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Biomedical subjects

Jack L Ferracane

Publications and source records attributed to Jack L Ferracane.

At least 19 recordsLinked to original sources
PubMed2007

Three cements used for orthodontic banding of porcelain molars.

OBJECTIVE: Objectives of this study were to (1) compare the mean shear-peel bond strength of orthodontic bands luted to porcelain molar denture teeth with glass ionomer cement (GIC), resin-modified glass ionomer cement (RMGIC), or compomer cement; (2) assess the amount of cement remaining on the teeth after debanding; and (3) compare the survival times of the cemented bands subject to mechanical fatigue. MATERIALS AND METHODS: Sixty banded denture teeth (20 per cement group) were used to determine shear-peel bond strength, and 30 banded denture teeth (10 per cement group) were used to determine fatigue survival time. Shear-peel bond strength was determined with a universal testing machine, and groups were compared by one-way analysis of variance. The amount of cement remaining on the teeth after band removal was scored, and a chi-square test was used to compare groups. Fatigue testing was conducted in a ball mill, and a log-rank test was used to compare differences in survival times. RESULTS: No differences were found in mean shear-peel bond strength among the three groups. The amount of cement remaining on the teeth varied between the compomer and GIC groups (P = .01), with more compomer cement remaining relative to GIC. The mean survival times of bands cemented with compomer or RMGIC were longer than for bands cemented with GIC (P < .001). CONCLUSION: The findings show that on porcelain teeth the band cements have comparable mean shear-peel bond strengths, but that band retention with RMGIC and compomer cement are superior to GIC when subjected to simulated mechanical fatigue.

Analysis of Variance↗
PubMed2006

Quantum yield of conversion of the photoinitiator camphorquinone.

The primary absorber in dental resins is the photoinitiator, which starts the photo polymerization process. We studied the quantum yield of conversion of camphorquinone (CQ), a blue light photoinitiator, in dental resin composites using a LED lamp (3M FreeLight) and a Quartz Tungsten Halogen (QTH) lamp (VIP) as the light curing units at five different irradiances. The molar extinction coefficient, epsilon(469), of CQ was 46+/-2 cm(-1)/(mol/L) at 469 nm. The reciprocity of irradiance and exposure time holds for changes of CQ absorption coefficient, that is, irradiance x exposure time (=radiant exposure)=constant. Both LED and QTH lamps yielded the same curing threshold (the radiant exposure when CQ absorption drops to 1/e) and the same quantum yield conversion under different irradiances. In our dental resin formulation (0.7 wt.% CQ with reducing agents 0.35 wt.% dimethylaminoethyl methacrylate (DMAEMA) and 0.05 wt.% butylated hydroxytoluene (BHT)) the quantum yield was measured as 0.07+/-0.01 CQ conversion per absorbed photon.

Absorption↗
PubMed2006

Is the wear of dental composites still a clinical concern? Is there still a need for in vitro wear simulating devices?

While once considered a major concern for posterior restorations, wear of dental composites has been substantially reduced by changes in formulation and is considered today by many to be a solved problem. However, minimal evidence exists in the literature to support this conclusion for large restorations, especially those involving the replacement of functional cusps, despite the fact that these restorations are routinely performed. Evidence shows that wear may be of minimal importance for restorations of small to moderate size. However, the literature does suggest that failure rates are higher for larger restorations, and that wear may still be a significant mode of failure for patients with bruxing and clenching habits. In this light, the wear of composites continues to be studied by many researchers, and it is justifiable to seek well-defined and reproducible in vitro methods for predicting this multifactorial phenomenon.

Bruxism↗
PubMed2006

Wear and fatigue behavior of nano-structured dental resin composites.

