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Biomedical subjects

M J Wagner

Publications and source records attributed to M J Wagner.

At least 55 records · Page 3Linked to original sources
PubMed1992

Human chromosome 8 linkage map based on short tandem repeat polymorphisms: effect of genotyping errors.

A linkage map consisting of 21 dinucleotide repeat polymorphisms, 1 tetranucleotide repeat polymorphism, and 3 RFLPs was constructed for human chromosome 8. The map spanned most of the chromosome length from near pter to q23-q24 on the distal portion of the long arm. The total 186 cM length of the female map was over two times the 84 cM length of the male map. Cytogenetic mapping of the polymorphisms using a panel of hybrids containing rearranged chromosomes was completely consistent with the linkage map. Special effort was made to remove as many genotyping errors, including parental phase errors, as possible. Removal of errors, in agreement with recent theoretical predictions, led to reduction of the total length of the sex-equal map by 10% from 145 to 130 cM.

Alleles↗
PubMed1992

Antibacterial activity of dental implant metals.

This study was conducted to investigate the specific in vitro antibacterial effect of seven dental implant metals on oral bacteria which have often been identified in failing implants. The metals chosen for evaluation were titanium, chromium, cobalt, aluminum, iron, gold, and vanadium. These metals were selected because they are contained in many commonly used dental implants. The bacteria selected for this study included isolates of Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella melaniogenica, Actinobacillus actinomycetemcomitans, Actinomyces naeslundii, and Actinomyces viscosus. Sets of tubes containing either supplemented trypticase soy broth, brain-heart infusion-yeast extract, or brain-heart infusion-yeast extract with 5 percent defibrinated rabbit blood were aseptically prepared with doubling dilutions of the seven metals starting at an initial concentration of 500 micrograms/ml and terminating at 0 microgram/ml. Cultures of each organism were inoculated into each set of broth tubes containing all concentrations of metals. Tubes were incubated either anaerobically or in an atmosphere of 5 percent carbon dioxide for 48 hours at 35 degrees C and then assayed for ATP content which was proportional to the viable cellular biomass. The results showed that, although being bacteria and concentration dependent, all seven metals suppressed the growth of each organism. The rank order of antibacterial activity expressed by dental implant metals was gold > titanium > cobalt > vanadium > aluminum > chromium > iron.

Actinomyces↗
PubMed1992

Bending strength of Fuji and Ketac glass ionomers after sonication.

Glass ionomer cements mixed by conventional methods contain voids that can decrease their overall strength. This study evaluated the effect of sonication on the reduction of air entrapment by measuring the bending strength in glass ionomer cements (Fujj-II and Ketac-fil). Glass ionomer cement was placed in identical-test vials and sonicated for 45s, 10s, or 0s. The bending strengths were measured (0.005 in min-1) after setting times of 1 or 2 weeks. Mean bending strengths (MPa +/- SD) for the 12 treatment both cements (P < 0.001) and sonication times (P < 0.001). The effect of setting time produced minimal increases in bending strength (P < 0.218). The sonication of freshly mixed glass ionomer cements is a possible solution for reducing voids to increase bending strength.

Analysis of Variance↗
PubMed1992

Effects of ultrasonic instrumentation on microleakage in composite restorations with glass ionomer liners.

The aim of this study was to determine the effect of ultrasonic instrumentation on composite resin restorations lined with glass ionomer cement by measuring the extent of dye penetration at the restoration/tooth interface. Preparations, 2.0 mm in diameter and 2.5 mm in depth, were made with a 331 bur in 96 human molar teeth without a bevel. The teeth were restored with glass ionomer cement liners (Shofu) and one of two types of composite resin (Silux and P-30). Half of the samples were ultrasonically instrumented for 10 s. The teeth were immersed in 0.5% methylene blue dye solution and vertically sectioned. Microleakage was scored visually using a scale of 0 to 4. Statistical comparisons were made with chi 2 analysis and the Mann-Whitney U-test at the P less than 0.05 level. Microleakage was significantly different between both resin types (P less than 0.001), and between the lined and unlined resins (P less than 0.001) that were instrumented, particularly in the P-30 restorations. Although P-30 restorations exhibited much less microleakage than Silux, the use of a glass ionomer liner did not reliably reduce microleakage in either type of material after instrumentation with an ultrasonic device.

