The congenitally missing upper lateral incisor. A retrospective study of orthodontic space closure versus restorative treatment.
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Orthodontic treatment for patients with uni- or bilateral congenitally missing lateral incisors is a challenge to effective treatment planning. The two major alternatives, orthodontic space closure or space opening for prosthetic replacements, can both compromise aesthetics, periodontal health, and function. The aim of this retrospective study was to examine treated patients who had congenitally missing lateral incisors and to compare their opinion of the aesthetic result with the dentists' opinions of occlusal function and periodontal health. In this sample, 50 patients were identified. Thirty had been treated with orthodontic space closure, and 20 by space opening and a prosthesis (porcelain bonded to gold and resin bonded bridges). The patient's opinion of the aesthetic result was evaluated using the Eastman Esthetic Index questionnaire and during a structured interview. The functional status, dental contact patterns, periodontal condition, and quality of the prosthetic replacement was evaluated. In general, subjects treated with orthodontic space closure were more satisfied with the appearance of their teeth than those who had a prosthesis. No significant differences in the prevalence of signs and symptoms of temporomandibular dysfunction (TMD) were found. However, patients with prosthetic replacements had impaired periodontal health with accumulation of plaque and gingivitis. The conclusion of this study is that orthodontic space closure produces results that are well accepted by patients, does not impair temporomandibular joint (TMJ) function, and encourages periodontal health in comparison with prosthetic replacements. (+info)
Development of Ag-Pd-Au-Cu alloy for multiple dental applications. Part 1. Effects of Pd and Cu contents, and addition of Ga or Sn on physical properties and bond with ultra-low fusing ceramic.
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Ag-Pd-Au-Cu quaternary alloys consisting of 30-50% Ag, 20-40% Pd, 10-20% Cu and 20% Au (mother alloys) were prepared. Then 5% Sn or 5% Ga was added to the mother alloy compositions, and another two alloy systems (Sn-added alloys and Ga-added alloys) were also prepared. The bond between the prepared alloys and an ultra-low fusing ceramic as well as their physical properties such as the solidus point, liquidus point and the coefficient of thermal expansion were evaluated. The solidus point and liquidus point of the prepared alloys ranged from 802 degrees C to 1142 degrees C and from 931 degrees C to 1223 degrees C, respectively. The coefficient of thermal expansion ranged from 14.6 to 17.1 x 10(-6)/degrees C for the Sn- and Ga-added alloys. In most cases, the Pd and Cu contents significantly influenced the solidus point, liquidus point and coefficient of thermal expansion. All Sn- and Ga-added alloys showed high area fractions of retained ceramic (92.1-100%), while the mother alloy showed relatively low area fractions (82.3%) with a high standard deviation (20.5%). Based on the evaluated properties, six Sn-added alloys and four Ga-added alloys among the prepared alloys were suitable for the application of the tested ultra-low fusing ceramic. (+info)
Surface composition and structure of titanium polished with aqueous slurry of ferric oxide.
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Cast plates were prepared from commercial titanium. The plates were polished with a slurry of fine ferric oxide powder. The surface composition and structure were investigated by electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). In the high pressure-polished surface, iron was non-uniformly distributed but oxygen was mostly uniformly distributed, while in a light pressure-polished surface, iron and oxygen were uniformly distributed though at lower and higher concentrations, respectively. EPMA state analysis and XPS suggested that the iron might exist as Fe2+ in the outermost surface, while it might be in a metallic state in the inner surface layer. (+info)
Corrosion characteristics of ferric and austenitic stainless steels for dental magnetic attachment.
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The corrosion behaviors of four ferric stainless steels and two austenitic stainless steels were examined in a simulated physiological environment (0.9% NaCl solution) to obtain basic data for evaluating the appropriate composition of stainless steels for dental magnetic attachments. The corrosion resistance was evaluated by electrochemical techniques and the analysis of released metal ions by atomic absorption spectrophotometry. The surface of the stainless steels was analyzed by X-ray photoelectron spectroscopy (XPS). The breakdown potential of ferric stainless steels increased and the total amount of released metal ions decreased linearly with increases in the sum of the Cr and Mo contents. The corrosion rate of the ferric stainless steels increased 2 to 6 times when they were galvanically coupled with noble metal alloys but decreased when coupled with commercially pure Ti. For austenitic stainless steels, the breakdown potential of high N-bearing stainless steel was approximately 500 mV higher than that of SUS316L, which is currently used as a component in dental magnetic attachments. The enriched nitrogen at the alloy/passive film interface may be effective in improving the localized corrosion resistance. (+info)
Mechanism of adhesion between 4-META resin and alloys based on Bolger's acid-base interaction.