Theoretically, nano-structured dental resin composites are purported to have increased wear and fatigue resistance compared with microfill composites and may favor the achievement of restoratives with better long-term performance. This study sought to assess the behavior of nano-structured composites resulting from either abrasion and fatigue loading. Ten specimens (12 x 5 x 2.5 mm) were prepared from each of five composites: Ceram-X mono, Filtek Supreme, Grandio, Premise, and Heliomolar (serving as the microfill control). A surface profile was recorded using a three-dimensional profiling system, and the specimens were subjected to 10(5) cycles of three-body abrasion in the new OHSU oral wear simulator. A second profile was generated and the before and after profiles were fit and analyzed. The volume loss and maximum depth of the wear facet on each specimen were calculated. Another 30 specimens (25 x 2 x 2 mm) were tested for flexural fatigue limit (FFL) in four-point bending via the staircase method. The test was carried out until 10(4) cycles were completed or until fracturing the specimen. One-way ANOVA and Tukey's test demonstrated greater volumetric loss for Grandio and Ceram-X than that observed for the remaining composites. Kruskal-Wallis and the least significant difference test ascertained that Heliomolar, Grandio, and Supreme showed significantly higher FFL than Ceram-X and Premise. In terms of wear and fatigue resistance, nano-structured composites may perform either similarly or comparatively worse than a microfilled composite.

Acrylic Resins↗
PubMed2006

In vitro wear evaluation of dental materials in primary teeth.

PURPOSE: To evaluate the effect of dental materials on primary enamel wear. METHODS: Four composites (Filtek Z250, Heliomolar, Point 4, SureFil), two compomers (Dyract AP, F2000) and a resin-modified glass-ionomer (Vitremer) were placed into box-shaped preparations in buccal surfaces of primary molars and stored for 24 hours in water at 37 degrees C. The specimens (n = 6) were subjected to abrasive three-body wear against a primary enamel cusp. Material wear, enamel wear (adjacent to the material), and wear on enamel cusps were estimated by profilometry and video-analysis software. Results were compared with ANOVA and Tukey's tests (P < 0.05). RESULTS: Vitremer showed the highest wear (P < 0.05), followed by Dyract AP and F2000, which were not statistically different (P > 0.05). There was no significant difference between Filtek Z250 and Dyract AP (P > 0.05). Filtek Z250, Heliomolar, Point 4 and SureFil, showed the lowest wear values and there was no difference among them (P > 0.05). The highest wear values on the enamel adjacent to the material were found with Dyract AP (P < 0.05) and the lowest next to Point 4 and SureFil (P < 0.05). There was no difference in the wear of the enamel next to Vitremer, F2000, Heliomolar and Filtek Z250 (P > 0.05). Vitremer and F2000 caused the highest wear on enamel cusps (P < 0.05), and there was no statistically significant difference (P > 0.05) between them; SureFil caused the lowest wear (P < 0.05) on the opposing enamel. There was a correlation (r = 0.85) between wear of materials and wear on the enamel cusps, but not (r = 0.53) for the wear on enamel besides the restoration and wear on enamel cusps. SEM micrographs showed different surface characteristics of the materials after the wear test.

Analysis of Variance↗
PubMed2005

A pilot study of a simple photon migration model for predicting depth of cure in dental composite.

OBJECTIVES: The purpose of this study was to build a photo migration model to calculate the radiant exposure (irradiancextime) in dental composite and to relate the radiant exposure with extent of cure using polymer kinetics models. METHODS: A composite (Z100, Shade A2) cylinder (21 mm diameter by 15 mm deep) was cured with a tungsten-halogen lamp emitting 600 mW/cm2, 1 mm above the composite for 60s. For each of the 2x1 mm grids along the longitudinal cross section (diameter versus depth), the degree of conversion (DC) and hardness (KHN) were measured to construct the curing extent distribution. The inverse adding-doubling method was used to characterize the optical properties of the composite for the Monte Carlo model simulating the photon propagation within the composite cylinder. The calculated radiant exposure (H) distribution along the cross section was related to the curing extent DC/DC(max) distribution and fitted with two polymer curing kinetics models, the exponential model DC=DC(max)[1-exp((ln0.5)H/H(dc)(50%))] and Racz's model [Formula: see text] , where H(dc)(50%) is a fitting parameter representing the threshold for 50% of the maximum curing level. RESULTS AND SIGNIFICANCE: The absorption and scattering coefficients of uncured composite were higher than that of cured composite at wavelengths between 420 and 520 nm. A roughly hemi-spheric distribution of radiant exposure in the Monte Carlo simulation result was comparable with the curing profiles determined by both DC and KHN. The relationship between DC (or KHN) and H agreed with the Racz model (r2=0.95) and the exponential model (r2=0.93). The H(dc)(50%) was 1.5(0.1), equal for the two models (P<0.05). The estimated radiant exposure threshold for 80% of the maximum curing level was between 3.8 and 8.8 J/cm2. The simulation results verify that the radiant exposure extends to a greater depth and width for composite with lower absorption and scattering coefficients. Given the optical properties and the geometry of the composite, and the spectrum and the geometry of the light source, the Monte Carlo simulation can accurately describe the radiant exposure distribution in a composite material to predict the extent of cure.

