Biomedical subjects

K A Agee

Publications and source records attributed to K A Agee.

6 recordsLinked to original sources

PubMed2006

Effects of resin hydrophilicity on dentin bond strength.

The purpose of this study was to determine if hydrophobic resins can be coaxed into dentin wet with ethanol instead of water. The test hypothesis was that dentin wet with ethanol would produce higher bond strengths for hydrophobic resins than would dentin wet with water. This study examined the microtensile bond strength of 5 experimental adhesives (50 wt% ethanol/50% comonomers) of various degrees of hydrophilicity to acid-etched dentin that was left moist with water, moist with ethanol, or air-dried. Following composite buildups, hourglass-shaped slabs were prepared from the bonded teeth for microtensile testing. For all 3 types of dentin surfaces, higher bond strengths were achieved with increased resin hydrophilicity. The lowest bond strengths were obtained on dried dentin, while the highest bond strengths were achieved when dentin was bonded moist with ethanol. Wet-bonding with ethanol achieved higher bond strengths with hydrophobic resins than were possible with water-saturated matrices.

Analysis of Variance↗

PubMed2003

Dimensional changes in acid-demineralized dentin matrices following the use of HEMA-water versus HEMA-alcohol primers.

Although dried acid-etched dentin can be reexpanded by hydroxyethyl methacrylate (HEMA)/water primers, the primed dentin collapses when the water is evaporated. Experimental HEMA/alcohol primers should stiffen the matrix and permit less shrinkage when the solvent is evaporated. The purpose of this study was to test the hypotheses that matrix shrinkage induced by solvent evaporation from HEMA primers is inversely related to solvent-induced matrix stiffness. Dentine discs were prepared from midcoronal dentine of unerupted human third molars. After demineralization in 37% phosphoric acid, the specimens were placed in the well of a linear variable differential transformer instrument, which measures changes in the matrix height and stiffness by load displacement after the application of weights. This was done in their hydrated state after water had been applied, after drying with dry nitrogen gas, and after the application of 35 vol % HEMA-water, HEMA-methanol, HEMA-ethanol, or HEMA-propanol primers. The degree of reexpansion after the application of the primers to the dentine in the dried state was found to be highest using the HEMA-water primer, followed by HEMA-methanol and HEMA-ethanol, with the HEMA-propanol primer producing no expansion. However, when the solvents were evaporated the HEMA-water-treated specimens shrank the most, the HEMA-ethanol-treated specimens shrank an intermediate amount, and the HEMA-methanol-treated specimens shrank the least. The net result of expansion minus shrinkage produced by evaporation determines how much HEMA remains in the hybrid layer just prior to polymerization.

Acids↗

PubMed2001

Solvent-induced dimensional changes in EDTA-demineralized dentin matrix.

The purpose of this study was to test the null hypothesis that the re-expansion of dried matrix and the shrinkage of moist, demineralized dentin is not influenced by polar solvents. Dentin disks were prepared from midcoronal dentin of extracted human third molars. After complete demineralization in 0.5M of EDTA (pH 7), the specimens were placed in the well of a device that measures changes in matrix height in real time. Dry, collapsed matrices were created by blowing dry N(2) on the specimens until they shrank to a stable plateau. Polar solvents [water, methanol, ethanol, n-propanol, n-butanol, formamide, ethylene glycol, hydroxyethyl methacrylate (HEMA), or mixtures of water-HEMA] as model primers then were added and the degree of re-expansion measured. These same solvents also were applied to moist, expanded matrices and the solvent-induced shrinkages measured. Regression analysis was used to test the correlations between matrix height and Hansen's dispersive, polar, hydrogen bonding, and total solubility parameters (delta(d), delta(p), delta(h), delta(t)). The results indicate that water-free polar solvents of low hydrogen bonding (H-bond) ability (e.g., neat HEMA) do not re-expand dried matrices and that they shrink moist matrices. When HEMA was mixed with progressively higher water concentrations, the model water-HEMA primers expanded the dried matrix in proportion to their water concentrations and they produced less shrinkage of moist matrices. Solvents with higher H-bonding capacities (methanol, ethanol, ethylene glycol, formamide, and water) re-expanded the dried matrix in proportion to their solubility parameters for H-bonding (delta(h)). They also induced small transient shrinkages of moist matrices, which slowly re-expanded. The results require rejection of the null hypothesis.

