Precision of Fit of Titanium and Cast Implant Frameworks Using a New Matching Formula

Statement of the Problem. Fit of prosthodontic frameworks is linked to the lifetime survival of dental implants and maintenance of surrounding bone. Purpose. The purpose of this study was to evaluate and compare the precision of fit of milled one-piece Titanium fixed complete denture frameworks to that of conventional cast frameworks. Material and Methods. Fifteen casts fabricated from a single edentulous CAD/CAM surgical guide were separated in two groups and resin patterns simulating the framework for a fixed complete denture developed. Five casts were sent to dental laboratories to invest, cast in a Palladium-Gold alloy and fit the framework. Ten casts had the resin pattern scanned for fabrication of milled bars in Titanium. Using measuring software, positions of implant replicas in the definitive model were recorded. The three dimensional spatial orientation of each implant replica was matched to the implant replica. Results. Results demonstrated the mean vertical gap of the Cast framework was 0.021 (+0.004) mm and 0.012 (0.002) mm determined by fixed and unfixed best-fit matching coordinate system. For Titanium frameworks they were 0.0037 (+0.0028) mm and 0.0024 (+0.0005) mm, respectively. Conclusions. Milled one-piece Titanium fixed complete denture frameworks provided a more accurate precision of fit then traditional cast frameworks

Tensille Bond Strength of Two Luting Agents to Various Implant Prosthetic Substrates

Master of ScienceProsthodonticsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/163684/1/20196028.pd

Severe abdominal pain and diarrhea – unusual multiple myeloma presentation with a severe prognosis: a case report

Abstract Background Multiple myeloma is a hematologic disease with high mortality rates all over the world. The diagnosis has always been challenging since the first case was reported in 1844. For that reason the diagnostic criteria have evolved over years to include the features of the disease more comprehensively. Unusual presentations are infrequent and a diagnostic challenge. For this reason we report this rare case in which diarrhea and abdominal pain were the initial presenting symptoms of multiple myeloma with a plasmacytoma. Case presentation An 87-year-old Hispanic man with a past medical history of hypertension, diabetes, and constipation, presented to an emergency department complaining of severe generalized abdominal pain and profuse diarrhea for 3 days. A physical examination revealed generalized pallor and dehydration but no signs of abdominal peritoneal irritation. Laboratory tests revealed neutrophilia and an elevated total protein. He received intravenously administered fluids and antibiotics. His abdominal pain became localized in the infraumbilical area and a small mass was palpated on the right lower quadrant on subsequent examination. An abdominal computed tomography scan showed a tumor lesion surrounded by fluid collection and a computed tomography-guided biopsy of the lesion confirmed it to be a plasmacytoma. A bone marrow biopsy revealed plasmatic cell augmentation but his beta-2 microglobulin levels were inconclusive. The diagnosis of multiple myeloma was finally confirmed with urine immunofixation. Bortezomib was initiated to decrease disease progression, but unfortunately 4 days later he developed acute pulmonary edema, had a cardiac arrest, and died. Conclusions This case illustrates the protean initial manifestations of multiple myeloma and the importance of an accurate diagnosis. Our patient’s initial presentation with gastrointestinal complaints is rare and the plasmacytoma location is even rarer, providing a challenging diagnostic problem. Prompt recognition of multiple myeloma is critical to institute appropriate therapy and prevention of disease progression

DFT+U study of the electronic structure changes of WO3 monoclinic and hexagonal surfaces upon Cu, Ag, and Au adsorption. Applications for CO adsorption

A periodic DFT+U study about the adsorption of Cu, Ag, or Au on the monoclinic and hexagonal (001) surface of WO3 is presented. The scope is to elucidate the changes in the electronic structure of these materials upon adsorption of Cu, Ag and Au, and to provide some insights about the adsorption of CO. The adsorbed Cu, Ag, and Au atoms provokes the formation of positive charge on the surfaces by transferring electrons to the oxide. The charge is located at the bottom of the conduction band, which causes the Fermi level to move into the conduction band and the materials become semimetals. The CO molecule is weakly adsorbed on the clean surfaces. The adsorption provokes a compression of the surface's states at the conduction band due to the appearance of new states belonging to the CO molecule. This result is a slight stabilization of the bottom of the conduction band, which is translated into a reduction of the band gap upon CO adsorption on the clean surfaces. On the other hand, the CO molecule is also chemisorbed on the doped surfaces through a back-donation bond. The doped surfaces states at the conduction band are also compressed by the appearance of new states belonging to the CO molecule, and the states at the Fermi level seems to increase. The results provide good insights for the application of WO3 in gas sensing chemistry and photocatalysis.Fil: Hurtado Aular, Oscar Enrique. Instituto Venezolano de Investigaciones Científicas; Venezuela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Añez, Rafael. Instituto Venezolano de Investigaciones Científicas; VenezuelaFil: Sierraalta, Aníbal. Instituto Venezolano de Investigaciones Científicas; Venezuel

