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Albert J Feilzer

Publications and source records attributed to Albert J Feilzer.

At least 19 recordsLinked to original sources
PubMed2006

Fracture toughness comparison of three test methods with four dental porcelains.

OBJECTIVE: The aim of this study was to compare three fracture toughness test methods, using four commercial dental porcelains. MATERIALS AND METHODS: The fracture toughness test techniques involved were: the single-edge-notched beam (SENB), the indentation strength method (IS), and a rather convenient ASTM standard for advanced ceramics, which is still rarely used in dental ceramic research, the Chevron-notched beam method (CN). Duceram, Duceram LFC, Sintagon Zx and Carrara Vincent were chosen for study. Data was analyzed by two-way and paired ANOVA. RESULT: No statistical difference was found between the CN and SENB methods with four dental porcelains, but IS was not always in statistical agreement with SENB or CN. Statistical agreement among all three methods occurred only with Duceram LFC. CONCLUSION: The different test methods did not always lead to the same ranking or values of fracture toughness. Yet the toughness results of the SENB method were comparable to those of the CN method for all the four dental porcelains tested in this study.

Analysis of Variance↗
PubMed2006

Effect of loading method on the fracture mechanics of two layered all-ceramic restorative systems.

OBJECTIVE: The aim of this research was to evaluate both the fracture and impact strength of two core veneered all-ceramic systems and to reveal whether the speed of loading affects fracture mechanism. METHODS: The absorbed energy by (IPS)Empress-Eris crowns and Cercon-Ceram S crowns in a fracture strength test was compared by the energy absorbed in an impact strength test. The principles of fractography were used to identify fracture origin and dimensions and to calculate the stress at failure. Finite element analysis (FEA) was used to rationalize the results. RESULTS: For the (IPS)Empress 2-Eris crowns, there was a significant difference in the energy absorbed for the fracture test and the impact test, where for the Cercon-Ceram S, there was no significant difference. Despite the high strength of the zirconia cores there was no significant difference in the energy absorbed between the two systems in the impact strength test. The dominant mode of failure of layered all-ceramic restorations under occlusal loading is cone cracking in the veneering ceramic. SIGNIFICANCE: It was concluded that to exploit the high strength of the zirconia cores the strength of the veneering ceramic has to improve as delamination and cone cracking of the veneer are the most expected failure modes.

Analysis of Variance↗
PubMed2006

Fracture toughness determination of two dental porcelains with the indentation strength in bending method.

OBJECTIVE: This study was to investigate the influence of the bending test configurations and the crosshead displacement speeds on the fracture toughness (K(Ic)) of dental porcelains obtained with the indentation strength in bending (ISB) method. METHODS: The strength of the dental veneering porcelains Duceram and Sintagon Zx, Vickers' indented at a load of 2 kg was measured at a crosshead speed of 0.5mm/min with three test configurations, which were 3-point, 4-point, and biaxial bending. Two more groups of Sintagon Zx were tested the same way, but at speeds of 0.1, and 0.05 mm/min, respectively. Both porcelains, the three crosshead speeds, and the three test configurations were compared statistically. RESULTS: Duceram had a higher toughness than Sintagon Zx with all three test configurations and there was no significant difference between three test configurations with either porcelain. Within the crosshead speed groups of Sintagon Zx, a significant difference was found only in the 0.5mm/min group between the 3-point, and 4-point configurations. Within the configuration groups, significant differences were found between all speeds with the 3-point configuration and only between the highest and lowest speed with the 4-point and the biaxial tests. CONCLUSION: The crosshead displacement speed can cause statistically different results of fracture toughness obtained with the ISB method.

Analysis of Variance↗
PubMed2006

Contraction stress and bond strength to dentinfor compatible and incompatible combinations of bonding systems and chemical and light-cured core build-up resin composites.

