Partial denture methods have long been applied as typical prosthetics of missing teeth.
In this regard, abutment devices have much clinical potential. However, on the occasion of new abutment device introduction, although clinicians have big expectations, clinical results have been unsatisfactory.
On reason for this may be that applied results have not been analyzed sufficiently thoroughly.
Clinicians follow standard decision-making processes when planning treatment for missing teeth, including choice of abutment.
As a matter of course, the abutment device must be chosen based on correct diagnosis-treatment planning.
This article proposes a strategy focusing on a background of diagnosis for prosthetic of missing teeth and selection rule of abutment device.

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Endodontics has been changing drastically in the last decade. Modern endodontics using microscope, Ni-Ti files, ultrasonic tips, microinstruments and cone beam CT has enabled predictable outcomes. In this article, the benefits of modern endodontics, successful techniques of conventional endodontics and surgical endodontics, are introduced.
Survival rate of endodontically treated teeth is >90%. Many studies have indicated that there is no difference of long-term prognosis between endodontically treated teeth and single-tooth implants. Clinical decision should not be determined by the survival rate of endodontically treated teeth and single-tooth implants.
Modern endodontic surgery is performed under illumination and magnification using special microinstruments. Success rate of modern endodontic surgery is higher than that of traditional endodontic surgery. No scar and little recession on the gingival margin are observed after modern endodontic surgery because of use of thin blade and fine suture.
Coronal leakage may occur due to unsatisfactory coronal restorations. Outcomes of endodontically treated teeth were influenced by the quality of restorations.
Perforation repair was done successfully using internal matrix technique and mineral trioxide aggregate. Many teeth that had been extracted were saved by this repair technique.
Endodontists can save teeth using the technique of modern endodontics. Dentists should save significantly more teeth by these modern techniques.

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Purpose: This study investigated the acid-resistance effect of CO₂ laser irradiation and dental fluoride solution on dentin surfaces.
Methods: Cubic dentin specimens were cut or trimmed from extracted human molars and were divided into two groups for laser irradiation with and without applying fluoride solution. Each sample was subjected to 2 ml of pH standard solution (pH 4). The concentration of dissolved Ca²⁺ in each solution was determined by an atomic absorption spectrophotometer and the morphological changes of the dentin surface were investigated by a scanning electron microscope and surface roughness profilometer.
Results: After the soaking test, the concentration of dissolved Ca²⁺ was significantly lowered by CO₂ laser irradiation, but the concentration was almost the same as that of the control with repeated soaking. Laser irradiation after applying fluoride solution significantly decreased the Ca⁺ concentration as compared to other conditions.
Conclusion: The results suggested that CO₂ laser irradiation of dentin enhances its acid resistance, and that CO₂ laser irradiation with dental fluoride solution is more effective.

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Purpose: The aim of this study was to examine the influence of the preparing condition of the working cast and mouthguard sheet on the thickness of mouthguard.
Methods: We used a mouthguard sheet (127 × 127 × 3.8 mm). The sheets were formed by a vacuum former when they were heated until they were hung 1.5 cm from baseline. The thickness of the mouthguard sheet was measured at the part fitted to anterior and posterior teeth. As the preparing conditions of the working cast, relations among the measurement point, setting position, and temperature of the working cast as well as among measurement point, setting position, and angle of the working cast were analyzed by Three-way ANOVA. As the condition of the mouthguard sheet, the relation between the measurement point and temperature of the sheet was analyzed by Two-way ANOVA.
Results: The thickness at anterior teeth became bigger at the condition that the working cast was set in the posterior position, and that of posterior teeth became bigger at the condition that the working cast was set in the center position. The thickness at anterior and posterior teeth became bigger at the condition that the angle of the working cast was set 80°. The thickness at anterior teeth became bigger when the temperature of the mouthguard sheet was high.
Conclusions: These results suggest that the thickness of the mouthguard could be maximized when the position of the part of the working cast that need to keep the thickness was set in the center, the angle of the working cast was set to 80°, and the temperature of the mouthguard sheet was high.

