Biomedical subjects

J L Ferracane

Publications and source records attributed to J L Ferracane.

At least 19 recordsLinked to original sources

PubMed2001

The in vitro cytotoxicity of eluates from dentin bonding resins and their effect on tyrosine phosphorylation of L929 cells.

OBJECTIVES: The aim of this study was to examine the relationship between the monomers eluted from dentin-bonding systems and their cytotoxicities, and to investigate the biochemical effect of the monomers on tyrosine phosphorylation, especially relating to the cell growth activity, of L929 cells in vitro. METHODS: The primers, uncured or cured adhesives (3M and Kuraray) were tested to determine the cytotoxicity of confluent L929 cells cultured by Eagle's MEM medium supplemented with 10% FCS. The area of cells affected by the eluted monomers were evaluated with an image analyzer and the concentrations of monomers eluted into the medium were measured with high performance liquid chromatography (HPLC) after 24h incubation. The protein composition of the stimulated cells was compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tyrosine phosphorylation was detected by Western blot. RESULTS: The primer and uncured adhesives revealed variable cytotoxicities. 2-hydroxyethyl-methacrylate (HEMA) was the major component eluted from uncured primers and adhesives. Small amounts of triethylene glycol dimethacrylate (TEGDMA) were also detected from the uncured adhesives. The cytotoxicities of the adhesives decreased as photo activation time increased. The amount of monomers eluted from the cured adhesives was almost undetectable and did not reach a sufficient concentration to suppress cell viability or cell growth. The cytotoxicities of the primers and adhesives correlated well with the amounts of either HEMA or TEGDMA eluted. Moreover, a high concentration of HEMA (4 mg/ml medium) affected intracellular tyrosine phosphorylation, which is related to cellular activities. SIGNIFICANCE: Although the monomers present in dentin bonding resins are cytotoxic to L929 cells, the amount from cured bonding resin is very small and does not provide a cytotoxic dose. This data does however suggest that clinical exposure to the uncured primers and adhesives of dentin bonding resins should be minimized.

Adhesives↗

PubMed2000

Properties of packable dental composites.

The introduction of many new packable composites suggests that these products are rapidly gaining popularity. The purpose of this study was to evaluate the in vitro properties of a variety of packable composites and to determine if significant enhancements in physical and mechanical properties have been achieved for these materials compared with two popular nonpackable posterior composites. For the five packable and two regular composites tested (ALERT, Pyramid-Dentin, Pyramid-Enamel, Solitaire, SureFil, Heliomolar, and Z100), the values for fracture toughness, flexure strength, flexure modulus, hardness, and volumetric polymerization shrinkage were determined. In general, although the packable composites were of heavier consistency, they had mechanical properties that were intermediate to (ALERT, Pyramid, and SureFil) or lower than (Solitaire) those of the nonpackable materials. These results could have been predicted based on the similar methacrylate resin chemistry and filler volumes of the various composites. No composite had adequate depth-of-cure when tested in increments greater than 2 mm thick. Polymerization contraction of the packable composites was similar to or higher than that of the nonpackable composites. In addition, the radiopacity of at least one material, Solitaire, was not considered to be adequate (less than 2 mm of aluminum). The results of this study suggest that these packable composites are unlikely to offer improved clinical performance over well-placed nonpackable composites.

Acrylic Resins↗

PubMed2000

The effects of adhesive thickness on polymerization contraction stress of composite.

A layer of an unfilled adhesive resin placed between the tooth and composite restoration has been shown to absorb some of the stress generated in the composite during polymerization and to reduce interfacial leakage. The objectives of this study were to measure the change in polymerization contraction stress of bonded composite as the thickness of the resin adhesive was systematically varied, and to correlate the effects of the adhesive thickness and reduced stress on marginal leakage in class V cavities. The maximum contraction force of composite (Herculite XRV) was measured in a tensilometer as the thickness of the adhesive bonding agent (Scotchbond MP) was varied from 20 to 300 microm. Composite was placed in Class V cavities prepared on the labial surfaces of bovine teeth to which different thicknesses of adhesive had been applied by layering, and a marginal leakage test was performed by means of staining with silver nitrate. Contraction stress decreased significantly as the adhesive thickness was increased. This result was supported by a theoretical examination of the data. In class V cavities, additional adhesive layering in the marginal area reduced the overall degree of microleakage. The contraction stress generated during the placement of a composite restoration contributes significantly to early marginal leakage, and this stress was significantly absorbed and relieved by the application of an increasing thickness of low-stiffness adhesive.

Adhesiveness↗

PubMed2000

Assessing the effect of composite formulation on polymerization stress.

