Showing papers by "Hideo Matsumura published in 2007"

Marginal and internal adaptation of zirconium dioxide ceramic copings and crowns with different finish line designs.

Abstract: The present study evaluated the marginal and internal adaptation of single-tooth zirconium dioxide (ZrO2) ceramic copings or crowns with three different finish line designs. Twenty-four steel dies were prepared for maxillary central incisor crowns with the following finish line designs: shoulder (S), rounded shoulder (RS), and chamfer (C) preparations. Twenty-four standardized ZrO2 ceramic copings were manufactured with a CAD/CAM system (Cercon Smart Ceramics), and the crowns were finalized by veneering with a feldspathic ceramic. Measurements for marginal and internal adaptation were performed at two stages: the copings and the completed crowns. No significant differences were observed between the three groups in terms of marginal discrepancy median value: S, 73/69; RS, 61/60; C, 64/55 (μm). However, significant differences in internal adaptation were widely found among all groups: S, 117/111; RS, 72/75; C, 56/57 (μm). As for intra-group comparisons of marginal and internal adaptation values for all groups, the differences were not significant. It was found that the finish line design seemingly wielded no influence on marginal adaptation of single-tooth ZrO2 ceramic copings and crowns. It was also observed that the marginal and internal adaptation values in the present study were all within the clinically acceptable range.

Effects of IL-6 and Soluble IL-6 Receptor on the Expression of Cartilage Matrix Proteins in Human Chondrocytes

Abstract: Elevated concentrations of interleukin (IL)-6 and soluble IL-6 receptor (sIL-6Rα) in synovial fluid have been implicated in joint cartilage destruction. We examined the effect of IL-6 and sIL-6Rα on cell growth, alkaline phosphatase (ALPase) activity, and the expression of Sox-9, type II collagen, aggrecan core, link protein, BMP-7, and BMP receptors in human chondrocytes. Cell proliferation increased slightly in the presence of both IL-6 and sIL-6Rα, whereas ALPase activity decreased markedly. The expression of Sox-9 and aggrecan core did not change in the presence or absence of IL-6 and sIL-6Rα, whereas the expression of type II collagen, link protein, BMP-7, and BMP receptors increased in the presence of both IL-6 and sIL-6Rα. These results suggest that IL-6 and sIL-6Rα suppress the differentiation of chondrocytes and induce the repair of arthrodial cartilage through an increase in the expression of cartilage matrix proteins, BMP-7, and BMP receptors in the cells.

Effect of single-liquid priming agents on adhesive bonding to aluminum oxide of a methacrylic resin.

Abstract: The purpose of this study was to evaluate the effects of acidic primers on adhesive bonding to sintered aluminum oxide (alumina). Alumina disks were primed with one of the following materials: Acryl Bond, All Bond 2 Primer B, Alloy Primer, Estenia Opaque Primer, Eye Sight Opaque Primer, M. L. Primer, MR. Bond, and Super-Bond Liquid. Specimens were then bonded with an acrylic resin initiated with partially oxidized tri-n-butylborane (TBBO), and bond strengths were determined. Unprimed specimen was employed as the control. Average bond strength before thermocycling ranged from 20.5 to 41.9 MPa, whereas post-thermocycling bond strength ranged from 0.0 to 40.0 MPa. Of the eight primers, Estenia Opaque Primer and Alloy Primer showed better adhesive performance than the other materials. It could thus be concluded that either Estenia Opaque Primer or Alloy Primer—which contained an adhesive monomer, 10-methacryloyloxydecyl dihydrogen phosphate (MDP)—was recommended for bonding alumina with TBBO-initiated resin.

Influence of porcelain-firing procedures on the marginal distortion of electroformed metal-ceramic restorations.

Abstract: Objective: To evaluate the influence of firing procedures on the marginal distortion of electroformed metal-ceramic crown restorations. Method and Materials: Twenty-four standardized specimens were fabricated using a gold-electroforming system and were characterized by 3 finish line forms: shoulder (S-type), rounded shoulder (RS-type), and deep chamfer (DC-type) preparations. Marginal discrepancies were measured at 6 stages: before the firing procedures, after the gold-bonder application, after the opaque porcelain firing, after the dentin porcelain firing, after the enamel porcelain firing, and after the glazing firing. Marginal discrepancy values were recorded at 60 randomly chosen points along the circumferential margin using a laser microscope. Marginal distortion values were defined as the differences in the marginal discrepancies between the baseline (prefiring) levels and those after each firing procedure. All statistical analyses were performed using the Friedman and Kruskal-Wallis tests (a = .05). Results: For all of the finish line forms, the marginal distortion values were altered by the subsequent firing procedures. The largest marginal distortion values were observed after the first firing procedure. The total marginal distortion values were 34.2, 6.9, and 5.2 µm for the S-, RS-, and DC-type preparations, respectively. Conclusion: The porcelain-firing procedures influenced the marginal distortion of electroformed metal-ceramic crown restorations. The marginal distortion values of the S-type preparations were the highest among the 3 groups tested.

