The Japanese Society of Prosthetic Dentistry (hereafter: JPS) began preparations for accreditation by the Japanese Dental Specialty Board (hereafter: JDSB) in the fiscal year 2017. It continued to exchange opinions with the JDSB until the fiscal year 2021. The new system was put into operation on April 1, 2022, and the JDSB will review the appropriateness of the new system.

Dental specialists certified by JDSB must be dentists who receive appropriate training and education in their specialty, have sufficient knowledge and experience, and can provide dental care that patients trust. Additionally, they must have a good sense of ethics based on their professional autonomy and assure quality through study and lifelong training. It was necessary to review the JPS system to comprehend the fundamental philosophy of JDSB, i.e., the public is a stakeholder.

Therefore, prosthodontists must be able to deal with complex prosthetic cases and be able to deal with primary cases. In addition, they need to receive training in knowledge, skills, and attitudes that general dentists should have, not only in the specialty of prosthodontics. This article overviews the introduced system that strengthened case training and acquisition of general knowledge.

The Japanese Prosthodontics Society (JPS) has held several meetings with the Japan Dental Specialty Board (JDSB) to exchange opinions on Board Certified Prosthodontist, and is now preparing for the official certification of the new system, which will start in April 2022.

Regarding the requirements and certification criteria for prosthodontist under the new system, the number of requirements and credits that must be obtained have increased compared to the old system, and the requirements and certification criteria differ depending on the applicant. In addition, common training and certification examinations for prosthodontist have been newly added as requirements, and the written examinations for prosthodontist have already been started in web style.

On the other hand, the requirements and certification criteria for training institution were also newly revised. In particular, the prosthetic cases required for each training institution are now classified into basic cases and severe cases, and the submission of treatment records for each case is mandatory. The appropriate number of cases will be determined by the number of residents, supervisors, and prosthodontists belonging to each training institution, and will ultimately be evaluated comprehensively by the JDSB through operational reviews and surveys. This paper describes the main points of the newly revised certification system for prosthodontist and training institutes.

Japan Prosthodontic Society (JPS) has been developing an education curriculum suitable for training board-certified prosthodontists as required by Japanese Dental Specialty Board (JDSB). The curriculum is now almost complete, and an overview of the curriculum was presented at the 131st Annual Meeting of JPS. Due to time constraints, we were not able to present some of the topics at the seminar, so we have written this article to let our members know about the contents of the education curriculum.

The curriculum design of board-certified prosthodontist system consists of a basic training program to acquire the basic knowledge and skills of a prosthodontist as a fundamental training program, which is followed by a case series-based evaluation and a competence-based evaluation from the viewpoint of the abilities that a prosthodontist should fulfill. These evaluations and the level of learning achievement are organized in the “Board-Certified Prosthodontist Training Evaluation Record”, which is a kind of practice book. This paper mainly outlines the method of filling out this evaluation record, and describes the credits and examinations required for certification as a specialist in prosthodontics accredited by JDSB.

The curriculum is currently being tested at various training institutions and will be revised from time to time to correct any inconsistencies or operational problems. We hope that it will serve as a reference for teaching young prosthodontists and for young dentists undergoing education.

If the posterior bite collapse is left untreated, the risk of decreased occlusal height, disorder of the occlusal plane, and non-vertical stop occlusion would be increased, and the difficulty of prosthetic treatment is often experienced in daily clinical practice. The occlusal reconstruction, which is generally performed as a response, is intended to be treated with a fixed prosthetic device using a bridge or implant. However, in actual clinical practice, it is often necessary to use removable dentures to deal with occlusal collapse of the molars including defects. In this paper, I will give my personal opinion on the problems and solutions when removable partial dentures are used in cases requiring occlusal reconstruction.

Many patients have problems with their occlusion, regardless of whether or not they have clinical symptoms. In order to obtain and perpetuate a good oral environment for such patients, it is necessary to correct inappropriate occlusal relationships and harmonize the temporomandibular system (temporomandibular joint, perioral muscles, teeth, and periodontal tissues). This paper classifies patient conditions into three categories: “ malpositioned teeth,” “periodontal disease,” and “multiple teeth missing”, and presents case examples to illustrate the key points of treatment for each. Orthodontic treatment is effective in eliminating “malpositioned teeth,” and appropriate sprinting is effective in cases of advanced periodontal disease. The use of implants is effective and also simplifies the treatment of occlusal reconstruction in “missing multiple teeth” cases.