Acid Etching, Dental↗
PubMed1991

Enamel surface roughness and dental pulp response to coaxial carbon dioxide-neodymium: YAG laser irradiation.

The purpose of this study was to evaluate the effect of a coaxial carbon dioxide/neodymium:yttrium aluminium garnet laser beam on enamel surface roughness and the dental pulps of mongrel dogs. In four dogs, four maxillary left posterior teeth were irradiated at 16 cm source-tooth distances. Two teeth were irradiated with 16 W CO2/16 W Nd:YAG and the remaining two with 16 W CO2/40 W Nd:YAG. Two maxillary right teeth were untreated controls. In addition, mandibular premolars were irradiated at the same distance and power levels, extracted, and analysed for surface roughness. Significant differences in surface roughness were found between control samples and either power level, but not between enamel surfaces at the two power levels. Maxillary teeth were removed at 10 days postoperatively, sectioned and stained (H & E). The reaction of pulpal cells to irradiation was scored. Data analysis revealed statistically significant differences between the control and lower power Nd:YAG groups and between the control and higher power Nd:YAG groups. The difference in pulpal response between both laser groups approached significance.

Aluminum Silicates↗
PubMed1991

Molecular analysis of overlapping chromosomal deletions in patients with Langer-Giedion syndrome.

We have obtained lymphoblastoid cell lines from three patients with Langer-Giedion syndrome who have overlapping deletions in 8q24.1. To isolate the deletion chromosomes from their normal homologs, patient cell lines were fused with hamster cells and hybrid cells were selected for retention of human chromosome 8. These hybrid cell lines were screened for the presence of chromosome 8 by fluorescence in situ hybridization and by Southern blot hybridization. We have hybridized 31 recombinant DNA clones derived from the 8q22-qter region to Southern blots of the hybrid cell lines; 8 were found to lie within the deletion of at least one patient. One clone identified sequences that were missing from one copy of chromosome 8 in all three patients. These clones help to further define the deletions in these patients and will serve as starting points for detailed characterization of the region.

Animals↗
PubMed1991

A hybrid cell mapping panel for regional localization of probes to human chromosome 8.

We have characterized a panel of somatic cell hybrids that carry fragments of human chromosome 8 and used this panel for the regional localization of anonymous clones derived from a chromosome 8 library. The hybrid panel includes 11 cell lines, which were characterized by Southern blot hybridization with chromosome 8-specific probes of known map location and by fluorescent in situ hybridization with a probe derived from a chromosome 8 library. The chromosome fragments in the hybrid cell lines divide the chromosome into 10 intervals. Using this mapping panel, we have mapped 56 newly derived anonymous clones to regions of chromosome 8. We have also obtained physical map locations for 7 loci from the genetic map of chromosome 8, thus aligning the genetic and physical maps of the chromosome.

Animals↗
PubMed1991

Microleakage in alloy-glass ionomer lined amalgam restorations after thermocycling.

Marginal microleakage was measured around amalgam restorations lined with alloy-glass ionomer cement and coated with a glass ionomer varnish. Preparations were made in 48 human extracted mandibular molar teeth. Alloy-glass ionomer liners and varnishes were placed into selected preparations. Tytin amalgam was inserted into all of the teeth and left unburnished and unpolished. Half of the total samples were thermocycled for 5 days and the remainder were left in deionized water. The teeth were immersed in a 0.5% methylene blue dye and sectioned vertically with a diamond saw. Microleakage was scored visually at x100 magnification, and the data were analysed using the Mann-Whitney U-test (P less than or equal to 0.05). Thermocycling did not have a significant effect on microleakage, except when both an alloy-glass ionomer liner and varnish were used. Overall, the use of an alloy-glass ionomer liner made the most significant difference in reducing microleakage.