Composite Resins↗
PubMed2005

Hygroscopic and hydrolytic effects in dental polymer networks.

OBJECTIVES: The objective of this manuscript is to outline the factors associated with hygroscopic and hydrolytic effects in dental polymer networks, and to review the literature generated over the past thirty years or more in this area. METHODS: Information was gathered from nearly 90 published articles or abstracts appearing in the dental and polymer literature. Studies were predominantly identified through a search of the PubMED database. RESULTS: Studies were included that provided direct evidence for the uptake of solvent by a polymer network and its subsequent physical or chemical effect, or the loss of molecular species into solvents. An attempt was made to select articles that spanned the timeframe from approximately 1970 to today to ensure that most of the classic literature as well as the latest information was included. CONCLUSIONS: Dental polymer networks have been shown to be susceptible to hygroscopic and hydrolytic effects to varying extents dependent upon their chemistry and structure. The importance of these effects on the clinical performance of polymer restoratives is largely unknown, though numerous investigators have alluded to the potential for reduced service lives. SIGNIFICANCE: While the physical and mechanical properties of these materials may be significantly altered by the effects of solvent uptake and component elution, what may constitute the greatest concern is the short-term release of unreacted components and the long-term elution of degradation products in the oral cavity, both of which should be strongly considered during restorative material development.

Chemical Phenomena↗
PubMed2005

Developing a more complete understanding of stresses produced in dental composites during polymerization.

The polymerization of dental composites is accompanied by significant shrinkage and the production of internal stress. This stress has been implicated as a causative factor for marginal discrepancies seen in composite restorations. This paper provides an overview of the origins of these stresses in polymerizing dental composites, a brief description of the methods for measuring them, a discussion of what little is known of the relationship between contraction stress and outcomes, an identification of the materials and placement factors that affect contraction stress, and a description of several strategies proposed to reduce the stresses. The phenomenon of contraction stress development in dental composite restoratives is highly complex, and despite many investigations, remains as a significant clinical concern.

Composite Resins↗
PubMed2005

Abrasive wear of resin composites as related to finishing and polishing procedures.

OBJECTIVES: Finishing and polishing procedures may cause topographical changes and introduce subsurface microcracks in dental composite restoratives. Since both of these effects may contribute toward the kinetics of wear, the purpose of this study was to assess and correlate the wear and surface roughness of minifilled and nanofilled composites finished and polished by different methods. METHODS: Specimens (n=10) made of a minifilled and a nanofilled composite were finished and polished with one of the four sequences: (1) tungsten carbide burs plus Al(2)O(3)-impregnated brush (CbBr) or (2) tungsten carbide burs plus diamond-impregnated cup (CbCp), (3) diamond burs plus brush (DmBr) or (4) diamond burs plus cup (DmCp). As a control, abrasive papers were used. After surface roughness had been quantified, three-body abrasion was simulated using the OHSU wear machine. The wear facets were then scanned to measure wear depth and post-testing roughness. All sets of data were subjected to ANOVA and Tukey's tests (alpha=0.05). Pearson's correlation test was applied to check for the existence of a relationship between pre-testing roughness and wear. RESULTS: Significantly smoother surfaces were attained with the sequences CbBr and CbCp, whereas DmCp yielded the roughest surface. Regardless of the finishing/polishing technique, the nanofilled composite exhibited the lowest pre-testing roughness and wear. There was no correlation between the surface roughness achieved after finishing/polishing procedures and wear (p=0.3899). SIGNIFICANCE: Nano-sized materials may have improved abrasive wear resistance over minifilled composites. The absence of correlation between wear and surface roughness produced by different finishing/polishing methods suggests that the latter negligibly influences material loss due to three-body abrasion.

