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Biomedical subjects

Steven K Nelson

Publications and source records attributed to Steven K Nelson.

4 recordsLinked to original sources
PubMed2006

Microtensile bond strength testing and failure analysis of hybrid and flowable composites.

PURPOSE: Few studies have been performed on the cohesive tensile strength of flowable resin composites and hybrids, or on the coupling strength of flowables to hybrid composites. Thus, the purpose of this study was to measure interfacial microtensile bond strengths between hybrid resin composite and flowable resin composite/compomer. MATERIALS AND METHODS: A polyvinyl siloxane mold was used to fabricate specimens for 9 groups, each consisting of 15 rectangular beams (2 x 2 x 20 mm). Flowable and hybrid resin composites and their paired couplings with each manufacturer's product line were tested. Materials include Heliomolarflow, Revolution, and Dyractflow as representative flowable resin composites and compomer. Heliomolar HB, Prodigy, and Esthet X were selected as representive hybrid resin composites. Resin specimens were cured for a total of 80 s and immersed in water for 7 days. A microspecimen former was used to trim rectangular specimens into specimens with a circular cross section (diameter = 1.0 mm) with a 2 mm gauge length. Specimens were subjected to tensile forces in a passive-gripping space mounted on a Vitrodyne machine. RESULTS: The results are expressed in MPa. Kruskal-Wallis one-way ANOVA on ranks demonstrated significant differences in microtensile bond strength among groups (p < 0.001). CONCLUSION: The cohesive tensile strength of resin composites were material dependent. Flowable and hybrid composites from the same manufacturer have comparable cohesive tensile strengths. The coupling strength of flowable/hybrid combinations were comparable to cohesive strength of the hybrid composites with the exception of Esthet X/Dyractflow, where the coupling was stronger than the cohesive strength of either resin composite alone.

Acrylic Resins↗
PubMed2003

A review of selected dental literature on contemporary provisional fixed prosthodontic treatment: report of the Committee on Research in Fixed Prosthodontics of the Academy of Fixed Prosthodontics.

One goal of the American Academy of Fixed Prosthodontics is regularly to publish comprehensive literature reviews on selected topics germane to the discipline of fixed prosthodontics. The following report is the result of this goal and focuses on provisional fixed prosthodontic treatment. Major subtopics include materials science and clinical considerations involving natural teeth and dental implants. The interrelationship between provisional and definitive fixed prosthodontic treatment is multifaceted and significant. Provisional therapy involves numerous materials and techniques that require special knowledge and technical experience. In this analysis, technical, clinical, and investigational articles are detailed and presented as a comprehensive literature review to provide contemporary guidelines. Referenced publications were found by conducting a Medline search and were limited to peer-reviewed, English-language articles published from 1970 to the present. Materials used with provisional treatment are discussed in terms of clinical selection and the influence of their physical properties on treatment outcome. Specific product names and manufacturers are included in this report only when they are cited in the original referenced publications.

Dental Abutments↗
PubMed2002

Effect of toothbrushing on the toxicity of casting alloys.

STATEMENT OF PROBLEM: The biological properties of casting alloys have been assessed largely under passive conditions. The effect of common intraoral stresses such as brushing, toothpastes, and low pH on alloy toxicity are not known. PURPOSE: This study assessed the toxicity of 5 types of casting alloys commonly used in prosthodontics after toothbrushing, brushing in an acidic environment, or brushing with toothpaste. These toxicities were compared with those observed without any brushing. MATERIAL AND METHODS: Au-Pt, Au-Pd, Pd-Cu-Ga, Ni-Cr-Be, and Ni-Cr (no Be) alloys were brushed for 48 hours in a toothbrushing machine at 90 strokes/minute and 200g force. Alloys were brushed with either saline at pH 7, saline at pH 4 (acidified with sodium lactate), or saline with 1:7 (wt/wt) toothpaste. After the brushing regimen, the cytotoxicity of the alloys was assessed in a standard in vitro test. Cytotoxicities of the alloys after different brushing treatments were compared with unbrushed (control) specimens. Analysis of variance (ANOVA) and Tukey multiple comparison intervals (alpha=.05) were used to identify significant differences among brushing conditions. RESULTS: Brushing at pH 7 significantly increased the toxicity of the Pd-Cu-Ga alloy (15% to 20% over unbrushed specimens). Brushing at pH 4 increased the toxicity of the Au-Pt and Au-Pd alloys by 30% and the Pd-Cu-Ga alloy by >40%. The Ni-based alloys were not affected by acid. After being brushed with toothpaste, both Ni-based alloys were significantly more toxic, but Ni-Cr-Be was the worst, increasing more than 60% in toxicity over the controls. The toxicity of the Au-Pd alloy also increased significantly (15%). CONCLUSION: Brushing dental casting alloys may increase their cytotoxicity in vitro, but the increase depends heavily on the alloy type and brushing condition.

3T3 Cells↗