OBJECTIVE: Recent studies have shown that adhesives containing acidic monomers combined with composites can adversely effect the polymerization reaction producing low bond strengths. This phenomenon may also occur in making composite build-ups, jeopardizing one of the key factors for a successful core build-up restoration. The aim of this study was to investigate the contraction stress development and bond strength to dentin of core build-up resin composites combined with adhesives of various acidities. In addition the hypothesis tested was that light irradiation through chemical-cured composites during curing does not influence contraction stress or bond strength to dentin. METHODS: The chemical-cured (Clearfil Core) and light-cured (Clearfil Photo Core) core build-up resin composites were combined with two light-cured adhesives, Clearfil SE Bond (pH=1.8) and One-Step Bond (pH=4.3) and two dual-cured adhesives, Clearfil Photo Bond (pH=2.5) and All-Bond 2 (pH=6.1). Contraction stress development (at C=3) was determined for a period of 30 min in a universal testing machine where the opposing bonding surfaces were glass and dentin. After the 30 min period, the specimens were loaded in tension to determine the bond strength to dentin. To test the hypothesis, the combinations of the chemical-cured composites with the four bonding systems were also light irradiated for 40s right at the start of curing. RESULTS: For all composite-adhesive combinations tested, the adhesion to dentin resisted the developing polymerization contraction stresses. Both, dentin as a substrate to bond at and the use of adhesives, were showed to play an important role in keeping the contraction stresses low. The chemical-cured composite (Clearfil Core) combined with the light-cured adhesive SE Bond (pH=1.8) showed for both contraction stress and bond strength significant lower values than the other combinations. The hypothesis was accepted for combinations of the chemical-cured composite with All-Bond 2 and One-Step Bond, but was not supported by combinations with Clearfil SE Bond or Clearfil Photo Bond, as a significant increase in contraction stress was found. The higher values found for bond strength were not significant. SIGNIFICANCE: Besides combinations of chemical-cured core build-up composites with light or dual-cured adhesives as recommended by the manufacturer, also combinations with adhesives of other manufacturers are compatible, provided that the pH is higher than approximately 4.3. Chemical-cured core build-up composites combined with light-cured adhesives with a pH as low as 1.8 lead to a significantly lower stress and bond strength compared to other combinations. Light irradiation during curing through a combination of a chemical-cured composite and a low pH adhesive reactivates polymerization.

Acids↗
PubMed2006

The influence of environmental conditions on the material properties of setting glass-ionomer cements.

OBJECTIVES: Aim of this study was to investigate the influence of temperature on the setting time and compressive strength of two conventional glass-ionomer cements (GIC's) and to determine the influence of storage medium, oil or water and storage time. MATERIALS AND METHODS: Two conventional GIC's, Ketac Molar (3 M-ESPE Dental Products, Seefeld, Germany) and Fuji IX Fast (GC Corp., Tokyo, Japan) were used to perform flow property tests and compression tests. Flow property measurements were performed using a displacement rheometer at six different temperatures. From the results of the rheometer tests, the working times and setting times could be determined. The samples for the compressive tests were stored at four different temperatures and in two different media. Testing took place at five time intervals reaching from 1 h to 3 months. RESULTS: The results of rheometer tests showed that a temperature increase speeded up the setting reaction significantly. The compressive strength results showed a jump in time as a result of the higher curing temperature but no long-term strength effect was observed. Materials curing in oil reached a significantly higher compressive strength compared to storage in water and Fuji IX Fast is significantly stronger than Ketac Molar. SIGNIFICANCE: It was concluded that a temperature between 333 and 343 K almost sets conventional GIC's on command and improves the early compressive strength.

Analysis of Variance↗
PubMed2006

Micro analysis of metals in dental restorations as part of a diagnostic approach in metal allergies.

In dentistry, a variety of potentially allergenic metals are used, such as mercury, palladium, nickel, gold, chromium, cobalt and other metals. This paper describes a diagnostic approach from a dentist's point of view, which enables analysis of metals in a patient's oral cavity. If metal allergy is suspected, a micro analysis can be used to determine which metals are present in the restorations. When the exact composition of the dental materials is known, the patient can be tested in vivo (patch test) and/or in vitro (lymphocyte proliferation test) to reveal sensitization. Two patients with nickel allergy are described where removal of nickel-containing materials (bridge and orthodontic wire) resulted in the marked alleviation of symptoms and improvement of health. Finally, if allergy to specific metals has been established, the restorations containing the implicated metals should be removed to discontinue the exposure and thus facilitate the patient's health.

