In recent years, it is possible to design prostheses using virtual articulators in CAD/CAM system. Conventional articulators are necessary for the fabrication of bio-harmonized prostheses with the indirect method in prosthodontics, and various ones have been developed. In this present report, we classified the virtual articulators based on conventional articulator classification (hinge articulator, average value articulator, semiadjustable articulator, fully adjustable articulator) to discuss the features and usefulness of the virtual articulators. Additionally, we introduce our own developed new-generation virtual articulator, which applied the high precision 3D reconstruction and jaw tracking technologies.

In the field of implant dentistry, it is no doubt that diagnostic imaging is important, and information technology (IT) has been already introduced to constitute three dimensional(3D) images of joe bones at the beginning of 21 century. In addition, introduction and development of IT enabled us to perform the simulation of not only implant surgery but also crown placement on the exclusive software. Moreover, the simulated position of implants can be reproduced in the patient mouth using surgical guide made by CAD/CAM. Consequently, application of those techniques established the immediate restoration termed as One Day Treatment. Recently, Dynamic navigation system was also developed, in which simulation of implant surgery was performed, images of drills and joes are superimposed, and ideal drill position was shown on PC monitor as the real time navigation. Thus, application of IT to implant therapy has been spreading and robot surgery has been developed as the next generation therapy. So far, limited data has been reported and clinical use is not available. However, drastic change and paradigm shift might be occurred, depending on the innovation of the specialized software, in this field.

Digital technology is getting popular in various fields of dentistry. It has become possible for doctors to perform treatments safely and securely, and to improve quality of treatment. In particular, the interdisciplinary approach, which promotes new workflow developments by conducting inter-sectional collaboration across multiple clinical departments, is considered to be well compatible with digital technology. We have developed an integrated simulation software. It is possible to share simulation data information among healthcare professionals such as dentists, dental hygienists, and dental technicians. Therefore, this software can lead to a successful interdisciplinary approach across oral implants, orthodontics, prosthetic dentistry and oral surgery. This manuscript introduces the functions of our software. We will continue to research and develop tools that will help dental industry and provide them to dental fields.

Sleep braxism (SB) is considered as a risk factor for various dental ailments. Treatments and managements of SB are important matters in dental clinical practice. Appropriate diagnosis and assessment are indispensable for the treatments and managements of SB. It has been earnestly desired to introduce an accurate and simple examination method to the dental practice. In April 2020, the electromyography (EMG) on masticatory muscle during sleep to diagnose and assess SB was covered by the Japanese government insurance system. The introduction of sleep electromyography using a wearable EMG device into daily clinical practice and the insurance coverage are expected to improve quality of dental practice, including realization of tailor-made treatments based on objective indicators, and its innovative effect is expected. In addition, the wearable EMG device has potential to be applied to various researches and clinical practices in a wide range of fields.

The alveolar bone is affected by systemic factors due to non-infectious diseases such as osteoporosis and lifestyle-related diseases, and local factors such as periodontal disease and excessive mechanical stress. However, the pathological condition of alveolar bone has been difficult to evaluate and has been left unattended. The method for evaluating alveolar bone density using Bone Right enabled quantitative diagnosis of alveolar osteopenia and alveolar sclerosis. It is effective for prolonging the life of teeth by promptly detecting the signs of excessive alveolar bone resorption, and difficulties caused by medication-related osteonecrosis of the jaw (MRONJ), etc. due to noncommunicable Diseases (NCDs) that cause systemic bone loss, which have raised difficulty in diagnosis until now, enabling safe and secure dental treatment.

Purpose: Quantifying the chewing function of denture wearers is important in evaluating the preoperative examination and postoperative course of denture prostheses. There are direct and indirect methods for measuring masticatory ability. When measuring masticatory ability in clinical practice, our department conducts a questionnaire survey using Sato’s chewing function evaluation table (“Chewing Score 20”). This is a method of comprehensively evaluating the chewing function of the denture wearer for ingestible food, and is a direct examination method. However, the method requires many food items and is time-consuming, and so further improvement is considered necessary.

The purpose of this study was to develop a chewing function evaluation table (“Chewing Score 10”) with 10 kinds of carefully selected food, and to examine its usefulness.

