Search PubMed⌕ Search

Biomedical subjects

B K Moore

Publications and source records attributed to B K Moore.

At least 37 records · Page 2Linked to original sources
PubMed1998

Influence of thermal cycling on dentin bond strength of two-step bonding systems.

PURPOSE: To investigate the influence of thermal cycling on bond strength to dentin of 2-step bonding systems. MATERIALS AND METHODS: The systems used were self-etching primer systems; Fluoro Bond (FB), Liner Bond II (LB), and Mac Bond II (MB); and self-priming adhesive systems; One-Step (OS), OptiBond Solo (OB), Prime & Bond 2.0 (PB), and Single Bond (SB). Bovine mandibular incisors were mounted in self-curing resin and the facial surfaces were wet ground with #600 SiC paper. Enamel and dentin surfaces were treated following each manufacturers' instructions. Adhesives were applied and composites were condensed into a Teflon mold (4x2 mm) placed on the dentin surface and light activated. Bonded specimens were divided into four groups; (a) stored in 37 degrees C water for 24 hours, (b) stored in 37 degrees C water for 24 hours followed by subjecting to thermal cycling between 5 degrees C and 60 degrees C for 3,000 times, (c) 10,000 times, and (d) 30,000 times. Twelve samples per test group were shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVAs followed by Duncan's multiple range test (P < 0.05) were performed. RESULTS: For FB, LB, and MB, a small decrease in bond strength was observed and no significant differences were observed among the thermal cycling groups. For OS, OB, PB, and SB, a significant decrease in bond strength was observed for the 30,000 thermal cycling groups. The changes in bond strength after TC were different between the bonding systems.

Analysis of Variance↗
PubMed1997

Corrosion behavior of 2205 duplex stainless steel.

The corrosion of 2205 duplex stainless steel was compared with that of AISI type 316L stainless steel. The 2205 stainless steel is a potential orthodontic bracket material with low nickel content (4 to 6 wt%), whereas the 316L stainless steel (nickel content: 10 to 14 wt%) is a currently used bracket material. Both stainless steels were subjected to electrochemical and immersion (crevice) corrosion tests in 37 degrees C, 0.9 wt% sodium chloride solution. Electrochemical testing indicates that 2205 has a longer passivation range than 316L. The corrosion rate of 2205 was 0.416 MPY (milli-inch per year), whereas 316L exhibited 0.647 MPY. When 2205 was coupled to 316L with equal surface area ratio, the corrosion rate of 2205 reduced to 0.260 MPY, indicating that 316L stainless steel behaved like a sacrificial anode. When 316L is coupled with NiTi, TMA, or stainless steel arch wire and was subjected to the immersion corrosion test, it was found that 316L suffered from crevice corrosion. On the other hand, 2205 stainless steel did not show any localized crevice corrosion, although the surface of 2205 was covered with corrosion products, formed when coupled to NiTi and stainless steel wires. This study indicates that considering corrosion resistance, 2205 duplex stainless steel is an improved alternative to 316L for orthodontic bracket fabrication when used in conjunction with titanium, its alloys, or stainless steel arch wires.

Chromium↗
PubMed1997

Bulge ductility of several occlusal contact measuring paper-based and plastic-based sheets.

Articulating paper/film is a sheet strip that is coated with ink- or dye-containing wax and is used for marking occlusal contacts and monitoring the results. New types of occlusal film systems have been developed recently, which are capable of being computer-interfaced to identify the occlusal contact points and digitize the occlusal force. The mechanical ductility and thickness of these occlusal sheets constitute some of their important properties. The objective of this study was to evaluate seven different occlusal sheets and compare their bulge ductility and thickness. A custom-designed photo-sensing bulge tester was used. Three paper-based sheets (BAP, BET and SFA), two plastic-based sheets (ACF and AOS), and advanced systems (TSS and FDP) were tested. The specimen size was 20 mm square. Fifteen samples were tested for each material. The sheet film thickness with coated layers was as follows: BAP, 62 microns; BET, 46 microns; SFA, 133 microns; ACF, 23 microns; AOS, 14 microns; TSS, 134 microns; and FDP, 82 microns. Ductility (standard deviation) was as follows: BAP, 2.10 (0.0060)%; BET, 2.14 (0.008)%; SFA, 5.19 (0.57)%; ACF, 8.68 (0.05)%; AOS, 16.26 (0.41)%; TSS, 16.26 (0.41)%; and FDP, 6.37 (0.09)%. One-way ANOVA analysis indicated that (1) there in no statistical difference between BAP and BET (p > 0.001), (2) there is a statistical difference (p < 0.001) among all the rest of the tested occlusal sheets, and (3) bulge ductility appears to be linearly related to film thickness, its correlation depending upon types of base materials.

