This article is a general overview of the symposium titled “Strategic Plan in Prosthetic Dentistry”, which was held on October 1-2, 2005 at Niigata Convention Center. In this article, outlooks of the future in the research, education, and clinics of prosthetic dentistry, and strategic plans in the prosthetic dentistry are delivered.
Prosthetic Dentistry involves the research works on the morphology and functions restored with the dental prostheses. It also involves the researches on the biological reactions at the interface between the host tissues and dental prostheses, which include the biomaterial research, the biological reactions induced by mechanical stresses, and so on.
As strategic plans for the development of prosthetic dentistry, the fundamental plan and the creative plans are proposed. The former indicate establishing the biological bases of the prosthetic dentistry, like as the biological reactions induced by mechanical stresses, and establishing the evidences of clinical outcomes for EDM. To obtain the scientific evidence, the criteria of objective estimations should be conducted. The later indicate the development and introduction of novel techniques and materials based upon the multidisciplinary alignment.

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Prosthodontics is a practical science based on life sciences and health sciences, and takes a role to contribute to improvement of health/welfare of peoples. By prosthodontic researches including life sciences and health science, it will be proved that the practice of prosthetic dental treatments is important to health/welfare. In addition, our research activities are expected because of the demographic change caused by the increase of aging population. The scientific research activity of our society is one of the activities for main medical/dental care demanded definitely in the 21st century. Especially, promotion of brain research is just going to be expected.
From a prosthodontic treatment point of view, the improvement of diagnostic study focusing on the examining method and the inspecting method is desired. It is included in a diagnosis to predict a degree of functional recovery after prosthodontic treatments. For the evaluation of masticatory function, the evaluating method for the organ and tissue constituting stomatognathic system is necessary as well as the evaluating method for masticatory function. It is hoped that efforts will be made to establish evaluating methods for each organ and tissue in stomatognathic system will be made.
As a corporate judicial person, we must build up public-interest activities. It is necessary to provide sufficient information to all dentists in order to offer a quality prosthodontic care by improvement of diagnostic and treatment abilities. Moreover, it is necessary to practice active enlightenment activity about clinical significance of prosthodontic treatment, and to develop strategies to make peoples recognize “prosthodontics as a health science” widely.

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In this article, intrinsic problems lying in Prosthodontics research and educational field were pointed out and Prosthodontics as it ought to be as a nature science was discussed. Prospect of prosthetic dentistry/Prosthodontics as a clinical science was categorized the following four and discussed: 1) systematizing of conventional Prosthodontics, such as crown, bridge, partial and complete denture, 2) contribution to oral rehabilitation of mastication, swallowing, and speech for elderly and inpatient elderly, 3) innovation of prosthetic dentistry using more comfortable and aesthetic prosthesis, such as Implant and Adhesive Dentistry, and 4) translational research.
Finally, essential prerequisites to achieve bright future of Prosthodontics were proposed.

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Fixed prosthodontics is the art and science of restoring defective or damaged teeth and/or replacing missing teeth. The primary objective of a restoration is to recover functional occlusion. Additionally, patients, regardless of their age and sex, have needs related to esthetic restoration. To please patients, the dentist must deliver an esthetic restoration that blends with the patient's natural teeth. These are some of the needs related to “basic research” in fixed prosthodontics.
Either ceramic materials or resin composites are used for indirect esthetic restoration. In general, toothcolored materials require incremental thicknesses to ensure adequate color and sufficient mechanical properties. However, the thick form of a prosthesis contradicts the concept of “minimal intervention”. Patients though require restorations that meet their esthetic needs without any significant loss of tooth structure.
The strategy for the “new (advanced) research” in fixed prosthodontics should be based on the two concepts of esthetics and minimal intervention. Although these two factors appear inconsistent, patients unquestionably require both to be provided with high quality care that will include both solutions in the context of a well-organized and sequenced comprehensive treatment plan. Consequently, in response to the growing popularity of esthetic dentistry, we dentists should develop a new dentistry field, one that introduces relevant new technologies along with newly developed materials.

