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Biomedical subjects

B K Moore

Publications and source records attributed to B K Moore.

At least 91 records · Page 5Linked to original sources
PubMed1980

Rheology of luting cements.

A rheometer has been developed to simulate the extrusion of luting cement from beneath a full crown during seating using clinically realistic shear rates. Five luting cements were studied, and differences in rheological behavior were illustrated. These measurements demonstrate the importance of consideration of the effects of shear rate on viscosity when evaluating a cement for optimal clinical utilization.

Cold Temperature↗
PubMed1979

The effect of relining on the accuracy and stability of maxillary complete dentures--an in vitro and in vivo study.

A technique was developed for evaluating in vitro the accuracy or fit of experimental denture bases using a low-viscosity impression material for determining the space between the master die and the processed denture base. These measurements indicated that relining heat-cured maxillary denture bases with autopolymerizing acrylic resin improved their adaptation to the ridges. Interestingly, if no teeth were present in the heat-cured denture base, markedly less distortion occurred after processing. Limited clinical measurements on the stability of maxillary dentures in function showed no statistically significant change in stability after relining, but the trend was toward increased stability with the relined denture.

Acrylic Resins↗
PubMed1977

Computerized prediction of optical density for diagnostic radiology.

A computer program was formulated and verified experimentally to predict the optical density on an image receptor for any given set of radiographic variables including tube kilovoltage, milliamperage, and wave form; x-ray beam filtration; nature of filters and absorbers, and type of x-ray film.

Absorption↗
PubMedDate not supplied

Effect of surface coatings on flexural properties of glass ionomers.

The purpose of this study was to investigate the change in flexural strength and fracture toughness of light-cured glass ionomer cements after long-term immersion in water, and to investigate the effect of surface coatings on their properties. 2 resin-modified and 1 conventional glass ionomer cements were employed. For the flexural strength, a 25 x 2 x 2 mm stainless steel mold was used. For the fracture toughness (KtC), single edge notch specimens with dimensions 25 x 2.5 x 5 mm and a 0.5 mm notch (a/W = 0.5) were prepared in a stainless steel mold. Specimens were subjected to the 3 point bending at 0.5 mm/min after storage in 37 degrees C water for the periods of 1 h, 24 h, 1 wk, 1 month, and 6 months. The glass ionomer cements tended to exhibit an increase in mechanical properties over the 24-h period and then to maintain a constant strength. The surface protection of the resin-modified glass ionomer cement has some effect on the mechanical properties during early setting reactions, and it is desirable that the cement should be protected from direct water contact for at least 1 h after cement mixing.

Analysis of Variance↗
PubMedDate not supplied

Luminescence spectra of dental porcelains.

The luminescence spectra were obtained for a series of porcelain teeth and powders currently used in this country. Comparison was made between the spectra of these materials and the spectra of plastic teeth and natural tooth structures. It was found that many of the porcelain teeth and powders have strikingly different luminescence characteristics than those of natural teeth.

Acrylic Resins↗
PubMedDate not supplied

Retentive strength of an amalgam bonding agent: chemical vs light vs dual curing.

Dentin bonding agents have been shown to enhance retention of amalgam restorations by mechanical means. Little research is available on which mode of curing may optimize amalgam bonding. This in vitro study compared the bond strengths exhibited by three variations of a bonding agent, each using a different curing mode, with two earlier versions of amalgam resin liners and cavity varnish. The six test groups of lining agents for amalgam restorations included [C] chemical-cured, [L] light-cured and [D] dual-cured versions of one filled adhesive resin (Clearfil Liner Bond 2V), [LF] Light-cured, Filled resin (Clearfil Liner Bond 2, Kuraray Co.); [LCF] Light- and Chemical-cured, Filled resin Clearfil Liner Bond + Protect Liner, Kuraray Co) and [V] Varnish (Copalite, Cooley & Cooley, Ltd). For each group, 20 Class V cavity preparations were cut in human molars. The preparations were 2.5 mm deep and 3 mm wide at the pulpal floor, with a slightly divergent taper. After treating the preparation with the bonding agent, a 3/4 inch, 18 gauge flat-headed wire nail was seated in the cavity with its head at the pulpal floor of the preparation, and Tytin amalgam (Kerr Corp, Romulus, MI) was condensed into the preparation around the nail. All restorations were stored for 24 hours in distilled water at 37 degrees C, then subjected to 2500 thermal cycles (8 degrees C to 58 degrees C). After one week the samples were tested to failure in tension using an Instron Universal Testing Machine (crosshead speed = 2 mm/min) and peak load (kg) was recorded. Significant differences in retention were found using ANOVA and the Games & Howell post hoc test (p = 0.05). The mean loads at failure (+/- SD) were C 13.1 (+/- 2.4), L 21.8 (+/- 6.1), D 26.8 (+/- 7.4), LCF 23.8 (+/- 7.4), LF 21.4 (+/- 3.3) and V 2.0 (+/- 1.8). All dentin-bonding agents exhibited significantly greater retention than the varnish. While the bond strengths of the dual cured (D) and the light-cured (L) liners were not significantly different from one another, both were significantly higher than the chemically-cured (C) resin liner in terms of retention.

Analysis of Variance↗
PubMedDate not supplied

Microleakage of posterior packable resin composites with and without flowable liners.

