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Biomedical subjects

T C Peters

Publications and source records attributed to T C Peters.

9 recordsLinked to original sources
PubMed1998

Clinical evaluation of Dyract in primary molars: 3-year results.

PURPOSE: To evaluate the 3-year clinical performance of Dyract in primary molars. MATERIALS AND METHODS: In 55 children (aged 4-9 years) 91 restorations were placed and 76 were available for evaluation after 2 years. After 3 years, 40 teeth were exfoliated leaving 37 restorations for evaluation. RESULTS: During the entire study, four restorations failed and had to be replaced. One restoration fractured after 6 months and another after 1 year. Two other restorations were completely lost between the second and third year's evaluation. Furthermore, three restorations showed minimal recurrent caries, which did not need additional treatment. Wear of the restorations was considerable. However, this was also true for the point of reference for the wear measurement on the primary molars. The excellent handling characteristics and the low failure rate during the 3-year study suggest that this compomer is a reliable restorative material in primary molars.

Child↗
PubMed1997

Changes to Dyract restorative resin immersed in various media.

PURPOSE: To examine changes in weight, strength, fluoride release, and surface changes to the polyacid-modified resin composite Dyract after immersion in various media for periods up to 16 weeks. MATERIALS AND METHODS: Properties investigated were change in weight, strength, release of fluoride ions, and surface changes. Specimens were immersed in reverse osmosis deionized water (ROW) and in acetate buffer solutions containing calcium hydrogen orthophosphate. The acetate media were of pH3, pH5 and pH7. All solutions were maintained at 37 degrees C without agitation. Solutions were changed weekly and retained for fluoride analysis and specimens were weighed each week. After periods of 1, 2, 3, 4, 8, 12 and 16 weeks, some specimens were subjected to shear punch testing and SEM examination. RESULTS: All specimens except those in pH3 medium gained weight for the first 2-5 weeks after which weight was lost until all specimens weighed less than at the commencement of the study. The specimens in pH3 medium lost considerable weight from weeks 1 and 2. SEM examination showed disintegration of the surface of all specimens examined. Fluoride release peaked at 1 week in all specimens except those in pH3 medium. Fluoride release was highest in pH3 media (approximately 46 ppm) after 1 week and remained high for 7 weeks, after which it was reduced to about 50% of the initial release. Specimens stored in ROW and pH5 media released approximately 5 ppm after 1 week, and this was reduced to approximately 1 ppm (pH7) and 2 ppm (ROW) by week 6.

Cariostatic Agents↗
PubMed1996

Cavity wall adaptation and voids in adhesive Class I resin composite restorations.

OBJECTIVES: Handling characteristics and adaptation modes of resin composites are important factors to achieve proper placement of the restorative materials. The present study was undertaken to assess the influence of the consistency of composite materials and the mode of application on voids and porosities in Class I adhesive restorations. METHODS: One hundred medium-sized Class I preparations with an adhesive design were restored with three composites of various consistencies using three different application modes. The restorations were sectioned, and each section of a restoration was inspected for the presence of voids. The total surface and the percentage of the cavity wall occupied by voids as well as the total number of voids in the sections were recorded. A Krusal-Wallis analysis of variance was carried out on the data. Differences between individual composite materials for each mode of application and between individual application modes for each composite material were analyzed using a Mann-Whitney U-test at p < 0.05. RESULTS: The injection technique with a Hawe Neos Centrix tip was the best mode of application. Both smearing and the condensation of composites appeared to produce unreliable results. Furthermore, there were more problems with voids and wall adaptation for the thicker-consistency composite than for the medium- and thin-consistency material. SIGNIFICANCE: The thick-consistency composite had more problems related to voids and wall adaptation than the medium- and thin-consistency composites.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1996

Consistency of resin composites for posterior use.

