Modern Applications in Technology of Post and Core Restorations

Post and core devices are elements that contribute to the complete restoration of the coronary abutment, over which the final prosthetic restoration will be created. Their role is to retain the coronary portion of the restoration and to protect the remaining coronary structures. The retention function is dictated by the major indication of the method, massive coronary destruction that does not provide conditions for coronary aggregation of the restoration. Thus, this material is approaching two unique methods of making post and core devices totally metallic and/or hybrid (metal + totally ceramic component), using both classical technology, modern technologies, but also combinations of them.

Ceramic bearings fracture: a literature review on risk factors, diagnosis, and treatment

Ceramic surfaces are commonly used in total hip arthroplasty (THA) in young patients due to their good tribological properties. Nonetheless, the fracture of ceramic components is among the most demanding complications of total hip arthroplasty. Ceramic failure is a matter of emergency and needs urgent revision arthroplasty. In this regard, the present study aimed to better understand how to diagnose a ceramic component fracture, identify the major risk factors for the fracture of ceramic components, and analyze the different techniques used in revision arthroplasty for ceramic bearing failure. The literature search was performed on PubMed, MEDLINE-Ovid, and Cochrane Reviews. The search keywords included ceramic fracture, ceramic failure, and ceramic arthroplasty revision surgery. A number of 47 articles were selected out of 126 articles found in the initial research. X-ray and computed tomography (CT) scan must be utilized on suspicion of ceramic component fracture. The most relevant risk factor for head fracture is short neck and 28-mm head combination. Moreover, acetabular cup malpositioning and liner misalignment during insertion are the two major risk factors for liner fracture. There is no consensus on the best revision treatment strategy. Nonetheless, it is necessary to perform a complete synovectomy and an accurate cleaning of the hip joint before the implant of the new components. Stability, integrity, and positioning of both femoral and acetabular components must be evaluated during surgery. If damaged, even well-fixed components should be removed. New ceramic bearing surface is the best option, whereas metal is not recommended for revision surgery.

Use of powder silicon as a photocurable resin filler for laser stereolithography and prospects for transforming stereolithographic parts with silicon from polymeric to ceramic ones.

The article deals with the peculiarities of using silicon micropowder as a chemically inert filler when creating photocurable resins (PCR) for laser stereolithography. The authors provide the results of their experiments on making three-dimensional parts from such resins and discuss the feasibility of transforming the parts from polymeric, containing a filler, into ceramic ones through annealing. The use of silicon allows for a two-fold increase in the mass of the ceramic component due to the interaction of silicon with air oxygen and with products resulting from the thermal decomposition of the photopolymer's polymer base.

Site Stratification and Cultural Stratification

This chapter describes site stratigraphy. Site deposition appears to have been dominated by windblown sand that was sufficient to bury lithic assemblages creating a stratified sequence at Harney Flats. Excavation profiles at Harney Flats were dominated by some two meters of pedogenically modified sands. The upper 1.6 meters of sand contained archaeological deposits dominated by a Bolen/Suwannee component concentrated from 100 to 130 centimeters below surface and a Newnan component from roughly 60 to 90 centimeters below surface. A much more ephemeral later period ceramic component was present from about 40 to 60 centimeters below surface. Of significance is that a dense hardpan soil zone present from about 75 to 85 centimeters below surface prevented stratigraphic mixing of the Newnan and Bolen/Suwannee assemblages.

Modeling the Lamination of a Multilayered Tape Cast Ceramic Component With Fugitive Phases Before Sintering

A small finished ceramic component with micro-channels or other complex geometry requires a high degree of dimensional accuracy. The accuracy of the finished ceramic component depends upon the accuracy of the unfired ceramic body before sintering. One approach to creating micro-channels in ceramics is the fugitive phase approach. In this approach a sacrificial material is placed within the unfired ceramic to form channels or voids. The fugitive phase is removed or sacrificed during the subsequent sintering. For this paper, the authors examine the lamination step of the fugitive phase approach computationally. In the lamination step layers of unfired tape cast ceramic and layers of fugitive phase material are pressed together before sintering. The geometry examined in this paper is a quarter-symmetry model of a ten ceramic layer and nine fugitive phase layer structure. Three dimensional modeling is used to capture out of plane motion, displacement of the fugitive phase pieces, viscoelastic deformation, and rebounding when the layered structure is removed from the die press. The unfired ceramic is modeled as tape cast mullite and the fugitive phase is paper. The fugitive phase is modeled as linear elastic while the unfired ceramic is modeled as viscoelastic at a range of temperatures. The authors examine the filling of voids, pressure gradients, and conditions during unloading.