Dental Restoration, Permanent↗
PubMed2005

Microtensile bond strength of different components of core veneered all-ceramic restorations. Part II: Zirconia veneering ceramics.

OBJECTIVES: The purpose of this research was to investigate microtensile bond strength between one type of zirconia substrate and various commercial veneer ceramics. The effect of an optional liner material between the core and veneer was also evaluated where applicable. METHODS: Bilayered zirconia veneer discs were fabricated from five layering and two pressable veneer ceramics. Additionally, discs from each veneer ceramic were prepared. The discs were cut into microbars of 6 mm in length and 1mm in cross-section. The microtensile bond strength was tested in a universal testing machine. The fracture surfaces of the microbars were examined with scanning electron microscopy (SEM) and EDAX. RESULTS: The microtensile strength of Rondo Dentine and Lava Dentine veneer ceramics were significantly higher than the other tested veneer ceramics. Furthermore, the layered systems Rondo Dentine and Ceram Express were significantly stronger than the other tested core-veneer ceramics. The application of liner material dramatically affected the bond strength and failure mode, which was also material dependent. SEM analysis showed that two pressable veneers and one type of layering veneer ceramic failed entirely cohesively in veneer side while the remaining test groups had higher percentage of interfacial failure. SIGNIFICANCE: Selection of stronger veneer ceramics which have good bond strength with zirconia can reduce the chances of chipping and delamination under function. The liner material should only be used with some layering veneers but not in combination with pressable veneers as it will result in weakening of the microtensile bond strength.

Analysis of Variance↗
PubMed2005

Fatigue testing of enamel bonds with self-etch and total-etch adhesive systems.

OBJECTIVE: Etching of enamel by self-etching adhesive systems is not as pronounced as with phosphoric acid employed with most total-etch adhesive systems. This may result in differences in the effectiveness of the bonds for the two types of systems. The aim of this study was to compare two such systems by bond strength and fatigue testing. MATERIALS AND METHODS: Shear bond strengths for Single Bond (SB) and Adper Prompt-L-Pop (PLP) were obtained on bovine enamel surfaces. Fatigue measurements were made with the same test fixtures using cyclical loading at 2 Hz for a maximum of 10(5) cycles or until the bond failed. Four selected loads between 40 and 70% of the shear bond strength were tested for each adhesive and the number of cycles to failure was recorded. S-N curves were constructed from the data and fatigue stress limits were determined. The Mann-Whitney U-test and t-tests were used for statistical comparisons of the results. SEM analysis of resin tag formation into enamel surfaces was carried out. RESULTS: A significantly greater bond strength was found for SB (25.3 MPa) than for PLP (19.2). Sustainable stresses after 10(5) load cycles were substantially lower than the corresponding shear bond strengths and fatigue limits were found to be 8.4 MPa for PLP and 14.6 MPa for SB. The ratio of fatigue limit to bond strength was less for PLP (44%) than for SB (57%). Resin tag penetration into enamel was substantially less for PLP than for SB. SIGNIFICANCE: Fatigue testing in conjunction with bond strength testing can provide a better means for assessing the performance of adhesive systems used for bonding to enamel.

Acid Etching, Dental↗
PubMed2005

The effects of common errors on sealing ability of total-etch adhesives.

