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Biomedical subjects

B K Moore

Publications and source records attributed to B K Moore.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Curing of pit & fissure sealants using Light Emitting Diode curing units.

Light Emitting Diode (LED) curing units are attractive to clinicians, because most are cordless and should create less heat within tooth structure. However, questions about polymerization efficacy have surrounded this technology. This research evaluated the adequacy of the depth of cure of pit & fissure sealants provided by LED curing units. Optilux (OP) and Elipar Highlight (HL) high intensity halogen and Astralis 5 (A5) conventional halogen lights were used for comparison. The Light Emitting Diode (LED) curing units were Allegro (AL), LE Demetron I (DM), FreeLight (FL), UltraLume 2(UL), UltraLume 5 (UL5) and VersaLux (VX). Sealants used in the study were UltraSeal XT plus Clear (Uclr), Opaque (Uopq) and Teethmate F-1 Natural (Kclr) and Opaque (Kopq). Specimens were fabricated in a brass mold (2 mm thick x 6 mm diameter) and placed between two glass slides (n=5). Each specimen was cured from the top surface only. One hour after curing, four Knoop Hardness readings were made for each top and bottom surface at least 1 mm from the edge. The bottom to top (B/T) KHN ratio was calculated. Groups were fabricated with 20 and 40-second exposure times. In addition, a group using a 1 mm-thick mold was fabricated using an exposure time of 20 seconds. Differences between lights for each material at each testing condition were determined using one-way ANOVA and Student-Newman-Keuls Post-hoc test (alpha=0.05). There was no statistical difference between light curing units for Uclr cured in a 1-mm thickness for 20 seconds or cured in a 2 mm-thickness for 40 seconds. All other materials and conditions showed differences between light curing units. Both opaque materials showed significant variations in B/T KHN ratios dependent upon the light-curing unit.

Dental Restoration, Permanent↗
PubMedDate not supplied

Tensile strength of preceramic solder joints formed using an infrared heat source.

Infrared soldering was compared to gas-oxygen torch soldering by testing specimens made from each of the following four classes of metal ceramic alloys: gold-platinum-palladium, gold-palladium, palladium-silver, and nickel-chromium-beryllium. There was no significant difference between infrared and torch soldering for the gold-palladium, palladium-silver, and base metal alloy specimens. However, infrared soldering of the gold-platinum-palladium alloy samples produced significantly weaker joints than those produced by torch soldering.

Chromium Alloys↗
PubMedDate not supplied

The effect of surface treatment on the Knoop hardness of Dicor.

One advantage cited for the use of Dicor over other ceramic materials is a reported Knoop hardness comparable to human enamel. However, when fabricating dental restorations, a Dicor glass-ceramic casting generally is subjected to several different surface treatments because of processing, esthetic, and functional requirements. Therefore, this study compared the Knoop hardness of Dicor specimens under three conditions: (1) cerammed, (2) cerammed and shaded, and (3) sectioned to reveal internal material. Knoop hardness differences between groups were significant (P less than or equal to .05). The cerammed surface was the hardest; it was harder than human enamel. Shaded specimens had a surface hardness comparable to dental porcelain. However, the internal glass-ceramic material, located beneath the shading porcelain and cerammed surface, had a Knoop hardness slightly higher than that of human enamel.

Analysis of Variance↗
PubMedDate not supplied

Hydrophilic poly(vinyl siloxane) impression materials: dimensional accuracy, wettability, and effect on gypsum hardness.

Three hydrophilic poly(vinyl siloxane) impression materials, containing an intrinsic surfactant, were compared with a hydrophobic poly(vinyl siloxane) and a polyether impression material. The hydrophobic poly(vinyl siloxane) material was dimensionally more accurate than the hydrophilic poly(vinyl siloxane) in two of three measured dimensions, but the difference was small. The polyether material was the most wettable, and the hydrophilic poly(vinyl siloxane) were more wettable than the hydrophobic poly(vinyl siloxane). However, when a topical surfactant was used, no difference in wettability was noted between the hydrophilic and hydrophobic poly(vinyl siloxane), and their wettability was comparable to the polyether material, indicating that the topical surfactant was more effective than the intrinsic surfactants. Stone dies made from the hydrophobic poly(vinyl siloxane) material were harder than those obtained from the other materials.