Analysis of Variance↗
PubMed2005

Measuring the residual stress in dental composites using a ring slitting method.

OBJECTIVES: The objective of this experiment was to employ the ring slitting method for the measurement of the residual stress (RS) produced in dental composite materials after polymerization. This study was designed to determine the effect of slitting and measuring time on the residual stress. METHODS: Rings were made in a split brass mold from three composites (Z100/3MESPE; Herculite/Kerr; Heliomolar/Ivoclar) and cured in a Triad II (Dentsply). Two points were scribed, and the rings were slit at either 1 h (Early-group) or 24 h (Delayed-group) after curing the composite. The change in the distance between the scribed points was measured using an image analyzer system at both 1 and 24 h after slitting. From the measured change, circumferential RS was calculated and statistically analyzed with ANOVA/Tukey's (P<0.05). The degree of conversion of each composite at 1 and 24 h was measured with FTIR and analyzed using Student's t-test (P<0.05). RESULTS: In general, the residual stress (range=0.42-2.84 MPa) was highest for Z100 and lowest for Heliomolar, but this depended upon the test conditions. The early cut (1 h slitting), 24 h measurement groups showed the highest residual stress values. SIGNIFICANCE: This study, describes a ring slitting method to measure residual stress generated in dental composites during and after curing. The stress of composite can be affected by the cutting and measurement time.

Acrylic Resins↗
PubMed2005

Factors involved in the development of polymerization shrinkage stress in resin-composites: a systematic review.

OBJECTIVES: Polymerization shrinkage stress of resin-composite materials may have a negative impact on the clinical performance of bonded restorations. The purpose of this systematic review is to discuss the primary factors involved with polymerization shrinkage stress development. DATA: According to the current literature, polymerization stress of resin composites is determined by their volumetric shrinkage, viscoelastic behavior and by restrictions imposed to polymerization shrinkage. Therefore, the material's composition, its degree of conversion and reaction kinetics become aspects of interest, together with the confinement and compliance of the cavity preparation. SOURCES: Information provided in this review was based on original scientific research published in Dental, Chemistry and Biomaterials journals. Textbooks on Chemistry and Dental Materials were also referenced for basic concepts. CONCLUSIONS: Shrinkage stress development must be considered a multi-factorial phenomenon. Therefore, accessing the specific contribution of volumetric shrinkage, viscoelastic behavior, reaction kinetics and local conditions on stress magnitude seems impractical. Some of the restorative techniques aiming at stress reduction have limited applicability, because their efficiency varies depending upon the materials employed. Due to an intense research activity over the years, the understanding of this matter has increased remarkably, leading to the development of new restorative techniques and materials that may help minimize this problem.

Chemical Phenomena↗
PubMed2004

Effects of resin formulation and nanofiller surface treatment on the properties of experimental hybrid resin composite.

This study evaluated the effects of nanofiller surface treatment and resin viscosity on the early and long-term properties of experimental hybrid composites. Three resin formulations (low, medium and high viscosity) were prepared by varying the ratio of TEGDMA:UDMA:bis-GMA (47:33:16 wt%; 30:33:33 wt%; 12:33:51 wt%). Composites contained 71.3 wt% silanated strontium glass (1-3 microm) and 12.6 wt% of either silanated or unsilanated silica (OX-50; 0.04 microm). Specimens (n=10) for flexural strength, flexural modulus, fracture toughness and Knoop hardness were tested after 24 h, 1 and 6 months exposure to water at 37 degrees C. Degree of conversion (DC) was determined 24 h after photoinitiation using FTIR. Resin viscosity only had a marginal influence on the mechanical response of composites but it can be adjusted to achieve a balance between DC and mechanical properties. Adding non-bonded nanofiller to hybrid composites had no systematic effect on DC. Non-bonded nanofillers had no significant effect on the long-term properties of hybrid composites.