OBJECTIVES: This study evaluated the effect of errors commonly made in using total-etch adhesives, on the resulting bond strength, fluid movement and nanoleakage of resin dentin bonds. METHODS: Two total-etch adhesives were used for bonding to dentin according to the manufacturers' recommendations, with meticulous solvent evaporation (control), or with the introduction of common bonding errors-wet bonding without solvent evaporation (no evaporation), and dry bonding. RESULTS: The 24-hour bond strength of the control was significantly higher than the other groups (p <0.05). For all groups, the higher initial permeability declined significantly after 24 h. The fluid movement across bonded dentin was similar in the control and dry bonding for both adhesives, whereas significantly higher permeability (p<0.05) was recorded for the no evaporation groups even after 24 h. Extensive silver impregnation within hybrid layers was seen by TEM in the no evaporation and dry bonding specimens after 24 h. Dry bonding caused collapse of the collagen matrix and interfered with resin infiltration. In contrast, inadequate solvent evaporation and/or residual water during dentin bonding results in dilution or incomplete polymerization of the resin, leading to severe nanoleakage formation. SIGNIFICANCE: Increased permeability associated with incomplete solvent evaporation in total-etch adhesives may lead to poor bond strength.

Acid Etching, Dental↗
PubMed2005

Polymerization shrinkage and contraction stress of dental resin composites.

OBJECTIVE: The aim of this study was to evaluate the shrinkage, contraction stress, tensile modulus, and the flow factor of 17 commercially available dental resin composites. METHOD: The volumetric shrinkage measurements were performed by mercury dilatometry, and the contraction stress and tensile modulus were determined by means of stress-strain analysis. The statistical analysis was conducted by ANOVA and Tukey's post hoc test, and linear regression. RESULTS: Strong linear correlation for most resin composites were found for (i) contraction stress and shrinkage (ii) contraction stress and tensile modulus, and (iii) shrinkage and tensile modules. For most of the materials the unpolymerized resin content determines the amount of shrinkage, contraction stress and tensile modules. The pre-polymerized clusters in Heliomolar results in improved shrinkage/contraction stress properties. The shrinkage/contraction stress for Filtek Z100, Aelite Flo, and Flow-it was too high for the amount of resin in the resin composite. This was rationalized by high polymerization rates, a flow factor, and the nature of the resin. SIGNIFICANCE: High shrinkage and/or high contraction stress may lead to failure of the bond between the resin composites and the tooth structure. This study shows that the unpolymerized resin content determines the amount of shrinkage, contraction stress and tensile modules. Therefore, using pre-polymerized clusters will improve shrinkage/contraction stress properties, as was shown in Heliomolar, while high polymerization rates, and low flow factors have a deteriorative effect on the shrinkage/contraction stress properties.

Acrylic Resins↗
PubMed2005

Low-shrinkage dental restorative composite: modeling viscoelastic behavior during setting.

Much attention has been directed toward developing dental direct restorative composites that generate less shrinkage stress during setting. The aim of this study was to explore the viscoelastic behavior of a new class of low-shrinkage dental restorative composite during setting. The setting behavior of an experimental oxirane composite has been investigated by analyzing stress-strain data with two-parametric mechanical models. Experimental data were obtained from a dynamic test method, in which the setting light-activated composite was continuously subjected to sinusoidal strain cycles. The material parameters and the model's predictive capacity were analyzed with validated modeling procedures. The light-activated oxirane composite exhibited shrinkage delay and low polymerization shrinkage strain and stresses when compared with conventional light-activated composite. Noise in the stress data restricted the predictive ability of the Maxwell model to the elastic modulus development of the composite only. Evaluation tests of their potential as restorative material are required, to examine if the biocompatibility and mechanical properties after setting of oxirane composites are acceptable for dental use.

Biocompatible Materials↗
PubMed2005

Effect of conditioning time of self-etching primers on dentin bond strength of three adhesive resin cements.

