It has been eight years since CAD/CAM indirect resin crowns were included in the national health insurance in Japan. During this period, members of the Japanese Society of Prosthodontics have been accumulating basic research data and clinical evidence to improve this treatment. This paper summarizes the results of the research, including “currently recommended bonding procedures” and “overall clinical outcomes”, and proposes “appropriate clinical techniques” and “principal patient explanations” based on the latest data and evidence. A wide range of factors contribute to the success of CAD/CAM indirect resin crown treatment, and dentists need to manage them comprehensively. In addition, we would like to examine the existing dogma that needs to be changed, and to attain close collaboration among the medical practice, industry, government, academia and private sector in order to disseminate this new metal-free treatment from Japan.

Zirconia ceramics are now widely used in dentistry as one of the golden standards of restorative materials. More recently, highly translucent zirconia ceramics and multi-layered zirconia have enabled us to apply monolithic zirconia restorations in both anterior and posterior regions. Several new zirconia materials, as well as different fabrication techniques, have been introduced, which makes difficult to sketch the current status of dental zirconia ceramics. In this paper, we focused on the three aspects of zirconia ceramics: 1) classification of zirconia, 2) sintering of zirconia, 3) additive manufacturing of zirconia, and 4) bonding strategy to zirconia-based restorations. We summarized the novel scientific evidence of dental zirconia ceramics.

Dental implant is a good option to replace a single missing tooth, but for various reasons patients may decide to choose other options like removable partial denture or fixed partial denture/bridge which is still a viable prosthetic option. Patients usually prefer fixed partial denture (bridge) over removable to restore one missing anterior tooth for esthetic reasons, but the disadvantage is the removal of tooth structure which may sometimes require preparing healthy teeth. Resin bonded bridges have been introduced and applied from some time ago due to minimal amount of preparation. This paper will discuss the key factors to consider when using single-retainer zirconia resin bonded bridges.

Japan Prosthodontic Society (JPS) holds scientific meetings and publishes Journal of Prosthodontic Research (JPR), to widely publicize the research activities of its members. Comparing the presentations at these conferences and the papers published in JPR with the presentations at prosthodontic societies in Europe and the United States and the papers published in their journals, there can be seen unique characteristics of the JPS/JPR, such as relatively larger number of biological and material researches. In addition, JPR has the highest impact factor among international journals related to prosthodontics, however, when we evaluate the journal in conjunction with other indicators, we feel that there is room for improvement in terms of the international spread of contributors and the international impact of the articles published.

All restoration materials are foreign matters for the organism. It is necessary to consider periodontal tissue and the relations of the tooth when restoration materials install subgingival margin. When restoration materials penetrates to the deep position in periodontal tissue, circumference tissue moves to apically to rebuild periodontal tissue or slight inflammation continues that is absorption and regeneration are repeated results by the circumference tissue of the high ability to regenerate. It is necessary it is diagnosed, and to consider the biotype of periodontal tissue of the patient next. The high-risk case of the aesthetic change may change periodontal tissue environment by connective tissue graft in a classification of biotype reported in the past. In addition, teeth contour are variously and restoration contour will be change at a setting position.

Purpose: To determine a horizontal arch applicable to designing the arrangement of artificial teeth constituting a complete denture, we statistically examined a method of expressing the artificial dental arch shape for complete dentures, with reference to the shape of the natural dentition in individuals with normal occlusion.

Method: The study examined the complete lower denture and normal natural dentition of the mandible of patients. Placing the central groove of the artificial lower molars at the mid-point of the buccolingual dimension of the lower molar alveolar ridge in edentulous individuals, points of measurement were set on the horizontal plane of the arch of artificial teeth constituting the complete lower denture, an approximation curve forming a standard arch was determined. Furthermore, to confirm the validity of the location of artificial teeth constituting the complete denture, the t-test was conducted on the mean coordinate value at each point of measurement selected on the complete denture in comparison to that on the normal natural dentition.

Results: A statistical analysis of the mean arch shape of the complete denture and that of the normal natural dentition, expressed by the approximation curve depicted with the mean coordinate values of selected measuring points, showed that the width did not differ significantly between them.

The mean artificial dental arch shape, representing the horizontal aspect of the artificial dental arch for complete dentures, was calculated with the regression formula and expressed as a quartic polynomial curve with a high degree of correlation.