Methods: The 34 subjects were all upper and lower complete denture wearers. The items “never eaten” and “dislike” were added to Chewing Score 20. Two types of food were selected from the five groups classified by chewing index. We developed Chewing Score 10 by excluding foods that many people dislike. In addition, the correlations among Chewing Score 20, chewing efficiency, and Chewing Score 10 were examined.

Results: A very strong positive correlation was observed between the prototype Chewing Score 10 and Chewing Score 20 (r = 0.97, p<0.01). In addition, Chewing Score 10 was found to have a significant correlation of the same degree as Chewing Score 20 (r = 0.62, p<0.01) for masticatory ability (r = 0.57, p<0.01).

Conclusion: The usefulness of Chewing Score 10 was verified.

Patient: The patient was a 69-year-old woman with a chief complaint of masticatory function and esthetic disorder caused by wearing of complete dentures. Dentures meeting her functional and esthetic requirements were constructed and fitted in the patient three times, and the mastication ability and satisfaction of the patient before and after treatment were evaluated by a multi-axis assessment protocol (OHIP-J54, psychological health condition). We report the long-term continuous application of a multi-axis assessment protocol in edentulous prosthetic treatment.

Discussion: All assessments showed an improvement tendency by treatment for the chief complaint at the first visit. On the other hand, in the treatment for the chief complaint at the return visit, immediately after the treatment there was no improvement compared to the denture in use, but it was observed to improve with longer period of use. In addition, the psychological health condition tended to return to the worse state at 1 to 2 years after denture insertion compared to the condition at 1 to 3 months after insertion. In the subscale analysis of OHIP-J54, “Psychological discomfort” and “Psychological disability” tended to worsen over time. This was considered to be a main trigger for the remaking of dentures.

Conclusion: In cases suspected of having psychological health condition problems, it was shown that continuous evaluation of patient satisfaction, masticatory function, and a multi-axis assessment protocol are important.

Patient: The patient was an 85-year-old man who visited our hospital with a complaint of food accumulation on the outside of his dentures, difficulty while speaking, and pain while eating. Based on the medical history and various examinations, his condition was diagnosed as “masticatory disorder and pronunciation disorder caused by incompatibility of upper and lower complete dentures and morphological defect of the polished surface of the denture base.” After improvement in oral hygiene and the alveolar ridges, new upper and lower complete dentures with cast metal were fabricated.

Discussion: Better stability of the new dentures rendered them satisfactory to the patient. Improvement in speech was achieved by palatography. By harmonizing the form of the denture flanges with the surrounding musculature, food accumulation on the polished denture surfaces disappeared. The masticatory score changed from 39.4 at the first visit to 81.1 after wearing the new dentures for 1 month.

Conclusion: After wearing the new dentures for 3 years, the patient is satisfied with the esthetics and function. It is considered that the dentures contributed to improving the patient’s health.

Patient: The patient was a 37-year-old woman. She visited our clinic to seek treatment to improve the esthetic appearance of her teeth, specifically the discoloration of the upper and lower front teeth because she had been unhappy since her permanent tooth eruption. An examination prior to the procedure revealed inadequate anterior guidance. Occlusal adjustment and tooth extraction were performed, and porcelain laminate veneers were placed as the final prosthetic device.

Discussion: The patient has not developed any inflammation of the periodontal tissue or tooth discoloration for the 10 years after placing the prosthetic device. The procedure led to high patient satisfaction with no abnormal findings on dental X-ray to date.

Conclusion: Esthetics and mastication improved significantly by restoring the anterior guidance and using porcelain laminate veneers for the upper and lower front teeth. Our findings suggest that porcelain laminate veneers may facilitate positive long-term outcomes.

Patient: The patient was a 67-year-old man. His chief complaint was difficulty in chewing due to lower right and upper left missing molars. Sleep bruxism (SB) existed subjectively and objectively. In order to improve the chief complaint, prosthodontic implant treatment that could withstand excessive occlusal force including SB was performed.

Discussion: After delivery of the final prostheses, the patient has been recalled periodically. The patient was very satisfied with this treatment without any specific problems during the 5-year follow-up period. Improvement of masticatory function and increase of occlusal support area by the implant treatment are considered to have led to good progress and high patient satisfaction.

Conclusion: The main complaint was improved by performing a minimally required number of implants and prosthetic treatment considering the occlusal force including SB.

