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Biomedical subjects

M T Barco

Publications and source records attributed to M T Barco.

12 recordsLinked to original sources
PubMed2005

Effects of coupling methods on galvanic corrosion behavior of commercially pure titanium with dental precious alloys.

BACKGROUND: When a dissimilar couple is exposed to corrosive environment, it will normally exhibit a galvanic corrosion. The galvanic corrosion might be influenced by various factors, including type and concentration of electrolyte, surface area ratio between anode and cathode, type of coupling material, and coupling manner. PURPOSE: The purpose of this study was to investigate and compare the galvanic corrosion behavior of commercially pure titanium when coupled with type IV Au alloy, Au-Ag-Pt alloy, and Ag-Au-Pd alloy by different coupling methods. MATERIALS AND METHODS: Couples were prepared by a laser welding or a mechanical adhering method. Electrochemical corrosion studies were conducted in a Ringer's solution at a scanning rate of 0.1 mV/sec in a range from -250 mV to +250 mV with respect to E(OCP). Corrosion parameters (E(OCP), I(CORR), E(CORR)) were obtained. RESULTS: It was found that (i) there was a significant difference between LWC and AJC for three couples (p<0.05), (ii) the crevice line caused all three couples more corrosive than weld joint line, (iii) for both joint, it was found that type (IV) Au alloy exhibited discoloration to some extent. CONCLUSIONS: It is concluded that among the three couples with two different coupling methods, Ti/Ag-Au-Pd couple exhibited best corrosion resistance in a room temperature Ringer's solution.

Corrosion↗
PubMed2004

Mechanical properties of four methylmethacrylate-based resins for provisional fixed restorations.

The use of a provisional restoration is an important phase in the treatment of the dental prosthetic patient. A good provisional restoration should satisfy the following requirements: pulpal protection, positional stability, ease in cleaning, accurate margins, wear resistance, dimensional stability, and serve as a diagnostic aid in treatment assessment and esthetics. There is a tendency for discoloration, occlusal wear, and fracture that eventually leads to unnecessary repair. Heat-processed and reinforced methacrylate-based resins have been used to improve the mechanical and physical properties of provisional restorations. Among various improvements, the interpenetrating network crosslinked PMMA (IPN) has been shown to have superior mechanical properties if manufactured through a dough compression molding process at 130 degrees C. However, there have been no published data that relate with the use of this material for fixed provisional restorations. The objective of this study was to compare four methyl methacrylate-based resins for provisional crowns and bridges with varying processing cycles, including JET [self-cure], ACRALON [heat-cured], titanium dioxide filled PMMA [heat-cured], and IPN [heat-cured denture tooth resin]. Properties studied included transverse strength, toughness, rigidity, and hardness. From the results of this study the following conclusions can be made: the IPN group may have had a lower degree of conversion as demonstrated by decreased strength, toughness, and hardness data as compared with Acralon. Increasing the polymerization cycle of unmodified Acralon resin causes a significant increase in strength.

Biocompatible Materials↗
PubMed2001

Electrochemical corrosion of titanium and titanium-based alloys.

STATEMENT OF PROBLEM: Two varieties of unalloyed titanium, Ti-6Al-4V and NiTi, commonly are used in medical and dental fields. Several other types of alloys for potential use in these fields have been developed, including Ti-4.5Al-3V-2Mo-2Fe and vanadium-free alloys (Ti-5Al-2.5Fe and Ti-5Al-3Mo-4Zr). The corrosion of these alloys under simulated physiologic conditions is not known. Purpose. This study compared the corrosion behaviors of 6 titanium materials through electrochemical polarization tests in 37 degrees C Ringer's solution. MATERIAL AND METHODS: The applied voltage was potentiostatically scanned from -0.6 to 1.0 V. From polarization curves, the corrosion rate (averaged over 3 samples) for each alloy was calculated and compared with that of other alloys. Analysis of variance (ANOVA) and the Student-Newman-Keuls multiple range test were performed at a 95% overall confidence level to identify statistically significance differences in corrosion rates. Surface oxide films were identified by electron diffraction, and the electrolyte medium was analyzed by atomic absorption spectrophotometry after each alloy was tested. RESULTS: Commercially pure titanium and Ti-5Al-2.5Fe were the most resistant to corrosion; Ti-5Al-3Mo-4Zr, Ti-6Al-4V, and NiTi were the least resistant to corrosion. NiTi exhibited pitting corrosion along with transpassivation. CONCLUSION: Electron diffraction patterns indicated that all titanium alloys were covered mainly with rutile-type oxide (TiO(2)) after corrosion tests. The oxides that formed on Ti-5Al-2.5Fe were identified as a mixture of TiO(2) and Ti(9)O(17), and those that formed on NiTi were identified as a mixture of TiO(2) and Ni(2)Ti(4)O.

Alloys↗
PubMed1992

Temperature extremes produced orally by hot and cold liquids.

Thermocycling in vitro is a common way of testing dental materials to aid in establishing suitability for in vivo use. There is no standard temperature range for dental material thermocycling. This research attempts to establish an appropriate temperature range by measuring extremes of temperature achieved orally in human volunteer subjects. By using an intraoral digital thermometer probe, 13 human subjects were observed as they drank very hot and cold liquids. The temperature extremes produced intraorally were measured and adjusted for possible error. The results of this study suggest that a range of 0 degrees to 67 degrees C may be appropriate for dental material thermocycling.