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The water durability at adhesion interfaces between 4-META resin and Au-In or Au-Si alloys was investigated by the peeling test and by surface analysis using X-ray photoelectron spectroscopy (XPS) as well as theoretical consideration based on Bolger's acid-base theory. XPS spectra demonstrated that several-nm thick layers of In2O3 and SiO2 were formed on the Au-In and Au-Si alloys. The water durability of the Au-In alloys increased with increases in In content. The Au-Si alloy and quartz glass specimens showed a total absence of water durability. Bolger's theory suggested that the interaction of 4-MET with In2O3 was considered to be ionic and stable in the presence of water while that of 4-MET with SiO2 was due to hydrogen bonds, which can easily be dissociated in the presence of water. These findings suggest that Bolger's theory is useful for evaluating chemical interactions between an adhesive monomer and oxides on a precious metal alloy. (+info)
XPS study on the weakest zone in the adhesion structure between resin containing 4-META and precious metal alloys treated with different surface modification methods.
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Three precious metal alloys, Type IV gold alloy, 14 K gold alloy, and silver-based alloy, were treated with different surface modifications including a metal primer (VBATDT) application, a SiOx coating method, high-temperature oxidation, modification method with a liquid Ga-Sn alloy, and tin electroplating. Then thin PMMA films were bonded with a resin containing 4-META. Water durability at the adhesion interface was evaluated after water immersion, followed by thermal cycling used liquid nitrogen. The weakest zone at the interface was investigated using XPS only for the Ag-Pd alloy specimens that had been surface-treated with as-polishing, adhesive primer, and the SiOx coating method, since peeling of the PMMA film on the surface of specimens surface-treated by other methods was not observed. Metal elements were detected from the resin side at the adhesion interface. The chemical states of Cu in the resin before argon ion etching were characterized as metal oxides and/or states of chemical interaction with 4-META, VBATDT, or SiOx. (+info)
Development of Ag-Pd-Au-Cu alloys for multiple dental applications. Part 2. Mechanical properties of experimental Ag-Pd-Au-Cu alloys containing Sn or Ga for ceramic-metal restorations.
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Eighteen Ag-Pd-Au-Cu alloys, consisting of nine Ag-Pd-Au-Cu mother compositions (Pd: 20, 30 or 40%, Au: 20%, Cu: 10, 15 or 20%, Ag: balance) containing either 5% Sn or 5% Ga as an additive metal, were experimentally prepared. Tensile strength, proof stress, elongation, elastic modulus, and Vickers hardness of these alloys were evaluated to clarify the potential of these alloys for use as ceramic-metal restorations as well as the effects of the Pd and Cu contents on their mechanical properties. The tensile strength, proof stress, elongation, elastic modulus and Vickers hardness of the 18 experimental alloys were in the range of 410.0-984.0 MPa, 289.7-774.3 MPa, 2.2-23.7%, 81.3-123.0 GPa and 135.7-332.3 HV1, respectively. Ten of the 18 experimental alloys can be used for ultra-low fusing ceramics based on their proof stress, elastic modulus, elongation and hardness. Between the Ga- and Sn-added alloys, differences in tensile strength, proof stress, elongation and hardness were found at several Ag-Pd-Au-Cu compositions. (+info)
Wearing behaviors of a hybrid composite resin for crown and bridge.
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The wearing behaviors of a hybrid composite resin for crown and bridge (ES) were examined using a two-body impacting-sliding wear test with a porcelain (PO), Au-Ag-Pd alloy (PD), direct restorative composite resin (CR) and tooth enamel (TO). Although PO was the hardest of all, it showed the largest wear together with ES in the combination of ES-PO, which was probably initiated from the superficial destruction by their impact. The wear in ES-PD was the second largest. It was noted in this combination that the surface of ES was partially contaminated by scraped thin layers of PD to a degree distinguished by the naked eye. The mutual wears of the components were relatively low in the combination of ES with CR, TO or ES itself. It is suggested from these findings that the hybrid composite resin may be useful as an alternative to porcelain for posterior crown and bridge unless it opposes porcelain or alloys. (+info)