Effect of metal priming agents on bond strength of resin-modified glass ionomers joined to gold alloy.

Abstract: The aim of this study was to evaluate in vitro the shear bond strength to a gold alloy of RMGICs combined with three metal priming agents. Gold alloy was primed with one of the following materials: Alloy Primer, Metal Primer II, or Metaltite. Non-treated group was considered as the control. Specimens were bonded with one of the following luting agents: Super-Bond C&B, Vitremer Luting Cement, Fuji Lute, or Xeno Cem Plus. Shear bond strength was then determined. The bond strengths of resin-modified glass ionomer cements primed with the metal priming agents were greater than that of non-treated group, except for the Vitremer Luting Cement-Alloy Primer combination. It was thus concluded that the priming agents employed in this study were substantially effective in improving the bonding of resin-modified glass ionomer cements to gold alloy.

Depth of cure and hardness of an indirect composite polymerized with three laboratory curing units.

Abstract: This study determined the hardness and curing depth of a light-activated indirect composite polymerized with three laboratory light-polymerizing units for the purpose of comparing the curing performance of the three units. A light-activated composite material for indirect application (Vita Zeta) was polymerized with three light-polymerizing units equipped with the following light sources: 1) one halogen lamp and two fluorescent lamps (α-Light II); 2) three halogen lamps (Twinkle HLG); and 3) one metal halide lamp (Twinkle LI). Knoop hardness and curing depth were determined for groups of five specimens using standardized testing methods. The results were compared using analysis of variance (ANOVA) and Scheffe's S intervals (α = 0.05). The Knoop hardness number (KHN) generated with the halogen-fluorescent unit (12.5 KHN) was significantly (P < 0.05) lower than those produced by the halogen unit (13.9 KHN) and the metal halide unit (14.2 KHN). Of the three units, the halogen-fluorescent unit exhibited the lowest depth of cure. Both the hardness and curing depth of the composite were influenced by the laboratory polymerizing units employed. (J. Oral Sci. 49, 25-29, 2007)

Application of a pre-impregnated fiber-reinforced composite in the fabrication of an indirect dowel-core

Abstract: The root canal space prepared for a foundation restoration is often elliptic or too large, and an unintentionally prepared undercut is sometimes detected. This article presents a dental laboratory technique to reconstruct an endodontically treated tooth using a pre-impregnated fiber-reinforced composite (FRC) system instead of a conventional fiber post. Particular attention was paid to increase the volume of the fiber in the root canal, and care was taken to achieve adequate primary laboratory polymerization of the matrix monomer. This simple technique is useful in the fabrication of an FRC dowel core with increased fiber content. (J. Oral Sci. 49, 179-182, 2007)

Effect of a metal priming agent on wear resistance of gold alloy-indirect composite joint.

Abstract: The purpose of the current study was to evaluate the effect of a metal priming agent on wear resistance of gold alloy-composite joint. Four types of plate specimen were prepared: composite (Estenia CB 21.0 for Estenia and 24.9 for Epricord) than the joined specimens without priming (57.8 for Estenia and 46.7 for Epricord). Wear depth of the single plate specimens when abraded with the gold alloy antagonist was ranked as follows: Estenia (9.6), gold alloy (12.8), and Epricord (19.1). It was concluded that the use of a metal priming agent at the alloy-composite interface effectively enhanced the wear resistance of the joined area when under cycled loading.

Effects of alumina air-abrasion and acidic priming agents on bonding between SUS XM27 steel and auto-polymerizing acrylic resin.

Abstract: The purpose of this study was to evaluate the effects of functional monomers contained in the primers, as well as alumina particle abrasion on bonding between stainless steel and acrylic resin. SUS XM27 steel was primed with one of the following materials; Alloy Primer, Estenia Opaque Primer, M. L. Primer, and Super-Bond Liquid. Steel disks were either ground flat or alumina-blasted, primed with one of the four agents, and bonded with an acrylic resin (Unifast Trad). Bond strength was determined both before and after thermocycling (2,000 or 20,000 cycles). Among the four priming agents, the Alloy Primer and Estenia Opaque Primer, both of which contain 10-methacryloyloxydecyl dihydrogen phosphate (MDP), exhibited better bonding performance than the others. Alumina air-borne particle abrasion considerably improved the durability of bonding between the steel and the resin material. It can be concluded that alumina blasting followed by priming with an MDP agent is recommended for bonding the resin and SUS XM27 steel.

Relation between attractive force and keeper surface characteristics of iron-neodymium-boron magnetic attachment systems.