Analysis of Variance↗
PubMedDate not supplied

Effect of age of sample on the shear bond strength of dentin bonding agents to dentin.

The effect of sample age on the shear bond strengths of two dentin bonding agents to human dentin was evaluated by bonding composite resins to human dentin treated with either Imperva-Bond or Prisma Universal Bond 3. One-half of the specimens were tested at 5 minutes, while the remainder were thermocycled and tested at 2 weeks. Results were analyzed using two sample t tests at the 0.05 probability levels. Failures were evaluated using light microscopy and categorized as adhesive, cohesive within resin, cohesive within tooth, or mixed. The bond strengths were significantly higher for Imperva-Bond than for Prisma Universal Bond 3 at both time periods. For both bonding agents, the 2 week bond strengths were significantly higher than the 5 minute bond strengths. The 2 week bond strength of Imperva-Bond approaches that of unfilled resin to etched enamel.

Adhesives↗
PubMedDate not supplied

Direct surface pH determinations of setting cements.

Surface pH measurements were made over a 24-hour period for several luting cements and glass-ionomer lining and restorative materials. Of the luting cements, the water-mixed glass-ionomer cement, Ketac-Cem, had the lowest initial pH and the polycarboxylate, Durelon, had the highest. Three glass-ionomer lining materials showed differences in pH that increased over the entire test period. Two of the three visible-light-cured glass-ionomer liners evaluated showed similar pH values, while the third exhibited a considerably lower pH. The lower pH values found with the water-mixed glass-ionomer luting agent suggest that acidity may contribute to the posttreatment sensitivity associated with this material.

Dental Bonding↗
PubMedDate not supplied

The effect of tooth preparation design on the breaking strength of Dicor crowns: 2.

Six maxillary first premolar tooth preparation designs for all-ceramic restorations were tested for their effect on the strength of Dicor crowns. Ten crowns were fabricated for each preparation design, and the breaking strengths were measured. Three finish line designs (1.2-mm shoulder with sharp axiogingival line angle, 1.2-mm chamfer, and 0.8-mm chamfer) and two total occlusal convergence angles (5 degrees and 15 degrees) were tested. All preparations possessed 2.0 mm of occlusal reduction. The average breaking strengths of the 10 Dicor crowns were compared to those of 10 metal ceramic control restorations. The three groups of restorations fabricated for preparations with 5 degrees of occlusal convergence were significantly weaker than those made for preparations with 15 degrees of convergence. The metal ceramic restorations were significantly stronger (247.45 kg) than the strongest Dicor crowns (56.2 kg).

Ceramics↗
PubMedDate not supplied

Comparison of two tests to determine the castability of dental alloys.

This study compared castability values in the Whitlock test with those obtained from a new castability monitor based on a dental restoration. Five metal ceramic casting alloys were induction cast with both a carbon-containing and a noncarbon phosphate-bonded casting investment to assess the reliability of the Whitlock mesh test in predicting alloy castability. Alloy performance in the Whitlock test did not parallel that of the replica coping test for all alloy-investment pairs, as would be anticipated for a reliable monitor of castability. In addition, the variability of the Whitlock castability values for some alloys was sufficient to question the test's usefulness in refining the casting process with a specific alloy.

Analysis of Variance↗
PubMedDate not supplied

Comparative study: bond strength and microleakage with dentin bond systems.

Four commercial bond agent-composite systems were tested with respect to the strength of the bond to bovine dentin and their ability to seal class 5 erosion lesions without cavity preparation. At seven days there was no significant difference in the bond strengths of the four bonding agents, Scotchbond, Gluma, Tenure, and Scotchbond 2. Restorations placed with Gluma had significantly less leakage than those placed with other bond agents. At 90 days the bond strength of Tenure was reduced and was significantly less than that of the other systems, while Gluma and Scotchbond 2 restorations exhibited significantly less leakage than Scotchbond and Tenure. There was an inverse correlation (r2 = .5460) between bond strength and marginal leakage of class 5 restorations.

