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Biomedical subjects

John F McCabe

Publications and source records attributed to John F McCabe.

28 records · Page 2Linked to original sources
PubMed2004

The adaptation and cavity sealing ability of compomer restorative materials.

PURPOSE: To examine the sealing ability of compomers, used in combination with dentin bonding agents, compared to other classes of tooth-colored materials. METHODS: Thirty wedge-shaped cervical cavities were cut in extracted teeth, with the gingival cavosurface margin involving dentin. Five cavities each were restored with one of the following: the compomers Dyract AP/Prime & Bond NT, F2000 Compomer/Adhesive or Hytac Aplitip/Prompt L-Pop; a conventional glass-ionomer, Ketac Fil Aplicap; a resin-modified glass-ionomer, Fuji II LC Improved; or a resin-based composite, Z100 MP/Scotchbond 1. All teeth were restored, stored moist for 24 hours, then varnished (except the restorations) before thermocycling in rhodamine B dye solution for 1000 cycles (between baths of 6 degrees C and 60 degrees C). The teeth were sectioned longitudinally through the restorations before examination with a confocal microscope. A scale of 0 to 3 was used to score the dye leakage along the enamel margin as well as the gingival margin. RESULTS: The results showed that at the enamel margin, all materials gave a median score of 0 except Z100 MP (median score 3). Leakage was noted at the gingival margin of all materials (median score of 3 except Dyract AP with a median score of 2).

Compomers↗
PubMed2003

Shear punch strength and flexural strength of model composites with varying filler volume fraction, particle size and silanation.

OBJECTIVE: The effect of filler volume fraction, particle size and silanation on shear punch strength, flexural strength and flexural modulus of model composites has been evaluated. METHODS: Hybrid type glass filled (0-65.2 vol%), composites some without filler silanation (30.7-51.0 vol%) and microfilled type (0-13.0 vol%) resin matrix (UDMA and EGDMA) composites (Shofu Inc., Japan) were used in the study. For the shear punch test, 10 disc specimens, 0.5mm thick and 9 mm diameter, were prepared for each composite and tested with a 3.2mm dia punch at 1.0mm/min. Flexural strength (n=10) was measured by the method outlined in ISO 4049. Data were analyzed using ANOVA and Fisher's multiple-range test. RESULTS: Shear punch strength and flexural strength increased with increasing filler content up to 52.2% for hybrid composites and between 0 and 9.1% for microfilled composites. Shear punch strength and flexural strength decreased with increasing filler volume fraction for un-silanated composites. Flexural modulus for all materials increased with increasing filler volume fraction. Hybrid composites with silanated fillers have significantly higher values of flexural strength, flexural modulus and shear punch strength than equivalent materials with un-silanated fillers. SIGNIFICANCE: The results showed that filler silanation is an important factor for determining material strength. Additions of small quantities of microfillers appeared to have a greater effect on shear strength than equivalent amounts of hybrid filler. The shear punch test may prove beneficial for routine testing of composites as specimen preparation was simple, specimen quality was easy to maintain and the results are meaningful.

Analysis of Variance↗
PubMed2003

Erosion of water-based cements evaluated by volumetric and gravimetric methods.

OBJECTIVES: To compare the erosion of glass ionomer, zinc phosphate and polycarboxylate cements using volumetric and gravimetric methods. METHODS: For the volumetric method, the eroded depth of cement placed in a cylindrical cavity in PMMA was measured using a dial gauge after immersion in an eroding solution. For the gravimetric method, the weight of the residue of a solution in which a cylindrical specimen had been immersed was measured. 0.02 M lactic acid solution (0.02 M acid) and 0.1 M lactic acid/sodium lactate buffer solution (0.1 M buffer) were used as eroding solutions. The pH of both solutions was 2.74 and the test period was 24 h. RESULTS: Ranking of eroded depth and weight of residue was polycarboxylate>zinc phosphate>glass ionomers. Differences in erosion were more clearly defined by differences in eroded depth than differences in weight of residue. In 0.02 M acid, the erosion of glass ionomer using the volumetric method was effected by the hygroscopic expansion. In 0.1 M buffer, the erosion for polycarboxylate and zinc phosphate using the volumetric method was much greater than that using the gravimetric method. This is explained by cryo-SEM images which show many holes in the surface of specimens after erosion. It appears that zinc oxide is dissolved leaving a spongy matrix which easily collapses under the force applied to the dial gauge during measurement. SIGNIFICANCE: The volumetric method that employs eroded depth of cement using a 0.1 M buffer solution is able to quantify erosion and to make material comparisons.

