Over the last decade, digital dentistry, based on computer-aided design (CAD) and computer-aided manufacturing (CAM), has become increasingly popular. The introduction of digital impressions made by intraoral scanners (IOSs) has dramatically changed the entire prosthodontic treatment workflow.

Recently several studies have reported successful applications of a variety of digital techniques for impression making, jaw registration, the arrangement of artificial teeth, the design of denture bases, and the manufacturing of artificial teeth and denture bases to removable partial denture (RPD) fabrication; however, these studies have mainly focused on the digitization of certain parts of the laboratory procedures.

This study aimed to introduce a fully digitalized workflow for RPD fabrication with various digital technologies, including IOS, three-dimensional (3D) printers, and CAD/CAM systems.

CAD/CAM technology is spreading in the field of removable denture, and complete denture production systems have been developed and applied to clinical treatment. It is also possible to fabricate frameworks using CAD/CAM technology. Intraoral scanners have been applied to edentulous jaws, but they have not yet been put into practical use because pressure impressions of mucosa ridge are required for partially edentulous dentition. This paper summarizes the research, clinical treatment, and education on removable partial denture using CAD/CAM technology carried out until now in our department. It also discusses the current status and issues of the application of digital dentistry to removable partial dentures.

We performed a systematic review of the literature to comprehensively review the current status of digital workflow and the challenge in fabricating removable partial dentures. In 2019, RPDs can be fabricated with a fully digital workflow without a definitive cast. However, the indication for full-digital RPD is limited for cases with Kennedy Class III/IV partially edentulous arches with few missing teeth. Intra oral scanners were used for digital impression taking and maxillomandibular relationship recording. CAD/CAM framework fabricated using selective laser melting is commercially available in Japan. Future challenges for improvement in accuracy of intra oral scanners, accuracy and durability of connections between the framework and denture base, and for reduction of fabrication cost remain to be solved in digital removable partial dentures.

Since various factors, namely, the number of missing teeth, the pattern of partial edentulousness, the conditions of abutment teeth and antagonistic teeth, the degree of periodontal disease, the occlusal force, and the patient’s requirements and background, are related to decisions regarding the permanent prostheses, knowing whether to choose a fixed or removable prostheses is often difficult. Prognosis is the most important aspect for prosthetic treatment, and the quality of the treatment cannot be judged by short-term progress; thus, prosthetic rehabilitation can be properly evaluated by long-term observation.

Regarding large prostheses, how to choose between a fixed bridge and a removable partial denture is reconsidered in this review. The selection criteria for fixed and removable prostheses and the factors that affected the oral conditions and prosthetic devices at 10 to 20 years after delivery were imagined based on long-term follow-up.

The presence of the last molar in the case of intermediate molar edentulous is considered to stabilize the jaw position by maintaining the interocclusal relation and contribute to the long-term prognosis and stability of the prosthetic device. From the viewpoint of the missing form, it is expected that the pressure factor will be reduced as the occlusal support tooth and the pressure receipt condition will be improved by avoiding the free end edentulous. In this paper, we would like to consider the significance of the residual molars, that is, the intermediate edentulous. Among them, looking back on the selection conditions of the abutment device considering the effect of connecting and fixing the abutment teeth (primary fixation / secondary fixation), and the intraoral changes in the implant overdenture case in which the free end edentulous was modified to an intermediate edentulous. I would like to consider the harmfulness due to the free end edentulous.

To achieve the long-lasting good result of the prosthodontic treatment, the weakened tooth with a poor prognosis should be extracted before the treatment. In contrast, tooth extraction may be occasionally avoided due to several reasons. Diversified considerations are required to utilize the weakened teeth with a poor prognosis for prosthetic treatment and protect them. For the treatments with bridges including weakened abutment teeth, bridges that are placed with temporary cement and can be easily removed by the operators are effective. For the treatments with removable partial dentures, the secondary splinting with dentures designed to be connected with abutments rigidly or the applications of root coping to improve the crown-root ratios of the abutments are effective. In the prosthetic treatment with abutment teeth with a poor prognosis, both sufficient informed consent in advance and high motivation of both the patients and the operators are important factors.

While restoring the patients with short-span partial edentulism, it is often difficult to determine the type of final prosthesis. In such cases that can be restored with both fixed and removable partial dentures, meticulous efforts should be made to fabricate prostheses with functionality, aesthetics, cleanability, and durability. The subject of this article is “Proper treatment planning for short-span partial edentulism.” Several cases restored with fixed or removable partial denture solely, or combined, would be presented. The decision-making progress would be discussed as well.

Purpose: To assess the effects of microwave heating of polyether ether ketone (PEEK) on the amount of deformation and bactericidal effects on Candida albicans (C. albicans), and to investigate the possibility of application as a denture base material.