Coloring Agents↗
PubMed1997

Reinforcement of acrylic resins for provisional fixed restorations. Part I: Mechanical properties.

Acrylic resins are commonly used in many dental applications; especially in the fabrication of provisional fixed partial dentures. Among noticed technical drawbacks associated with this material are unsatisfactory mechanical properties. Moreover, if acrylic resins are exposed to moist environment, water sorption results in further mechanical deterioration. In order to improve the mechanical properties, aluminum, magnesium, and zirconium oxide powders and pulverized E-glass particles were separately admixed with pre-polymerized acrylic resin beads prior to mixing with monomer liquid. Particle loading ratios were 1, 2 and 3 vol.% with respect to pre-polymerized beads. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(isobutyl methacrylate) were used as resin matrices. Furthermore, a metal primer agent was employed in order to form a strong interphase between admixed particles and polymer matrix phase. Samples were subjected to three-point transverse bending tests at a crosshead speed of 10 mm/min. It was concluded that (1) addition of particles generally increases the water sorbed by the composite resins systems, (2) however, two vol.% admixtures in a PMMA resin matrix showed significant improvements in the mechanical properties (p < 0.05), (3) among the oxide particles, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness and hardness, and (4) mechanical properties (transverse strength, 0.2% offset yield strength and modulus of elasticity) were linearly correlated to hardness numbers.

Acrylic Resins↗
PubMed1997

Reinforcement of acrylic resins for provisional fixed restorations. Part II: Changes in mechanical properties as a function of time and physical properties.

In Part I, it was found that (i) 2 vol.% admixture of reinforcing elements in PMMA (Jet) resin matrix had a significant beneficial effects on the mechanical properties, and (ii) among these, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness, and hardness number. Using the best combination (i.e., PMMA resin matrix and 2 vol.% ZrO2), exothermic temperature raise and polymerization shrinkage were further investigated. Deterioration in mechanical properties due to prolonged water sorption were also studied for 5 weeks. The following can be concluded: (1) By increasing liquid/powder ratio for PMMA control samples, the peak temperature occurrence was retarded by 3 min and raised by 8 degrees C. (2) The effect of admixed oxide particles to PMMA resin matrix or the heat generated during polymerization was not significant. (3) The polymerization volumetric shrinkage was influenced by the a mixture of particles, with increases as large as 0.9% (or 0.3% in linear shrinkage). (4) PMMA resin admixed with 2 vol.% of zirconia particles showed a continuous weight gain due to water sorption, mechanical properties appears to be increasing up to 1-week sorption, followed by rapid drop of all properties. (5) Autopolymerizing acrylic resins are a resin-resin composite material of pre-polymerized beads embedded in a newly formed acrylic matrix. The main fracture modality appears to occur through the matrix and at the interface, although some trans-beads fractures were identified. (6) It was suggested that incorporating certain type of oxide particles into the pre-polymerized beads would provide stronger resin matrix.

Acrylic Resins↗
PubMed1997

Microleakage evaluation of bonded amalgam restorations: confocal microscopy versus radioisotope.