Coated Materials, Biocompatible↗
PubMed2004

Effect of energy density on properties and marginal integrity of posterior resin composite restorations.

OBJECTIVES: The purpose of this study was to determine the minimal extent of cure required by the base of a Class 2 resin composite restoration (Z250, 3M ESPE, St Paul, MN, USA) that allows it to support the rest of the restoration and maintain its marginal seal under simulated clinical conditions. METHODS: Resin composite (Z250, 3M ESPE, St Paul, MN, USA) was placed incrementally or in bulk into Class 2 preparations in extracted human molar teeth and exposed to various light-curing energy densities. The restorations were subjected to 1000 thermal cycles (5-55 degrees C) and 500,000 fatigue cycles from 18 to 85 N using a stainless-steel sphere. Marginal integrity was evaluated using visual rating (ridit analysis) and microleakage. Degree of conversion (DC) and Knoop hardness (KHN) were determined at the occlusal and gingival surfaces using a reusable tooth template with identical preparation dimensions. Percentage of maximum DC and KHN were determined. Mechanical properties were tested in resin composite bars having similar KHN values as the resin composite at the gingival margins. RESULTS: Energy density had a significant effect on gingival marginal defects as determined by ridit analysis but not on microleakage. Water had a significant dissolving effect on gingival margin integrity at very low degrees of conversion and energy densities (4000 mJ/cm2). There was no overall significant effect of thermal-mechanical stressing on gingival marginal defects or microleakage. SIGNIFICANCE: Based on ridit analysis, a recommended lower limit of gingival margin acceptability in the bulk-filled Z250 resin composite restoration was created by 80% of maximum conversion, 73% of maximum hardness and approximately 70% of maximum flexural strength and modulus in the gingival marginal area.

Analysis of Variance↗
PubMed2003

Contraction stress of flowable composite materials and their efficacy as stress-relieving layers.

BACKGROUND: The authors compared the polymerization contraction stress produced by flowable resin-based composites with stress values produced by nonflowable composites. They also measured the stress reduction produced by placing a precured layer of flowable composite under a nonflowable composite. METHODS: The authors first tested four flowable and six nonflowable composite materials for contraction stress in a tensiometer. In the second part of the study, they applied a 1.4-millimeter-thick layer of flowable composite or unfilled resin and precured it in the test apparatus to assess the stress relief produced by a low-modulus material during light curing of a subsequent layer of highly filled composite. Flexural moduli of the precured materials were determined via a three-point bending test. RESULTS: The stress values ranged between 6.04 and 9.10 megapascals. The authors found no significant differences in stress between flowable and nonflowable composites. Microfilled composites produced lower contraction stress than did hybrids. The flexural modulus of the flowable composites varied between 4.1 and 8.2 GPa. Regarding the effect of a precured layer of composite on contraction stress, the authors observed significant reductions with only one of the flowable materials and with the unfilled resin. CONCLUSIONS: The flowable composites produced stress levels similar to those of nonflowable materials. Most of the flowable materials tested did not produce significant stress reductions when used under a nonflowable composite. CLINICAL IMPLICATIONS: Using a flowable resin-based composite as a restorative material is not likely to reduce the effects of polymerization stress. When used in a thin layer under a nonflowable composite, the stress reduction depended on the elastic modulus of the lining material.

Composite Resins↗
PubMed2003

Evaluation of the amalgamation reaction of experimental Ag-Sn-Cu alloys containing Pd using a mercury plating technique.