Patient: An 82-year-old man had masticatory disturbances caused by high mobility of the upper posterior teeth and absence of the lower posterior teeth. As the initial treatment, the patient was motivated to improve plaque control, and periodontally hopeless teeth were extracted. Provisional restorations were prepared immediately after the extraction. After occlusion was stabilized, final restorations were manufactured for the patient. Esthetic and masticatory disorders were resolved by a telescopic denture, which improved the long-term prognosis and facilitated oral hygiene. The patient was satisfied with the function and esthetics in three years.

Discussion: A telescopic denture was successful in providing rigid support for residual teeth, and the patient’s oral prognosis was good.

Conclusion: As a treatment for missing teeth in elderly patients, a cone crown telescopic denture helps resolve esthetic and masticatory disorders and improves the patient’s oral condition.

Patient: A 61-year-old woman visited our clinic complaining of inability to bite at the molars due to gingival swelling. The upper and lower bilateral molars were missing, and the root of the upper left canine and second premolar were fractured. Implant prosthetic treatment was done on the affected area to restore masticatory functions and esthetics.

Discussion: Due to loss of molars, excessive occlusal force had caused root fracture of the canine and premolar. Despite this, the patient’s periodontal tissue has been stable for a long time by the appropriate distribution of occlusal force on the bilateral posterior tooth and by relieving lateral force by canine guidance.

Conclusion: Periodontal tissue care and the use of provisional restorations are necessary in the treatment of missing unilateral distal extension by using implant prostheses.

Patient: The patient was a 67-year-old edentulous woman complaining of poor retention of her mandibular denture. Further investigations indicated that it was due to insufficient extension of the anterior lingual periphery. To improve this, an appropriate dimension was applied to the new denture with border molding, and closed mouth functional impression techniques.

Discussion: With the previous denture, the anterior lingual periphery did not extend beyond the mental spine, which tends to happen when severe residual ridge reduction and a thin layer of mucosa are present. The key to establishing absolute functional retention against functional force was to extend the anterior lingual periphery and cover the mental spine entirely, thus significantly improving retention as well as masticatory function.

Conclusion: Determination of the position and shape of the denture periphery is one of the most important components for a mandibular complete denture to achieve absolute retention.

Patient: The patient was a 62-year-old male who complained of an esthetic problem due to tooth attrition. Sleep bruxism was suspected as the etiology of attrition, which was confirmed by his spouse and his masticatory muscle pain.

Discussion: The esthetic problem was solved by full-mouth rehabilitation combined with increasing the occlusal vertical dimension. During the follow-up period, the patient wore a night guard when he slept, and so did not experience fracture of the prosthesis.

Conclusion: Full-mouth rehabilitation combined with increasing the occlusal vertical dimension seems effective for esthetic problems caused by tooth attrition.

Patient: A 74-year-old man visited our clinic with a chief complaint of mobility of a complete lower denture and pain in the mucosa below the denture base at occlusion. There was marked absorption of the alveolar ridge in the mandible. The occlusal condition of the complete mandibular denture was poor and mobility was noted at the traction of the angle of the mouth. We diagnosed that the patient’s pain and masticatory disturbance were caused by poor occlusal contact and morphology of the polished base surface of the complete mandibular denture and the poor arrangement position of the artificial teeth, and decided to prepare new maxillary and mandibular dentures. For the mandibular denture, we used the flange technique and a soft relining material.

Discussion: In this case, it was considered that good results could be obtained by the harmony with the surrounding mobile tissue by the flange technique and the buffering effect of the soft relining material.

Conclusion: Pain and masticatory disturbance in an edentulous patient were resolved using the flange technique and a soft relining material with marked absorption of the alveolar ridge.

Patient: A 61-year-old female who underwent partial maxillectomy suffered from mastication difficulties, dysphasia, articulation disorders and esthetic concerns. The maxillectomy defect was restored with an interim obturator prosthesis prior to fabrication of the definitive implant-retained obturator prosthesis.

Discussion: The interim obturator prosthesis restored oral function and esthetics, which increased her motivation for dental treatments. The fixed dental prostheses were delivered after orthodontic treatment in the posterior mandible. The definitive implant-retained obturator prosthesis enhanced retention, stability, and support and improved mastication efficiency and oral health-related quality of life (OHRQoL).

Conclusion: The interim obturator prosthesis restored function and esthetics, and the definitive implant-retained obturator prosthesis provided better results.