label: url

en: Novel Magnetic Attachment System Manufactured Using High-Frequency Heat Treatment and Stamp Technique: Introduction and Basic Performance

en: Recently, a novel magnetic attachment with extremely low cost and high performance was developed. This article aims to introduce a novel magnetic attachment and to evaluate its basic eligibility for denture retention in clinical practice. The novel magnetic attachment system used in this study was the direct-bonding root-keeper-type Magteeth™ MT800 (MagneDesign, Nagoya, Japan). The retentive force without displacement (position 0) and after horizontal displacement to positions 0.5, 1, 1.5, 2, 2.5, and 3 mm were measured. The values relative to the retentive force without displacement were gradually decreased to 82.7 ± 16.3%, 68.8 ± 17.1%, 62.4 ± 15%, 47.2 ± 13.1%, 35.7 ± 9.9%, and 20.7 ± 6.5%, respectively. The retentive force and magnetic field strength did not change significantly after the load test (100 N load, 10,000 times). No new gap between the metal and resin was found in the root keeper- and magnet assembly-embedded blocks after the load test. Some scratches on magnetic assembly and root keeper surface, while no change in the resin texture after the load test were observed. Based on the findings of this preliminary study, this novel low-cost magnetic attachment exhibited favorable retention, strength, and durability for clinical use.

en: Dentistry Journal

ja: Dentistry Journal


en: Geometric assessment of imaging methods for complete denture form: Comparisons among cone-beam computed tomography, desktop dental scanning, and handheld optical scanning.

en: Journal of Prosthodontic Research

ja: Journal of Prosthodontic Research


en: Effect of polishing protocols on the surface roughness of polyetheretherketone.

en: The purpose of this study was to evaluate the influence of various polishing protocols on the surface roughness of polyetheretherketone (PEEK) and identify an effective polishing method of dental prostheses at the chairside. The PEEK specimens were assigned to seven groups with different protocols: no additional polishing (NT); polishing using a rubber point (C); polishing using "silky shine" (S); polishing using "aqua blue paste" (A); protocol C followed by protocol S (CS); protocol C followed by protocol A (CA); and protocol C followed by protocols S and A (CSA). The surface roughness (Sa and Ra) of the polished surfaces was measured. The surface roughness decreased in the following order of groups: NT, C, S, CS, CSA, CA, and A. In Groups C and S, wide deep pits formed by abrasive grains of SiC paper were observed, whereas only fine linear structures were observed on the surface in other groups. With respect to the polishing protocol of PEEK, clinically acceptable surface roughness was obtained using a soft polishing brush and agent for more than 3 min.

en: Journal of Oral Science

ja: Journal of Oral Science


en: Effect of the temperature of water on ultrasonic denture cleaning

en: Denture plaque is a biofilm composed of various microorganisms aggregated with saliva. Various denture cleansers and cleaning apparatuses have been developed and studied. However, the optimum water temperature for denture cleaning is unknown. Therefore, the present study investigated the effects of water temperature during ultrasonic denture cleaning. In vitro, resin disks with artificial Candida albicans biofilm were pressed onto Candida GE media after ultrasonic cleaning with water at different temperatures for 5 min. The media were subsequently cultured at 37°C for 24 h. The colonies formed were observed and colony areas were quantified using ImageJ software (US National Institutes of Health, Bethesda, MD, USA). In situ, the bacterial count and degree of cleanliness on the tissue surface of maxillary dentures were measured before and after ultrasonic cleaning with water at different temperatures for 5 min. Changes in bacterial counts and cleanliness were calculated for each temperature. The ratio of the area occupied by bacterial colonies in vitro and reduction rates in situ after cleaning with warm water were markedly less than those observed after cleaning with cold water. Therefore, ultrasonic denture cleaning with warm water is more effective.


en: Use of a Polyetheretherketone Clasp Retainer for Removable Partial Denture: A Case Report

en: Clasp retainers made of metal alloys may be esthetically unappealing or cause allergic reactions. To investigate alternative materials, we used the nonfiller polyetheretherketone (PEEK) to fabricate the clasp retainer of a removable partial denture for the mandibular bilateral distal free-end abutment of an 84-year-old female. Two years later, few color and texture changes of PEEK were found macroscopically. The rest part and the clasp arm fitted well without any deformation. There were no particular occlusal or periodontal problems. Subjective satisfaction was expressed by both the practitioner and the patient.


en: Duplicate complete dentures made by general digital devices: Evaluation of material properties and clinical trial

ja: 汎用デジタル機器を用いて製作した複製義歯:材料特性と臨床評価

en:
Purpose: The purpose of this study was to investigate the validity of the process of duplicating complete dentures using general digital devices through the following tests: cytotoxicity test of materials used, adhesion test of materials to a silicone impression material and a self-curing resin, and questionnaires to operators on duplicate dentures in clinical situations.