Abstract: The purpose of this study was to evaluate the influence of heating, cast bonding, and subsequent polishing procedures on attractive force of magnetic attachments. Two magnetic attachment systems with keepers of different chemical compositions (Hicorexslim 3013, 447J1; Magfit EX400, AUM20) were employed. Keepers examined were: (1) untreated; (2) heated; (3) cast-bonded with Ag-Pd alloy; (4) cast-bonded with Ag-Pd alloy and polished; (5) cast-bonded with gold alloy; and (6) cast-bonded with gold alloy and polished. Attractive force was determined with a force gauge, and surface structure was evaluated with scanning laser and electron microscopes. Attractive force of the Hicorex system was reduced by cast bonding, whereas that of the Magfit system was reduced by both heating and cast bonding. However, attractive force of both systems was somewhat recovered through the polishing process. Based on the findings of this study, it was suggested that careful polishing after cast bonding was indispensable to the recovery of attractive force for both attachment systems.

International telephone code used for citizenship identification in a denture.

Abstract: This case report describes a simple method for identifying the citizenship of a denture wearer by marking the telephone country code number inside the denture base. A wax pattern for the denture framework was prepared on the refractory cast. A piece of embossing tape, containing the country code (81, Japan), Japanese prefectural code, and abbreviation of the dental clinic where the denture was fabricated, was placed on the metal framework. A titanium-aluminum-niobium (Ti-6Al-7Nb) alloy was cast in the mold, and the denture was then fabricated by the conventional method. The casting satisfactorily reproduced the embossed letters, and the plate was identifiable through the gingiva-colored acrylic denture base resin. Since an embossed metal plate integrated with the skeleton is embedded in the denture base resin material, the current denture marking technique serves as a simple procedure for insertion of an undegradable denture identification mark which makes it possible to identify the nationality of the denture wearer. (J. Oral Sci. 49, 337-340, 2007)

Effects of monomer composition and original filler content on filler loading in the resulting centrifuged composites.

Abstract: This study examined the effects of monomer composition, original filler content, and application of centrifugal force on the resulting filler loading of composites. Either Bis-MPEPP or UDMA was mixed with TEGDMA at a molar ratio of 1 : 1. Silane-treated silica (14-20 wt%) was added to each mixture. After the mixtures were centrifuged and light-polymerized, rate of increase was determined as the filler increment of 2.0-mm-high, disk-shaped sections of specimen when compared against the uncentrifuged filler content. Both the original filler loading and monomer composition influenced the filler content of the centrifuged composites. Fillers in Bis-MPEPP-based composites exhibited a higher rate of condensation after application of centrifugal force than did UDMA-based composites. The results were suggestive of underlying relationships among the composition, component stability, and post-polymerization properties of flowable composites.

Bending Property of Super-Elastic Ti-Ni Alloy Dental Castings with Different Heat Treatments

Abstract: Bending property of Ti-Ni alloy dental castings was evaluated in comparison with that of Co-Cr alloy in a cantilever test. Heat treatment effect on the bending property was also investigated in relation to phase transformation. Ti-50.85Ni (mol%) alloy was used, and the shape of bending test specimens was half-rounded in cross section, 2.0 mm in diameter. The bending test was carried out at 310 K. Distance between the loading point and the grip edge was 5.0 or 10.0 mm. Maximum bending deflection was 0.50 mm. Thermal behavior accompanying phase transformation of Ti-Ni alloy was examined by differential scanning calorimetry. Load-deflection diagrams of Ti-Ni alloy castings in the bending test showed elastic and super-elastic deformation, while those of Co-Cr castings showed elastic and permanent deformation. Maximum bending load and residual deflection of the Ti-Ni castings were lower than those of the Co-Cr castings and were decreased by heat treatment under a high-stress condition at the 5-mm loading point. Transformation temperature was increased by heat treatment, which was thought to influence the change in bending property. Super-elasticity of the Ti-Ni alloy castings in bending was shown to be improved by heat treatment, offering the potential to improve the design and clinical performance of cast dental prostheses. [doi:10.2320/matertrans.48.428]

A Nine-year Follow-up of a Porcelain Laminate Veneer Restoration Applied to an Adolescent with Traumatized Dentition: A Clinical Report

Abstract: Patients: A 9-year-old Japanese female patient with an unremarkable medical history was initially examined for the chief complaint of slight pain and discomfort in a traumatized maxillary central incisor. Four years after endodontic treatment, the patient complained of dark discoloration of the tooth. Among the treatments/restorations indicated, the patient and her parent consequently selected and approved of a porcelain laminate veneer restoration because of its advantage of minimal tooth reduction. The maxillary diastema was gradually closed after insertion of a porcelain laminate veneer, and 9 years of follow-up have revealed that the prosthodontic treatment successfully restored the tooth.Discussion: Many methods have been introduced as aesthetic solutions to discoloration. Although the patient was satisfied with the prosthodontic approach from a functional as well as an aesthetic point of view, direct composite restorations might be an alternative for younger patients in mixed dentition.Conclusion: The treatment in a growing individual should be carefully planned and performed, considering the development of permanent dentition.