Animals↗
PubMedDate not supplied

The effect of tooth preparation design on the breaking strength of Dicor crowns: Part 1.

Six maxillary first premolar all-ceramic tooth preparation designs were tested for their effect on the strength of Dicor crowns. Ten crowns were fabricated for each preparation design, and their breaking strengths were measured. Three finish line designs (1.2-mm shoulder with sharp axiogingival line angle, 1.2-mm shoulder with rounded axiogingival line angle, and 0.8-mm chamfer) and two total occlusal convergence angles (10 degrees and 20 degrees) were tested. All preparations possessed 2.0 mm of occlusal reduction. The average breaking strengths of the 10 Dicor crowns were compared to that of 10 metal ceramic control restorations. The tooth preparation with a 1.2-mm shoulder finish line, sharp axiogingival line angle, and 10 degrees of total occlusal convergence produced the strongest Dicor crowns (88.6 kg). The weakest restorations were observed when a 0.8-mm chamfer finish line (66.8 kg) was used. The metal ceramic restorations were significantly stronger (247.45 kg) than the strongest Dicor crowns (88.6 kg).

Ceramics↗
PubMedDate not supplied

A comparison of resins for fabricating provisional fixed restorations.

Four acrylic resins and two composite resins for fabricating provisional fixed prosthodontic restorations were studied to determine temperature change during polymerization, surface hardness, marginal fit, wear resistance, transverse strength, transverse repair strength, surface roughness and polishability, color stability, and stain resistance. While certain materials exhibited advantageous properties in one or more of the tests, no one material was superior to the others in all tests.

Acrylic Resins↗
PubMedDate not supplied

Microwave energy polymerization of poly(methyl methacrylate) denture base resin.

Several physical property tests were conducted to compare microwave energy and conventional hot water bath polymerization techniques. The two methods of polymerization produced similar dimensional accuracy in complete denture bases. No differences were found in transverse strength, Knoop hardness, density, and residual monomer content of resin test strips. Comparable strength was found between microwave-polymerized and autopolymerized repairs of resin test strips. No porosity was observed in complete or removable partial denture bases polymerized by either technique. The Knoop hardness of microwave-polymerized removable partial denture bases was found to be slightly lower near the metal framework.

Denture Bases↗
PubMedDate not supplied

Bonding strengths of etched porcelain discs and three different bonding agents.

Forty porcelain disks were resin bonded to etched base metal surfaces to measure tensile bond strengths. One metal surface was bonded to each porcelain surface, making each test specimen "sandwiched", with a porcelain disk between two metal surfaces. The mean bond strength values of the Conclude group was 3017 +/- 869 psi. The mean for the Mar-Bond group was 3747 +/- 693 psi, and the mean for the two Chameleon groups combined was 3172 +/- 544 psi. No two groups were significantly different.

Acid Etching, Dental↗
PubMedDate not supplied

Influence of surface treatment on bond strength between a heat-activated and a light-activated resin composite.

The shear bond strength of two light-activated resin composite materials to a preformed heat-polymerized resin material was measured. The substrate was a urethane dimethacrylate material designed for use as a direct bonded pontic. In the first phase of the study, the shear bond strength between the substrate and a urethane-based resin composite and seven surface treatments was evaluated. In the second phase, a Bis-GMA resin composite and three surface treatments were studied. The study showed that a bonding agent was essential for the achievement of an adequate bond strength between the light-activated and heat-polymerized resin. However, there was a significant difference in bond strength depending on the type of light-activated resin composite and bond agent used. A Bis-GMA-based light-activated composite, together with its bond system (22.82 MPa), provided higher bond strength than a urethane-based resin composite and its bonding system (14.45 MPa). There was a direct relationship between cohesive failure and bond strength; as bond strength increased, the number of cohesive failures increased as well.

Acetone↗