For many years, fixed dental prostheses (FDPs) have been widely used, and FDPs have been reported for longevity primarily used with living abutment teeth. On the other hand, conventional FDPs require of both side of abutment teeth preparation, so those are being questioned as a choice of the recent concept of “minimal intervention dentistry (MID).” Therefore, dental implants and resin-bonded FDPs are often used. On a different topic, full-coverage cantilever FDPs are sometimes selected depending on prostheses. In this article, based on the evidence and models, I will discuss the factors when selecting cantilever bridge FDPs.

The optimal treatment of tooth defect depends on the individual patient’s background, oral and external environment, and the availability of insurance coverage in Japan.

The single retainer fixed partial denture is the treatment of choice for single tooth defect, and excellent clinical outcomes have been reported in basic researches and case reports. Since the dramatic improvement of bonding technology has been recognized, the bonding technique established for conventional bonded fixed partial dentures (two abutment type), which are covered by health insurance in Japan, is also important for single retainer fixed partial denture. Furthermore, with the development of CAD/CAM technology, high-density sintered zirconia has become the mainstay of fixed partial dentures, and we believe that the use of zirconia for single retainer fixed partial denture will expand and that a good prognosis can be expected.

Since implants have become a highly reliable treatment, the treatment options for restoring missing teeth have been increasing. In the treatment planning of implant treatment, it is important to propose treatment options with a high level of evidence based on the patient’s request after planning the number of implants to be placed and the placement position and direction of implants that can withstand sufficient occlusal force, considering the extraction of remaining teeth, restoration of adjacent teeth, treatment period and esthetics. Especially in anterior implant treatment, it is necessary to present a treatment plan that takes into consideration the patient’s desires such as esthetics, degree of invasion, treatment period, and prognosis of treatment. It is important to understand that implant treatment is not superior to other prosthetic treatments for natural teeth, and is only an alternative treatment.

Purpose: The purpose of this review is to evaluate accuracy and practicality of various intraoral scanners and verification method of intraoral scanners.

Study selection: This narrative review employed “Oral Scanner, Intraoral Scanners, Desktop Scanner, and Digital Impression” as main keywords.

Result: It was reported that illuminance and color temperature affected trueness and precision of intraoral scanners. The repeatability of intraoral scanners indicated the possibility of producing fixed prostheses within the range of being partially edentulous. It is considered difficult to use intraoral scanners in fabricating cross-arch fixed prostheses. However, with intraoral scanners, it may be considered possible to fabricate mouth guards and dentures equivalent to those of desktop scanners. Current intraoral scanner scans are considered more comfortable than traditional impressions that use irreversible hydrocolloid and elastomeric impression materials.

Conclusion: Since the intraoral scanner is an evolving device, further improvement in accuracy is expected in the future. In addition, verification of the accuracy of intraoral scanners must be conducted accordingly.

Dementia is a pressing issue in Japan’s super-aged society, and dentists are required to be actively involved in national policies (the New Orange Plan). In dental research, the relationship between cognitive and oral function is of great interest, and many basic and clinical studies have been enough reported. On the other hand, in the medical specialty, oral factors have not yet been recognized as a risk factor for cognitive decline or the development of dementia. The Japan Prosthodontic Society is promoting a research project in collaboration with the Japanese Psychogeriatric Society to conduct a new study on the correlation between cognitive function and oral function. This paper outlines the background of establishing the ECCO project and its activities.

Purpose: Based on the Ministry of Health, Labour and Welfare’s survey of social medical practice, eight years have passed since its report on changes in removable dentures treatment for the 16 years from 1996 to 2013. To clarify the impact of changes in social conditions, we conducted an 8-year survey from 2014 to 2021 and analyzed the results together with the previous results.

Method: From the results of the survey of medical care activities in the public health insurance system of the Ministry of Health, Labour and Welfare in Japan, removable dentures treatment was analyzed according to the following categories: dentures, clasps, bars and reinforcing wires, repairs, and relines.