Buffers↗
PubMed2003

Tooth brush abrasion of paint-on resins for shade modification of crown and bridge resins.

The purpose of this study was to evaluate the surface roughness and resistance to toothbrush abrasion of three experimental paint-on composite resins developed for the shade modification of crown and bridge resins. The paint-on resins had less filler volume fraction than restorative composites or the crown and bridge resins and consequently were of low viscosity. The maximum surface roughness (Rmax) and the maximum depth loss by abrasion for the paint-on resins following 40,000 cycles of brushing ranged from 2.45 to 4.07 microm and 8.63 to 13.67 microm, respectively. Rmax values were 37.7-67.5% lower than that for the crown and bridge resin subjected to the same test. Wear depth was 19.9-49.4% lower than for the crown and bridge resin. These results suggest that the paint-on resins are expected to have adequate resistance to toothbrush abrasion and may therefore be suitable for clinical use.

Color↗
PubMed2002

Adhesive bond strength and compliance for denture soft lining materials.

Peel bond strength and tensile bond strength between three polyvinylsiloxane denture soft liners and a heat-cured acrylic resin denture base were measured using two adhesive systems. The soft lining materials differed only in regard of their filler content and compliance. The values of bond strength and mode of failure were explained in terms of the inherent strength of the bond and varying compliance and tear strength of the soft material. For tensile testing, when bond failure occurred through an adhesive debonding mechanism, materials of low compliance (stiffer materials) produced the greatest tensile bond strength. Conversely, when the same materials were subjected to peel testing a different trend emerged; the material with lowest compliance produced the lowest peel bond strength. When de-bonding occurs by tearing or snapping of the soft material, the measured value of bond strength was controlled by the tear strength of the soft material. The results could be explained by a consideration of stress concentrations at the soft-hard material interface during 180 degrees peel testing. Adhesives based on ethyl acetate solvents produced stronger bond strengths than equivalent toluene based adhesives, particularly for materials of low compliance. Bond failure for toluene based adhesives was predominantly adhesive, whereas that for ethyl acetate based adhesives was predominantly cohesive. Overall, the least resistance to peeling was exhibited by a material of low compliance (i.e. relatively stiff) bonded with a toluene based adhesive. When an ethyl acetate based adhesive was used, all materials exhibited a resistance to peeling with a predominantly cohesive mode of failure.

Acetates↗
PubMed2002

Determining low levels of fluoride released from resin based dental materials.

Fluoride release determinations were made on two resin matrix dentine bonding systems using an ion-selective electrode and ion chromatography. Calibrations were made on serially diluted samples of standard fluoride solutions. The electrode method consistently gave higher values than the chromatographic method for one of the materials, and this was considered to be due to the use of total ionic strength adjustment buffer in electrode determinations. The lower limit of fluoride determination using the electrode was 0.5-0.1 p.p.m. Below this concentration the output from the electrode became meaningless. The chromatographic method gave meaningful results down to 0.001 p.p.m. The fluoride release results for the meter were meaningful only for the first 2 d for one test material and for up to 10 d for the other material. Using chromatography, fluoride release could be monitored for the full 44 d of the trial for both materials. Over the range of concentrations where fluoride determinations were possible by both methods, the values were correlated (R = 0.98). Ion chromatography appears to have an advantage over the ion-selective electrode for measuring low levels of fluoride release from dental materials.

