Biomedical subjects

J L Ferracane

Publications and source records attributed to J L Ferracane.

At least 37 records · Page 2Linked to original sources

PubMed1998

In vitro aging of dental composites in water--effect of degree of conversion, filler volume, and filler/matrix coupling.

The purpose of this study was to evaluate the long-term effect of aging in water on the physical properties of experimental composites having systematically controlled differences in degree of conversion (DC), filler volume fraction (Vf), and percentage of silane-treated fillers. Composites were made with a 50% Bis-GMA:50% TEGDMA light-cured resin and a 1-2 microm (average size) strontium glass filler (+ 5 wt% SiO2 microfiller). For composites A-E, the DC was varied from 56-66% by changing the curing time; for D and F-I, the Vf was varied from 28-62 vol%; and for D and J-M, the percent of fillers with a silane coupling agent (gamma-MPS) was varied from 20-100%. Fracture toughness (KIc), flexure strength (FS), elastic modulus (E), and hardness (KHN) were tested after soaking in water at 37 degrees C for 1 day, 6 months, 1 year, and 2 years. The KIc was reduced 20-30% for all composites after 6 months, with minimal changes thereafter. The FS was reduced for several composites at 6 months, but only those with poor cure (A and B) were lower at 2 years than they were initially. The E was not reduced for most composites. Hardness was reduced for most composites after 6 months, but many returned to their original levels at 2 years. Long-term aging in water caused a reduction in the KIc, independent of composition, but had little effect on other properties, suggesting limited degradation of composites in water.

Composite Resins↗

PubMed1998

Stress transfer from polymerization shrinkage of a chemical-cured composite bonded to a pre-cast composite substrate.

OBJECTIVES: (1) To develop and test a strain gauge-based method for evaluating the strain transferred through a bonded interface to a deformable substrate; and (2) to develop and test a finite element (FE) model for evaluating the stress development in a chemical-cured composite during polymerization. METHODS: A generic light-cured resin composite was used to fabricate a rectangular plate with an internal slot filled with a chemical-cured composite. Strain gauges on the surface of the composite in the channel and on the plate adjacent to the channel-plate interface were used to record strain continuously up to 500 s after mixing the composite paste. A quadrant three-dimensional (3D) finite element model used strains measured on the channel to simulate the experimental conditions. The model was used to estimate stresses in the channel and at the bonded interface. RESULTS: Strain in the plate reached a plateau 200 s after mixing the composite. Strain of the composite paste in the channel continued to rise with time but at a steadily decreasing rate. Maximum principal stress predicted by the FE model on top of the plate, on top of the channel and within the channel was 5.12 MPa, 3.78 MPa, and 5.26 MPa, respectively. SIGNIFICANCE: Stresses were effectively transferred through the bonded interface in this test configuration, and results were in close agreement with previously reported literature values for polymerization contraction stresses generated in composite configurations with similar bonded to unbonded surface ratios.

Composite Resins↗

PubMed1998

Reduction of composite contraction stress through non-bonded microfiller particles.

OBJECTIVES: To determine the reduction in composite polymerization stress through the addition of non-bonded microfiller particles. METHODS: Microfillers that were unsilanated, silanated, and treated with a nonfunctional silane were added to dental resin and to a small-particle composite. The contraction stress generated by these materials was measured by polymerizing them between glass plates mounted in a mechanical testing machine. The maximum force was recorded 15 min after photo-initiation. Results were analysed by ANOVA (analysis of variance)/Turkey's test (p < or = 0.05). RESULTS: The addition of non-functional silanated microfillers to dental resin resulted in a significant 50% decrease in polymerization stress. The addition of unsilanated microfillers did not reduce the contraction stress. When added to small-particle composite, the unsilanated microfillers produced a significant 30% reduction in contraction stress compared to the composite containing silanated microfillers. The non-functional silanated microfillers did not reduce the contraction stress in the small-particle composite. SIGNIFICANCE: The polymerization shrinkage of dental composite can impose high levels of stress on the tooth surfaces to which it is bonding. This contraction stress can lead to failure of bond formation with the surrounding tooth structure. Microfiller particles that are not bound to the resin matrix might provide sites for relief of internal stresses, significantly reducing contraction stress in dental composite.