A mercury plating technique was used to determine the phases forming on experimental Ag-Sn-Cu alloy powders (with and without Pd) exposed to electrolytically deposited mercury. Four series of alloy powders were made: a) 1.5% Pd with 10-14% Cu (CU series); b) 1.0% Pd with 10-14% Cu (1PD series); c) 1.5% Pd with different ratios of Ag3Sn (gamma) to Ag4Sn (beta) with 12% Cu (AGSN series); and d) 9-13% Cu with no Pd (NOPD series). Each powder was pressed on a freshly prepared amalgam specimen made from the same powder and metallographically polished until cross sections appeared; mercury was electroplated on the alloy particles. Alloy powders, amalgams and electroplated specimens were examined using XRD and SEM/EDS. XRD confirmed the presence of gamma2 in amalgams made from alloys with Cu < 13% or with Ag3Sn/Ag4Sn > 0.8. Specimens with moderately plated Hg showed gamma1 (Ag2Hg3) polyhedra and eta' Cu6Sn5, but not gamma2. This method effectively identifies alloys prone to forming gamma2.

Copper↗
PubMed2003

Flexural fatigue strength of CAD/CAM composite material and dual-cured resin luting cements.

PURPOSE: To evaluate the flexural strength and flexural fatigue strength of a CAD/CAM composite and three resin luting cements. MATERIALS AND METHODS: Specimens of CAD/CAM composite (2 x 2 x 25 mm) were fabricated from a composite block (GN-I) using a low-speed cutting saw. Similar specimens of three dual-cured resin luting cements, Linkmax HV, Panavia Fluoro Cement, and RelyX ARC were polymerized in a laboratory-photo-curing unit (Triad II). Flexural strengths were measured at a cross-head speed of 1 mm/minute in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm). The cyclic fatigue test was performed at 1.0 Hz on a fatigue tester. The staircase method was employed using a 10,000 cyclic load limitation, 5 MPa stress increment, and 20 specimens for each material. The initial test was performed at approximately 50% of the mean flexural strength. RESULTS: The flexural fatigue strength results followed the same relationship as those of the static flexural strength, and all mean values were statistically different between the four materials. The ratio of the fatigue strength to the flexural strength ranged from 0.5-0.7, with the dual-cured resin luting cements being lowest.

Analysis of Variance↗
PubMed2003

Relationship between composite contraction stress and leakage in Class V cavities.

PURPOSE: The purpose of this study was to determine the relationship between polymerization contraction stress and leakage in Class V composites. METHODS: A microfill (Heliomolar) and two minifill hybrid composites (Herculite, Z100) were tested. Maximum contraction stress (n = 5) for the composites was evaluated in a MTS machine at a C-factor of 3 (ratio of bonded to non-bonded surface area). Composite was placed in the gap between the surfaces of glass stubs that had been air abraded, silane treated and coated with a layer of resin adhesive. Specimens were light-cured through the top glass stub for 60 seconds and maximum force was recorded during the first 10 minutes. Leakage (n = 10) was evaluated by cutting cylindrical cavity preparations with all enamel margins (C-factor = 3) in bovine incisors. The cavities were treated with two layers of Scotchbond MP adhesive. Composites were applied in one increment, light-cured at the same intensity used in the stress tests, and immediately finished on SiC paper. After 1 day in water, the restorations were placed in silver nitrate, developed and evaluated as a single cross-section (2-D) and multiple cross-sections (3-D) for leakage: 0 (none), 1 (minimal leakage), 2 (to the DEJ), 3 (to line angle), 4 (along the pulpal wall). RESULTS: The maximum stresses (MPa) recorded were lowest for Heliomolar (7.0 +/- 0.4), intermediate for Herculite (10.5 +/- 0.6) and greatest for Z100 (11.6 +/- 1.3). 3-D leakage was as follows: Heliomolar--two specimens scored 1, seven scored 2 and one scored 3; Herculite--six scored 2 and four scored 3; Z100--eight scored 3 and two scored 4. The Kruskal-Wallis test showed a significant difference in leakage for the three composites (P < 0.05), and leakage was greater when evaluated in 3-D. The leakage results correlated with the stress values, i.e. composites with higher contraction stress showed more extensive marginal leakage.

Acrylic Resins↗