Analysis of Variance↗
PubMed2002

The relationship between acid-etch patterns and bond survival in vivo.

The aim of this study was to investigate the relationship between acid-etch quality and bond survival in vivo. The subjects were 29 orthodontic patients. High-resolution silicone impressions were taken of the buccal tooth surfaces after etching for 30 seconds with 37% phosphoric acid. The impressions were replicated in epoxy resin and examined under high magnification in a scanning electron microscope. A 4-point classification system and histometric techniques were used to evaluate etch patterns on the enamel surfaces where orthodontic brackets were to be bonded. After impressions were made, all teeth (including first molars) were bonded with 0.022-in Andrews' prescription brackets ("A" Company, San Diego, Calif) and Right-On composite (TP Orthodontics, Leeds, England). The first date of bond failure for each tooth was recorded; it varied from 1 to 806 days. An ideal etch pattern was found on less than 5% of the orthodontic bonding area; type C pattern (pitted enamel surface) occupied the greatest area. Overall, the failure rate was 55.8% over 26 months; the greatest failure rate occurred in first molars. Multiple regression analysis revealed a positive and statistically significant relationship between the area occupied by ideal etch type and the length of survival of the bond (P <.001).

Acid Etching, Dental↗
PubMedDate not supplied

Comparison of halogen, plasma and LED curing units.

This study evaluated the characteristics of two kinds of recently developed light-curing unit; plasma arc and blue light emitting diodes (LED), in comparison with a conventional tungsten-halogen light-curing unit. The light intensity and spectral distribution of light from these light-curing units, the temperature rise of the bovine enamel surface and the depth of cure of composites exposed to each unit were investigated. The light intensity and depth of cure were determined according to ISO standards. The spectral distributions of emitted light were measured using a spectro-radiometer. The temperature increase induced by irradiation was measured by using a thermocouple. Generally, light intensities in the range 400-515 nm emitted from the plasma arc were greater than those from other types. Light in the UV-A region was emitted from some plasma arc units. The required irradiation times were six to nine seconds for the plasma arc units and 40 to 60 seconds for the LED units to create a depth of cure equal to that produced by the tungsten-halogen light with 20 seconds of irradiation. The temperature increased by increasing the irradiation time for every light-curing unit. The temperature increases were 15 degrees C to 60 degrees C for plasma arc units, around 15 degrees C for a conventional halogen unit and under 10 degrees C for LED units. Both the plasma arc and LED units required longer irradiation times than those recommended by their respective manufacturers. Clinicians should be aware of potential thermal rise and UV-A hazard when using plasma arc units.

Animals↗
PubMedDate not supplied

Fluoride release and neutralizing effect by resin-based materials.

This study evaluated the fluoride-releasing and neutralizing abilities of resin-based materials containing fluoride in water and aqueous lactic acid. Two composites, containing a low-solubility fluoride component (Heliomolar) and a fluoroalumino-silicate glass (UniFil S), and two giomers, containing surface reaction type prereacted glass-ionomer filler (Beautifil) and full reaction type glass-ionomer filler (Reactmer paste), were used. Resin-modified glass-ionomer cement (Fuji II LC) was used as a control. The fluoride release and pH value in storage medium, after immersion in each material, was measured for 10 weeks. For UniFil S and Beautifil, the amount of fluoride released in acid solution markedly increased compared to storage in water (p<0.05). Although all materials, except Heliomolar, neutralized the storage media, the neutralizing ability of these resin-based materials in acid solution sharply decreased with aging of the specimens, except for Fuji II LC. These results suggest that the nature of fluoride incorporated into resin-based materials affect the fluoride-releasing and neutralizing ability of materials in water and aqueous lactic acid.

Acrylic Resins↗