Coloring Agents↗
PubMed1991

Molecular definition of the shortest region of deletion overlap in the Langer-Giedion syndrome.

The Langer-Giedion syndrome (LGS), which is characterized by craniofacial dysmorphism and skeletal abnormalities, is caused by a genetic defect in 8q24.1. We have used 13 anonymous DNA markers from an 8q24.1-specific microdissection library, as well as c-myc and thyroglobulin gene probes, to map the deletion breakpoints in 16 patients with LGS. Twelve patients had a cytogenetically visible deletion, two patients had an apparently balanced translocation, and two patients had an apparently normal karyotype. In all cases except one translocation patient, loss of genetic material was detected. The DNA markers fall into 10 deletion intervals. Clone L48 (D8S51) defines the shortest region of deletion overlap (SRO), which is estimated to be less than 2 Mbp. Three clones--p17-2.3 EE (D8S43), L24 (D8S45), and L40 (D8S49) - which flank the SRO recognize evolutionarily conserved sequences.

Bacteriophage lambda↗
PubMed1990

Microleakage in restorations with glass ionomer liners after thermocycling.

The purpose of this study was to compare microleakage around two types of restorations lined with polyalkenoate (glass ionomer) cements after thermocycling. Preparations were made in 48 molars to a diameter and depth of 2.0 mm. Half of the preparations were lined with glass ionomer, and the remainder were not lined. Dental amalgam or glass ionomer restorative material was placed and the amalgams were left unburnished and unpolished. Selected restorations were thermocycled 625 times between 4 degrees C and 50 degrees C. Teeth were immersed in 0.5 per cent methylene blue solution, sectioned and visually scored for microleakage at X 100 magnification. Data analysis indicated significant differences in microleakage because of: thermocycling (chi 2 = 103.38, d.f. = 19,2P less than 0.0004); presence of glass ionomer liners (chi 2 = 53.28, d.f. = 19,2P less than 0.0001); and type of restorative material (chi 2 = 103.44,d.f. = 19,2P less than 0.0004). The use of a glass ionomer liner significantly reduced microleakage in both amalgam and glass ionomer restorations when subjected to thermocycling.

Chi-Square Distribution↗
PubMed1990

Effect of undercut placement on crown retention after thermocycling.

The aim of this study was to examine the effect of undercuts in castings and/or tooth structure on the retention of crowns luted with glass ionomer cement. After routine full-crown preparations had been made in 48 human premolars, wax patterns were fabricated for each tooth. Retentive coves were then produced with a round bur in either the tooth structure or the wax patterns, or in both. One group of teeth and patterns did not receive any undercuts; this was the control group. Castings were made in non-precious metal. All crowns were luted with glass ionomer cement. Half of the samples were thermocycled, and the remainder were kept at 37 degrees C. Crowns were removed using tension (0.012 cm min-1) and the mean bond strengths calculated. The differences in retentive strengths were tested for statistical significance using ANOVA and Scheffe's test. The presence of coves in castings and/or tooth structure significantly increased the retentive strength of castings cemented with glass ionomer, as compared with conventional crown preparations without retentive undercuts. The effect of thermocycling on the retentive strength of castings cemented with glass ionomer was not statistically significant.

Analysis of Variance↗
PubMed1985

Format selection in machine-scored classroom achievement tests.

Performance on classroom achievement tests should reflect student accomplishment on a targeted set of instructional objectives. One prerequisite for meaningful edumetric assessment is the structuring of each component item in an appropriate format. In a comparative study measuring the effect of item format on student performance, incorrect choices were selected 2.4-fold more frequently on multiple choice items than on their content-identical, multiple true-false derivatives. On similar trials, scores on complex multiple-choice items ranged upward of 20 percent higher than on their content-identical, multiple true-false counterparts. The strengths and weaknesses of various test item formats are discussed and specific recommendations for format selection are made.

Achievement↗