BACKGROUND: In this study, the authors measured the magnitude of the polymerization stress of a variety of dental composite materials and explored the effect of a novel monomer, a methacrylated derivative of styrene-allyl alcohol, or MSAA, in reducing polymerization stress. METHODS: Eleven commercially available composites and a series of experimental composites were evaluated in a mechanical testing machine to measure the maximum stress generated during placement in a confined setting. RESULTS: A significant relationship between higher filler volume and increased polymerization stress was found among the commercial materials. Introduction of MSAA produced a 30 percent reduction in polymerization stress in an experimental composite material. CONCLUSIONS: Composites that contain lower levels of inorganic filler particles are less likely to produce high levels of polymerization stress during placement. Modifications to traditional composite chemistry can result in materials that produce lower polymerization stress levels. CLINICAL IMPLICATIONS: The polymerization stress produced by dental composite materials during light-curing is a leading reason for bond failures in adhesive restorations, resulting in postoperative sensitivity, marginal staining and recurrent caries.

Analysis of Variance↗

PubMed2000

Mercury evaporation from amalgams with varied mercury contents.

This study examined the relationship between mercury content and mercury evaporation from amalgams during setting. Two different types of commercial high-copper amalgams (single composition and admixed types) were used. Cylindrical specimens of each amalgam were prepared with five different mercury contents according to ADA Specification No.1. Specimens were also prepared by hand condensation. Mercury evaporation from amalgam specimens maintained at 37 degrees C was measured using a gold film mercury analyzer from 10 min after the end of trituration until the mercury concentration in air reached an undetectable level. The mercury content more clearly influenced the mercury evaporation from the admixed type amalgam specimens when the mercury content decreased below the manufacturers' recommended trituration conditions. Triturating with less mercury than the manufacturers' recommended amount cannot lower the evaporation of mercury from freshly made amalgam. Proper condensing procedures can minimize the mercury evaporation from the amalgam surface.

Chemistry, Pharmaceutical↗

PubMed1999

In vitro evaluation of the marginal degradation of dental composites under simulated occlusal loading.

OBJECTIVES: Our objective was to use an in vitro oral wear simulator to compare the susceptibility to marginal breakdown of different classes of dental composites. METHODS: Two microfill composites (Silux Plus, 3M and Heliomolar, Vivadent), two minifills (Z100, 3M and Herculite, Kerr) and two midifills (Fulfil, Caulk and Clearfil, Kuraray) were placed in two increments (40 s cure) into class I cavities (5 x 3.5 x 2 mm3 deep) cut into the facial enamel surfaces of bovine incisors treated with an adhesive (Scotchbond MP, 3M). The restored teeth were aged 1 day in water, mounted in the OHSU oral wear simulator, covered with a slurry of poppy seeds/PMMA beads and subjected to 50 K cycles of wear against an enamel stylus [J.R. Condon, J.L. Ferracane, Evaluation of composite wear with a new multi-mode oral wear simulator, Dent. Mater. 12 (1996) 218-226). The specimens (n = 10) were positioned to produce abrasive wear (load = 20 N] across one margin and attrition wear (load = 70 N) across the second margin. Volume loss of material (mm3 x 1000) was estimated from 10 profilometric tracings perpendicular to the attrition margin, and then differentiated into composite and enamel degradation. Fracture toughness of the composites was measured in bending with the single-edge notch technique. Results were compared with ANOVA and Tukey's test at p < 0.05. RESULTS: Significant wear of the composite was produced at the attrition margin. Enamel degradation at the margin paralleled the composite results. The microfills, and to a lesser extent the minifills, showed more marginal breakdown than the midifill composites. Marginal breakdown shows an excellent inverse correlation with fracture toughness for these composites. SIGNIFICANCE: These results are in general agreement with clinical studies showing greater marginal degradation for microfill composites and suggest that the OHSU oral wear simulator may be a useful adjunct for the study of the marginal degradation of dental composites.

Analysis of Variance↗

PubMed1999

Cavity preparation factors and microleakage of Class II composite restorations filled at intraoral temperatures.

PURPOSE: To determine if alteration of any of the following factors could reduce microleakage following placement of Class II resin-based composites (RBC) at intraoral temperature: cavity preparation (vertical wall bevels), finishing technique (delayed vs. immediate), or postoperative re-bonding (marginal sealing). An additional purpose was to determine if a decalcification/clearing protocol was a valid technique for assessing three-dimensional microleakage. MATERIALS AND METHODS: 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 imbedded in a stone template, warmed to 37 degrees C and restored immediately upon removal from the oven with visible light-cured (VLC) adhesive (All-Bond 2) and three horizontal increments of VLC RBC (Bisfil P) using a metal matrix. Teeth were placed into one of four groups: (1) Control; (2) The preparation was modified to include 0.5-1.0 mm enamel bevels on the vertical walls (facial and lingual); (3) Finishing of the RBC was delayed 24 hours; (4) Following immediate finishing, all margins of the RBC restorations were sealed by dentin bonding agent application. Teeth were stored at 37 degrees C for 2 weeks, thermocycled 1000x at 5/55 degrees C, stained with silver nitrate, underwent a decalcification and clearing protocol, and evaluated for three-dimensional dye penetration. RESULTS: Axial-occlusal enamel margins exhibited minimal leakage and no differences among the groups. Vertical walls without bevels exhibited pronounced microleakage. Beveled vertical proximal walls exhibited significantly less facial and lingual wall microleakage compared to all other groups, and less gingival marginal leakage compared to the control group.

Acid Etching, Dental↗

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↗