Conclusion: The horizontal arch for creation of a complete denture could be designed from the mean shape of artificial dental arches. This arch is expected to serve as a standard arch allowing simplified designing of the arrangement of artificial teeth constituting a complete denture and is thus clinically useful in arranging artificial teeth in individual patients and developing new connected artificial teeth.

Purpose: In the 2016 dental fee revision, prosthetic crown shade selection tests, denture chewing function tests, and tongue pressure tests were introduced into health insurance. The purpose of this study was to clarify the implementation status of dental prosthesis-related examinations in clinical practice since 2016.

Method: The number of tests conducted was investigated based on the medical practice identified in the Social Medical Practices Survey of the Ministry of Health, Labour, and Welfare conducted from 2016 to 2020. The proportion of prosthetic crown shade selection tests performed for metal crowns with resin-facing and hard resin jacket crowns, the proportion of jaw movement-related tests performed for multiple tooth bridge impressions, the proportion of masticatory function tests performed for removable partial and complete dentures, and the proportion of tongue pressure tests performed for palatal augmentation prostheses were analyzed and compared with the estimates in the Health Technology Assessment Proposal.

Results: The implementation rate of crown prosthetic shade selection tests at the time of crown prosthesis increased slightly (8.0%) compared to the previous survey (until 2018), however, it was less than the estimated 40%. Jaw movement-related tests were performed at a constant rate of about 11%. Almost no denture masticatory function tests were performed in 2016, but increased in 2018 (1.9%) and 2020 (2.9%), however, the rate was less than the estimated 7.5%. The tongue pressure test has been calculated multiple times for necessary cases since 2016, but it was 12 to 13% of the estimated number. From 2018, adaptation has expanded and has increased significantly.

Conclusion: Newly introduced tests were on the rise. However, the implementation rate was lower than the rate expected in the Health Technology Assessment Proposal, suggesting that it is necessary to continue efforts to disseminate the tests and to continuously inspect and evaluate the implementation rate.

Patient: The patient was a 67-year-old female who complained of difficulty during mastication due to tooth mobility and problems concerning esthetics of the maxillary anterior teeth. Extraction of maxillary posterior teeth and periodontal treatment were performed. A maxillary removable partial denture with onlay-type occlusal rests was fabricated after providing splinted crowns on the anterior teeth in the maxillary and mandibular arches.

Discussion: Primary splinting of the anterior teeth reduced the tooth mobility and satisfactory esthetics could be achieved through correction of the tooth axis. Improvement of chewing ability was achieved by fabricating a stable denture.

Conclusion: Adequate periodontal and prosthetic treatment resulted in a good prognosis in the patient with severe periodontitis.

Patient: The patient was a 16-year-old male with congenital partial edentulism presenting esthetic disorders due to the edentulous spaces. He had 11 congenitally missing teeth in the upper and lower jaws. The edentulous spaces were rearranged by orthodontic treatment to improve the condition for further prosthetic rehabilitation. Subsequently, acquired spaces were restored by either non-metal clasp dentures or resin-bonded prostheses.

Discussion: Five years have passed since the treatment was completed. The patient has not experienced any complications, and is satisfied with our treatments from an esthetic point of view.

Conclusion: This case suggests that non-metal clasp dentures and resin-bonded prostheses can be used to treat patients with congenitally missing teeth.

Patient: The patient was a 57-year-old female who visited the clinic with a chief complaint that she could not chew foods with her back teeth. There was no occlusal support in the molars, and the maxillary anterior teeth were pushed up by the mandibular anterior teeth when the mouth was closed.

Discussion: It was suggested that occlusal reconstruction could improve the masticatory function and esthetic disorder.

Conclusion: The information obtained from the treatment denture was transferred to the final prosthetic device to ensure a good long-term prognosis. The use of magnetic attachments resulted in a high degree of patient satisfaction.

Patient: The patient was a 60-year-old female, with the chief complaints of tooth mobility, masticatory disturbance due to pain while eating, and esthetic problem. After examinations, the patient was diagnosed with severe chronic periodontitis and temporomandibular disorder (TMD).

Discussion: The patient’s TMD was managed before prosthetic treatment, and cognitive behavioral therapy and physical management were continued to prevent recurrence of TMD. The treatment denture was placed after tooth extraction, and the definitive denture was placed 8 months later.