OBJECTIVES: To evaluate the effect of increasing the dentin conditioning time with self-etching primers of different aggressiveness (pH) on the microtensile bond strength (muTBS) of three resin cements. MATERIALS AND METHODS: Pre-cured composite blocks were cemented with M-Bond, Bistite II DC, or Panavia F to flat occlusal dentin surfaces of human third molars, which were conditioned with M-Bond or Bistite II-primer for 30, 60 or 180 s or with Panavia-primer for 60 or 180 s. Each dentin-composite block assembly (four in each group) was longitudinally sectioned to obtain 1x1 mm microbars and tested for the muTBS. The morphology of the conditioned dentin surface and the hybrid layer was examined with SEM. RESULTS: Extending the primer conditioning time for Bistite II DC from 30 to 60 s significantly increased the muTBS (p<0.001) but did not further increase from 60 s to 180 s. For M-Bond there was only a significant increase from 30 to 180 s (p<0.05). For Panavia F the primer-conditioning time had no influence on the muTBS. SEM observations of conditioned dentin showed that the Bistite II DC and M-Bond self-etching primers with the lowest pH completely dissolved the dentin smear layer and plugs and formed well-defined hybrid layers. This was not found for Panavia F. SIGNIFICANCE: Dentin bond strength of resin cements using more aggressive self-etching primers is improved by increasing the conditioning time. To enable resin infiltration of highly filled resin cements, sufficient smear layer dissolution is necessary.

Acid Etching, Dental↗
PubMed2005

Relations in color among maxillary incisors and canines.

OBJECTIVES: To establish the strength of color relation among the maxillary central incisor, lateral incisor and canine teeth by using digital photography. This relation might be useful for the color reconstruction of the missing part of a tooth from the color obtained from neighboring teeth. METHODS: The L*a*b* values of the maxillary incisors and canines were determined in 100 subjects. Paired t-tests, Pearson correlations and linear regression analyses were used to describe the relation of the L*a*b* values between the three teeth for each segment (cervical, middle and incisal). RESULTS: The mean L*a*b* values of the canines differed statistically significantly from the values of the central incisors (p<0.001) except for L* and a* values in the cervical segment between the lateral incisor and canine. The color differences between the incisors were statistically significant in fewer cases. The relation in color was the highest between the cervical segments of the three teeth, with respect to L* (r = 0.45-0.65; p < 0.001), b* (r = 0.49-0.55; p < 0.001), and a* (r = 0.38-0.61; p < 0.001), and no relation was found between the incisal segments of central incisor and canine. SIGNIFICANCE: There is a relation in color between the maxillary incisors and canines, which is stronger between the cervical than between the middle and incisal segments. Therefore, the color prediction is most reliable when the cervical parts of the teeth are used.

Adult↗
PubMed2005

The influence of design parameters on the FEA-determined stress distribution in CAD-CAM produced all-ceramic dental crowns.

INTRODUCTION: Knowledge of factors, which influence stress and its distribution is of key importance to the successful production of durable all-ceramic restorations. The objective of this study was to evaluate, by finite element analysis (FEA), the influence of the shape of the preparation and the cement layer on the stress distribution in CAD-CAM produced all-ceramic crowns and in their cement layer. MATERIAL AND METHODS: The CAD models of multi-layer all-ceramic crowns for posterior tooth 46 of three patients produced with CAD-CAM-technology were translated into a three-dimensional FEA program. The stress distribution due to the combined influences of bite forces, residual stresses caused by the difference in expansion coefficient of the two ceramic layers, and the influence of shrinkage of the cement was investigated. RESULTS: The tensile stresses in the crown for the chamfer knife-edge preparation might put the integrity of the currently available ceramic materials at risk, while a non-uniform cement layer might result in stresses exceeding the bond strength. It was concluded that for long lasting restorations in the posterior region it is advisable to make a chamfer with collar preparation, the cement layer as uniform, and the difference in thermal expansion for the two ceramics as small as possible. SIGNIFICANCE: This study indicates that for full ceramic crowns in the posterior region, specific design rules should be followed, and that FEA utilizing CAD-CAM data can be a successful tool to develop design guidelines for all-ceramic restorations.

Bite Force↗
PubMed2005

Finite element analysis model to simulate the behavior of luting cements during setting.