Adult↗
PubMed1991

Wear of human enamel against a commercial castable ceramic restorative material.

This study determined the effect of castable ceramic, with and without shading porcelain applied, on enamel wear. The wear produced by conventional dental porcelain was used as a control. Cusp tips from extracted human third molars were precision-machined into cones of enamel approximately 1 mm long. Three groups of nine cones each were abraded against rotating disks of (1) castable ceramic with shading porcelain, (2) castable ceramic without shading porcelain, and (3) conventional dental porcelain. Enamel wear was calculated from microscopic measurements of the enamel cones before and after abrading. Mean and standard deviation values were 1.220 +/- 0.218 for castable ceramic with shading porcelain, 0.639 +/- 0.218 for castable ceramic without shading porcelain, and 0.785 +/- 0.311 for glazed conventional dental porcelain (all values are X 10(-3) cm3). Significant differences were found between castable ceramic with and without shading porcelain and between conventional dental porcelain and castable ceramic with shading porcelain (p less than 0.001 ANOVA and 0.05 Scheffe's test). These findings suggest that castable ceramic with shading porcelain should not be used in regions that will function against opposing natural teeth.

Ceramics↗
PubMed1987

Cast aluminum denture base.

The laboratory procedures for a cast aluminum base denture have been presented. If an induction casting machine is not available, the "two-oven technique" works well, provided the casting arm is kept spinning manually for 4 minutes after casting. If laboratory procedures are executed precisely and with care, the aluminum base denture can be cast with good results.

Aluminum↗
PubMed1979

The effect of relining on the accuracy and stability of maxillary complete dentures--an in vitro and in vivo study.

A technique was developed for evaluating in vitro the accuracy or fit of experimental denture bases using a low-viscosity impression material for determining the space between the master die and the processed denture base. These measurements indicated that relining heat-cured maxillary denture bases with autopolymerizing acrylic resin improved their adaptation to the ridges. Interestingly, if no teeth were present in the heat-cured denture base, markedly less distortion occurred after processing. Limited clinical measurements on the stability of maxillary dentures in function showed no statistically significant change in stability after relining, but the trend was toward increased stability with the relined denture.

Acrylic Resins↗
PubMed1978

Inconspicuous retention for removable partial dentures.

Many dentists and patients believe that removable partial dentures have an unesthetic appearance when they replace anterior teeth because of the visible clasps. Two methods of obtaining inconspicuous retention have been described.

Dental Abutments↗
PubMedDate not supplied

Surface characterizations of variously treated titanium materials.

The attachment of cells to titanium surfaces is an important phenomenon in the area of clinical implant dentistry. A major consideration in designing implants has been to produce surfaces that promote desirable responses in the cells and tissues. To achieve these requirements, the titanium implant surface can be modified in various ways. This research was designed to elucidate the relationship between surface roughness (Ra) and contact angle (theta) of various engineered titanium surfaces of commercially pure titanium, titanium-aluminum-vanadium alloy (Ti-6Al-4V), and titanium-nickel (TiNi) alloy. The contact angle was measured using distilled water, 1% sodium chloride solution, human neutrophils, and osteoblast-like cells. Surface oxide crystallography was identified by transmission electron diffraction. It was found that: (1) there were no significant differences in contact angles among the 4 media; (2) for commercially pure titanium, a combined treatment (hydrofluoric acid/nitric acid/water --> sodium hydroxide --> oxidation) showed the lowest theta (10.51 degrees in water), while the surface treated with sulfuric acid showed the highest value (72.99 degrees in water); (3) for all commercially pure titanium samples, when theta is greater than 45 degrees, the contact angle increases linearly with Ra (hydrophobic nature) and the surface is covered with rutile-type oxide only, while the contact angle decreases linearly with Ra when theta is less than 45 degrees (hydrophilic nature) and the surface is covered with a mixture of rutile and anatase oxides; and (4) a similar trend was found on Ti-6Al-4V and TiNi surfaces.

Acid Etching, Dental↗
PubMedDate not supplied

Effects of denture teeth on the dimensional accuracy of acrylic resin denture bases.

The Michigan Computer-Graphics Coordinate Measurement System was used to determine the effects of artificial denture teeth on the accuracy of acrylic resin denture bases. Two poly(methyl methacrylate) acrylic resins and two processing techniques were tested. Groups processed with denture teeth reproduced more accurate points than groups processed without denture teeth. Groups processed with a conventional heat-polymerized acrylic resin reproduced more accurate points than groups polymerized with an injection pressing type of acrylic resin.

Acrylic Resins↗
PubMedDate not supplied

Precision metal occlusal surfaces for removable partial dentures.

The prosthodontist is often limited in developing the desired occlusal pattern when integrating removable partial dentures with natural dentitions or fixed partial dentures. A technique that allows the development of an esthetic, accurate metal occlusal surface for a removable partial denture is described. The occlusion developed allows an occlusal harmony with the removable partial denture that is not possible with stock denture teeth or metal occlusal surfaces developed with stock denture teeth.

Dental Occlusion↗