Conclusion: Continuous management for TMD and suitable prosthetics consideration may improve masticatory dysfunction and esthetic dissatisfaction with TMD patients, and contribute to a good prognosis and high satisfaction.

Patient: A 65-year-old female was referred by an oral surgeon for preoperative examination of a maxillary gingival tumor. After tumor resection, she had a defect with perforation into the maxillary sinus in her right-side maxillary bone. An interim obturator prosthesis was inserted and adjusted as the soft tissue changed during the postoperative wound healing period. After the perforation was closed, the definitive prosthesis was delivered.

Discussion: The interim obturator prosthesis restored mastication function and esthetics. Careful adjustment of the obturator and stability of the prosthesis may have led to spontaneous closure of the perforation into the maxillary sinus.

Conclusion: A maxillectomy patient was effectively rehabilitated by collaborating with the surgeon, using surgical, interim and definitive prostheses.

Patient: A 78-year-old female patient complained of difficulty during mastication due to the mobility of her mandibular complete denture. Severe mandibular residual ridge resorption was observed and her mandibular complete denture lacked enough retention and stability. The patient was diagnosed with masticatory dysfunction due to poor retention of the mandibular denture which was caused by severe residual ridge resorption. She underwent prosthetic treatment using an implant overdenture (IOD).

Discussion: A bar attachment was selected for this case. An occlusal pressure impression was used to consider settling of the denture after it was placed. This led to reduced stress of the implant body and improved the fit between the denture and the underlining mucosa during function. As a result, good long-term outcomes were obtained.

Conclusions: Prosthetic treatment with IOD was performed on a mandibular edentulous patient with severe residual ridge resorption and good results were obtained.

Patient: The patient was a 56-year-old man who complained of masticatory disturbance due to caries of molar teeth. The right dentition had a reverse articulation including canines. At the request of the patient, only the molar region was prosthetically treated. Group function was selected as the occlusal scheme on the right side when using a provisional restoration. After 9 months, the occlusal surface of the provisional restoration was reproduced in the definitive prosthesis by the functional bite impression technique.

Discussion: A stable occlusal relationship was maintained by reproducing in the definitive prosthesis the occlusal surface of the provisional restoration after long-term follow-up and by dispersing the lateral occlusal pressure of the molar region.

Conclusions: In the patient with reverse articulation including canines, the group function of only the molar region was effective in maintaining a stable occlusal relationship.

Patient: The patient was a 79-year-old woman who complained of gingival swelling and pain. After diagnosis, unsalvageable teeth were extracted, the present denture was repaired, and initial periodontal therapy was performed. A metal plate denture was selected due to its strength because the antagonistic dentition included dental implants. As preprosthetic treatment, crowns were placed on the abutment teeth, following which the metal plate denture was inserted.

Discussion: In order to reduce denture mobility, prosthetic treatment was performed using a metal plate denture with a rigid connection type retainer. A good prognosis was obtained because the denture functioned with appropriate support, bracing, retention, and strength, making it possible to distribute the occlusal force and transfer the force in the direction of the tooth axis.

Conclusions: In this case, implants were included in the opposing dentition, and the masticatory performance was improved by wearing a definitive prosthesis with enhanced connector rigidity.

Patient: A 79-year-old woman had masticatory disorders due to inadequate mandibular complete dentures. The maxilla was fitted with Kennedy class 1 removable partial dentures and a panoramic radiograph showed a defect in the right mandibular condyle. The mandible had a discord in the facing relationship with the upper jaw and severe ridge resorption.

Discussion: It was judged that the right deviation of the mandible due to the defect of the right mandibular condyle caused a decrease in the retention of the entire mandibular denture, and piezography was performed when manufacturing the therapeutic denture. It is considered that the maintenance of the entire mandibular denture was improved by setting the artificial tooth arrangement and the denture base polishing surface morphology in the neutral zone.

Conclusions: Retention and stabilization of the denture were effectively achieved by paying attention to the arrangement position of the artificial teeth and morphology of the polished surface.

Patient: The patient was a 53-year-old male who presented with the chief complaint of masticatory disturbance due to fracture of a maxillary denture. The patient received fixed prosthodontic treatment consisting of a dental implant procedure for missing teeth under sedation or general anesthesia in consideration of a severe gagging reflex. The patient was extremely satisfied by the greatly improved esthetics and functionality resulting from the treatment.