Biocompatible Materials↗

PubMed2001

Effects of sodium hypochlorite and RC-prep on bond strengths of resin cement to endodontic surfaces.

There is concern that the use of sodium hypochlorite (NaOCl) and RC-Prep may lower the bond strength of resin cements. The objective of this study was to evaluate the effect of 5% NaOCl and RC-Prep treatment on the bond strength of a resin cement, C&B Metabond. Control roots (group 1) were biomechanically prepared using 0.9% NaCl as an irrigant; group 2, roots with 5% NaOCl; group 3, roots with RC-Prep; group 4, roots with 0.9% NaCl followed by 10% ascorbic acid; group 5, roots with 5% NaOCl followed by 10% ascorbic acid (pH 4); group 6, roots with 5% NaOCl followed by 10% neutral sodium ascorbate; and group 7, roots with RC-Prep followed by 10% ascorbic acid. All roots were then filled with C&B Metabond, incubated in water for 24 h, and then cross-sectioned into six 1-mm thick slabs representing cervical and middle root dentin. The slabs were trimmed and tested for tensile bond strength. The results demonstrated that both 5% NaOCl and RC-Prep produced significantly (p < 0.05) large reductions in resin-dentin bond strengths, and the reductions could be completely reversed by the application of either 10% ascorbic acid or 10% sodium ascorbate.

Analysis of Variance↗

PubMed2000

Permeability of demineralized dentin to HEMA.

OBJECTIVES: The objectives of this study were to develop a macromodel of the demineralized layer of dentin that is formed after acid-etching, and to determine if the amount of HEMA uptake was responsive to air drying. The hypothesis that was tested was that HEMA uptake by demineralized dentin depends upon the degree of expansion of the collagen fibril network. METHODS: Dentin cubes (2 x 2 x 2 mm) were prepared in coronal dentin from extracted unerupted human third molars. They were incubated in 100% HEMA for up to 1000 min and then removed and blotted free of excess adherent HEMA. The HEMA taken up by each cube was extracted in 2 ml of water for 1 hr with shaking. This was repeated and the extracts combined. HEMA was quantitated spectrophometrically. The dentin cubes were then demineralized in 0.5 M EDTA for 10 days and the HEMA uptake remeasured at 1, 10, 100 and 1000 min. Then the cubes were air-dried and the HEMA uptake remeasured. After re-expanding the specimens in water, the cubes were stiffened in ascending concentrations of acetone of 100%, then allowed to air dry again in a more expanded state, and HEMA uptake was remeasured. Finally, after rehydration, the dentin cubes were "acid-etched" for 1 or 10 min with 37 wt% phosphoric acid and HEMA uptake remeasured. RESULTS: Before demineralization, the dentin took up little HEMA (ca. 4.8 x 10(-7) moles min-3) compared to after demineralization when the uptake for 10, 100 and 1000 min was 27.4, 43.8 and 51.4 x 10(-3) moles mm-3, respectively. Acid etching for 1 or 10 min had no effect on HEMA uptake. Air drying produced a 72% volumetric shrinkage but a 97% reduction in uptake. When the demineralized matrix was stiffened in acetone prior to air-drying, the volumetric shrinkage was only 27% and the HEMA uptake only fell 16% compared to the wet, fully expanded condition. SIGNIFICANCE: The results support the hypothesis that the uptake of HEMA by demineralized dentin depends on the degree of expansion of the dentin matrix.

Acid Etching, Dental↗

PubMed1992

Concentration dependencies of immunoturbidimetric dose-response curves: immunoturbidimetric titer and reactivity, and relevance to design of turbidimetric immunoassays.

To characterize polyclonal antisera for two-point immunoturbidimetric applications, we defined, as functions of antiserum concentration, two parameters derived from dose-response curves: the maximum bichromatic optical response, Tmax, and the antigen concentration in the region of excess antibody corresponding to one-half Tmax, or C50. We raised monospecific polyclonal antisera in goats against several human immunoglobulins, C-reactive protein, C3, C4, apolipoproteins A-I and B, and several other proteins. We could linearly relate the logarithm of the antiserum concentration to log C50 and to log Tmax. The concentration of polyethylene glycol affected not only C50 and Tmax but also their functional dependencies on antiserum concentration. We devised two definitions of immunoturbidimetric titer and related them to the titer obtained by the single radial immunodiffusion method of Becker (Immunochemistry 1969; 6:539-46).

Apolipoprotein A-I↗