OBJECTIVES: The aim of this study was to compare a large set of resin composites suitable for application in stress-bearing areas on the basis of their consistency. METHODS: A variety of posterior resin composites were tested using an apparatus that was originally designed for determination of the consistency of elastomeric impression materials (ISO 4823, 1992). The consistency of a standardized volume of resin composite was tested in a dark room at 23 degrees C by loading the samples during 60 s with 1625 g. After loading, the circumference of each sample was determined by a digitizer. Results were analyzed using Tukey-HSD multiple comparisons test and Student's t-tests. RESULTS: The consistency of different brands of composites varied considerably. P50 was the material with the thinnest consistency. Significant differences (p < 0.05) in consistency were found between the same brands of material which were applied directly out of the syringe or out of a preloaded tip. Loading a Centrix tip with one composite out of a syringe resulted in a thinner consistency of the material than when taken directly from the syringe. SIGNIFICANCE: A ranking of posterior resin composites is presented to enable a material selection based on consistency.

Bicuspid↗
PubMed1996

Clinical evaluation of Dyract in primary molars: 1-year results.

PURPOSE: To evaluate the 1-year clinical performance of Dyract in primary molars. MATERIALS AND METHODS: 55 children (aged 4-9 years) received 1-3 restorations (n = 91) utilizing Dyract, a new restorative material combining properties of both glass ionomers and composites. RESULTS: The so-called compomer material showed good handling characteristics and a survival rate of 97% after 1 year. Nevertheless, the material demonstrated an average wear of 190 microns during 1 year, with 67% of the restorations having occlusal wear of less than 200 microns. The combination of a low failure rate and the ease of application makes the compomer material very suitable for application in the primary dentition.

Child↗
PubMed1990

A minor arginine tRNA mutant limits translation preferentially of a protein dependent on the cognate codon.

The Escherichia coli argU gene encodes a rare arginine tRNA (anticodon UCU) that translates the similarly rare AGA codon. The argU10(Ts) mutation is a transition that changes the first nucleotide of the mature tRNA from G to A, presumably destabilizing the acceptor stem. This mutation, when present in haploid condition in the chromosome, reduces the growth rate at 30 degrees C and results in cessation of growth after 60 to 90 min at 43 degrees C. The mutation also preferentially limits (compared with total protein synthesis) translation of an induced gene that depends on five AGA codons, i.e., the lambda cI repressor gene. Translation of another inducible protein, beta-galactosidase, which does not involve AGA codons, was inhibited to a much lesser extent. The chromosomal argU(Ts) mutation also confers the Pin phenotype, that is, loss of ability of the host, as a P2 lysogen, to inhibit growth of bacteriophage lambda, probably the result of reduced translation of the P2 old gene, which contains five AGA codons (E. Haggård-Ljungquist, V. Barreiro, R. Calendar, D. M. Kurnit, and H. Cheng, Gene 85:25-33, 1989).

Alleles↗
PubMed1984

Postmortem examination of 22 pancreatic carcinoma patients treated with helium ion irradiation.

Postmortem findings are available in this report in 22 patients with pancreatic carcinoma treated with helium ions at Lawrence Berkeley Laboratory; California. This represents the largest group evaluated histologically in the literature and is the first report evaluating effects of particle radiation in pancreatic tissue. Patient survival after therapy averaged 9 months. Most died of infection and/or pulmonary emboli. Local control was achieved in 27%. The pancreatic tumors had histologically more severe radiation changes than nontumor bearing pancreas. Irradiated bone marrow was severely hypocellular, and irradiated skin was atrophic. Five patients had radiation injury in the gastrointestinal tract. The spinal cord, liver, and kidneys showed no damage. This study demonstrates the safety of helium particle irradiation with present therapeutic planning. Injury to tumor was seen without excessive damage to adjacent tissues.

Adult↗
PubMedDate not supplied

Voluntary morphine ingestion, morphine dependence, and recovery from withdrawal signs.

We are reporting on conditions (without forced drinking or premedications) where rats voluntarily drink high quantities of sucrose-morphine solutions in preference to water. The volume ingested is inversely related to the morphine concentration in the liquid. The morphine antagonist, nalorphine, produced a clear set of opiate withdrawal signs in these (voluntarily) morphine-drinking rats. The severity of withdrawal signs was a function of the amount of ingested morphine. The present finding is the first report to show that rats ingest high quantities of sucrose-morphine without premedication or forced hydration procedures.

Animals↗