Prosthodontics is a practical science based on life sciences and health sciences, and takes a role to contribute to the improvement of people's health and welfares. It is true the main field of prosthodontics and/or prosthodontic treatments is oral rehabilitation including recoveries of morphological defects and the functional disability caused by teeth loss. From this point of view, I am sure that the ultimate target of prosthodontics and/or prosthodontic treatments is maintenance and improvement of patient's QOL. To achieve this purpose, I think research, education, and clinical practice to be inseparable and integral in prosthodontics. This ensures that prosthodontics become more academic which can contribute to the society more greatly.
Advertisement disclosure of “Prosthodontic Specialist certified by Japan Prosthodontic Society” is our earnest wish. The specialist system is regarded to be effective for the improvement of the medical treatment level, the information provision to the patient, and the promotion of cooperation hospital and clinic. On the other hand, the high quality treatments are severely requested and the specialists are strictly evaluated by the many people more than before. We have to be aware of our responsibility as Prosthodontic Specialists.
In addition, Japan Prosthodontic Society is a corporate judicial person, and there is obligation and a responsibility that transmit necessary information to the society certainly and promptly, and present various proposals based on EBM as the opinion leader. Concretely, it is necessary to promote basic researches as well as clinical researches on prosthodontic treatments, and to examine the improvement of educational methods of prosthodontics.
Let's reconfirm the purpose of our Society written in the article of incorporation and make an effort to achieve this purpose!

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Purpose: In the last two decades, the Shortened Dental Arch (SDA) concept has been introduced as a treatment strategy for posterior edentulous patients. This study investigated whether the SDA concept applies to all posterior edentulous patients.
Study selection & Results: In the first study, objective evaluations for the temporomandibular joint (radiographic evaluation and measurement of condylar positioning during maximal voluntary contraction) were performed in patients with unilaterally posterior missing teeth. Abnormal condylar appearances were observed in 73% of subjects by radiographic evaluation and these phenomena coincided with edentulous-side in 55% of them. Condylar positioning during clenching was significantly larger on the edentulous-side compared to that in the dentulous-side.
In the second study, we investigated the mandibular positioning during maximal voluntary contraction related to simulated loss of posterior occlusal supports in volunteers with natural dentitions. A greater bilateral loss of posterior occlusal support was associated with increased distances of positioning of both condyles. Moreover, subjects could be divided into two groups depending on the condylar mobility following reduced occlusal support. In the first group, the distance of condylar positioning significantly increased by cutting the splint sequentially from the posterior toward the anterior side. On the other hand, in the second group, no significant difference was observed between the distances measured under all the experimental occlusal conditions.
In the supplemental study, a significant negative correlation was observed between the sagittal condylar guide inclination and the distance of ipsilateral condylar positioning. This result suggests that the steepness of the articular eminence is an important factor in condylar positioning during clenching. Conclusion: We propose that clinical guidelines should be developed for determining whether to adopt a “Wait and See” approach for SDA patients without any proactive treatment, or to start prosthetic intervention immediately.

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Reports supporting the shortened dental arch concepts showed that the SDAs were stable in occlusion and TMJ for several years, and that effects of partial dentures on distal extension edentulous patients were unclear. However some studies are difficult to understand their conclusions after careful reviewing. Our data of 921 subjects demonstrated the prevalence of SDA, percentage of denture wearers in distal extension missing patients, and comparisons of occlusal force and masticatory performance between denture wearers and non-wearers (SDAs). To clarify the effect of prostheses, longitudinal studies or randomized controlled trials on oral function must be needed in further investigation.

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The aim of this multi-center study was to explore the relationship between missing occlusal units and oral health-related quality of life (OHRQoL) in subjects with the shortened dental arches (SDAs). Subjects with SDAs were recruited consecutively for one month from six university-based prosthodontic clinics. In total, 115 SDA subjects participated (mean age, 58.5± 10.0yrs; 71% female). The location and number of missing teeth were examined and the number of missing occlusal units was calculated. To evaluate OHRQoL, the Japanese version of the Oral Health Impact Profile (OHIP-J) was administered and the summary score of OHIP-J was calculated. The SDA subjects were categorized depending upon the anterior-posterior lengths of the missing or remaining occlusal units. Regression analyses were performed to investigate 1) the association between missing OU and OHIP-J summary scores and 2) the OHIP-J differences between groups of subjects with various anterior-posterior SDA lengths. The first analyses revealed that one missing OU was significantly related to an increase of 2.1 OHIP-J units (95% CI: 0.6-3.5, P=0.016). The second analysis revealed that subjects who only lost the second molar contact exhibited significantly better OHRQoL than those who lost more teeth (Coefficient: 11.1, 95% CI: 2.8 -19.2, P=0.02). Furthermore a statistically significant group difference was observed between the groups with and without the first molar occlusal contact (Coefficient: 12.8, 95% CI: 1.4 to 24.1, P=0.03). These results suggest that missing occlusal units are related to the OHRQoL impairment in subjects with SDAs. They also suggst that the patterns of missing occlusal units are likely to be related to the OHRQoL impairment in SDA subjects with the presence of first molar contact having an important role.

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For any kind of research, ‘Research Design’ is the most important. The design is used to structure the research, to show how all of the major parts of the research project. It is necessary for all the researchers to begin the research after planning research design for what is the main theme, what is the background and reference, what kind of data is needed, and what kind of analysis is needed. It seems to be a roundabout route, but, in fact, it will be a shortcut.
The research methods must be appropriate to the objectives of the study. Regarding the hypothesistesting research that is the traditional style of the research, the research design based on statistics is undoubtedly necessary considering that the research basically proves ‘a hypothesis’ with data and statistics theory. On the subject of the clinical trial, which is the clinical version of the hypothesis-testing research, the statistical method must be mentioned in a clinical trial planning.
This report describes the basis of the research design for a prosthodontics study.

