It remains unclear whether digital impressions obtained using an intraoral scanner are sufficiently accurate for use in fabrication of removable partial dentures. We therefore compared the trueness and precision between conventional and digital impressions in the partially edentulous mandible. Mandibular Kennedy Class I and III models with soft silicone simulated-mucosa placed on the residual edentulous ridge were used. The reference models were converted to standard triangulated language (STL) file format using an extraoral scanner. Digital impressions were obtained using an intraoral scanner with a large or small scanning head, and converted to STL files. For conventional impressions, pressure impressions of the reference models were made and working casts fabricated using modified dental stone; these were converted to STL file format using an extraoral scanner. Conversion to STL file format was performed 5 times for each method. Trueness and precision were evaluated by deviation analysis using three-dimensional image processing software. Digital impressions had superior trueness (54-108μm), but inferior precision (100-121μm) compared to conventional impressions (trueness 122-157μm, precision 52-119μm). The larger intraoral scanning head showed better trueness and precision than the smaller head, and on average required fewer scanned images of digital impressions than the smaller head (p<0.05). On the color map, the deviation distribution tended to differ between the conventional and digital impressions. Digital impressions are partially comparable to conventional impressions in terms of accuracy; the use of a larger scanning head may improve the accuracy for removable partial denture fabrication.

This position paper proposes a definition and naming standard for removable partial dentures (RPDs) using thermoplastic resin, and presents a guideline for clinical application. A panel of 14 experts having broad experience with clinical application of RPDs using thermoplastic resin was selected from members of the Japan Prosthodontic Society. At a meeting of the panel, "non-metal clasp denture" was referred as the generic name of RPDs with retentive elements (resin clasps) made of thermoplastic resin. The panel classified non-metal clasp dentures into two types: one with a flexible structure that lacks a metal framework and the other having a rigid structure that includes a metal framework. According to current prosthetic principles, flexible non-metal clasp dentures are not recommended as definitive dentures, except for limited cases such as patients with a metal allergy. Rigid non-metal clasp dentures are recommended in cases where patients will not accept metal clasps for esthetic reasons. Non-metal clasp dentures should follow the same design principles as conventional RPDs using metal clasps.

Patients perceive the impact of oral disorder in four major areas, the dimensions of oral health‐related quality life (OHRQoL) Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact. The functional aspect is essential given the need of chewing, biting, speech and swallowing. The objective of this study was to identify OHRQoL information for dental subjects with functional oral health problems. In a systematic review, distinct and clinically relevant groups of dental subject samples, in this study called “population groups,” with such functional OHRQoL information based on the Oral Health Impact Profile (OHIP) were identified (PROSPERO registration: CRD42017064033). The search strategy was “Oral Health Impact Profile” or OHIP. Searches were conducted in the PubMed interface of the Medline database, EMBASE, Cochrane, CINAHL and PsyINFO on 8 June 2017 and updated on 14 January 2019. Published OHIP domain data of different versions were recalculated into OHIP‐14`s Physical Disability domain score, characterising the subject's Oral Function impact. 3,653 potentially abstracts were screened. We identified 78 publications reporting dimensional information on 154 subject samples with 52 populations. A typical mean functional impact for partially dentate subjects was 1.6 units on a 0 to 8 unit metric, while for edentate subjects, the mean functional impact was 2.6 units. The functional impact score ranged from 0 to 7.9 units with 50% of the patient samples located between 0.8 and 2.6 units. For the first time, we provide normalised and therefore comparable metric information about the functional OHRQoL impact for a substantial number of functional oral conditions.

This position paper reviews physical and mechanical properties of thermoplastic resin used for non-metal clasp dentures, and describes feature of each thermoplastic resin in clinical application of non-metal clasp dentures and complications based on clinical experience of expert panels. Since products of thermoplastic resin have great variability in physical and mechanical properties, clinicians should utilize them with careful consideration of the specific properties of each product. In general, thermoplastic resin has lower color-stability and higher risk for fracture than polymethyl methacrylate. Additionally, the surface of thermoplastic resin becomes roughened more easily than polymethyl methacrylate. Studies related to material properties of thermoplastic resin, treatment efficacy and follow-up are insufficient to provide definitive conclusions at this time. Therefore, this position paper should be revised based on future studies and a clinical guideline should be provided.