OBJECTIVES: Besides the fixation of the restoration, an important function of dental luting cements is to seal the gap between tooth and restoration. However, as a result of adhesion, curing contraction is hindered, creating stresses. To maintain the seal these stresses neither exceed the bond nor the cohesive strength of the cement. The aim of this study was to evaluate a rather simple model, which mimics the setting behavior of luting cements based on the division of the setting process into a liquid, visco-elastic and elastic phase, for its suitability to predict in Finite Element Analysis (FEA) the magnitude of the setting stresses occurring clinically. METHODS: Commercial luting cement, RelyX ARC, was used in this study. In a dynamic test set-up the stresses, the elastic strain, and the shrinkage were determined. Two layers with different thicknesses and different ratios between bonded and free surface (C-factor) were examined. The parameters were used in three-dimensional FEA models. The experimental contraction stresses were compared with the results of the FEA. RESULTS: In cement layers with uniform layer thickness, it is possible to predict the contraction stresses with the found parameters. The smallest plastic deformations and contraction stresses were found in the thinnest layer. The studied model was reliable in predicting the experimental stresses. SIGNIFICANCE: The results of this study may be used for the prediction using FEA of the actual stresses occurring in dental restorations.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2005

The influence of multiple firing on thermal contraction of ceramic materials used for the fabrication of layered all-ceramic dental restorations.

OBJECTIVES: During the production of layered all-ceramic restorations transient and/or residual thermal stresses may be formed which may affect a restoration's longevity. The aim of this study was to evaluate the influence of multiple firings on the thermal behavior of veneering porcelains and a ceramic core. METHODS: The materials tested were: Empress 2 Core, Empress 2 Veneer and Eris glass-ceramics, Carrara Vincent and an experimental leucite-based veneering porcelain, Vitadur-Alpha aluminous porcelain, and two porcelains designed for titanium (i.e. Duceratin Dentine and Enamel). The thermal contraction coefficient of the materials was measured by means of dilatometery. The thermal contraction coefficient was measured during cooling and calculated over the temperature range of 450-20 degrees C by linear regression. One and two-way analysis of variance together with Tukey post-hoc tests were used as statistical analysis. RESULTS: Repeated firing affects the thermal contraction coefficients of Empress 2 Veneer, Carrara Vincent porcelain and the experimental porcelain. The thermal contraction coefficients of Empress 2 Core were significantly different from Vitadur-Alpha, Carrara Vincent, experimental porcelain, and Duceratin porcelains. The contraction coefficients of Empress 2 Veneer and Eris were closest to that of Empress 2 Core. SIGNIFICANCE: The Empress 2 Core and Eris glass-ceramics, the aluminous porcelain and Duceratin porcelains showed better thermal stability after repeated firing than leucite porcelains. It can be concluded that due to the thermal stability of glass-ceramic materials, layered all-ceramic restorations of these materials may perform better.

Aluminum Silicates↗
PubMed2005

The effects of thermal mismatch and fabrication procedures on the deflection of layered all-ceramic discs.

OBJECTIVES: Residual thermal stress caused by thermal incompatibility of ceramic core and veneering porcelain in all-ceramic restorations might induce fracture or distortion of the restoration. The aim of this study was to evaluate the thermal compatibility between a ceramic core and veneering porcelain by measuring the bending of layered discs and to compare the result with the thermal mismatch values. METHODS: Thirty-five heat-pressed ceramic core discs were made and divided into seven groups (n=5). One group of discs was used as control and subjected only to firing cycles, while the other groups of discs were veneered with porcelains. The mismatch of thermal contraction coefficient values of the Empress 2 Core and veneer porcelains used ranged from -3.7 to 3.8 ppm/ degrees C. RESULTS: The Empress 2 Core disc without a veneer (control) was not significantly deflected by the fabrication procedures. The deflection of layered discs was strongly influenced by the degree of thermal mismatch during fabrication procedures. The greatest deflection occurred during the 2nd dentin firing and with the largest mismatch either positive or negative. SIGNIFICANCE: The deflection test proved to be a reliable test method for the evaluation of thermal compatibility of porcelains in all-ceramic systems.

Dental Porcelain↗