Analysis of Variance↗

PubMed1998

Evaluation of cure, properties and wear resistance of Artglass dental composite.

PURPOSES: (1) To evaluate the degree of conversion (DC) and the physical properties of a new dental composite, Artglass (Kulzer), designed primarily as a replacement material for porcelain in PFMs; and (2) to compare the efficacy of two different curing units for two dissimilar composites (Artglass and Charisma, Kulzer). MATERIALS AND METHODS: Specimens (n = 10) were prepared by curing either in a continuous light exposure unit (Triad II, Dentsply) or in a high intensity strobe unit (Uni XS, Kulzer) for 180 s. Specimens were aged 24 hrs in water at 37 degrees C and tested for fracture toughness (FT-MPa m1/2; x-head = 0.13 mm/min), flexural modulus (E, GPa), flexural strength (FS, MPa; x-head = 0.5 mm/min), hardness (KHN, kg/mm2), and in vitro wear resistance (OHSU oral wear simulator). DC (%) was determined by transmission micro-FTIR. Results were compared by ANOVA/Turkey's test (P < or = 0.05). RESULTS: DC, FT, E and FS were improved for Artglass and DC and E were improved for Charisma when the strobe curing unit was used, probably due to its increased intensity. Artglass showed a greater DC and FT but a lower E, KHN and wear resistance compared to Charisma when similar curing methods were used.

Analysis of Variance↗

PubMed1998

Laboratory evaluation of adhesively crimped surgical ball hooks.

The aim of this study was to examine the effect of the addition of sandblasting and/or dental adhesive on the stability of the crimpable hook when positioned and crimped onto surgical arch wires. Ninety crimpable ball hooks were divided into six test groups: crimp only; apply Panavia 21 and crimp; apply C & B Metabond and crimp; sandblast and crimp; sandblast, apply Panavia 21, and crimp; and sandblast, apply C & B Metabond, and crimp. Each hook was treated according to the criteria of the relevant test group and then crimped to the arch wire. The force required to dislodge each hook from the arch wire was measured. The results demonstrated that sandblasting caused a significant increase in the force required to dislodge the crimped hook. The addition of either Panavia 21 or C & B Metabond adhesives also resulted in a significant increase in the required dislodging force. The force required to dislodge the hook was increased by a factor of 10 where sandblasting and Panavia 21 were applied. The same increase was observed where C & B Metabond was applied, without sandblasting. However, it was concluded that the use of Panavia 21, together with an intraoral sandblasting machine, would be more appropriate in the clinical setting, primarily due to the ease of use associated with Panavia 21.

Air↗

PubMed1998

Fluoride penetration into the hybrid layer from a dentin adhesive.

PURPOSE: To evaluate the in vitro microleakage of a new fluoride-containing dentin adhesive and to provide evidence for fluoride release from the adhesive and penetration into the dentin. MATERIALS AND METHODS: Class V preparations with margins in enamel and dentin were made in the buccal and lingual surfaces of six extracted human third molars. Six preparations were restored with Scotchbond Multipurpose (SBMP)/Z100 composite and six with a new fluoride containing dentin adhesive (FB)/Litefil composite. After aging for 30 days in water at 37 degrees C, the teeth were stained with silver nitrate, sectioned and graded by two observers for leakage at the enamel and dentin margins. Selected FB specimens were examined in the scanning electron microprobe using WDS for fluoride and EDS for calcium and phosphorous. Fluoride release into water from disks of FB adhesive was evaluated for up to 112 days using a specific ion electrode. RESULTS: Fluoride leached from the adhesive at a decreasing rate with time. The final rate over 112 days was 0.02 ppm/day (0.2 microgram/cm2/day). Leakage at the enamel and dentin margins was similar for both adhesives (Mann-Whitney U-test; P < or = 0.05). SEM evaluation showed the presence of a discontinuous hybrid layer of 2-3 microns. Fluoride was present within, but limited to, the hybrid layer for the FB adhesive. The penetration of fluoride could only be confirmed in areas where leakage had occurred.

