Bond strength of cements to nickel-chromium and silver-palladium alloys

The bonding of zinc phosphate, polycarboxylate, and reinforced ZOE cements to nickel-chromium and silver-palladium alloys was measured by cementing flat surfaces of the metals together. Polycarboxylate cement produced higher bond strengths than the other two cements to both metals. Polycarboxylate cement bonded better to nickel-chromium alloys than to a silver-palladium alloy. Zinc phosphate and reinforced ZOE cements had similar bond strengths except for Biobond, to which zinc phosphate cement provided higher bond strength. Polycarboxylate cement failed cohesively to both types of metals, and zinc phosphate and reinforced ZOE cements failed adhesively.

Build-up and repair of light-cured composites: bond strength

Interfacial bond strengths of light-activated composites were measured as a function of age using a transverse strength test. Bond strength between layers decreased with the age of the initial layer and reflected the setting curves of the composites. The highly-filled composites exhibited the greatest bond strengths. Uncut surfaces provided a better substrate for bonding than did ground surfaces. Use of a bonding agent on both uncut and ground surfaces improved bond strengths. Mean repair strengths of light-activated composites were similar to those of self-curing composites. Composites with ground surfaces aged for one wk had mean repair strengths 27% of the cohesive strength without bonding agent and 48% with bonding agent.

Variations in (Ca2+ + Mg2+)-ATPase, its inhibitor protein and calmodulin of density (age) separated rabbit erythrocytes

Density (age) separated rabbit erythrocytes were examined for differences in the activities of calmodulin and the protein inhibitor of membrane (Ca2+ + Mg2+)-ATPase (Lee, K.S. and Au, K.S. (1983) Biochim. Biophys. Acta 742, 54-62) as well as response of the ATPase towards these protein modulators. It was found that activities of the cytosol protein-bound and free inhibitor as well as membrane-bound inhibitor were higher in top (young) cells as compared to bottom (old) cells. Though the activity of the divalent cation associated membrane calmodulin pool was also higher in young cells, calmodulin activity in the erythrosol remained constant in cells from both age groups. The pool of membrane-associated inhibitor was shown to have greater influence on the ATPase than the membrane-associated calmodulin pool. The influence was more pronounced with inhibitor derived from old than from young cell membranes. Response of the young cell ATPase towards the protein inhibitor was better than the old cell enzyme at low inhibitor concentration. At higher inhibitor concentration, however, response of the ATPase from both cell types was similar.

Correlation between strength of bonding to enamel and mechanical properties of dental composites

The strength of bonding of dental composites to enamel was measured in shear. The compressive strength, proportional limit, elastic modulus, and tensile strength of the composites were measured for correlation with the bond strength. Conventional and microfilled composites with a range of filler concentrations were studied. The densities of the composites and their fillers and the concentrations of the fillers were determined. The mechanical properties that were most highly correlated with bond strength to enamel were proportional limit and elastic modulus. Tensile strength and filler concentration had lower correlation coefficients, and compressive strength was not correlated with bond strength. Using unfilled resins as bonding agents between the composites and enamel resulted in increased bond strength with half of the composites.

Bond strength of cements to crown bases

Amalgam crown bases provided more bond strength to cements than composite resin and cast gold. Modified zinc oxide-eugenol and polycarboxylate cements served better with composite resin bases. Modified zinc oxide-eugenol cement bonded to cast gold better than polycarboxylate and zinc phosphate cements. Polycarboxylate cement bonded to amalgam better than modified zinc oxide-eugenol and zinc phosphate cements. Amalgam was the material of choice for a crown base.

Staining calcified dental tissues with food

The discoloration of enamel caused by food substances was found to be superficial and for dentin and cementum ingressive. Discoloration of cementum exceeded that of dentin, and dentin stained more than enamel. Coffee and soy sauce stained the calcified dental tissues more than the cola beverage and tea. The longer the staining time, the deeper was the discoloration.

Auxiliary retention for complete crowns provided by cement keys

1. Cement keys were an effective means of increasing the retention of complete cast gold crowns to preparations in extracted teeth. 2. Single grooves placed in either the dentin or in the crown alone were not effective in increasing retention in 30-degree crowns. In 7-degree crowns, a single groove in the crown gave better retention than a single groove in the dentin. 3. Crowns with a 7-degree taper had greater retentive strengths than 30-degree crowns treated identically. The retentive strength of 7-degree crowns with cement keys approached the tensile strength of zinc phosphate cement.

Marginal leakage of compacted gold, composite resin, and high-copper amalgam restorations

Amalgam and compacted gold were found to have the least marginal leakage in Class V cavities. Composite resin with acid etching performed at an acceptable level. Without acid etching the marginal seal was unsatisfactory. The following conclusions can be drawn: 1. High-copper amalgam and compacted gold are the materials of choice for Class V restorations when esthetics are not of primary concern. 2. If composite resins are to be used, they should be placed with an acid-etch technique.

Auxiliary retention for intracoronal cast gold restorations

The retention of Class V inlays cemented to cavities in extracted teeth was significantly increased by placing opposing retentive grooves in the inlays and cavity walls. The set cement formed a bridge between the two retentive grooves.

The ability of foods to stain two composite resins

In this bench study, coffee and soy sauce stained composite resin restorations to a significantly greater degree than did tea or cola beverage. Generally, the greatest degree of staining with all samples occurred during the first week of the study time. The stain penetration was superficial and was estimated to be 5 mu or less.

Effect of clinical finishing procedures on amalgam microstructure

Spherical amalgam specimens were burnished, burnished-polished, polished (wet), or polished (dry). The amalgams were sectioned normal to the prepared surface, elemental analyses were made at a series of depths from the surface with the electron microprobe and the phase fractions were calculated. Significant variations in phase distributions exist within 100 micrometers of the surface.