When considering the 100-year life, the key is how to extend healthy life expectancy. In this regard, childhood is an important period to lay the foundation for proper health care. Infancy is the period for acquiring oral function, and it is also an important period for gaining proper lifestyle habits to promote the development of oral function. School age is a time when educational approaches to maintain lifestyle and improved health skills are required. In adolescence, it is necessary to practice health promotion and raise awareness of health management. In other words, based on the health promotion, continuous oral management from children to adolescents is important.

In prosthetic dentistry, the concept of prevention of aggravation and preemptive medicine is important, and preventive managements depending on the condition of each patient are required so as not to cause a high-risk oral condition that makes the prosthodontic treatment difficult. We need clinical indicators that allow prosthodontists to predict such risks, and at the same time, it is also important to set clinical indicators that make general medical staffs and patients themselves realize the situation.

In our prosthodontic field, we should understand that “zest for eating” is a total ability, considering not only oral factors but also eating behavior and eating habit factors, as well as environmental factors and individual factors. Ultimately, clinical indicators of “zest for eating” and final outcomes in the patients need to be established and made known to the public and healthcare professionals.

Prosthodontic treatments aim to improve patients’ health and quality of life through rehabilitation of “masticatory function”. Prosthodontic treatments have attracted much attention in recent times as a strategy to prevent or minimize the need for nursing care in patients with frailty and dementia. Several studies have reported a positive association between deterioration of masticatory function secondary to tooth loss or disuse of dentures and cognitive dysfunction or dementia onset; however, this association remains controversial. This could be attributed to the unavailability of a standardized method in dental practice for evaluation of masticatory function. In this article, we discuss strategies to establish standardized indicators to “measure” masticatory function.

While dentists routinely provide prosthodontic treatment in patients with teeth missing, we do not fully understand its effectiveness on their lives. Maintaining oral function by prosthodontic treatment enables patients to intake a variety of foods and nutrition. Through the advantage, prosthodontic treatment can not only improve oral health related quality of life, but also prevent long-term care and frailty, and cognitive decline in independent community-dwelling older individuals. In this article, we introduce the evidences from the results of recent high quality systematic reviews and original articles, that depict higher number of present teeth can improve their life prognosis more in community-dwelling older individuals. Additionally, the joint research by Japan Prosthodontic Society and Tokyo Metropolitan Institute of Gerontology also demonstrated that number of functional teeth can more strongly predicts all-cause mortality than number of present teeth in those individuals. In older people at the earlier stage requiring support/long-term care, mastication and dysphagia rehabilitation combined with nutritional therapy is also important as well as routine prosthodontic restoration, while in significantly disabled older people at the latter stage requiring long-term care, adjustment of eating environment and food texture as well as dietary supplements administration combining with various nutritional intake routes are important. By interpreting clinical evidences according to various life stages, we would like to emphasize that medical and social responsibilities of prosthodontic specialists are pivotal at any life stage.

Purpose: Although the modern diet tends to be softer than in the past, the effects of a softer diet on temporomandibular disorders have not been clarified. Therefore, this study investigated the effects of eating soft food on the morphology and surface of the mandibular condyle by comparing mice that consumed a powder diet with mice that consumed a traditional solid diet.

Methods: We used the Senescence-Accelerated Mouse Prone 8 (SAMP8) that develops degenerative joint disease of the mandibular condyle in an age-dependent manner. Thirty male SAMP8 mice were divided into three equal groups of ten: 1) Solid diet (SD) group, fed a solid diet until the age of 7 months, 2) Powder diet (PD) group, fed a powder diet until the age of 7 months, and 3) Weaning group (WG), which were weaned at 3 weeks.

In the experiment, the mandibular condyle was photographed under a stereomicroscope. The condylar surface was evaluated using Chen’s classification, and its morphology was image-analyzed using image J software to assess condylar length, width, area and circularity. In addition, bone mineral density (BMD) was evaluated by analyzing soft X-ray images.

Results: In terms of morphology, the SD group showed significantly larger changes than the PD group and WG in condylar length, width, area, and BMD. Circularity showed increasingly large values in the order of WG>PD>SD, with significantly greater circularity in the WG as compared to the SD group. Additionally, the condylar surface did not change in the WG according to Chen’s classification. However, the SD and PD groups showed significant changes. The differences between all groups were significant.