Calcium↗

PubMed1997

Factors effecting dental composite wear in vitro.

The wear of posterior dental composite restorations takes place through a complex combination of wear mechanisms. To isolate and measure the contribution of the different tribological phenomena in a controlled manner, an oral wear simulator was employed. Results previously reported demonstrated the simulator's ability to form strong correlations with clinical results for both abrasion and attrition wear. These results were generated with the device configured to mimic masticatory dynamics, specifically employing a human enamel stylus, physiologic load levels, and a foodlike slurry for a third body. In this study the slurry was replaced with water to examine the role of the third body in producing abrasion. The third body was found to reduce wear for most materials. In a separate test the enamel stylus tip was replaced with steatite, a semiporous ceramic with wear characteristics similar to enamel when opposing dental composite. The use of a steatite antagonist increased abrasion for the larger particle filled materials. The adhesive wear mechanism was found to be a contributing factor in dental composite wear.

Biocompatible Materials↗

PubMed1997

Surface characterization of amalgam made with Hg-In liquid alloy.

When amalgam was triturated with Hg-In liquid alloys instead of pure mercury, the resultant amalgams released a significantly smaller amount of mercury vapor during setting. To understand the mechanisms responsible for the drastic decrease in mercury evaporation from the In-containing amalgam, we used Auger Electron Spectroscopy to examine surface oxide films on amalgams made with Hg-10 wt% In or pure mercury. The surface of the In-containing amalgam was rapidly covered with both indium and tin oxide films. Greater amounts of oxygen were found on the gamma 1 Ag-Hg matrix in the In-containing amalgam than in the amalgam without indium. The rapid formation of the oxide film contributes to a reduction in the mercury release from the In-containing amalgam by forming an effective barrier to evaporation.

Copper↗

PubMed1997

In vitro wear of composite with varied cure, filler level, and filler treatment.

For the clinical wear of composite filing materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-stimulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 micron avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120 degrees C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (micron: n = 5) was measured by profilometry. Results for each series were analysed by ANOVA/Turkey's (p < or = 0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator.

Analysis of Variance↗

PubMed1997

Wear and marginal breakdown of composites with various degrees of cure.

Loss of anatomical form due to wear has been cited as one factor limiting the clinical use of posterior composites. The physical properties and possibly the wear resistance of composite are influenced by the extent to which it is cured. The aim of this study was to vary degree of conversion (DC) in composites to test the hypothesis that resistance to wear and marginal breakdown could be improved by enhanced curing. A light-cured hybrid composite containing a 50% Bis-GMA/50% TEGDMA resin and 62 vol% of strontium glass (1 to 2 microm) with microfill silica was formulated (Bisco). Composite was placed into two 2.5-mm-diameter cylindrical holes in Co-Cr teeth replacing first and second molars in the mandibular dentures of 50 edentulous patients. The composites were light-cured for different time periods (9 s, 12 s, 25 s, 40 s, and 40 s + 10 min at 120 degrees C) and then polished. The microfill Heliomolar was also tested. DC (%) was measured by FTIR and ranged between 55% for 9 s of light-curing and 67% for 40 s of light-curing followed by heat application. Impressions were evaluated at baseline, 6 mo, 1 yr, and 2 yrs. Stone casts were evaluated independently by three observers to determine the % of the total margin exhibiting breakdown. Epoxy replicas were measured with a profilometer for wear. Wear of the hybrid composite at 2 yrs ranged from a high of 144 microm with 9 s of light-curing to a low of 36 microm with 40 s of light-curing followed by heat. Heliomolar exhibited from 11 to 16 microm of wear at 2 yrs. There was a strong negative correlation (r2 = 0.91) between the degree of cure and the abrasive wear of the hybrid composites. Marginal breakdown was negligible for the hybrids, and was reduced for the microfill from 40% to 15% of the margin by heat treatment. This study showed that the resistance to abrasive wear of a dental composite could be improved by enhancement of its degree of conversion.