Method: 1) PEEK and other test pieces formed from resins for denture bases were subjected to microwave heating and deformation resistance was measured. 2) PEEK bearing C. albicans was subjected to washing with denture cleanser or microwave heating sterilization, and remaining live bacteria were then counted. 3) PEEK bearing a C. albicans biofilm was similarly subjected to washing with denture cleanser or microwave heating sterilization and remaining live bacteria were then counted.

Results: 1) Deformation of PEEK under microwave heating was negligible, with no apparent effect of repeated heatings, whereas deformation of denture base resins increased with the number of times of heating. 2) The bactericidal rate on PEEK was 99.9% by denture cleanser washing and 100% by microwave heating sterilization. 3) The bactericidal rate in the biofilm formed on PEEK was 99.7% by denture cleanser washing and more than 99.9% by microwave heating sterilization.

Conclusion: PEEK offers superior deformation and bactericidal effects under microwave heating and holds promise as a material for dentures and other intraoral appliances.

Patient: The patient was a 72-year-old female with edentulous upper and lower jaws, wearing no dentures. The case was diagnosed with masticatory dysfunction, dysarthria and esthetic disorder caused by edentulous upper and lower jaws after surgery for lower gingival cancer. The patient was treated using the usual treatment steps for complete dentures.

Discussion: In this case, denture-support areas of the mandibular residual ridge had been lost due to lower gingival cancer. It was considered that high patient satisfaction on both subjective and objective evaluations was achieved by establishing an adequate denture border, polished surface form, arrangement of artificial teeth, and elimination of factors that hindered the stability of the lower denture.

Conclusion: Maxillofacial prosthetic treatment with complete dentures, functionally harmonizing the remaining tissue and oral cavity after surgery, was performed. Both functional and esthetic improvements were observed, contributing to improvement of the patient’s QOL.

Patient: The case was an 85-year-old female patient who complained of a damaged mandibular denture. The only remaining tooth was the upper left canine. The mandibular ridge was highly absorbed, and the denture had a poor shape and lowered occlusal vertical dimension. We made a duplicate denture, and improved its shape and occlusal vertical dimension, before fabricating a treatment denture. After confirming that the patient could adapt to the treatment denture, the definitive denture was fabricated.

Discussion: By confirming the fit by using the treatment denture, the patient could smoothly adapt to the definitive denture.

Conclusion: Using a duplicate denture as a treatment denture is useful when it is necessary to judge whether a patient can adapt to the new shape and occlusal vertical dimension.

Patient: A 71-year-old female presented with the chief complaint of esthetics problems and masticatory disturbance. She was referred to the department of prosthodontics to have full mouth reconstruction after delivering an immediate denture for 71|12567 at the division of comprehensive clinical dentistry. Occlusal support was found only on the left premolars. The interocclusal space was reduced on the anterior and the occlusal vertical dimension was also reduced anatomically. Full mouth reconstruction was performed by increasing the vertical dimension to improve her chief complaints.

Discussion: The occlusal support was restored, and masticatory function was improved by a final restoration that increased the vertical dimension based on a mandibular rest position. Moreover, esthetics were improved due to the design using an attachment.

Conclusion: Full mouth reconstruction achieved both functional and esthetic satisfaction for the patient, thus improving her quality of life.

Patient: A 67-year-old female patient presented with the chief complaint of chewing difficulties due to poor retention of a mandibular complete overdenture. The mandibular residual ridge was resorbed and knife-edged. The existing overdenture was not well retained or stable due to the movement of |12 . Therefore, |12 was extracted, two implants were placed in the mandible, and an implant overdenture with a stud attachment was placed.

Discussion: Masticatory function was improved by using the form of the denture that had been worn to determine the placement of the implant and by fabricating a final denture with stud attachments to provide retention.

Conclusion: The placement of two implants and an implant overdenture in an edentulous patient with a mandibular knife-edge ridge showed good results.

Patient: A 52-year-old female patient visited the hospital in October 2010 with a chief complaint of difficulty in chewing. She was diagnosed with masticatory disorders due to missing bilateral mandibular molars. She wore a splint-type treatment denture for the purpose of dentition recovery and occlusal elevation of the molar defect, and no functional problems were observed. Prosthetic treatment was planned and performed with reconstructions using dental implants and fixed dental prostheses.

Discussion: Due to the treatment plan considering the age, hope for treatment, and living conditions, improvement of masticatory function and esthetics was obtained, and the patient has been highly satisfied.

Conclusion: In this patient with missing mandibular molars due to deep overbite and a lack of prosthetic space, occlusal reconstruction was performed using an implant prosthesis and crown prosthesis, which improved the patient’s satisfaction.

Patient: The patient was a 72-year-old male with the chief complaint of eating difficulty 5 years after right segmental mandibulectomy without reconstruction. The occlusal contacts on the non-surgical side had been lost due to deviation of the remaining mandibular segment toward the resected right side. A mandibular removable partial denture and maxillary prosthesis with palatal ramp guiding the mandible to the left side were fabricated. Additionally, he was educated and encouraged to take nutritional supplementary food. After insertion of the prostheses, the time required to eat meals was shortened, and body weight and maximum tongue pressure were increased.