Influence of Screw Channel Angulation on the Fracture Resistance of Zirconia Abutments: An In Vitro Study

PurposeThe aim of this study was to investigate the effect of implant screw channel angulation on the fracture resistance of zirconia abutments without artificial aging.Materials and MethodsTen implant replicas were embedded in a jig of autopolymerizing acrylic resin. Using a surveyor and a metallic platform, the implant replicas were mounted centrally and with an angulation of 30°. A maxillary left central incisor crown was fabricated from pattern resin and scanned. The digital design of a monolithic zirconia implant abutment- crown was completed using a 3D imaging software. For all specimens of this group (ASC25), the screw channel was positioned at 25° to the lingual. Following fabrication, the samples were attached onto the embedded implant replicas and manually torqued to 35 Ncm as recommended by the manufacturer. The monolithic zirconia implant abutment- crowns were mounted in a metallic platform, positioned perpendicular to the indenter, and subjected to loading until failure. Crosshead speed was set at 0.5 mm/min for the universal testing machine. Data from a similar in vitro study where straight zirconia custom abutments (ASC0) were subjected to static load until failure was used as a control group. An unpaired Student’s t- test was used to determine if fracture resistance based on load at failure and maximum load in each group were significantly different from each other (ASC25 vs ASC0). Statistical significance level was inferred at p - ¤ 0.05ResultsGroup ASC25 fractured at a mean (SD) load of 215.49 (47.10) N and a mean (SD) maximum load of 420.50 (17.18) N. Group ASC0 fractured at a mean (SD) load of 534.04 (133.77) N and a mean (SD) maximum load of 762.69 (109.59) N. The difference was statistically significant for both mean load and mean maximum load at failure (p - ¤ 0.05). The survival rate of 0° zirconia abutments was significantly higher than that of 25° ASC zirconia abutments.ConclusionsWithin the limitations of this in vitro study the mean fracture load was significantly higher in the group with a straight channel angulation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/167526/1/jopr13275_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/167526/2/jopr13275.pd

Performance of Density Functional Methods. Some Difficult Cases for Small Systems Containing Cu, Ag, or Au

Twenty-six density functional theory (DFT) methods were tested in conjunction with three different effective core potentials (ECPs) and their corresponding valence basis sets, for studying the behavior of DFT methods in small systems containing Cu, Ag, or Au where it is well-known that some functionals fail. The DFT results were compared with those obtained with post Hartree–Fock methods: second-order many-body perturbation theory (MP2), coupled cluster singles-doubles (CCSD), and coupled cluster singles-doubles with perturbative triples, CCSD­(T). Calculations were carried for M₃ (M = Cu, Ag, Au); M₄^–, (M = Cu, Ag) and [H₂O–Cu]⁺². The comparison of the DFT calculated values with the Post Hartree–Fock values showed that, in general, all generalized gradient approximation (GGA) type functionals fail to describe these systems. The hybrid GGA functionals (H-GGA) showed a better behavior; however, when the Lee–Yang–Parr (LYP) exchange-correlation functional was used, wrong results were obtained. The results with the hybrid meta (HM-GGA) functionals, as in the case of H-GGAs, showed that, to obtain similar results to MP2 or CCSD­(T), it is necessary to have a high Hartree–Fock exchange percentage. Spurious results obtained with the H-GGA or HM-GGA methods can be eliminated increasing the Hartree–Fock exchange percentage in the H-GGA or HM-GGA type functionals. Among the different functionals tested, the BB1K and MPWB1K functionals showed the best agreement with the MP2 and CCSD­(T) results