Conclusions: These results show that the morphology of the mandibular condyle remains almost unchanged from that in the weaning period by feeding a powder diet, and that a powder diet tends to suppress the growth of the condyle.

Purpose: This study aimed to examine the positional effect of a removable partial denture palatal bar on speech-related discomfort using a subjective scale (visual analog scale: VAS) and objective brain activity measurements.

Methods: Twenty-five adults (mean age, 31.8 years) without speech function abnormalities wore a palatal bar on the maxilla and uttered the following sentences: “Sakura no Hana ga sakimashita” (first) and “America no Mississippi” (second). The VAS was used to evaluate the subjective discomfort experienced by the subjects during speech. The brain activity during speech was objectively evaluated using functional near-infrared spectroscopy (fNIRS). The dependent variables were the VAS score and the change in the oxy/deoxyhemoglobin (oxy/deoxy-Hb) concentrations in the prefrontal cortex.

Results: The VAS scores showed a tendency to increase with the posterior palatal bar (“posterior PB”) attached when uttering both sentences. Conversely, no significant changes in brain activity were observed for the first spoken sentence. For the second spoken sentence, the oxy-Hb concentration was high with the middle palatal bar (“middle PB”) attached, and it was significantly different from that when the anterior palatal bar (“anterior PB”) was attached. The deoxy-Hb concentration was high with the anterior PB attached. A significant difference in the deoxy-Hb concentration was found between the anterior PB and the middle PB as well as the anterior PB and the posterior PB.

Conclusions: The outcomes of the subjective evaluations of the anterior PB and middle PB were similar; however, that for the posterior PB was higher than the other palatal bars, reflecting the degree of inhibition of tongue movement. fNIRS showed that brain activity varied with the position of the palatal bar and speech content, possibly reflecting the cognitive load required for smooth utterance under the altered internal conditions of the oral cavity.

Patient: The patient was a 39-year-old man with the main complaint of masticatory disorder and esthetic dissatisfaction due to severe chronic periodontitis. Intensive periodontal treatment succeeded in improving the overall periodontal pockets. After correcting the protrusion and flare-out of the anterior teeth without changing the occlusion of the molars, the occlusion was reconstructed using provisional prostheses, followed by the placement of fixed dental prostheses.

Discussion: Maintaining the patient’s motivation for periodontal treatment and the reflection of occlusion and configuration of the provisional prostheses to the definitive prostheses led to a stable prognosis.

Conclusion: Comprehensive treatment and management, including periodontal treatment and occlusion improvement, for this patient with severe periodontal disease suggests that fixed prosthetic devices can be maintained for a long period of time.

Patient: The patient was a 65-year-old male. The chief complaint was masticatory disorder in the molar region and concerns about the esthetics of the edentulous anterior maxilla. Intraoral examination revealed reduced occlusal support, infraocclusion, and inability of the mandible to move laterally. The occlusal vertical dimension was restored by a treatment denture, and the provisional restoration was adjusted to provide canine guidance. Finally, fixed prostheses and a removable partial denture were provided.

Discussion: Appropriate vertical occlusal height and anterior guidance were determined using provisional restorations and a treatment denture. Transferring the occlusal relationship to the final prostheses using a custom incisal guide table led to satisfactory clinical results.

Conclusion: In this case, masticatory function was improved by restoration of occlusal support and appropriate anterior guidance. Appropriate occlusion led to the preservation of masticatory function and occlusal support without any complications.

Patient: A 78-year-old woman visited our prosthodontics department with the chief complaint of masticatory disturbance caused by movement of the upper and lower jaw removable partial dentures. The patient had only seven teeth left, and panoramic radiograph and periodontal histology showed severe jaw periodontitis. In the removable partial denture, there was incompatibility of the abutment device and mandibular artificial teeth wear, with poor retention and stability. We decided to fabricate an implant overdenture that would be easy to maintain in the future. Moreover, it was set using a design that uses a metal frame for denture manufacturing.