The use of flowable composites as liners in Class II packable composites has been suggested by some manufacturers. However, the contributions of this technique are unproven. This study evaluated marginal microleakage in Class II packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Microleakage at occlusal and gingival margins of Class II cavities was evaluated using 45Ca and autoradiographs. Fifty non-carious, restoration-free human molar teeth were used. Separate mesio-occlusal and disto-occlusal Class II cavity preparations were made in each tooth. Gingival margins of all cavities were placed 1 mm apical to the cementoenamel junction (CEJ). Four Packable composites (Alert, Surefil, Pyramid and Solitaire) and one conventional microhybrid composite (Renew) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The restored teeth were thermally stressed and 45Ca was used to evaluate microleakage. Two independent evaluators scored leakage based on the autoradiographs. The results showed flowable composites helped reduce microleakage at gingival margins of Class II restorations (p < 0.05). Gingival margins had higher microleakage than occlusal margins (p < 0.05). Without flowable liners, three packable composites (Alert, Pyramid and Surefil) showed higher leakage (p < 0.05) than the microhybrid control. Only Solitaire packable composite without liner showed no significant difference in microleakage to the control (p > 0.05). Although the flowable liners help reduce microleakage, Alert and Pyramid packable composites with liners still showed higher leakage than the control (p < 0.05). Surefil and Solitaire packable composites with flowable liners showed no significant difference in microleakage (p > 0.05) to the control.

Analysis of Variance↗
PubMedDate not supplied

The effect of double adhesive application on the shear bond strength to dentin of compomers using three one-bottle adhesive systems.

The development of one-bottle dentin adhesive systems resulted in much optimism about providing simplified predictable esthetic dentistry. However, laboratory testing of these systems continues to provide significant variations between facilities. A potential effect of the number of applications was noted in this author's laboratory. This study evaluated the effect of doubling the manufacturer's recommended number of applications on shear bond strength to dentin. Ninety human molars were divided into groups of 15. The occlusal surfaces were finished to 600 grit SiC to provide a flat dentin bonding surface. Prime & Bond NT-Dyract, Optibond Solo-Elan and One Step-Dyract were evaluated. Each material was tested using: (1) the recommended number of adhesive applications and (2) twice the number of applications recommended. All adhesive applications were accomplished before light curing the adhesive. The specimens were thermocycled after one week of storage and tested in shear after two weeks. Specimens were also fabricated after adding Rhodamine D to the adhesive to allow for visualization using confocal microscopy. These teeth were sectioned and viewed 24 hours after fabrication. A t-test was used to compare differences within product groups. The results showed a significant effect (p < 0.001) when a double application of Prime & Bond NT was used. No difference was seen with Optibond Solo or One Step. All specimens appeared to have a uniform, glossy appearance of adhesive during fabrication. Therefore, the appearance of the adhesive after application may not be a reliable predictor of acceptable bonding. Confocal microscopy showed that single application Prime & Bond NT specimens did not exhibit a uniform thickness of adhesive across the entire interface. Tubule penetration and hybridization was apparent for all specimens.

Bisphenol A-Glycidyl Methacrylate↗
PubMedDate not supplied

Carbamide peroxide bleaching: effects on enamel surface hardness and bonding.

Three 10% carbamide peroxide home bleaching agents were evaluated to determine their effects on tensile bond strength of resin to enamel and enamel surface hardness. Eighty extracted bicuspid crowns were divided into four groups (three bleaching agents and control), and treated with the bleaching agents for five consecutive days. A bonding site on the buccal surface of each crown was etched with phosphoric acid and an orthodontic bracket bonded in place. The specimens were thermocycled and loaded to failure in an Instron Universal Testing Machine. Five hardness specimens per group were measured prebleaching and after five days' exposure. Analysis by one-way ANOVA indicated no significant differences in bond strength between the four groups (P > 0.05). There were also no differences in pre- or postbleaching Knoop hardness values for the four groups (P > 0.05). This study indicated that in short-term regimens 10% carbamide peroxide does not significantly affect enamel surface hardness or bonding ability.

Analysis of Variance↗
PubMedDate not supplied

Influence of curing time and distance on microhardness of eight light-cured liners.

Eight visible-light-activated liners were evaluated to assess the degree of polymerization by microhardness comparison. Knoop hardness number values were measured on 1.0 mm-thick specimens with varied exposure times (20, 40, 60 seconds) and distances from the curing source (0, 3, 6 mm). Statistical analysis of the nine groups within each material revealed significant differences for time and distance (P < 0.05). Application of the light for at least 40 seconds resulted in significantly higher Knoop hardness number values than specimens cured for 20 seconds. The highest Knoop hardness values were obtained if the tip of the light source was 3 mm away from the light-activated liner.

Acrylic Resins↗
PubMedDate not supplied

In vitro evaluation of the use of resin liners to reduce microleakage and improve retention of amalgam restorations.

This in vitro study evaluated the ability of three commercially available adhesive resins to reduce microleakage and provide retention between amalgam restorations and tooth structure. Results indicated that Amalgambond reduced leakage significantly more than Panavia EX, Prisma Universal Bond 2, and Copalite. In addition Amalgambond and Panavia EX exhibited the ability to bond amalgam to tooth structure. These results suggest that Amalgambond has the potential for serving successfully as a cavity liner with amalgam.

Analysis of Variance↗