Adult↗

PubMed1997

Effect of Pd and In on mercury evaporation from amalgams.

The amount of Hg vapor released from "synthesized" gamma 1 with 1% (wt) Pd was reported to be less than 30% of that from gamma 1 with no Pd. This study tested the hypothesis that Hg evaporation from Pd-containing amalgams decreases with Pd concentration and that In also reduces Hg vapor. Specimens (4 mm dia, 8 mm long) were prepared by triturating Ag-Sn(25%)-Cu(12%) alloy powder containing 0.5-9.0% Pd with pure Hg and by triturating 3% Pd alloy powder with Hg containing 1-5% In (all residual Hg approximately equal to 62%). The total amount (ng/mm2) of Hg vapor released at 37 degrees C from freshly prepared amalgams was measured. Pd (3-9%) in the powder significantly (p < 0.05) decreased Hg vapor release from amalgams during setting. Use of In-containing Hg also reduced Hg vapor release (5% In, p < 0.05). The reduction in the Hg vapor pressure by adding Pd and the rapid oxide film formation on the In-containing amalgam appear to work together to reduce Hg vaporization from these amalgams.

Calorimetry, Differential Scanning↗

PubMed1997

Microleakage of four Class II resin composite insertion techniques at intraoral temperature.

Twenty recently extracted human molars had standardized Class II slot cavities prepared on the mesial and distal surfaces with the gingival floor located on dentin. The teeth were embedded in a stone template, warmed to 37 degrees C, and restored immediately using one of two incremental placement techniques with visible light-cured composite (VLC), or one of two directed shrinkage placement techniques using an autocure/VLC composite combination. Teeth were stored at 37 degrees C for 2 weeks, thermocycled, stained, sectioned in the middle of the preparation, and evaluated for dye penetration. Reevaluation of the microleakage following removal of the resin composite from the preparation revealed greater microleakage at the gingival margin than did the initial sectioning technique. There were no differences among any of the groups. Enamel margins exhibited minimal leakage and no differences among the groups.

Composite Resins↗

PubMed1996

Cyclic voltammetry of dental amalgams.

OBJECTIVES: This study used cyclic voltammetry to examine the effect of the composition of dental amalgams on their electrochemical behavior, including reactions occurring outside of oral conditions. METHODS: Amalgams (residual mercury 47.5%) were prepared using two low-copper (3 wt% Cu) powders and five high-copper powders (40-80 wt% Ag, 12-30 wt% Cu) with and without zinc (1.5 wt%). Cyclic voltammograms were obtained at 37 degrees C in 1.0% NaCl scanning at 2 mV/s in the potential range from -1.5 V to +0.8 V vs. Ag/AgCl. RESULTS: During the anodic scans, AgCl and Hg2Cl2 films were formed on all amalgams except the one with only 40 wt% Ag. In all high-copper amalgams, a prominent Cu (oxidation) peak was found at -0.1 V, indicating the release of copper during corrosion. Zinc affected the oxidation process for both low- and high-copper amalgams. When zinc was absent, a peak for Sn2+ oxidation appeared at -0.4 V. When zinc was present, a Sn4+ oxidation peak was revealed at -0.6 V. In some amalgams, there was evidence of the selective corrosion (pitting corrosion) of tin and copper. In the lowest silver-content amalgam, no protective films were formed, which is indicative of its poor corrosion resistance. As expected, in all the low-copper amalgams, an extreme increase in current density was recorded immediately at 0 V, due to the release of tin from gamma 2. SIGNIFICANCE: Cyclic voltammetry is useful for the rapid examination (less than an hour) of the electrochemical behavior of amalgams, specifically to obtain information on the formation of compounds and the sequences of electrochemical reactions.