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Purpose: The purpose of this research was to establish the standard value of the inclination of anterior guidance during lateral excursion.
Methods: Previously reported excursion data (29 males; 9 females; age, 23.31 years) were re-analyzed. The standardized rotation angle around the kinematic axis defined as the rotation angle around the kinematic axis per unit displacement (1 mm) of the incisal point during excursion was calculated. Moreover, the difference of inclination between incisal and condylar paths was calculated. Then, the relation between the standardized rotation angle of the kinematic axis and the difference of inclination between incisal and condylar paths was analyzed statistically (SPSS15.0J, SPSS Inc.).
Results: First, the correlation coefficient between the standardized rotation angle of the kinematic axis and the difference between the actual inclinations of the incisal path and the balancing side condylar path during lateral excursion was r = 0.84 (P < 0.001, Pearson's correlation coefficient). The relation between the inclination of the incisal path and the balancing side condylar path was as follows: inclination of incisal path = inclination of balancing side condylar path –5° ± 9.5° (reference: Camper plane). Second, computer simulation revealed that the standard value of inclination of anterior guidance during lateral excursion could be achieved with the following articulator settings: Sagittal incisal table angle = inclination of balancing side condylar path +5°; lateral incisal table angle = 15° ± 13°.
Conclusion: The standard value of inclination of anterior guidance during lateral excursion and the settings of articulator for it were clarified.

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Purpose: The most appropriate way to form the thermoplastic hard resin made of the PET for oral appliance (PRT-sheet) has not been established yet. This study aimed to determine the most suitable temperature to form a PET-sheet to obtain optimal fit.
Method: PET-sheet (125×125×1.5 mm) was heated at each 10°C increment between 120°C and 160°C on the plaster model (M-Model) and given pressure immediately thereafter until the sheet temperature became 50°C. The trial temperature depended on the static load examination (load: 400 gf). Plaster was poured into the mold (sheet taken off), and that which hardened was taken out (W-Model). Images of M-Model and W-Model were obtained by flatbed scanner, and superimposed. The distance between the formed PET-sheet and the plaster model was evaluated for the fit using image analytic software.
Results: In the outside-center group (O-C) and outside-edge group (O-E), the gap became shorter with higher softening temperature, whereas in the inside-center group (I-C), the gap became longer. The gap was not different in the inside-edge group (I-E). There was no difference between C-E and O-C. However, the gap in the edge was significantly longer than that in the center (p<0.05).
Conclusion: The most suitable temperature to form PET-sheets for obtaining maximum fit is in the range 130–150°C with consideration of their ductility with heat.

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Purpose: During the Great Hanshin-Awaji Earthquake, denture loss was one of the serious problems that many elderly disaster victims encountered. A simple and effective denture fabrication procedure for these patients is reported and discussed in relation to the properties of this large-scale disaster.
Materials and Methods: Snap impression was taken as a final impression using irreversible hydrocolloid impression material. Base plate was made on the cast using self-curing acrylic resin. Joint artificial teeth were directly arranged on the base plate in the mouth. After artificial teeth arrangement, self-curing resin, which was mixed to show low viscosity, was poured on the surface of the base plate around the teeth directly to mold the polished surface. Finally, tissue conditioner was applied to the mucosal surface of the denture prosthesis.
Discussion: The denture prosthesis fabricated according to this procedure would not be suitable for long-term use. However, it was designed to minimize fabrication time at the disaster site using conventional dental materials only and also to minimize the possible necessity of denture adjustment after insertion.
Conclusions: This technique enables a handy, efficient denture fabrication at a large-scale disaster. After the whole experience of our rescue activity, it was suggested that denture fabrication at disaster sites should be selected according to the features and properties of the district and the type of disaster.

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Patient: A 15-year-old female complained of swelling and pain from the mental region to the left side of the mandible. The pathological diagnosis was ameloblastoma. The tumor, anterior teeth, and left canine on the lower jaw were extirpated. Since the missing part of the mandible was large, autogenous bone from the ilium was grafted therein. Following this, implants were inserted and implant-supported fixed prostheses placed theron.
Discussion: Bone graft for the missing part of the mandible and dental implants improved the patient's QOL both esthetically and functionally. Inflammation of the soft tissue and resorption of bone around the implants were scarcely observed and the prostheses showed no complications.
Conclusion: Autogenous bone grafts and dental implants for missing parts of the mandible after extirpation of ameloblastoma can provide esthetic and functional improvement, and are useful to obtain a satisfactory prognosis.