Discussion: When prosthodontic rehabilitation of mastication is insufficient, nutritional management for the patient is important.

Conclusion: To maintain masticatory function and improve nutritional status, both prosthetic rehabilitation and nutrition education must be included for segmental mandibulectomy patients without bone reconstruction.

Patient: A 59-year-old woman presented with poor esthetics because of reverse articulation and masticatory disturbance caused by missing teeth. After increasing the occlusal vertical dimension and occlusal reconstruction using treatment dentures, fixed prostheses with dental implants in the maxilla and mandibular molars improved the patient’s masticatory function. The anterior teeth of the maxilla ware esthetically improved with all-ceramic crowns.

Discussion: The acquisition of occlusal support with the implant prostheses and the improvement of esthetics with all-ceramic crowns of maxillary anterior teeth significantly enhanced the patient’s oral health-related quality of life.

Conclusion: A case with esthetic dissatisfaction and masticatory disturbance was treated with implant and fixed prostheses, resulting in an excellent treatment outcome.

Patient: The patient was a 73-year-old female who came to our hospital complaining of chewing difficulty due to mobility of the right lower central incisor. Inadequate fit of the denture, horizontal resorption of alveolar bone in the whole jaw, secondary caries of crown margins, crowding in the anterior teeth of the mandible, and disturbance of the occlusal plane were observed. After orthodontic treatment and correction of the occlusal plane using provisional restorations, the upper jaw was fitted with a Konus Krone denture and the lower jaw with a porcelain baked bridge, and the occlusion was reconstructed.

Discussion: The Konus Krone denture, with its strong secondary fixation effect, provided favorable denture retention and stability.

Conclusion: A stable prognosis with improved mastication and esthetics was achieved with the Konus Krone denture.

Patient: A 73-year-old woman suffered from chewing difficulties due to detached dentures. The dentures in use were too small, and hypertrophy of her tongue and protrusion of buccal mucosa were evident. Complete dentures were newly manufactured by the flange technique and arrangement of artificial teeth based on her previously occupied natural dentition.

Discussion: It is suggested that making the polished denture surface functional in harmony with the tongue and perioral muscles, and arrangement of artificial teeth based on natural dentition contributed to stability of the dentures and provided a good prognosis.

Conclusion: In prosthetic treatment of an edentulous patient with hypertrophy of the tongue and perioral muscles, new complete dentures by using the flange technique and artificial teeth arrangement considering the natural dentition were effective for restoration and maintenance of masticatory function.

Patient: A 76-year-old female patient complained of incompatibility with the mandibular denture and masticatory dysfunction due to pain in 21| . An intraoral examination revealed a high degree of residual ridge resorption in the mandibular molar region bilaterally, resulting in instability of the denture. Extraction of 21| was performed after obtaining informed consent. Subsequently, a mandibular implant overdenture was inserted.

Discussion: By preserving the remaining teeth, it was possible to protect the wound surface immediately after implant placement. The implant-supported overdenture using a magnetic attachment made it easier for the elderly patient to put on and take off the dentures.

Conclusion: An implant-supported overdenture was applied to a patient with a high degree of mandibular residual ridge resorption, resulting in a good prognosis.

Patient: The patient was a 36-year-old female who had esthetic dissatisfaction with the maxillary anterior teeth. After examination, the patient’s chief complaint was diagnosed as severe periodontitis associated with occlusal interference. The tooth that was diagnosed as hopeless and the tooth that was causing occlusal interference were both extracted. After periodontal therapy and an evaluation of the occlusal position, an implant prosthesis was delivered to improve the esthetic and occlusal problems.

Discussion: The occlusal position was evaluated by a dental articulator, in order to determine where the occlusal interference was occurring. Implant prosthesis treatment was planned accurately by re-evaluating the occlusal position at the time of reexamination after basic treatment for periodontal disease, resulting in a favorable outcome.

Conclusion: Implant prosthesis treatment with the evaluation of occlusal position utilizing a dental articulator improved the esthetic dissatisfaction of a patient caused by occlusal disorder.

Patient: The patient was a 63-year-old female. She presented to the dental office with the chief complaints of inadequate denture retention, pain in residual ridges and esthetics. The bases and clasps of her upper- and lower-jaw dentures were incompatible. She had complex non-vertical stop occlusion, which had led to seriously absorbed residual ridges and increased tooth mobility. After cutting off the crowns of the mandibular teeth, oral rehabilitation applying an overdenture with magnetic attachment was performed.

Discussion: Applying an overdenture in the mandible improved esthetics, partially resolved the non-vertical stop occlusion and decreased the occlusal force. This may have improved denture retention and decreased the load on residual teeth and ridges, and thus reduced pain.

Conclusion: In this case, partially resolving non-vertical stop occlusion decreased pain disorder and improved masticatory dysfunction.