The purpose of this study was to compare the degree and pathway of microleakage in bonded amalgam restorations utilizing fluorescent dyes with scanning laser confocal microscopy and 45Ca radioisotope with autoradiographs. Mesial slot preparations with enamel cervical margins and distal preparations with dentin margins were prepared in extracted human molars. Four liners, Copalite (control) All-Bond 2/Resinomer, Amalcoden, and Panavia 21, were used. Teeth were restored with Dispersalloy or Tytin. After thermocycling, 7 days' storage, and staining, the degree of microleakage was measured on an ordinal scale. Dental adhesive liners minimized microleakage; the ranking was, from most to least effective, All-Bond 2, Panavia 21, and Amalcoden. The control exhibited the greatest microleakage. Microleakage occurred most frequently at the liner-tooth interface. No significant difference was observed between amalgams. The high correlation between the results of the fluorescent and radioisotope studies indicated that these two microleakage tests can be directly compared.

Autoradiography↗
PubMed1996

Effect of light exposure on fracture toughness and flexural strength of light-cured composites.

OBJECTIVES: This study was conducted to investigate the curing characteristics of light-cured composites and their related mechanical properties. METHODS: Single-edge notch specimens [25 mm x 2.5 mm x 5 mm with a 5 mm notch (a/W = 0.5)] were prepared for fracture toughness measurements. For flexural strength testing, a stainless steel mold (25 mm x 2 mm x 2 mm) was used. Light-cured composites were condensed into the mold, and the middle third of the specimen was first activated for 30 s with 400 mW/cm2, for 60 s with 200 mW/cm2, or for 120 s with 100 mW/cm2. Then the remaining thirds were activated at the same intensity and curing time as the middle third. After 24 h storage in 37 degrees C water, three-point bending tests were performed with a span length of 20 mm at a crosshead speed of 0.5 mm/min. A one-way ANOVA, followed by a Newman-Keuls test (p < 0.05), were used to compare the data obtained from each group to test the effect of the curing conditions. RESULTS: Fracture toughness, flexural strength, and flexural modulus varied with resin composites. Among the three curing conditions for each material, there were no significant differences in fracture toughness, flexural strength, or flexural modulus. SIGNIFICANCE: The fracture toughness and the flexural strength were the same when irradiations with the same amount of energy (light intensity multiplied by curing time) were used. It was found that, at lower light intensity, longer curing was required to provide comparable mechanical properties. An accumulated irradiation energy obtained through a product of the light intensity and curing time may serve as a guideline to produce samples exhibiting equivalent fracture toughness as well as flexural strengths.

Analysis of Variance↗
PubMed1996

An evaluation of microwave-polymerized resin bases for removable partial dentures.

PURPOSE: The hardness, porosity, and adaptation of removable partial dentures fabricated with one heat-polymerized denture base resin and two resins designed for microwave polymerization were evaluated. MATERIALS AND METHODS: Five prostheses were evaluated for each resin. Adaptation of the denture bases to the master cast was evaluated by spatial orientation and mean weight of residual impression material. The prostheses were than embedded in epoxy resin and sectioned for evaluation of resin hardness (Knoop hardness) and microporosity. RESULTS: There were no significant differences in the adaptation of the acrylic resin bases for Acron MC and Ch Lucitone. There was no significant difference in the mean Knoop hardness values for any of the resin bases near and away from the metal. None of the denture bases showed porosity greater than 100 microns. CONCLUSIONS: Both resin bases formulated for microwave polymerization were effectively polymerized around metal frameworks without adverse effects on resin hardness or porosity. Justi Denture Base material had poorer base adaptation than the other two resins.

Acrylic Resins↗
PubMed1996

Using a resin-modified glass ionomer as an occlusal sealant: a one-year clinical study.

The authors compared the retention and clinical performance of a resin-modified glass ionomer, or RMGI, restorative and a light-cured resin sealant. The first permanent molars on one side of the dental arch in 50 children were sealed with an RMGI, and the same teeth on the other side were sealed with a resin sealant. At baseline, six months after placement and one year after placement, examiners documented sealant retention, secondary caries, marginal discrepancy and marginal staining. In general, the RMGI appeared to wear markedly. At one year, the retention of the RMGI was significantly less than the resin, but the RMGI had significantly fewer marginal discrepancies. There were no significant differences in caries development or marginal discoloration.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1995

Influence of filler addition to bonding agents on shear bond strength to bovine dentin.