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Patient: A 65-year-old female presented to us with discomfort in the mucosa of the cheek. Based on biopsy results, the condition was diagnosed as lichen planus by our hospital dental surgery staff. The patient was referred to our department for treatment because of suspicion of metal allergy. The symptoms improved following a metal-free restoration.
Conclusion: The cause of lichen planus in this case was thought dental metal allergy, which was relieved by a metal-free restoration.

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Patient: The patient was a 78-year-old female who complained of difficulty of mastication at first dental examination. A bridge restoration was attached, but dental caries and periodontitis were seen with the dental articulation collapsed and advanced fluctuation. Therefore oral rehabilitation with applied Cone-crown Telescope was done. During 5-year follow-up, her prosthesis presented no problems.
Discussion: By the above prosthesis attachment, the secondary fixation effect, prevention of Occlusal-trauma by bite-plane continuity using rigid support, could prevent periodontal disease with sanitary prosthesis.
Conclusion: Occlusal reconstruction with Cone-crown Telescope therapy is a useful method that allows biting-force support mainly by periodontal ligament, and facilitates plaque control.

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Patient: A 40-year-old female was referred to us for prosthetic treatment after removal of a failed implant and abutment tooth. Bilateral missing molar teeth in mandible were treated by removable partial denture (RPD) with a metal framework, proximal plates and a magnetic attachment.
Consideration: Application of rigid support concept and magnetic attachment provided favorable prosthetic treatment with good patient satisfaction. Two years after insertion of the RPD, one of the abutments was extracted due to a root fracture, even though stability of the RPD was maintained after the denture repair by adding a tooth.
Conclusion: Bilateral distal extension metal-base denture was fabricated for a female patient who had a failed implant supported bridge. Consideration of esthetics and denture stability improved oral function and social activity.

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Patient: The patient was a 54-year-old male who had undergone maxillary resection. At the time of initial examination, the maxillary defect extended to both the hard and soft palate and had perforated the nasal cavity. Therefore there were serious mastication, speech, and swallowing disorders. A maxillofacial prosthesis with magnetic attachments was fabricated for oral rehabilitation.
Discussion: Generally, the load to abutment teeth of maxillofacial prosthesis is larger than that of conventional removable partial dentures. In this case, the magnetic attachments placed in the prosthesis may well have contributed to long-term good prognosis.
Conclusion: Fabrication of maxillofacial prosthesis including magnetic attachments is an effective means to restore oral function in patients with maxillary resection.

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Patient: The patient had difficulty in chewing and swallowing, and had an esthetic dissatisfaction after maxillo-mandibular reconstruction with a rectus abdominis free flap for squamous cell carcinoma of the right buccal mucosa. The maxillofacial prostheses using milling and Riegel telescopic method were fabricated after insertion of interim dentures at the same time as the maxillo-mandibular alveoloplasty so as to make a denture space.
Discussion: It was thought that an early wearing of maxillary and mandibular interim dentures contributed to early making a denture space, and enabled the fabrication of rigid connected maxillofacial prostheses using residual teeth.
Conclusion: Prosthetically driven treatment using alveoloplasty is effective for the treatment of patients with maxillary or mandibular reconstructions.

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Patient: A 61-year-old man complained of masticatory disturbance caused by loss of occlusal support and attrition in molar areas. Since the cause of disturbance was considered infraocclusion, occlusal vertical dimension was increased by insertion of occlusal splint-type treatment denture that covered occlusal surfaces of the remaining teeth and functional recovery was observed. Finally, a definitive denture was fabricated, which was supported by onlay-type rests on the worn occlusal surfaces of abutment teeth.
Discussion: Former vertical dimension was modified by insertion of the treatment denture, and based on it, final vertical dimension and design of the definitive dentures were determined. These steps facilitated good convalescence and satisfaction of the patient with the definitive denture. Tooth preparation for the bridges was able to be avoided by applying the onlay type rest.
Conclusion: Use of occlusal splint-type treatment dentures and application of onlay-type rest resolved the chief complaint regarding masticatory disturbance.

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