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Musculoskeletal disorders in orofacial region are known to induce mastication disability and decrease the patients' quality of life levels. Additionally, the prevalence of those disorders tends to increase in elderly. However, since the existing therapies are not fully effective and medical expenses for those disorders are expanding, a prompt solution is necessary especially in aging societies like Japan. In addition, investigations for those disorders are important, because the research findings would be useful for the investigation of similar disease in other organs. Therefore, it is possible to consider that they can directly associate with general health and the universality of prosthodontics. In order to solve the above problems, two different research strategies are desirable. First, to improve the current curative effect, the effectiveness of existing diagnostic system and treatment modalities should be evaluated using high quality clinical studies. Second, as the research strategies on a long-term basis, investigations, which target the pathology and the contributing factors in a biological point ofview are essential. This article will discuss about the research strategy to elucidate the pathology and the factors, which play important roles in the disease mechanisms, based on the previous and ongoing physiological research findings. Furthermore, I would like to review the useful newly developed technologies for the research strategy and new research fields, to enhance the value of prosthodontics and discuss about our future research direction.

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Purpose: In this study, we investigated the conditioning efficacy of a self-etching primer consisting of methacrylamide, N-methacryloyl-w-amino acid (MωA) derivatives for enhancing the bond strength of resin to crown and root dentins.
Methods: A series of four MωA derivatives, with different methylene chain numbers, were synthesized, as follows. 1: N-methacrylole glycine (Gly); 2: N-methacrylole-β-alanine (βAla); 3: N-methacrylole-4-aminobutyric acid (Bu); 4: N-methacrylole-5-aminovaleric acid (Va). The dissociation equilibrium pH (pKa) of carboxylic acid in each of the MωA derivatives was determined. The shear bond strengths of resin to the crown and root dentins, primed with the Gly solution were measured for various conditioning times. We also measured the bond strength to boththe dentins following application of the MωA adhesives with different pKa values for 30 seconds.
Results: For the Gly primer, the bond strength of resin to both dentins increased with the conditioning time until 30 seconds, leveled off thereafter by increase in the methylene chain number. The effects of conditioning time on the bond strength to the crown and the root dentin were the same. Furthermore, the bond strengths to the dentins, conditioned with each of the four MωA derivatives for 30 seconds, were the same, even though the decalcified amounts of the dentin apatite noted following conditioning with Bu and Va were lower than that noted following conditioning with Gly. This was attributed to the pKa value of the acidic groups in the acidic monomer directly relating to the decalcified amount of dentin apatite.
Conclusions: Application of the MωA solutions, resulted in an increase in the bond strength of resin to both crown and root dentins. In particular, the Bu and Va primers were very useful as primers promoting the bond of resin to dentin, since the etching potential was very low.

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Purpose: For the purpose of evaluating the flow properties influencing the formativeness of commercial hard resin pastes used in the construction of crowns and bridges, we examined the behaviors of various resin pastes and their temperature dependence during manipulation.
Methods: Five types of hard resins currently in use for the construction of crowns and bridges in the clinical setting, namely, New Meta Color INFIS, Solidex, Ceramage, Gradia, and Estenia C&B, were examined. The components and flow properties of each resin paste were investigated in relation to the dentine and enamel colors. The viscosities of the resin pastes before curing were measured by a cone-plate viscometer.
Results: Each resin paste demonstrated a non-Newtonian flow, and the flow curve showed a hysteresis loop, in which the upward and downward curves were different. When the shear stress at the beginning of the holding time of the flow curve (20°C, 25°C, 30°C) of each resin paste was measured, the shear stress at 20°C was found to be significantly higher than that at 25°C and 30°C, and the shear stress at 25°C was found to be significantly higher than that at 30°C. The viscosity was found to be higher at lower temperatures than at higher temperatures. Comparison of the shear stresses at the beginning and at the end of the holding time revealed that the stress at the beginning of the holding time was significantly higher than that at the end of the holding time for all except the Estenia C&B resin paste.
Conclusions: Each of the resin pastes used in the present study showed temperature dependence of its characteristics in the temperature range examined (20-30°C) and thixotropic fluidity. However, the flow characteristics of these resin pastes differed significantly, suggesting that the flow characteristics may affect the manipulation of resin formativeness.

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Purpose: The purpose of this experiment was to objectively evaluate the masticatory function in TMD (Temporomandivular disorders) patients.
Methods: The quantitative indicators of muscular activity, stability of movement, and masticatory efficiency during mastication were compared among the following three groups; 10 healthy subjects, 10 patients with arthrogenous TMD, and 10 patients with myogenous TMD. For muscular activity, the integral value of the masseter muscular activity was calculated. For stability of movement, a comprehensive indicator was established after principal component analysis using the data of the seven indicators of stability of path and rhythm. For masticatory efficiency, the amount of glucose extraction after gummy-jelly chewing was measured by a blood glucose testing device.
Results: The cumulative value of masseter muscular activity and the amount of glucose extraction after gummy-jelly chewing were larger in the healthy subject group than in the groups with arthrogenous or myogenous TMD, and these differences between the healthy subject group and the other two groups were statistically significant. On the other hand, the value of the comprehensive indicator was significantly smaller in the healthy subject group than in the groups with arthrogenous or myogenous TMD.
Conclusion: It was suggested that the masticatory function in TMD patients is much inferior to that in healthy subjects.

