Biomedical subjects

Albert J Feilzer

Publications and source records attributed to Albert J Feilzer.

36 records · Page 2Linked to original sources

PubMed2005

Early and long-term wear of 'fast-set' conventional glass-ionomer cements.

OBJECTIVE: Fast setting high viscous glass-ionomer cements have been introduced to reach the set state sooner and to improve early mechanical properties. The aim of this study was to investigate whether 'fast-set' cements have improved the early three-body wear. METHOD: The three-body wear of four glass-ionomer cements was measured after 1, 4, 7, 30, 90, and 365 days. The chemical composition of the cements was determined with EDAX. The particle size of the powders was determined with a Mastersizer 2000. RESULTS: The three-body wear of Fuji IX Fast was only slightly less than that of 'regular-set' Fuji IX, but Ketac Molar Quick showed a higher wear compared to the regular-set Ketac Molar. The wear rate of all four glass-ionomer cements decreased over a period of 1 year and could be described by second order reaction kinetics and depended on polyalkenoic acid content, chemical composition, and the size of the glass particles. SIGNIFICANCE: Based on the results of this laboratory study on long-term wear, the glass-ionomer cements investigated may compete with composites, but the early wear characteristics should be further improved. Furthermore, a better understanding of the wear and reaction behavior of glass-ionomer cements is obtained.

Electron Probe Microanalysis↗

PubMed2005

The influence of surface treatment and luting cement on in vitro behavior of two-unit cantilever resin-bonded bridges.

OBJECTIVES: The purpose of this study was to find the optimal combination of surface pretreatment and luting cement for two-unit CoCr cantilever resin-bonded bridges. METHODS: Tensile peel, load and torque strength tests were performed using flat ground bovine teeth as substrate, four different commercially available luting cements, and CoCr beams as simulated cantilever resin-bonded bridges. The CoCr beams were pretreated with sandblasting or Rocatec. Tensile peel, load and torque strengths were determined 72h after cementation. The effects of sandblasting and Rocatec pretreatments on the morphology of the CoCr surface was investigated with SEM and EDAX analysis. RESULTS: The average strengths of the three tests showed that Rely X ARC, Resiment and Panavia were the same and significantly lower than UniFix. Rocatec showed a significantly higher average bond strength than sandblasting considering all tests. The peel test, which showed the lowest failure values, is clinically the most relevant test. This test showed that only UniFix as luting cement with sandblasting as pretreatment generates a significantly higher bond strength compared with the other cements and pretreatments. SIGNIFICANCE: Based on the results of this study the use of Unifix with sandblasting as metal surface pretreatment, is preferred for cementation of two-unit CoCr cantilever resin-bonded bridges.

Aluminum Oxide↗

PubMed2005

Microtensile bond strength of different components of core veneered all-ceramic restorations.

OBJECTIVES: The present study aims to evaluate the core-veneer bond strength and the cohesive strength of the components of three commercial layered all-ceramic systems. Two surface treatments for the core surface finish and different veneering ceramics with different thermal expansion coefficients (TEC) were applied. The selected systems were two CAD-CAM ceramics; Cercon and Vita Mark II and one pressable system; (IPS)Empress 2 for layering technique. METHODS: Standardized core specimens were fabricated according to the manufacturer's instructions, or polished with 1200 siliconcarbide polishing paper. The core specimens were veneered with either its manufacturer's veneer or an experimental veneer with higher TEC. The obtained micro-bars were subjected to the microtensile bond strength test. The obtained data were analyzed using one and two-way ANOVA. A finite element analysis (FEA) model of the test setup was analyzed. Scanning Electron Microscopy (SEM) was carried out at the fracture surface. RESULTS: The core materials were significantly stronger than the veneering materials and the layered core-veneer specimens of which the results were statistically comparable. Polishing the core surfaces did not have an effect on the core-veneer bond strength. Experimental veneer with higher TEC resulted in massive fractures in both the core and veneering material. SEM and FEA demonstrated fracture pattern and mechanism of failure. SIGNIFICANCE: The core-veneer bond strength is one of the weakest links of layered all-ceramic restorations and has a significant role in their success. To exploit fully the high strength of zirconium oxide cores, further research work is needed to improve its bond with its corresponding veneering material.

Biocompatible Materials↗

PubMed2005

Application of biologically-oriented dentin bonding principles to the use of endodontic irrigants.

