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Biomedical subjects

R Blackman

Publications and source records attributed to R Blackman.

7 recordsLinked to original sources
PubMed1992

Marginal accuracy and geometry of cast titanium copings.

The biocompatibility of titanium with human tissue is well established; its potential as an alternate metal for crown restorations has yet to be fully investigated. This study measured the geometry and accuracy of coping margins cast in Ti, 99.5% chemically pure. Twenty castings with 45-degree facial and 90-degree palatal margins were made by indirect technique with a commercial system using recommended procedures. They were then cemented with ZnPO4 cement. The coping and die assemblies were embedded in resin, sectioned longitudinally, and measured with a microscope at x50 power. Casting shrinkage was characteristic, particularly along the horizontal axis in the plane of the shoulder. Although horizontal linear shrinkage of 45-degree margins was greater than that for the 90-degree form, the surface of marginal discrepancy was greatest with the 90-degree configuration.

Analysis of Variance↗
PubMed1992

Modern concepts in endodontics. Part 1. Diagnosis.

Diagnosis is the basic procedure from which further endodontic treatment decisions flow. Although we still use diagnostic tools which differ little from those of 50 years ago, our understanding and interpretation of their results has been slowly changing. As an example, we now believe that the painful responses to hot and cold occur via different a delta and C fibre pathways, involving changes in intra pulpal pressure and neuropeptides such as VIP and SP. As treatment planning is becoming more sophisticated and treatment modalities and options are expanding, correct endodontic diagnosis is even more important in the new age of rising patient expectations and ever-increasing legal complexities. Endodontists are frequently called upon to deal with difficult diagnostic situations, or manage situations of misdiagnosis where treatment has been initiated but the original chief complaint mysteriously persists. In the future, new exciting techniques such as pulse oximetry or laser doppler analysis may be clinically available as endodontic diagnostic aids. This paper will try and cover some of the broader concepts involved in correctly diagnosing a patient's chief complaint.

Dental Pulp Diseases↗
PubMed1991

Dimensional changes in casting titanium removable partial denture frameworks.

The difficulties encountered in casting titanium and its alloys have until recently hindered any widespread use of titanium in restorative dentistry. Now both equipment and materials are available for the routine use of titanium in the dental laboratory. This study used one of the casting systems and examined dimensional changes that occur during the construction of a removable partial denture framework. Nineteen castings were measured for horizontal and vertical plane changes. Results show these castings to have cross arch contraction, vertical plane expansion, and near neutral anterio-posterior change. It seems that pure titanium is within the range of dimension changes generally accepted for base metal removable partial denture alloys of the nickel-chromium variety.

Dental Casting Investment↗
PubMed1990

Influence of ceramic thickness on the polymerization of light-cured resin cement.

The curing of two light-activated resin cements under two ceramic materials was examined to assess the influence of ceramic thickness on polymerization. The degree of resin cure was determined by microhardness measurements (Knoop) on resin cement samples cured under five ceramic thicknesses with light exposures of 30 to 120 seconds. These cements cured under thin ceramic specimens with recommended exposures. With thick ceramics, both cements cured better under the glass-ceramic, but neither reached a level of maximum cure under the porcelain.

Ceramics↗
PubMed1989

An evaluation of the biocompatibility of a glass ionomer-silver cement in rat connective tissue.

Pellets of a glass ionomer-silver cement and a zinc oxide-eugenol cement were implanted into the soft tissues and bones of 30 rats. Following experimental periods of 14, 30, and 80 days, the animals were killed and tissue sections were prepared. The responses to each of the materials initially and at 30 days consisted of mild inflammation. No severe inflammatory responses were noted in any of the groups. By 80 days, although mild inflammation persisted, the materials appeared to be well tolerated. Bone apposition occurred in the glass ionomer-silver cement group; the zinc oxide-eugenol group produced fibrosis.

Animals↗
PubMedDate not supplied

Gastrointestinal tissue diagnosis by laser-induced fluorescence spectroscopy at endoscopy.

An endoscope-compatible, optical fiber system has been developed which can be used to obtain laser-induced fluorescence spectra of mucosal abnormalities during endoscopy in real time. The results of our previous in vitro studies have suggested that laser-induced fluorescence tissue spectra are sufficiently unique that they can be used to accurately diagnose mucosal abnormalities in some systems. To test this hypothesis in vivo, laser-induced fluorescence spectra were obtained during colonoscopy from 31 colonic adenomas, 4 hyperplastic polyps, and 32 examples of normal mucosa in 20 patients. The resulting spectra could be used to correctly differentiate adenomas from normal colonic mucosa and hyperplastic polyps in 97% of the specimens studied with the resulting sensitivity, specificity, and positive predictive value of 100%, 97%, and 94%, respectively. These results, although preliminary in nature, suggest that laser-induced fluorescence spectra can be used in the recognition and differential diagnosis of mucosal abnormalities at endoscopy.

Adenoma↗