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Purpose: The aim of this study was to examine root fractures in the doweled lower premolars and their relationship to alveolar bone absorption on the buccal aspect of the abutment teeth.
Methods: Experiment 1. Fractures in the roots of the abutment teeth and absorption of the surrounding alveolar bone were visualized by Multi-image Micro CT (3DX) in nine lower premolar abutment teeth that had lost both their posts and their. Experiment 2. The stresses in the teeth were analyzed using a three-dimensional finite element model, both models with and without alveolar bone absorption, as determined from Experiment 1. The stress distributions of von Mises equivalent stress and the shear stresses in the XZ, YZ and XY direct ions were examined.
Results: Experiment 1. The absorption of the alveolar bone was observed on the buccal side, and the fractures in the roots were observed in the lingual to buccal direction. Experiment 2. In the case without alveolar bone absorption, the XY shear stress in the root for mesial or distal loads was concentrated near the cervix with a positive stress value, and close to the end of the post with a negative stress value. In the alveolar bone absorption model, the XY shear stress in the root for mesial or distal loads was concentrated close to the end of the post on the lingual side with a positive stress value and on the buccal side with a negative stress value.
Conclusion: In the case without alveolar bone absorption, on stress concentration was observed at the end of the post. Otherwise, based on the results of the finite element model analysis, for mesial or distal loads, the root fracture in the abutment teeth would be considered to be caused by absorption of the alveolar bone on the buccal aspect.

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Purpose: This study was conducted to histomorphologically determine the quantity of bone formation induced by TAK-778, a 3-benzothiepin derivative, (Takeda Pharmaceutical Co.Ltd.), in various amounts, using b-tricalcium phosphate granules (β-TCP; OLYMPUS Corp.) as a carrier for the osteogenetic agent.
Methods: Ten-week-old female SD rats were used. An incision was made over the parietal region of the head. The cranial periosteum was ablated and a titanium tube was fixed with an adhesive resin cement to the central part of the head, through which a mixture of TAK-778 and /3-TCP was implanted under various conditions. Tissue specimens were prepared at 4, 8, and 16 weeks after the implantation for histomorphological examination, and the proportion of new bone formation was compared at fixed time points using the NIH imaging software. The amount of new bone formation was examined every week after the implantation of TAK-778 at various doses, and the mean values were compared using Fisher's PSLD test (P<0.05).
Results: The histomorphological observations revealed new bone formation in all the groups, irrespective of the amount and the duration of implantation of TAK-778. A comparative study revealed that the amount of new bone formation was the largest at 16 weeks following the implantation of a mixture of /3-TCP and 100 mg of TAK-778.
Conclusions: 1. The present study confirmed the acceleration of new bone formation soon after TAK-778 implantation. 2. The results suggested that the action of TAK-778 could be maintained over time if the agent was used in combination with β-TCP. 3. The time-course of bone formation differed depending on the proportion of TAK-778 and β-TCP in the mixture used. 4. TAK-778 at the dose of 10 mg or 50 mg was more effective than that at the dose of 100 mg for the early formation of new bone. These results indicate that TAK-778 accelerates the formation of new bone and that β-TCP is a useful carrier for TAK-778.

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The purpose of this study was to investigate the possibility of applying measurement of the Current Perception Threshold (CPT) to the oral mucosa. Methods: Forty healthy volunteers (20 males and 20 females; mean age, 29.5 ± 5.1 years) were recruited for the study. CPT measurements were performed over the nasopalatine nerve area and greater palatine nerve area with 5, 250 and 2000Hz electrical stimulation using the Neurometer^® NS3000. The CPTs were measured on three separate days, and each measurement was carried out once a day by a single operator. Results: Each of the electrical stimulations of 5, 250 and 2000 Hz had a specific CPT. There were no significant differences in the CPT values measured over the three days. The CPTs were lower in the females than in the males. There were no significant differences in the CPTs in the greater palatine nerve area between the right and the left side. No order effect was observed on the CPTs in the greater palatine nerve area of either side in the first and second measurements. The intraclass correlation coefficient of the CPT measurements was as high as 0.80.
Conclusion: It was concluded based on the high reliability of the measurements obtained, that CPT measurement can be applied to the oral mucosa.