Discussion: In this case, it was considered that the retention and stability of dentures in the implant led to the improvement of masticatory ability and quality of life.

Conclusion: We could successfully improve the patient’s masticatory ability by designing an implant overdenture for edentulous jaws.

Patient: The patient was a 67-year-old woman with a chief complaint of difficulty in mastication due to lower denture mobility. Vertical root fractures in the remaining teeth were suspected because a periodontal pocket of 6 mm or more was detected. After the extraction of abutment teeth, masticatory function was improved by placing a four-implant-supported overdenture on the lower jaw.

Discussion: During the 4-year follow-up, neither bone resorption around the implant body nor absorption of the residual ridge was observed. Stabilization of the denture by a rigid support was achieved using four implants.

Conclusion: The problem of mastication difficulty in this case was improved by a mandibular implant overdenture.

Patient: An 80-year-old female patient visited our hospital with a chief complaint of mastication disorder due to maladaptation of a mandibular compete denture. The patient had bilateral severe residual ridge resorption. We restored the masticatory function by fabricating an implant-supported overdenture by placing two implants and applying immediate loading with computer-guided flapless surgery.

Discussion: The support and retention effects of the magnetic attachment on the two implant abutments contributed to stabilizing the implant overdenture.

Conclusion: This case indicated that an implant overdenture is an effective option for edentulous patients with severe residual ridge resorption of the mandible and improves the oral health-related quality of life for patients.

Patient: A 50-year-old woman presented with the chief complaints of mastication difficulties because of a missing lower right premolar caused by occlusal trauma to the lower-left premolar area. The patient had developed a bilateral mandibular distal extension missing following tooth extraction owing to the difficulty of conserving it. We performed dental implant treatment on the defect, with good results.

Discussion: Through repeated occlusal adjustment and morphological correction of the temporary prostheses and cross-mounting, it was possible to reflect the occlusion and morphology of the temporary prostheses in the final prostheses.

Conclusion: Implant treatment can be effective in the restoration of masticatory function, maintenance of esthetic appearance, and improvement of the oral health-related quality of life of patients with mandibular distal extension missing.

Patient: The patient was a 69-year-old female who was admitted to our Removable Prosthodontics Division with an eating disorder caused by instability of a mandibular complete denture after glossectomy for oropharyngeal cancer. She had been diagnosed with dysarthria and dysphagia with lingual movement disorder after the glossectomy. Therefore, a palatal augmentation prosthesis (PAP) on maxillary complete denture and mandibular complete denture were manufactured.

Discussion: It was considered that the functional evaluation and rehabilitation of the patient enabled a suitable polished surface shape to be prepared, and also enhanced the patient’s motivation toward daily training and the therapeutic effect.

Conclusion: In this case, a PAP with a suitable shape in the oral cavity and continuous rehabilitation improved dysarthria and dysphagia after a glossectomy for oropharyngeal cancer.

Patient: The patient was a 57-year-old woman who complained of an esthetic problem. She exhibited severe tooth attrition due to sleep bruxism. Sleep bruxism had been pointed out by her sleep partners, and it is probable that excessive occlusal force was exerted on the dentin and prosthesis over a long period of time.

Discussion: The esthetic problem due to sleep bruxism associated with severe tooth attrition was improved by the occlusal rehabilitation followed by increasing the vertical dimension, which was maintained with occlusal splint therapy.

Conclusion: Occlusal rehabilitation followed by increasing the vertical dimension seems effective for esthetic problems caused by tooth attrition.

Patient: The patient was a 71-year-old male who visited our hospital with the chief complaint of erosion on the left mandibular molar gingiva. As a result of examination, the erosion was diagnosed to be a malignant tumor. After performing marginal mandibulectomy and then simultaneously replacing the wound with an implant under general anesthesia, an implant-supported overdenture was then fabricated.

Discussion: In this case, a favorable result was obtained by means of an implant-supported overdenture which was fabricated and delivered at an early postoperative stage.

Conclusion: By planning and preparing to perform prosthetic treatment before surgery in anticipation of a good postoperative functional recovery, not only the number of operations, but also the waiting period until the final prosthesis could be shortened, and a good functional recovery was rapidly achieved.