Results: The total number of removable dentures has decreased since 2014. The total number of clasps has decreased in response to the decrease in the number of removable dentures, but the downward trend of Akers clasps (precious metal: gold-silver-palladium alloy) continued after 2014, and Akers clasps (base metal: Cr alloy) increased slightly. The number of precious metal bars has been decreasing since 2014, and the number of Cr alloy bars has increased slightly. The ratio of repairs to new removable dentures has continued to increase, but the ratio of relining has been on a downward trend.

Discussion: The above changes might be related to changes in society (economy, demographics, changes in dental diseases, metal prices, spread of infectious diseases, etc.), technologies (implants, etc.), and social systems (health insurance rules, out-of-pocket payments, etc.).

Conclusion: The number of denture repairs has remained almost constant, while the number of new dentures has decreased. As for the materials of clasps and bars, the tendency to shift from gold-silver-palladium alloys, whose prices are unstable, to base metals (Co-Cr) has progressed further.

Patient: A 67-year-old male underwent resection and postoperative radiotherapy for left maxillary sinus cancer. Mandibular trismus remained as a late disorder of radiotherapy, and he complained of masticatory dysfunction. In order to obtain sufficient space between the upper and lower teeth, the occlusal plane and occlusal vertical dimension were corrected by pulpectomy and crown prosthesis, and then a new maxillary denture for the defected jaw and a mandibular removable partial denture were fabricated.

Discussion: In this case, space between the upper and lower teeth could be secured by fabricating the new maxillary denture and the new mandibular removable partial denture after correcting the occlusal plane and occlusal vertical dimension, thus improving masticatory function and obtaining good results.

Conclusion: In patients with mandibular trismus, performing appropriate preprosthetic treatment before fabricating removable dentures is effective for restoring masticatory function and thereby improving patient satisfaction.

Patient: The patient was a 20-year-old female. She visited our prosthodontic clinic with the chief complaints of esthetic problems due to dwarfed lateral incisors and masticatory disturbance due to missing maxillary molars. Dwarfed lateral incisors and missing maxillary molars were treated by porcelain laminate veneers and a resin-bonded fixed dental prosthesis with a zirconia framework to reduce the amount of tooth reduction by minimally invasive prosthodontic treatment and to preserve the intercuspal position.

Discussion: Resin-bonded prostheses based on the diagnostic waxing, appropriate prosthetic design, preparation for abutment teeth, bonding procedures, and material selection led to long-term stable function.

Conclusion: The application of porcelain laminate veneers and resin-bonded fixed dental prostheses provided long-term stable esthetic improvement and masticatory function recovery.

Patient: The patient was a 67-year-old male with a chief complaint of masticatory disorder resulting from frequent denture fracture. The patient had composite non-vertical stop occlusion resulting from the condition of the residual teeth. A metal base denture was applied to improve the stability of the denture and masticatory function.

Discussion: Specific considerations are required for patients with non-vertical stop occlusion because the occlusion is influenced by the alveolar ridge condition and the pressure caused by residual teeth. Therefore, appropriate intervention such as occlusal adjustment and denture relining is important.

Conclusion: In this case with composite non-vertical stop occlusion, a metal base denture was applied to obtain rigidity and strength, which minimized changes in the intraoral condition and resulted in long-term stability.

Patient: The patient was a 70-year-old man who complained of masticatory difficulties due to mobility and pain in the left lower molar area. The teeth that were diagnosed as having severe periodontitis were extracted. Next, while maintaining the occlusal vertical dimension as much as possible with removable dentures, four implants were placed and fixed full-mouth implant-supported prostheses were inserted in both jaws.

Discussion: Cleaning instructions and adjustment of the basal surface form were performed with provisional restorations. It was considered that a good prognosis was obtained by transferring the form to the final prostheses, which were not only functional but also easy to clean.

Conclusion: Fixed full-mouth implant-supported rehabilitation using removable dentures while treating the patient who had masticatory disturbance due to severe periodontitis led to improved oral health-related quality of life and chewing ability.

