillary alveolar region, tooth 8 elongation and tooth 4 defect. Periodontal and orthodontic treatments were therefore performed for esthetic and functional recovery.
Discussion: After prosthodontic therapy, postoperative management techniques are crucial, including thorough plaque control, use of a retainer to prevent teeth from moving back towards the original positions (Begg technique), muscle function therapy (improving tongue movement patterns and strengthening the lingual and oral sphincter muscles) and occlusal adjustment.
Conclusion: In the present patient, the effectiveness of orthodontic therapy before prosthodontic therapy was reaffirmed: dentine can be preserved, prosthodontic therapy is easier to perform, and therapeutic outcomes are highly predictabel.

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Patient: A patient visited our hospital for fabrication of functional complete dentures to resolve masticatory disturbance. The case was diagnosed as edentulous jaws with inadequate mandibular position and movement. Therefore, new complete dentures were fabricated and set without reference to the old dentures.
Discussion: For the diagnosis, clinical treatment and recall, each objective examination was suggested to be useful.
Conclusion: The patient was satisfied as a result of the improvement of denture base, mandibular position, and mandibular movement after informed consent.

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Patient: A 49-year-old male was referred to our hospital in February 1999, complaining of esthetic problems of a mandibular partial denture and poor retention of a maxillary denture. This case was treated with a Konus mandibular denture for obtaining the patient's esthetic satisfaction.
Discussion: The abutment teeth and dentures have been kept in good condition since the dentures were delivered six years ago. According to panorama x-ray, however, the maxillary alveolar ridge appears to have already started to gradually resorp. Therefore, it is very important to carefully check the symptoms of what is wrong with his teeth, dentures, and alveolar ridge during every visit.
Conclusion: The Konus denture has given the patient a great satisfaction, although the potential symptom of maxillary alveolar ridge resorption exists.

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Patient: A 53-year-old male presented with the chief complaint of masticatory disturbance caused by many teeth missing in the upper and lower jaws. There was extensive attrition on incisors and canines which only had occlusal contact, so the case was diagnosed as overclosure. To improve masticatory disturbance as the chief complaint, removable partial dentures were made after treating the abutment teeth. An adequate vertical dimension was planned in order to restore the worn teeth on the cast, and to arrange artificial teeth in the edentulous area.
Discussion: An anterior teeth core made as an inter-occlusal record was useful and the arrangement of artificial teeth in the edentulous area useful for estimating the adequate vertical dimension.
Conclusion: It is important to diagnose an adequate vertical dimension by creating acast of the original tooth form in the case of prosthetic treatment of severely worn teeth.

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Patient: A 70-year-old man. Eczema of the palm (Pustulosis palmaris et plantaris). A positive response to chromium was identified by a dermatological patch test. Metal elements used in his dental restorations were analyzed by non-destructive metal element analysis, and chromium was identified only in the porcelain-fused-to-metal crowns restored in his maxillary central and lateral incisors and canines. Resin facing crowns made of a gold, silver and palladium alloy were installed after those crowns were removed.
Discussion: With all of the interviews performed with this patient, identification of the allergenic restoration in his mouth was difficult. For this kind of metal allergy patient, a combination of metal element analysis of intra-oral restorations with a dermatological patch test seems to be very useful.
Conclusion: This patient' s allergic symptoms were ameliorated with minimal selective removal of his intra-oral metal restorations by non-destructive, intra-oral metal element analysis.

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Patient: A 77-year-old male who had been treated with an upper left maxilla resection for a malignant carcinoma was having difficulty eating with the unstable denture due to a defective jaw. Since dentures made by the ordinary method cannot be fixed firmly to the upper jaw, the functional impression technique was used to produce dentures for the defected jaw.
Discussion: The patient was satisfied with his new dentures, which enabled him to masticate as the denture were placed in the jaw properly, with an improved fit between the dentures and oral mucosa.
Conclusion: It is concluded that the functional impression technique of taking an impression is one of the most useful methods for producing dentures for defective jaws.

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Patient: A 23-year-old female was seen with a major complaint involving problems of esthetic and masticatory function, since her posterior teeth had collapsed due to enamel hypocalcification. Radiographic examination suggested that many teeth were affected by periodontitis apicalis.
Discussion: Combined periodontal and prosthetic treatments including a crown lengthening procedure enabled us to fabricate esthetic and functional restorations.
Conclusion: The crown lengthening procedure sometimes involves the loss of alveolar bone. In this case, however, the treatments were successful owing to the sufficient volume of bone available. As a result, the prosthesis achieved optimal plaque control. This clinical report describes the effectiveness of the periodontal and prosthetic treatments for enamel hypocalcification.

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Patient: A 54-year-old female patient visited our dental office July 1997. The patient's chief complaint was difficulty of chewing due to loss of the right mandibular molars. She had a collapsed occlusal plane with loss extended over a long period of time. This case report describes restoration of the occlusal plane and occlusal supporting area by fixed prosthesis including implant-supported crowns.
Discussion: Anterior guidance and provisional restoration are useful for reconstruction of the occlusal plane. In a dental arch with implant-supported and tooth-supported crowns, periodical dental checkup and occlusal equilibration are very important due to the existence of biomechanically different factors.
Conclusion: The patient was very satisfied with the fixed prosthesis including implant-supported crowns. It is thought that implant treatment improves the quality of life of free-end partially edentulous patients.

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Patient: A 24-year-old female patient visited our dental office with esthetic complaint. Implantsupported fixed prostheses were placed on the upper right and left side canine area. The cusps of bone anchored crowns were made to contact with the lower canine cusps during mandibular translation. The patient was followed for 5 years with no surgical or prosthetic complications.
Discussion: Stability of the intercuspal position and reduction of lateral force are of importance when providing occlusal contacts for bone-anchored prosthesis in eccentrec relations.
Conclusion: This case offers useful information on occlusal contact for implant-supported prostheses.

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A 57-year-old male patient visited our dental office with complaints of difficulty in chewing and esthetic dissatisfaction. He had collapse of the anterior teeth with labial inclination of the incisors. This case report describes a reconstruction of the occlusal plane and occlusal supporting area by implantsupported and tooth-supported prostheses after periodontal and orthodontic treatment.
Discussion: Improvement of the tooth axis by orthodontic treatment was effective for biomechanical force and establishment of anterior guidance. The implant-supported and tooth-supported prostheses led long-term preservation of occlusion success.
Conclusion: The implant treatment was effective for reconstruction of the occlusal support area and an as anchor for orthodontic treatment.

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