Methods: The cell viability of mouse fibroblast-like cells in acrylonitrile- butadiene-styrene (ABS) and polylactic acid (PLA) were evaluated as a cytotoxicity test. The tensile strength between the silicone impression material/self-curing resin and ABS/PLA specimen was measured as adhesive strength using a universal testing machine. Six practitioners who used duplicate PLA complete dentures in 7 patients were asked to evaluate the duplicate denture using the original questionnaire.

Results: The cytotoxicity test showed that the cell viabilities in ABS and PLA were similar to that in acrylic resin at the cell culture times of 24, 48 and 72 hours. The adhesion test showed that the adhesive strength between the ABS/PLA and silicone impression material was significantly lower than that between the conventional self-curing resin and silicone impression material. Although the adhesive strength between the PLA and self-curing resin was low, there was no significant difference between the ABS and self-curing resin. The results of the questionnaire showed that the duplicate denture made of PLA would be of similar value compared to the conventional duplicate denture made of acrylic resin.

Conclusions: The present study suggests that the duplicate complete dentures made by our proposed digital process are clinically effective.

ja:
目的:われわれが提案した汎用デジタル機器を用いた複製義歯製作法の有用性を示すために，使用するアクリロニトリル-ブタジエン-スチレン(ABS)共重合樹脂，ポリ乳酸(PLA)樹脂の細胞毒性試験，シリコーン印象材および常温重合レジンとの接着試験，使用感に関する主観的評価を行った．

方法:細胞毒性試験では，ABS樹脂とPLA樹脂の浸漬液を用いてマウスの線維芽細胞様細胞の細胞生存率を測定した．接着試験では，専用の保持体にそれぞれの試験片を固定し，シリコーン印象材および常温重合レジンを圧接した後に，万能試験機を用いて引張試験を行った．使用感の評価には，専用の評価票を作成し，PLA製の複製義歯を使用する術者に回答させた．

結果:細胞毒性試験では，ABS樹脂，PLA樹脂ともに72時間までの細胞生存率の低下は認められなかった．接着試験では，トレー用レジンと比較して両試料ともにシリコーン印象材への接着強さは低かった．常温重合レジンとの接着強さでは，PLA樹脂は低かったが，ABS樹脂では従来のトレー用レジンと同等の接着強さであった．術者による複製義歯使用感の評価結果としては，従来のアクリルレジン製の義歯とほとんど変わらない評価が得られた．

結論:三次元プリンターで製作した複製義歯における材料的，臨床的評価から本術式の有効性が示唆された．

en: Annals of Japan Prosthodontic Society

ja: 日本補綴歯科学会誌


en: Duplication of complete dentures using general-purpose handheld optical scanner and 3-dimensional printer: Introduction and clinical considerations

en: To introduce a new clinical procedure for fabricating duplicates of complete dentures by bite pressure impression using digital technology, and to discuss its clinical significance. The denture is placed on a rotary table and the 3-dimensional form of the denture is digitized using a general-purpose handheld optical scanner. The duplicate denture is made of polylactic acid by a 3-dimensional printer using the 3-dimensional data. This procedure has the advantages of wasting less material, employing less human power, decreasing treatment time at the chair side, lowering the rates of contamination, and being readily fabricated at the time of the treatment visit.


en: Part-digitizing system of impression and interocclusal record for complete denture fabrication

en: Few studies have reported the application of digital technology to removable dentures, particularly for the process of impression and interocclusal recording for complete denture fabrication. This article describes a part-digitizing system of impression and interocclusal records for complete denture fabrication. The denture foundation area in an edentulous mouth, including the border areas and residual ridge, is outlined by tracing the surfaces with a 3-D pen-type digitizer. Specialized trays for final impressions and interocclusal records were generated using computer-aided design and manufactured using the digital data. Final impression and interocclusal records were carried out using these specialized trays. The computer-aided method using preliminary digital impressions and specialized trays would be feasible for clinical use for complete denture fabrication.