OBJECTIVES: The purpose of this study was to investigate the influence of adding filler particles to a bonding agent on dentin bond strength and of the temperature change during curing in order to determine the optimum filler level for an experimental bonding agent. METHODS: Experimental light-cured bonding agents with microfiller (average size: 0.05 micrometers) content of 0, 10, 20, 30, 40, 50, 60, and 70 wt% were used with the Imperva Bond / Lite-Fil II A (Shofu) restorative material. Bovine incisors were mounted in self-cured resin, and the facial surfaces were prepared with 600-grit SiC paper. After dentin surface pretreatment with dentin primer, experimental bonding agents were applied to the dentin surface and bonded with resin composite. Ten samples per test group were stored in 37 degrees C water for 24 h, then shear tested at 1.0 mm/min. The temperature change of the bonding agent was monitored during the exthothermic polymerization reaction according to the method of ISO standard #4049. The peak temperature and the time required to reach peak temperature were recorded. RESULTS: Bond strength to dentin and the temperature change were greatly affected by the filler level. Maximum dentin bond strength (14.3 +/- 2.3 MPa) was obtained with a filler level of 10 wt% and decreased with filler level higher than 30 wt% (10.4 +/- 1.7 MPa - 5.3 +/- 2.6 MPa). Peak temperature decreased and the time required to reach peak temperature increased with the higher filler levels. There were strong correlations between the bond strength and temperature change of experimental bonding agents. SIGNIFICANCE: The initial setting behavior of bonding agents containing filler particles may be one of the important factors influencing dentin bond strength. When bonding agents with filler particles are used, it is important to determine if optimum filler levels exist in order to optimize the dentin bond strength.

Analysis of Variance↗
PubMed1995

Influence of light irradiation of dentine primers on dentine-resin bond.

OBJECTIVE: The purpose of this study was to examine the influence of light irradiation of dentine primers that contain camphoroquinone (CQ) on the shear bond strength to dentine and their contact angle. METHOD: Three dentine bonding systems which contain CQ, Imperva Bond, OptiBond and XR-Bond; and Light Bond, which does not contain CQ, were employed. Labial surfaces of freshly extracted lower bovine incisors were ground with no. 600 grit SiC paper. Dentine primers were applied to the dentine surfaces in two groups, irradiated and non-irradiated. A shear bond strength test was performed and the direct contact angle was measured. RESULTS: Statistical analysis (Newman-Keuls multiple comparison P < 0.05) of the data indicated that light irradiation of the dentine primer for systems containing CQ resulted in increased bond strength and decreased contact angle. CONCLUSION: This study indicates that for these dentine bonding systems containing CQ in their primers, light irradiation of the dentine primer is effective in improving wettability and increasing the bond strength to dentine.

Analysis of Variance↗
PubMed1995

Effect of two opaquing techniques and two metal surface conditions on metal-ceramic bond strength.

The optimal conditions for opaquing techniques during porcelain application have not been confirmed. In this study the metal-ceramic bond strength was measured among one porcelain and three dental alloys, namely a gold-platinum-palladium alloy, a silver-free gold-palladium alloy, and a base metal alloy, with two opaquing techniques (a single masking layer versus a thin overfired layer followed by a second masking layer). In addition, the opaque porcelain was fired over an oxidized and nonoxidized alloy surface for the silver-free gold-palladium alloy. No significant differences in bond strength were recorded between the two opaquing techniques with the gold-platinum-palladium and base metal alloys. There was no substantial differences between the two opaquing techniques when opaque was applied over an oxidized gold-palladium alloy surface and bond strengths were substantially greater over an oxidized surface. However, when the opaque was applied to a nonoxidized gold-palladium surface the two-layer technique created a significantly greater bond strength.

Chromium Alloys↗
PubMed1995

An in vitro study of apical extrusion of sodium hypochlorite during endodontic canal preparation.

One hundred fifty-three single rooted teeth were divided into four groups. Canals were cleaned and shaped using the balanced forces technique. In one group of 50 teeth, irrigation was delivered with the irrigation needle deep within the root canal. In the other group of 51 teeth, the needle was placed passively in the coronal access cavity and the irrigation carried into the root canal during filing. The remaining 52 teeth in the control groups were treated in the same manner using distilled water as the irrigation solution. The concentration of sodium extruded apically was measured by means of atomic emission spectrophotometry, and the volume of sodium hypochlorite extruded was calculated. Significantly more sodium hypochlorite was extruded apically during deep delivery of the irrigation (p<0.05). It is concluded that the use of a reservoir of irrigation in the coronal access cavity results in significantly less apical extrusion of irrigation solution than with deep delivery.