Analysis of Variance↗

PubMed1996

Evaluation of composite wear with a new multi-mode oral wear simulator.

OBJECTIVES: The goals of this study were to develop a machine which simultaneously produces wear through the two main oral wear mechanisms of abrasion and attrition by the action of an enamel antagonist and to compare the results obtained for dental composites using this machine to those obtained from clinical studies and other in vitro studies. METHODS: The accuracy of this new wear tester was determined by examining 11 commercial composite filling materials and 1 amalgam. Specimens were subjected to three-body abrasion and attrition wear for 50,000 cycles. Profilometry was used to quantitate wear of the composites. Linear regression analysis was used to correlate the results to those obtained from clinical studies, as well as from other in vitro wear testers. The area of enamel wear was also determined by image analysis. The SEM was used to evaluate the wear surfaces. RESULTS: The lowest abrasion wear was recorded for the amalgam and for the microfill and smaller-particle composites. Attrition wear was enhanced for the microfill composites and one small-particle hybrid. There was a strong correlation between the results obtained with the new wear tester and those obtained in the clinical trials cited in the literature. Wear of the enamel antagonist was the greatest for the composites with the largest particle sizes. The wear tester showed a reasonable correlation with other wear-producing machines. SIGNIFICANCE: A new wear tester developed to evaluate and discriminate abrasion and attrition wear provided results similar to those reported in the literature for a variety of commercial composites. The new machine is capable of characterizing the behavior of a material in multiple wear modes simultaneously with one simple, realistic test.

Analysis of Variance↗

PubMed1996

Comparison of four modes of fracture toughness testing for dental composites.

OBJECTIVES: Investigators have reported on the measurement of fracture toughness (K(lc)) of dental composites using a variety of testing methods. However, fracture toughness has been shown to be dependent upon several variables, including crack-tip sharpness and specimen geometry. This study was designed to compare the fracture toughness values obtained for two experimental and three commercial posterior composites, using four popular testing methods. METHODS: The four methods for testing fracture toughness included single-edge notched, compact tension, short rod with chevron notch and double torsion. The results were compared by ANOVA and Tukey's multiple comparison test (p < or = 0.05). RESULTS: The values obtained from the short rod test were significantly higher than those from the three other tests. Evaluation of the load-deflection curves and fracture surfaces suggested that the data for this test may not have been valid because a stable crack growth region could not be identified. In general, the fracture toughness results obtained from the double torsion test were lower than values obtained from the single-edge notched and compact tension methods. The double torsion test was the most difficult to conduct, resulting in only a 50% success rate. SIGNIFICANCE: The double torsion test, though possibly the most technique-sensitive of the four fracture toughness methods evaluated provides the most information about crack initiation and propagation and may be most indicative of the true fracture toughness of dental composites.

Acrylic Resins↗

PubMed1996

Initial mercury evaporation from amalgams made with in-containing commercial alloys.

This study examined the Hg evaporation behavior during the early setting of amalgams that contain In in the alloy powders. Two different types of commercially available In-containing alloys were tested: an In-particle admixed powder (Indisperse, D) and an In-containing single-composition powder (Indiloy, S). Mercury evaporation from specimens (4 mm in dia, 8 mm tall) was monitored 10 min after trituration to 180 min using a mercury vapor analyzer according to the methods used in a previous study. The amounts released from 10 min to 180 min were compared with the results of our previous study on a single-composition amalgam (Tytin, T) with pure Hg and with Hg-In liquids (5 or 10%). Amalgam S and In-containing T terminated Hg evaporation within 180 min. There was no significant (p > 0.05) difference in the amount released between T amalgam made using pure mercury and D, and between T amalgam made with 5% In-containing mercury and S amalgam. Mercury release from amalgam D was significantly (p < 0.05) higher than from S or both types of In-containing T amalgam. Adding In to mercury or alloying In into the alloy particles appeared to be more effective in reducing the mercury vapor than admixing pure In particles into the amalgam.