en: Journal of Prosthodontics

ja: Journal of Prosthodontics


en: Digital assessment of preliminary impression accuracy for edentulous jaws: Comparisons of 3-dimensional surfaces between study and working casts

en: The aim of this study was to compare 3-dimensional surfaces of study and working casts for edentulous jaws and to evaluate the accuracy of preliminary impressions with a view to the future application of digital dentistry for edentulous jaws. Forty edentulous volunteers were serially recruited. Nine dentists took preliminary and final impressions in a routine clinical work-up. The study and working casts were digitized using a dental 3-dimensional scanner. The two surface images were superimposed through a least-square algorithm using imaging software and compared qualitatively. Furthermore, the surface of each jaw was divided into 6 sections, and the difference between the 2 images was quantitatively evaluated. Overall inspection showed that the difference around residual ridges was small and that around borders were large. The mean differences in the upper and lower jaws were 0.26mm and 0.45mm, respectively. The maximum values of the differences showed that the upward change mainly occurred in the anterior residual ridge, and the downward change mainly in the posterior border seal, and the labial and buccal vestibules, whereas every border of final impression was shortened in the lower jaw. The accuracy in all areas except the border, which forms the foundation, was estimated to be less than 0.25mm. Using digital technology, we here showed the overall and sectional accuracy of the preliminary impression for edentulous jaws. In our clinic, preliminary impressions have been made using an alginate material while ensuring that the requisite impression area was covered.


en: Development of a digital impression procedure using photogrammetry for complete denture fabrication

en: We developed an innovative procedure for digitizing maxillary edentulous residual ridges with a photogrammetric system capable of estimating three-dimensional (3D) digital forms from multiple two-dimensional (2D) digital images. The aim of this study was to validate the effectiveness of the photogrammetric system. Impressions of the maxillary residual ridges of five edentulous patients were taken with four kinds of procedures: three conventional impression procedures and the photogrammetric system. Plaster models were fabricated from conventional impressions and digitized with a 3D scanner. Two 3D forms out of four forms were superimposed with 3D inspection software, and differences were evaluated using a least squares best fit algorithm. The in vitro experiment suggested that better imaging conditions were in the horizontal range of ± 15 degrees and at a vertical angle of 45 degrees. The mean difference between the photogrammetric image (Form A) and the image taken from conventional preliminarily impression (Form C) was 0.52 ± 0.22 mm. The mean difference between the image taken of final impression through a special tray (Form B) and Form C was 0.26 ± 0.06 mm. The mean difference between the image taken from conventional final impression (Form D) and Form C was 0.25 ± 0.07 mm. The difference between Forms A and C was significantly larger than the differences between Forms B and C and between Forms D and C. The results of this study suggest that obtaining digital impressions of edentulous residual ridges using a photogrammetric system is feasible and available for clinical use.

en: International Journal of Computerized Dentistry


en: Literature Review of Setting the Occlusal Plane for Edentulous Patients

ja: 無歯顎補綴における咬合平面設定に関する文献考察

en: The maxillomandibular registration is one of important processes to achieve patientsatisfaction with the function and esthetics for complete denture fabrication. Over the years, clinical decision of vertical and horizontal jaw relationship has been mainly discussed in the maxillomandibular registration. With regard to the occlusal plane setting, many clinicians have believed to decide the occlusal plane parallel to Camper's plane, however there is little information on the effect of occlusal plane setting on clinical meanings and outcome. The aim of this study is to analyze published literature focusing on the occlusal plane and the related oral function and esthetics, and to clarify clinical implications of occlusal plane setting. Two databases, "PubMed" and "Japana Centra Revuo Medicina" were searched to retrieve research papers focusing on the occlusal plane.Seventy four papers were selected from the database, and they were reviewed.Literature reviews suggests that many landmarks were described on the occlusal plane setting for edentulous patients; and Camper's plane has been most frequently referred, showed a good result in function, but not always good in esthetics. The influence of occlusal plane setting on clinical results: oral function, esthetics, denture stability, and patient satisfaction after denture delivery has to be examined.

en: Journal of Oral Health and Biosciences

ja: Journal of Oral Health and Biosciences