Patient: A 66-year-old male patient presented to our hospital with the main complaints of dissatisfaction with the look of his teeth and chewing problems. A severe inappropriate occlusal plane caused by tilted and extruded teeth was observed. The occlusal plane was treated by fabricating a crown, bridge, maxillary removable partial denture, and mandibular removable complete denture after increasing the occlusal vertical dimension.

Discussion: This case needed reconstruction of the maxillomandibular relationship, which involved increasing the occlusal vertical dimension to remedy the occlusal plane. First, the appropriate vertical dimension was judged to be acceptable by the patient using treatment dentures, and then the definitive prostheses were fabricated; they produced excellent results.

Conclusion: Correcting the occlusal plane resulted in the recovery of masticatory function and high esthetic satisfaction of the patient. His progress remains good more than 3 years after treatment.

Patient: A 75-year-old man visited our hospital complaining of difficulty in chewing due to detachment of the facing crown of the lower canine. The patient stopped visiting after making the crown and the lower removable denture. The patient then returned because of detachment of the full cast crown of the upper second premolar. After extracting the hopeless teeth, an overdenture with magnetic attachments was inserted for the maxilla, crowns and removable partial denture for the mandible.

Discussion: The crown-root ratio was improved by the magnetic attachment. The mandibular denture was designed to provide an appropriate bracing effect. As a result, the oral health-related quality of life and masticatory ability were improved and high patient satisfaction was obtained.

Conclusion: The use of an overdenture with magnetic attachment for remaining teeth resulted in a satisfactory therapeutic effect on a partially edentulous patient.

Patient: The patient was a 78-year-old edentulous female with a chief complaint of fatigue due to wearing a denture. The denture caused the tongue space to be narrow. The mandibular residual ridge was located buccolingually in relation to the maxilla. Therefore, the maxillomandibular residual ridge relationship was confirmed on an articulator, and bilateral balanced occlusion by arranging reverse articulation on the right-side molar was planned. A sheet for transferring the position of the residual ridge crest was developed and used as an indicator for arranging artificial teeth.

Discussion: The patient’s feeling of supraocclusion was solved by arranging reverse articulation, and long-term stability of the denture was achieved.

Conclusion: In this case of functional reconstruction for an edentulous patient with abnormal maxillomandibular relation, it is considered that arranging reverse articulation contributed to the patient’s satisfaction.

Patient: The patient was a 56-year-old man at the first visit, who presented to our hospital with the complaint of difficulty in chewing due to tooth mobility. An examination showed that he had a masticatory disorder due to severe generalized chronic periodontitis and occlusal disharmony. Since all the remaining teeth were difficult to preserve, we fabricated immediate treatment dentures by using optical impressions. The patient did not complain of esthetic, speech, or masticatory disorders due to the dentures during the treatment. Then, upper and lower definitive complete dentures were fabricated.

Discussion: By fabricating treatment dentures by using optical impressions, the prosthetic treatment was conducted smoothly while maintaining oral function.

Conclusion: In cases with teeth that may be removed by taking a conventional impression, optical impressions can be used to minimize patient discomfort.

Patient: An 87-year-old man presented with difficulty in mastication and problems related to dental esthetics. Intraoral examination revealed a decreased occlusal vertical dimension due to dental erosion, which was thought to be caused by reflux esophagitis. After an occlusal appliance and provisional restorations were provided and adjusted, the final prosthesis was fabricated in harmony with jaw movement based on information obtained from the provisional restorations, and occlusal reconstruction was successfully performed.

Discussion: Since the morphology and occlusal relation of the provisional restorations were reproduced in the final prosthesis, the final crown prosthesis was in harmony with jaw movement.

Conclusion: This case of occlusal reconstruction in a patient with masticatory and esthetic disorders suggests that occlusal appliances and provisional restorations are effective for determining the morphology of the final prosthesis.

Patient: The patient was an 82-year-old male who complained of lack of mandibular complete denture stability and inability to masticate properly. The stability of the denture was poor when the patient opened his mouth and masticated, and premature contact occurred when he closed this mouth. The old denture was duplicated to make a treatment denture, and the denture was adjusted. A dynamic impression was made using a treatment denture to fabricate the definitive complete denture.