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Patient: A 20-year-old female whose chief complaint was esthetic disturbance of a crown placed on the maxillary left central incisor.
Discussion: The interdental papilla was reconstructed only by the prosthodontic treatment of maxillary left central incisor. This case suggests that the proximal and subgingival contours of provisional crown is very important to the reconstruction of interdental papilla, and also suggests that the transmission of the information regarding the configuration of a provisional crown to the lab side is very important.
Conclusion: This case shows that the emergence profile of a single crown, especially of its proximal aspect, is important to reconstruct the interdental papilla.

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Patient: A patient presented with malocclusion caused by generalized periodontal disease, subgingival caries, and poorly designed restorations and prostheses. Occlusal reconstruction was carried out in this case according to occlusal guidance that was determined based on mandibular head movement, following periodontal surgery. The emergence profile of the prostheses was made to match the periodontium.
Discussion: By achieving an occlusal form, where the maxillary and mandibular molar teeth could be instantly separated through proper anterior guidance corresponding to the internal structure of the mandibular joint, it was possible to attain long-term stability while maintaining harmony with the temporomandibular joint without damaging the periodontium.
Conclusion: Occlusal guidance corresponding to the internal structure of the temporomandibular joint is important for maintaining the stability of the periodontium, teeth and temporomandibular joint.

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Patient: A 49-year-old female patient presented to Prosthodontic Clinic at Nihon University School of Dentistry at Matsudo with the chief complaints of chewing difficulty and poor appearance. She was diagnosed moderate to severe periodontitis and partially edentulous dentition on both maxilla and mandible. Occlusal reconstruction was conducted with crown restorations and removable partial dentures (RPD). From the esthetic request of patient, Dimple-bar telescopic (DBT) system was applied to the mandible with bilateral distal coping abutments.
Discussion: DBT system has been functioning well for more than 5 years without abutment tooth loss. It was thought that bilateral distal coping abutments can help to resolve problem with bilateral distal extension RPD dilemma.
Conclusion: It is suggested that DBT system has great potential to resolving weak points of clasps, such as low retentive forces and/or esthetic problem. Furthermore, author got a new understanding of the importance of maintenances.

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Patient: The patient is a 71-year-old woman who had undergone a gingivectomy due to a gingival carcinoma of right maxillary sinus and a denture was made for the defected jaw.
Discussion: During three years and six months, 3 serves as the guidance tooth had suffered from various symptoms, from the detachment of the neighboring tooth to the use of an OP anchor followed by a partial fracture of the cuspid root. However, 3 has not been removed in accordance to the patient's request. In addition, a relining provided indirectly to the denture, it is still maintained and used for mastication, pronunciation and swallowing functions without difficulty.
Conclusion: This is a case that a denture was made for the defected jaw. However, it is important to take measures in the future, as the remaining tooth is not expected to be preserved for long.

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Patient: This is a clinical case report of esthetic and masticatory impairment due to a mandibular protrusion during occlusion. The patient was a complete edentulous subject who complained about esthetic and masticatory disturbance. First of all, treatment dentures were done, in order to improve the mandible position and recover the facial aspect. Objective evaluations were carried out to compare the improvements achieved after the insertion of the new dentures.
Discussion: The treatment dentures were used to improve patient's mandible position as well as vertical dimension. Once the facial appearance was recovered as a result of an appropriate mandible position, a reduction of the angle formed between the FH plane and the A-B plane from 87 to 83 was recognized after the insertion of the new dentures through the analysis of lateral cephalograms. It indicates that the mandible's position changed to backward position resulting in an improvement of the facial aspect.
Conclusion: In the present clinical case report, not only subjective evaluation for appropriate mandible position and vertical dimension, but also including objective evaluation methods allowed us to evaluate and compare objectively the patient's pre and post operative condition.

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Patient: This clinical report describes the treatment of a patient who experienced a hypersensitivity reaction associated with prosthetic restorations fabricated with a silver-palladium-copper-gold alloy.
Discussion: Patch testing revealed an allergy to the palladium substrate. Allergic symptoms disappeared from the patient's mucous membrane after all the prosthetic restorations in the patient were replaced with those fabricated using some alternative alloys. The case presented indicates that the release of palladium from prosthesis fabricated with dental metal alloys is able to induce hypersensitivity reactions resulting in soft-tissue changes in the buccal mucosa.
Conclusion: Dental procedures as a multidisciplinary approach to the care taking of patient are presented.

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