THE CURRENT VIEW ON THE USE OF RECONSTRUCTION MATERIALS IN DENTISTRY

The hardest tissue in the human body is the enamel which covers the anatomical crowns of teeth. It must be resistant to mechanical stress and the chemical attack of many substances from food, drinks and products of the metabolism of bacteria present in the oral cavity. These low pH substances dissolve the mineral components of enamel, cause tooth demineralization, and lead to decay or erosion damage with the irreversible loss of dental hard tissues and the necessity of their reconstruction. The range of dental materials intended for dental tissue reconstruction is extensive. Dental amalgam can be mechanically applied into the strongly stressed lateral segments of teeth. The use of amalgam is, however, in decline, with the possible health risks attributed to it, coupled with the need to extensively prepare tooth tissue promoting a shift towards using aesthetically and biologically favourable dental ceramic and polymeric materials instead. Current developments also concentrate on these materials to reinforce this, with polymeric composite materials based on methacrylates with varying amounts of inorganic fillers at the forefront. These materials are distinguished by their good mechanical and aesthetic properties and wear resistance. However, polymerization shrinkage and a strong hydrophobic nature does not allow for their direct bonding to hard dental tissues. Risks associated with the release of residual free monomers from the structure to the environment, which may cause health complications, mainly allergic reactions in sensitive individuals, have been monitored recently. Further development in the field of composite materials aims to reduce or completely eliminate these negatives

Tribomechanical Properties of a Carbon-Based Nanolayer Prepared by Nitrogen Ion Beam Assisted Deposition for Finger Joint Replacements

This paper presents the tribomechanical test results of Ti6Al4V alloy modified by carbon-based nanolayers with a thickness of 20 nm and 40 nm, prepared by nitrogen ion beam assisted deposition. The presence of carbon and nitrogen compounds was observed in the modified surface after ion bombardment. Nonstoichiometric TiNx was mainly detected near the interface nanolayer/titanium substrate and in the substrate itself. Ion bombardment led to an improved surface hardness of ~13 GPa in comparison to unmodified Ti6Al4V titanium alloy (~5.5 GPa) and alloy coated by carbon nanolayer without nitrogen ion assistance (~7 GPa). The decreasing of friction coefficient was achieved from 0.5–0.6 for untreated Ti6Al4V alloy to 0.1 for treated Ti6Al4V alloy. Wear testing using a joint wear simulator proved that the modified Ti6Al4V alloy has a higher resistance compared to the unmodified Ti6Al4V alloy. The primary local wear fault of the treated surface was observed after 240,000 cycles in comparison to enormous wear on the untreated surface after just 10,000 cycles. Treating the Ti6Al4V load-bearing components of implants with carbon-based nanolayers assisted by nitrogen ions is very promising in terms of extending the lifetime of implants and thereby reduces patient burden

THE CURRENT VIEW ON THE USE OF RECONSTRUCTION MATERIALS IN DENTISTRY

The hardest tissue in the human body is the enamel which covers the anatomical crowns of teeth. It must be resistant to mechanical stress and the chemical attack of many substances from food, drinks and products of the metabolism of bacteria present in the oral cavity. These low pH substances dissolve the mineral components of enamel, cause tooth demineralization, and lead to decay or erosion damage with the irreversible loss of dental hard tissues and the necessity of their reconstruction. The range of dental materials intended for dental tissue reconstruction is extensive. Dental amalgam can be mechanically applied into the strongly stressed lateral segments of teeth. The use of amalgam is, however, in decline, with the possible health risks attributed to it, coupled with the need to extensively prepare tooth tissue promoting a shift towards using aesthetically and biologically favourable dental ceramic and polymeric materials instead. Current developments also concentrate on these materials to reinforce this, with polymeric composite materials based on methacrylates with varying amounts of inorganic fillers at the forefront. These materials are distinguished by their good mechanical and aesthetic properties and wear resistance. However, polymerization shrinkage and a strong hydrophobic nature does not allow for their direct bonding to hard dental tissues. Risks associated with the release of residual free monomers from the structure to the environment, which may cause health complications, mainly allergic reactions in sensitive individuals, have been monitored recently. Further development in the field of composite materials aims to reduce or completely eliminate these negatives

RD50 Status Report 2008 - Radiation hard semiconductor devices for very high luminosity colliders

The objective of the CERN RD50 Collaboration is the development of radiation hard semiconductor detectors for very high luminosity colliders, particularly to face the requirements of a possible upgrade scenario of the LHC.This document reports the status of research and main results obtained after the sixth year of activity of the collaboration