Analysis of Variance↗
PubMed1995

Influence of light intensity on shear bond strength to dentin.

PURPOSE: To investigate the influence of light intensity on dentin bond strength of five dentin bonding systems. MATERIAL AND METHODS: The light intensity used to polymerize specimens was controlled at the levels of 100, 200, 400, 600, 800, and 1000 W/m2 (470 +/- 40 nm). Labial surfaces of freshly extracted lower bovine incisors were ground with #600 grit SiC paper to expose dentin. After primer application, bonding agents were applied and bonded with resin composites. A shear bond strength test was performed and the data were analyzed by a one-way ANOVA followed by Newman-Keuls multiple comparison (P<0.05). RESULTS: Statistical analysis of the data indicated that light intensity affected the bond strength to dentin. The mean bond strength of all bonding systems decreased with lower light intensity. The tendency of decreasing bond strength was different among the test materials and each test material had a threshold light intensity that resulted in statistically the same bond strength obtained using a light intensity of 1000 W/m2.

Analysis of Variance↗
PubMed1994

Correlation of bond strength with surface roughness using a new roughness measurement technique.

OBJECTIVES: The correlation between shear bond strength and surface roughness was investigated using new surface measurement methods. METHODS: Bonding agents and associated resin composites were applied to set amalgam after mechanically roughening its surface. Surface treatments were noe (as set against glass), 80 grit, and 600 grit abrasive paper. Surface roughness (R(a) as measured parallel and perpendicular (+) to the direction of the polishing scratches and true profile length were measured. A knife-edge was applied (rate = 2.54 mm/min) at the bonding agent/amalgam interface of each sample until failure. RESULTS: Coefficients of determination for mean bond strength vs either roughness (R(a), of profile length were significantly higher for measurements in parallel directions than for those measurements in (+) directions. The shear bond strength to set amalgam for a PENTA-containing adhesives system (L.D. Caulk Division) was not significantly different from that of a PENTA-free adhesive (3M Dental Products Division), even though PENTA has been reported to increase bond strength to nonprecious metals. SIGNIFICANCE: The shear bond strength of resin composite to amalgam is correlated to surface roughness when it is measured parallel to the polishing scratches. This correlation is significantly lower when surface roughness is measured in the typical manner, perpendicular to the polishing scratches.

Dental Alloys↗
PubMed1994

Evaluation of an apatite cement as a root end filling material.

A self-setting apatite cement, EBA cement, and amalgam with varnish were tested for root end sealing ability using a fluid filtration and dye technique. Single-rooted human teeth were prepared in vitro to receive root end fillings. Experimental groups were amalgam with two layers of varnish, EBA cement with dry cavity, EBA cement within a wet cavity, apatite cement within a dry cavity, and apatite cement within a wet cavity. Fluid filtration measurements were made at 6, 24, and 7 days, and 1 and 3 months. Each specimen was also subjected to a dye leakage test using Procion Green dye at 3 months. Results indicated that apatite cement provided a comparable seal to amalgam and EBA cement. This finding, in conjunction with its excellent biocompatibility, suggests that apatite cement is an acceptable alternative to present-day root end filling materials.

Aluminum Oxide↗
PubMed1994

The effects of load misalignment on tensile load testing of direct bonded orthodontic brackets--a finite element model.

A finite element model (FEM) of an orthodontic bracket bonded to enamel with glass ionomer cement was developed. The loading on the model simulated tensile loading conditions associated with the testing of bonding system strength. The primary purpose of this project was to ascertain the effects of load misalignment on the calculated stresses within the cement layer. The results indicate that peak stress values increase as the load deflection angulation increases. If the tensile load is inadvertently applied entirely on one wing of the bracket, the stress components nearly double in magnitude.

Dental Bonding↗