Biomedical subjects

R A Giordano

Publications and source records attributed to R A Giordano.

6 recordsLinked to original sources

PubMed1996

Mechanical properties of dense polylactic acid structures fabricated by three dimensional printing.

Polylactic acid (PLA) is a bioresorbable polymer that is used in a number of clinical situations. Complex shapes of PLA are commonly machined for bone fixation and reconstruction. Solid free from fabrication methods, such as 3D printing, can produce complex-shaped articles directly from a CAD model. This study reports on the mechanical properties of 3D-printed PLLA parts. 3D printing is a solid free-form fabrication process which produces components by ink-jet printing a binder into sequential powder layers. Test bars were fabricated from low and high molecular weight PLA powders with chloroform used as a binder. The binder printed per unit line length of the powder was varied to analyze the effects of printing conditions on mechanical and physical properties of the PLA bars. Furthermore, cold isostatic pressing was performed after printing to improve the mechanical properties of the printed bars. The maximum measured tensile strength for the low molecular weight PLLA (53 000) is 17.40 +/- 0.71 MPa and for high molecular weight PLLA (312 000) is 15.94 +/- 1.50 MPa.

Binding Sites↗

PubMed1996

Dental ceramic restorative systems.

Esthetic restorative materials have rapidly grown in number and use. Ceramic materials are often the restorative of choice because they can replicate the color and shape of the natural dentition. Metalceramic restorations are still the most widely used type of ceramic system. However, there has been rapid development of all-ceramic restorative systems that do not require a metal substructure. The intent is to create a translucent restoration that mimics the appearance of the natural tooth. A variety of systems with different methods of fabrication, translucency, and strength are available for use. This article reviews the conventional metal-ceramic system and discusses all-ceramic systems with an eye to clinical selection based on material properties.

Aluminum Oxide↗

PubMed1995

Flexural strength of an infused ceramic, glass ceramic, and feldspathic porcelain.

In-Ceram material is a relatively new all-ceramic restorative material with improved properties that require research. The clinical selection of restorative materials is based on a number of parameters such as esthetics, fit, and strength. This study determined the flexural strength of In-Ceram system components and compared the core material with conventional feldspathic ceramics and with Dicor all-ceramic restorative material. Four-point flexural strength values of bend bars of each ceramic were 18.39 +/- 5.00 MPa for In-Ceram sintered alumina, 76.53 +/- 15.23 MPa for In-Ceram infusion glass, and 236.15 +/- 21.94 MPa for In-Ceram infused alumina core. Flexural strength of self-glazed feldspathic porcelain was 69.74 +/- 5.47 MPa, as-cast Dicor ceramic 71.48 +/- 7.17 MPa, and polished Dicor ceramic was 107.78 +/- 8.45 MPa.

Aluminum Oxide↗

PubMed1995

Effects of firing cycle and surface finishing on distortion of metal ceramic castings.

The "as-cast" fit of metal ceramic restorations has been reported to deteriorate during the high-temperature firing cycles used for application of porcelain veneer. In this study, thermocycling and surface finishing or cold working were examined for their effects on marginal adaptation of metal ceramic castings. Methods for minimizing the loss of marginal adaptation were evaluated, and casting variables were eliminated by construction of acrylic resin measuring dies directly in the restorations. Thermocycling of metal ceramic restorations resulted in increased marginal openings, and all of the loss of marginal fit occurred during the first thermocycling of the alloy. The restorations that were cold worked and then oxidized by conventional manipulation had substantially more marginal opening than any other group. A fourfold, statistically significant improvement (p < 0.001) in the marginal adaptation of a metal ceramic restoration was observed when the initial thermal cycle was completed before the specimens were finished.

Acrylic Resins↗

PubMed1995

Dimensional and formation analysis of a restorative ceramic and how it works.

In-Ceram ceramic appears to use conventional powder/liquid processing techniques to form the coping substructure; however, the process results in a near net-shape restoration with minimal sintering shrinkage. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, particle size classification, and linear dimensional changes during sintering were used to analyze In-Ceram ceramic. In-Ceram ceramic had a minimal linear shrinkage of 0.21% after the sintering of the alumina powder. This shrinkage can be readily compensated for by the expansion of conventional gypsum products and should result in acceptable clinical fits for In-Ceram ceramic restorations. Theories and explanations were described to account for the near net-shape and high strength of In-Ceram. Continuous interpenetrating phase composite technologies were used to create a substantial increase in strength. Future applications of this technology are encouraging.

Aluminum Oxide↗

PubMed1994

Flexural strength of feldspathic porcelain treated with ion exchange, overglaze, and polishing.

Feldspathic porcelains, which are used in the construction of porcelain-fused-to-metal (PFM) restorations, have an inherent weakness because of their brittle nature and processing flaws. A relatively new product, the Tuf-Coat ion exchange system, claims to substantially strengthen feldspathic porcelains. This study compared the strengthening effect of the Tuf-Coat system with that of surface treatments such as overglazing, polishing, and finishing. Bend bars of Vita VMK 68 porcelain were made and randomly assigned to eight different surface treatment groups to examine these effects. The flexural strengths revealed that although Tuf-Coat treatment strengthened the porcelain, it was not significantly different from overglazing, and the strengthening effect was lost if the porcelain was subsequently self-glazed or finished.

Analysis of Variance↗