Discussion: The patient was hesitant to undergo treatment due to a severe gagging reflex, but showed a positive response when consulted about intravenous sedation or general anesthesia.

Conclusions: Using sedation or general anesthesia was effective in overcoming a severe gagging reflex while carrying out prosthodontic treatment including an implant-supported fixed denture.

Patient: The patient was a 73-year-old male who was edentulous and referred by a head and neck surgeon for fabrication of a palatal augmentation prosthesis (PAP). After operating for tongue and oropharyngeal cancer, reconstruction was performed using the femoral muscle. Partial tongue resection was performed for the tongue cancer, and quadriceps femoris flap reconstruction was performed after oropharyngectomy for the oropharyngeal cancer. In order to improve masticatory and swallowing function, eating functional training was conducted and a complete denture having a PAP was fabricated.

Discussion: At the three-year follow-up, it was found that the prosthodontic treatment together with eating functional training had improved the oral functions of mastication and swallowing, which allowed the patient to adopt a new prosthesis with a standard palatal form.

Conclusions: Both prosthodontic treatment and eating functional training improved oral functions such as mastication and swallowing for the patient who had undergone tongue and oropharyngeal resection.

Patient: The patient was a 64-year-old woman who presented with the chief complaint of a mastication disorder caused by a maxillary anterior tooth defect and bilateral mandibular free-end missing. Uneven alignment of the occlusal plane and occlusal collapse were present. We performed occlusal reconstruction with an implant prosthesis of the maxillary and mandibular defects for rehabilitation.

Discussion: Fixed-implant rehabilitation improved masticatory function. Our goal was to achieve occlusal stability by providing a full-maxillary prosthesis. Approximately four years after installing the final prosthesis, the alignment of the remaining teeth in the implanted region has been retained over time through successive maintenance.

Conclusions: The mastication disorder in this patient was rehabilitated by occlusal reconstruction with implant prosthetics for the defect and occlusal elevation of the remaining teeth by crown restoration.

Patient: A 70-year-old woman presented with difficulty in mastication because of her unstable mandibular denture, as well as difficulty in speaking owing to a drop of her maxillary denture. Intraoral examination revealed severe ridge resorption in both her maxillary and mandibular bones. Piezography was used to fabricate new complete dentures, and consequently, her oral function improved.

Discussion: Piezography enabled us to make complete dentures with artificial teeth positioned in harmony with the perioral muscles and tongue movements, as well as the functional shape of the denture base on the polished surface.

This resulted in improvement of oral function.

Conclusions: Patient satisfaction was achieved by using piezography to fabricate complete dentures for a patient with severe jaw crest resorption.

Patient: A 65-year-old male patient visited our hospital complaining of difficulty of mastication caused by the mobility of maxillary anterior fixed dental prostheses and esthetic dissatisfaction. An irregularity of the occlusal plane and a decrease of vertical dimension of occlusion (VDO) due to severe attrition of teeth were observed. The patient was diagnosed with attrition and masticatory disturbance due to a lack of posterior teeth. Full-mouth rehabilitation was performed after determining the VDO and correcting the occlusal plane using interim restorations and a removable partial treatment denture based on the diagnostic waxing.

Discussion: The patient’s oral health-related quality of life was improved and high satisfaction was obtained by improving masticatory ability and restoring esthetics with full-mouth rehabilitation.

Conclusions: This case indicates that applying full-mouth rehabilitation in the case of irregularity of the occlusal plane and a decrease of VDO leads to longevity and predictability.

Patient: The patient was a 54-year-old man who complained of difficulty eating due to missing molars. He had an occlusal support with the left first premolars, and was diagnosed with dysmasesis due to the loss of occlusal support by molars. Occlusal support was recovered with an implant-supported fixed prosthesis and a fixed bridge. The final prosthesis was fabricated with an improved occlusal plane that provided disocclusion of molars.

Discussion: The dysmasesis was improved by the prosthesis. Furthermore, the improved occlusal plane led to long-term stability and disocclusion of molars, thus protecting the natural teeth and prosthesis from damage and occlusal force, and providing long-term stability.

Conclusions: In this case of distal extension missing molars, the prosthesis including implant-supported fixed prosthesis improved the dysmasesis and occlusal plane. The treatment led to good results for four years and six months.