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.
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.
The aim of this research was to examine the effects of metals used in dentistry upon magnetic resonance imaging (MRI). Ten disk-shaped samples of metals have been used in this study. Each sample has been set into a volunteer who had produced a normal MR image when tested. The subject was imaged in the sagittal, frontal and coronal plane with a 0.1 T MRI device and results examined for MR defects. Au, Ag, Au-Ag-Pd and amalgam produced no defect. Ni-Cr, Co-Cr and SUS304 expressed small amounts of MR defects, but SUS405, Pd-Co-Ni and Sm-Co expressed large defects. Those metals which create MR image degradation must not be used for fixed prosthesis or orthodontic devices both of which could easily be made from other metals. If the MR image degrading metals are to be used in dentistry, their application should be restricted to removable prosthesis.
BackgroundThe aim of the present study was to evaluate the physical properties of “admixture paste”, which is a commercially available gel containing hinokitiol for use against severe stomatitis, and its characteristics as a moisturizing gel and denture adhesive.MethodsThe admixture paste, which contained dexamethasone (Dexaltin®), gel for oral care (Refrecare H®) and petrolatum, and its 3 components, either alone or in different combinations, were subjected to viscosity, adhesiveness and elution testing to compare their physical properties. Viscosity was measured with a stress-controlled rheometer. Adhesive force was measured by tension test. Elution under a simulated oral environment was evaluated by monitoring with a fixed-point camera and absorbance. Both adhesiveness and elution were evaluated every hour for 6 h. A linear mixed-effects model was used to assess differences in the time course of elution between samples. In 3 og-rank test was used to compare time to elution into saliva among samples.ResultsThe results of viscosity testing demonstrated that the admixture paste had similar viscosity to cream-type denture adhesives and this was temperature independent. In the adhesiveness tests, the admixture paste showed stronger adhesiveness than that of cream-type denture adhesives. In the elution test, the admixture paste demonstrated gradual dissolution and apparent temporal changes for 6 h in a simulated oral environment.ConclusionsThe results of the present study demonstrated that the admixture paste has adhesive force similar to those of denture adhesives and good local retention in saliva, and that it might be suitable for therapeutic use in patients with severe stomatitis derived from radiotherapy and/or chemotherapy for cancer.Electronic supplementary materialThe online version of this article (10.1186/s12885-018-4017-2) contains supplementary material, which is available to authorized users.
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