Showing papers by "Christopher J. Frederickson published in 1997"
TL;DR: It is hypothesised that the increased zinc level in AD patients is caused by an increase in the amount of ZEN terminals, which could be the result of a sprout of Zen terminals in diseased areas of the brain.
168 citations
02 May 1997
TL;DR: In this article, the degradation products formed by diode laser and Nd:YAG laser irradiation of indocyanine green (ICG) and carbon black based ink sensitized tissues, including bone, tendon and sheep's teeth, were identified.
Abstract: Organic dyes have found increasing use a s sensitizers in laser surgical procedures, due to their high optical absorbances. Little is known, however, about the nature of the degradation products formed when these dyes are irradiated with a laser. Previous work in our laboratories has shown that irradiation of polymeric and biological tissues with CO2 and Nd:YAG lasers produces a host of volatile and semivolatile by-products, some of which are known to be potential carcinogens. This work focuses on the identification of the chemical by-products formed by diode laser and Nd:YAG laser irradiation of indocyanine green (ICG) and carbon black based ink sensitized tissues, including bone, tendon and sheep's teeth. Samples were mounted in a 0.5-L Pyrex sample chamber equipped with quartz optical windows, charcoal filtered air inlet and an outlet attached to an appropriate sample trap and a constant flow pump. By-products were analyzed by GC/MS and HPLC. Volatiles identified included benzene and formaldehyde. Semi-volatiles included traces of polycyclic aromatics, arising from the biological matrix and inks, as well as fragments of ICG and the carbon ink components. The significance of these results will be discussed, including the necessity of using appropriate evacuation devices when utilizing lasers for surgical procedures.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
8 citations
15 May 1997
TL;DR: In this article, micro-drops of photoabsorptive 'promoters' are placed on the enamel to enhance absorption of individual laser pulses in order to perform ablation of healthy enamel.
Abstract: Nd:YAG lasers have been used previously for selective removal of various material from teeth To permit ablation of healthy enamel with the Nd:YAG laser, we have adopted a strategy in which micro-drops of photoabsorptive 'promoters' are placed on the enamel to enhance absorption of individual laser pulses Ink-jet technology dispenses the micro-drops with micron- and millisecond-scale precision Various promoters using drug and cosmetic dyes, indocyanine green, or carbon-black pigments have been studied Typical ablation parameters are 1064 micrometers ; 20-180 mJ per pulse; 100 microsecond(s) ; 10-30 pulses/sec; 02-20 nl drops Recent results from the program include: (1) For a variety of promoters, a monotonic relationship obtains between absorption coefficient at 1064 micrometers and the efficiency of ablation of enamel (2) With different promoter volumes, the efficiency of ablation rises, plateaus, then falls with increasing volume (3) At drilling rates of 30 pulses/sec, ablation efficiency approaches rates of 01 mm3/sec LM and SEM observations show a glassy 'pebbled' crater surface indicative of hydroxyapatite that has cooled, condensed, and solidified on the crater walls Together these results favor the view that a micro-drop promoter-assisted Nd:YAG drill can five clinically useful ablations hard dental tissue© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only
4 citations