Analysis of Variance↗

PubMed1995

Properties of heat-treated composites after aging in water.

OBJECTIVES: Post-cure heat treatments have been shown to increase the fracture toughness and elastic modulus of composites. The objective of this study was to determine if the increase remained after the composites were aged in water. METHODS. The fracture toughness (K(lc)), flexural modulus and flexural strength of four experimental and one commercial composite (Z-100, 3M Dental Products) were tested after 1, 7, 30, 60 and 180 d of aging in 37 degrees C water. The four experimental composites were made with a BisGMA/TEGDMA resin and were characterized as follows: Micro = 38 vol% silane-treated silica, Fine = 65 vol% silane-treated quartz of 1-2 micrometer average size, Hybrid = 65 vol% silane treated quartz of a mixture of 1-2 micrometer average and 8 micrometer average size, and Large = 65 vol% quartz of 8 micrometer average size (of which only 75% were silane-treated). All specimens were light-cured (normal-cured; Triad II - 80 s). One set of each composite was further heat-cured at 120 degrees C for 10 min (heat-cured). A third set of the Hybrid was heat-cured with simultaneous light exposure (Elipar, Espe) for the first 3 min. RESULTS: By 30 d, normal-cured and heat-cured specimens showed significant (ANOVA/Tukey's test; p < or = 0.05) reductions in fracture toughness (avg. 16% and 22%, respectively), flexural modulus (avg. 11% and 11%, respectively) and flexural strength (avg. 25% and 29%, respectively). Further aging had little effect. The use of additional light-curing during heating did not affect the properties more than heat-curing alone. SIGNIFICANCE: The improvements in some of the properties of composites produced by heat-treating are of only short-term benefit, and are for the most part negated due to an alteration of the resin matrix as the composite equilibrates with water.

Analysis of Variance↗

PubMed1995

Shear bond strength of four commercial bonding systems to cp Ti.

OBJECTIVES: The purpose of this study was to evaluate the bond strength of veneering composite to commercially pure titanium (cp Ti) using several different bonding systems and a post-cure heat treatment. METHODS: Four commercial bonding systems (Cesead, Kuraray; New Metacolor, Sun Medical; Silicaoater MD, Kulzer; Termoresin LC II, GC) were evaluated. Bonding was attempted with the opaque resin provided by each bonding system as well as with the New Metacolor opaque resin. New Metacolor resin composite was used for the veneering composite. Half of the specimens were subjected to a post-cure heat treatment at 100 degrees C for 30 min. The shear bond strengths were tested after aging the specimens in water at 37 degrees C for 1 d and also after thermocycling for 16.5 d (20,000 cycles). RESULTS: Strong bonds, exceeding 20 MPa, were achieved with all of the bonding systems with the exception of Thermoresin LC II, which is designed for noble metals. Bond strengths were only increased by the post-cure heat treatment for the New Metacolor system. Thermocycling caused a significant reduction in bond strength for the New Metacolor adn the Thermoresin LC II systems. The use of the New Metacolor opaque resin produced increased bonding for the Silicoater MD and the opaque resin produced increased bonding for the Silicoater MD and the Cesead systems, but the effect was eliminated after thermocycling. SIGNIFICANCE: Strong, durable bonds can be achieved between composite and sandblasted cp Ti, thus enhancing the usefulness of this metal for esthetic resin-veneered crowns and other fixed prosthetics.

Acrylic Resins↗