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Purpose: This study investigated the effects of silanation and adhesive monomer, 10-methacryloyloxydecyl dihydrogen phosphate (MDP), on the bond durability of resin cement to zirconia.
Methods: Two sizes of zirconia disk were prepared. The bonding surfaces of the disks were air-particle abraded with 50μm Al₂O₃, and then bonded with one MDP-containing or three non-MDP-containing cements to fabricate test specimens. For the silanated specimen group, air-particle abraded surfaces were treated with respective silane coupling agents, including two MDP-containing or two non-MDP-containing agents, before the bonding procedure. Five test specimens for each group were subjected to thermocycles before shear bond strengths were determined. The data were statistically analyzed.
Results: For test groups without silanation, the specimens bonded with MDP-containing resin cement showed significantly higher bond strength. In contrast, all specimens bonded with non-MDP-containing resin cements failed during the thermo-cycling process. For the silanated groups, the specimens pretreated with MDP-containing silane coupling agent and bonded with non-MDP-containing resin cement exhibited the highest shear bond strength. The shear bond strength of specimens pre-treated with MDPcontaining silane coupling agent and bonded with MDP-containing resin cement was the next highest. In contrast, all specimens pre-treated with non-MDP-containing silane coupling agent bonded with non-MDP-containing resin cements failed during the thermo-cycling process.
Conclusion: Within the limitations of this study, MDP adhesion monomer was effective in improving thebond durability of resin cement to zirconia.

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Purpose: The purpose of this study was to develop a new device to measure continuously the vertical dimension of the human jaw relation using magnetic sensors.
Methods: A sensor unit was made of six MI (Magneto-Impedance) sensors (AMI302 4.0×3.5×1.4mm, Aichi Steel Corp.) placed in a line at intervals of 4 mm. The unit was positioned to the head by a glassestype sensor holder. A target magnet (3mm in diameter, 12mm in length) was set in a resin board positioned on the mentum with adhesive tape. 1) In vitro experiments using a precision-movement stage were conducted. 2) One healthy volunteer (age: 25 years) was instructed to perform a jaw opening-closing task with 10 mm range of motion. Before and after the task his jaw position in the intercuspal position was measured forfive minutes. The jaw movements were recorded simultaneously using a 6-degree-offreedom jaw-tracking device.
Results: The mean square error of the in vitro experiment was 0.06 mm under the worst conditions. The mean square error of the positional accuracy was 0.35mm. The reproducibility of the intercuspal position was 0.33mm. These values correspond to about 16% of the value of the shift phenomenon of the resting position (approximately 2.2mm).
Conclusion: Our new device using an MI sensor enables the vertical dimension to be recorded continuously with sufficient accuracy.

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Purpose: To establish a simple and objective assessment of the residual ridge height of edentulous patients, we investigated the utility of a newly developed “examination scale”based on our clinical research.
Methods: The sites corresponding to the right and left first molars in study models (100 sets) of edentulousmaxillae and mandibles were examined. Subjective assessment and assessment with the three-grade examination scale (high, middle, low) were performedby 16 dentists (less than 3 years of clinical experience: 8, more than 7 years of clinical experience: 8). Objective assessment of residual ridge vertical height was performed with digital vernier calipers. Agreement among the subjective assessment, objective assessment, and assessment with the examination scale was analyzed with kappa values.
Results: Marked variations were noted in the relation between the subjective assessment and objective assessment regardless of the individual's clinical experience. Agreement between the subjective assessment and objective assessment was low (maxillae: less than 3 years of clinical experience: 0.38, more than 7 years of clinical experience: 0.32, mandibles: less than 3years of clinical experience: 0.35, more than 7 years of clinical experience: 0.43). However, agreement between the assessment with the examination scale and objective assessment was high (maxillae: less than 3 years of clinical experience: 0.68, more than 7 years of clinical experience: 0.69, mandibles: less than 3 years of clinical experience: 0.57, more than 7 years of clinical experience: 0.60).
Conclusion: The assessment by the newly developed examination scale for residual ridge height of edentulous patients agreed well with the objective assessment, indicating the usefulness of this scale.

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Purpose: The aim of this study was to evaluate the effects of wearing a palatal plate on swallowing and its habituation.
Methods: Nine healthy dentate subjects participated in this study. They wore palatal plates of 1.5mm thickness. While they were eating agar jelly, jaw movements and surface EMGs were recorded andthe changes of duration of mastication, number of times of mastication, durationfrom the end of mastication to the beginning of pharyngeal stage, and duration of pharyngeal stage immediately after insertion of the palatal plate from the control were evaluated. We also investigated habituation from the daily changes of duration from the end of mastication to the beginning of the pharyngeal stage.
Results: Although no difference was found in duration of mastication, number of times of mastication or duration of pharyngeal stage, a significant prolongation in duration from the end of mastication to the beginning of the pharyngeal stage was found. This prolongation decreased by one day after wearing the plate tothe same level as the control. Although a significant decrease was found in the duration one day after wearing from immediately after wearing the plate, no difference was found two days after, and a significant decrease was found again fromthree days after. No difference was found in the change within subjects.
Conclusion: These results suggested that the duration from the end of mastication tothe beginning of the pharyngeal stage was affected by wearing the palatal plate, but habituation was obtained about 3 days after wearing and its effect disappeared.

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