Discussion: Stability and occlusion of the complete denture were improved by replicating the old denture to produce a treatment denture and using it for treatment.

Conclusion: By fabricating a complete denture using a treatment denture that corrected the problems of the old denture, the patient’s satisfaction and recovery of masticatory function were finally achieved.

Patient: The patient was a 21-year-old woman who was admitted to our hospital with a complaint of anterior esthetic disorders. She had a unilateral cleft lip and palate at birth and had a history of lip plasty, bone grafting, and orthodontic treatment. We performed prosthetic treatment of the maxillary anterior teeth with a porcelain laminated veneer and all-ceramic crown.

Discussion: We were able to perform prosthetic treatment with high patient satisfaction by diagnostic wax-up and sharing the goal of treatment with the patient and dental technician.

Conclusion: The patient remains in good condition 3 years after the final prosthesis was delivered. By using porcelain laminated veneers and all-ceramic crowns, we obtained good esthetics with minimal invasiveness.

Patient: The patient was a 79-year-old male who complained of masticatory dysfunction caused by severe mobility of the maxillary anterior teeth and poor fitting of maxillary and mandibular removable partial dentures (RPDs). There were non-vertical stop occlusion at the posterior teeth and decreased occlusal vertical dimension (OVD) with an irregular occlusal plane even when wearing the RPDs. Periodontally hopeless teeth were extracted, and then the existing RPDs were modified to raise the OVD and align the irregular occlusal plane. The modification process ensured the frame design for new RPDs followed by fabrication and insertion.

Discussion: Modification of the existing RPDs enabled clarification of the existing problem and achievement of an appropriate denture design. Accordingly, the new RPDs resulted in suitable function for this case.

Conclusion: Appropriate preprosthetic treatment and careful denture design for non-vertical occlusion greatly contributed to the improvement of masticatory function and satisfactory progress.

Patient: This article reports the case of a 64-year-old female who presented to the hospital with a chief complaint of difficulty in chewing with her anterior teeth and of esthetics concerning the missing front teeth upon removing her dentures. The patient was diagnosed with masticatory disturbance and esthetic dissatisfaction due to an ill-fitting denture. Thereafter, four implants were placed in the defects, including the anterior teeth, and her masticatory dysfunction and esthetics were restored by an implant-supported fixed prosthesis and crown prosthesis.

Discussion: The implant-supported fixed prosthesis contributed to the improvement in masticatory dysfunction and esthetics.

Conclusion: The choice of fixed prosthesis using implants for masticatory dysfunction and esthetic dissatisfaction resulted in good outcomes with high patient satisfaction in terms of improvement of oral function and esthetics.

Patient: The patient was a 63-year-old woman who complained of difficulty in chewing due to defective molars. Occlusal support of the molars was lost; occlusal support was provided by only two premolars. After performing right maxillary sinus floor elevation, prosthodontic treatment with dental implants was performed on both sides of the maxilla and on the left side of the mandible.

Discussion: It is considered that root fracture had been caused by overload due to the inability to obtain appropriate occlusal force support in the molar parts. By establishing molar occlusion by implant treatment, a good course was obtained three years after treatment, and it is considered that the loss of residual teeth can be prevented in the future.

Conclusion: Prosthodontic treatment with implants combined with maxillary sinus floor elevation was performed, and occlusal support by the molars was restored, resulting in improvement of masticatory disturbance.

Patient: The patient, who was a 65-year-old female, complained of masticatory dysfunction owing to frequent fracture of an interim fixed prosthesis induced by absence of posterior occlusal support and partial edentulism in the maxilla. The bilateral canines and molars of the maxilla were reconstructed by implant fixed prostheses, and the existing implants of the mandible and the remaining restored teeth were replaced with new fixed prostheses.

Discussion: It has been 3 years and 2 months since the fixed prosthetic treatments were completed; there have been no functional or esthetic complications. Implant fixed prosthetic treatment alone can reestablish occlusal support in cases with partial posterior edentulism and, therefore, most likely provides high therapeutic efficacy even in the absence of posterior occlusal support.

Conclusion: For the present case with loss of posterior occlusal support, implant fixed prosthetic treatment provided occlusal support, improved masticatory function, and attained good efficacy.