[Study on mechanical properties of titanius alloy samples fabricated with vacuum-sintered powder metallurgy]

OBJECTIVE

To investigate mechanical properties of titanium alloy samples with vacuum-sintered powder metallurgy.

METHODS

Titanium based metal powder mixtures were compacted into green bodies in the double action press and sintered at 1000 degrees centigrade for 15 minutes in a vacuum furnace at 0.025Pa. Then the mechanical properities of the sintered compacts were evaluated.

RESULTS

Compressive strength of sintered bodies were 111-921MPa when compacted pressure increased from 100MPa to 300MPa. Compressive strength of sintered bodies increased with compacted pressure. Three particle sizes of titanium powder, -160 mesh, -200/+300 mesh, -300 mesh, did not affect the mechanical properties of sintered bodies. The compressive strength of sintered bodies with the plating of copper and tin were higher than those without the plating. Three-point bending strength and elastic modulus of sintered bodies were respectively 102-182MPa and 12193-26630 when compacted pressure affect the mechanical properties pf sintered compacts. Titanium powder plated with copper and tin is compacted and sintered easily, the mechanical properties of sintered compacts are greatly improved.

A frameshift mutation at Gly975 in the transmembrane domain of GPIIb prevents GPIIb-IIIa expression--analysis of two novel mutations in a kindred with type I glanzmann thrombasthenia

Two Hispanic siblings presenting with lifelong mucocutaneous bleeding were diagnosed clinically with Glanzmann thrombasthenia on the basis of a normal platelet count, prolonged bleeding time and absent platelet aggregation in response to multiple agonists. Quantitative analysis of the probands' platelets by flow cytometry showed a complete absence of GPIIb-IIIa, consistent with Type I thrombasthenia. Genetic analysis showed the probands to be compound heterozygotes for two novel mutations of GPIIb: a C1414>G mutation in exon 14, resulting in a premature termination codon replacing residue Tyr440, and the insertion of a G at position 3016 in exon 29, leading to a frameshift affecting the C-terminal half of the transmembrane domain and the cytoplasmic tail. The frameshifted sequence alters residues from Gly975 onwards and is predicted to significantly alter the hydropathy and charge profiles of the GPIIb transmembrane domain. The Type I phenotype associated with this mutation suggests that GPIIb residues 975-1008 contain critical structural motifs for heterodimer assembly, membrane retention, export from the ER and surface expression.

Study on hydroxyapatite-coated titanium implants used as orthodontic anchorage--an experimental investigation of implant stability and peri-implant neck tissue in dogs

OBJECTIVE

Hydroxyapatite-coated titanium endosseous implants as orthodontic anchorage were studied.

METHODS

These implants, installed in the mandibles of two dogs, were loaded with the orthodontic force of 150 g for 3 months. The stability of the implant and peri-implant neck tissue were investigated with radiograph and index evaluation.

RESULTS

No implants were mobile, loosened or dislocated at the 3-month follow-up. The soft tissue around the cervical part of the implants had slight inflammation because of poor oral hygiene and stimulation of residual foods attached to the stainless steel spring. However, no resorption of marginal alveolar bone was found under sustained orthodontic force.

CONCLUSIONS

The HA-coated titanium implant can be used as anchorage for short-term orthodontic treatment.

[Study on the compatibility of slip casting aluminous ceramic crowns]

One of the key factors for a good slip casting aluminous ceramic crown is good compatibility between its core material and the veneering porcelain.The chemical and thermal compatibility of two slip casting aluminous ceramic crown systems(In-Ceram and GI-I) were investigated by means of SEM and EDAX,thermal shock tests were also performed to evaluate the crazing resistance.The results showed: the crazing resistance of In-Ceram was 158 degrees centigrade,and that of GI-I was degrees centigrade;there existed tightly bonded interfaces between the slip casting aluminous ceramic cores and the veneering porcelains in both of the two systems,where ion transferences were found.The results also suggested good compatibility of the two slip casting aluminous ceramic crown systems.

The incomprehensible success of the implant stabilised overdenture in the edentulous mandible: a literature review on transfer of chewing forces to bone surrounding implants

The approach of implant stabilised overdentures has become one of the routine treatment modalities for compromised edentulous ridges. The purpose of this literature review is to analyze survival rates of loaded implants, occlusal forces and stress distributions of implant stabilised overdentures in edentulous mandibles and of fixed loaded implants at least over a medium-term period. which is comparable with fixed prostheses. Patients with implant stabilised overdentures and with fixed bridges on implants generate similar occlusal forces. The number of implants under a prosthetic construction seems to have less influence on stress distribution than design of the superstructure and related direction of forces.

[A study on the clinical application of thinner porcelain laminates for upper anterior teeth]

Porcelain laminates can be used to treat the stained or discolored teeth effectively. In this paper, 18 cases were selected, 102 porcelain laminates (in thickness of 0.5 mm) were fabricated and bonded to the upper anterior teeth through the light curing composite. Following more than three years tracing observation, the results expressed satisfactorily. The questions including the fabrication of porcelain laminate and its clinical application were discussed.

Purification of Bungarus multicinctus antivenin by affinity chromatography

Bungarus multicinctus horse antivenin was purified by ammonium sulfate fractionation, gel filtration on Sephadex G-200 column, and affinity chromatography. The specific neutralizing capacity of the antibody preparations showed 2.21-fold, 3.12-fold, and 29.6-fold higher than that of the crude antivenin, respectively.