PURPOSE: To compare the removal of smear layer and the structure of the hybrid layer formed after the use of EDTA or MTAD solutions when used as a final flush. METHODS: Single-rooted extracted premolars (n=18) were collected and treated for root canal therapy using NaOCl irrigation followed by a final rinse of 17% EDTA, Biopure MTAD, or saline (negative control). The roots were obturated with gutta-percha and a hydrophilic HEMA-containing root canal sealer. The TEM specimens were impregnated with 50% silver nitrate to visualize sealing imperfections and nanoleakage. The structure of the coronal, middle and apical parts of root canal walls was examined using transmission electron microscopy. RESULTS: After NaOCl irrigation, a final rinse with BioPure MTAD or 17% EDTA completely removed the 2 microm-thick smear layer on mechanically instrumented root canal walls. The BioPure MTAD hybrid layer was thicker than the 17% EDTA hybrid layer. Both the BioPure MTAD and EDTA caused a collapse of the dentin matrix structure which impeded sealer infiltration and the formation of high quality hybrid layer bonding. The hybrid layers created in smear layer-covered dentin exhibited less potential for nanoleakage than the MTAD or EDTA hybrid layers.

Bicuspid↗

PubMed2004

Thermal dimensional behavior of dental ceramics.

The aim of this study was to characterize the relation of dimensional changes of dental ceramic materials as function of temperature. The thermal dimensional behavior of one glass ceramic core, four commercially available veneering porcelains and two experimental veneering porcelain materials was determined on cooling from 450 degrees C to 20 degrees C by means of a vertical differential pushrod thermal dilatometer. The thermal dimensional behavior of the ceramic materials was expressed in three different ways: as linear relation with a linear line fitting procedure; as non-linear relation by a quadratic curve fitting procedure and according to ISO 9693 by a thermal expansion coefficient. For all ceramic materials except the one consisting of aluminum oxide fillers, the thermal dimensional behavior is best described with the polynomial function: Deltal/l = C + alpha1T + alpha2T2. The description of the thermal expansion coefficient according to the ISO standard on metal is not appropriate for the prediction of a thermal incompatibility of ceramic materials. Except for Vitadur Alpha, the ceramics materials tested showed non-linear expansion; their thermal dimensional behavior can be best described according to the quadratic relation method, second by the linear relation, third as recommended by ISO.

Biocompatible Materials↗

PubMed2004

The effect of adhesives with various degrees of hydrophilicity on resin ceramic bond durability.

OBJECTIVES: To investigate the role of different acid surface-treatments and hydrophilic and hydrophobic bonding agents on resin ceramic bond durability. METHODS: Two resin cements, Tetric Flow and Nexus 2, were applied to CAD/CAM Cerec Vitablocs with six bonding strategies: (1) HF-etching and silanization, (2) HF-etching, silanization and application of a hydrophilic bonding agent, (3) HF-etching, silanization and application of a hydrophobic bonding agent, (4) H3PO4-treatment and silanization, (5) H3PO4-treatment, silanization and application of a hydrophilic bonding agent, and (6) H3PO4-treatment, silanization and application of a hydrophobic bonding agent. The hydrophilic agents were Syntac Single-Component and OptiBond Solo Plus. The hydrophobic agent was Visio Bond. After 1d water storage at 37 degrees C, 1 mm2 microbars were cut for the microtensile bond strength test (microTBS test). The microbars were subjected to a tensile load using a modified testing device immediately after trimming and after 7 and 28d water storage. The fractured specimens were examined with a stereomicroscope and scanning eslectron microscopy to determine the failure mode. RESULTS: HF-etching resulted in significantly higher microTBS than H3PO4-treatments (p < 0.001) The 1d microTBS with hydrophilic bonding agents was significantly higher than with the hydrophobic bonding agent (p < 0.001) but decreased with time after water storage ( p < 0.001) while bonds with the hydrophobic bonding agent remained stable. The percentages of adhesive failures after 1, 7, and 28d were 60, 86, and 94, respectively. SIGNIFICANCE: Bonding agents that contain hydrophilic monomers have a negative influence on the resin ceramic bond durability.

Acid Etching, Dental↗

PubMed2004

The apparent increase of the Young's modulus in thin cement layers.

OBJECTIVES: The bond of adhesive luting cements to the tooth tissues and restorative materials is expected to hinder their transverse contraction for the layer thickness applied in dental restorations. It was hypothesized that the hindering of the transverse deformation will influence the relation between stress and strain (the stiffness) in the direction perpendicular to the substrate surface. The aim of this study was to investigate the relation between cement layers with different ratio between bonded and free surface (C-factor) and the stiffness of these layers, i.e. an apparent increase of the Young's modulus of the dental luting cement. METHODS: A commercial luting cement RelyX ARC (3M, St Paul, MN, USA) was used in this study. The 'real" Young's modulus and the Poisson ratio were determined and these values were used in models with layers with different C-factors (0.5, 1.0, 2.0, 3.0, 4.0, 5.0 and 6.0) in a three-dimensional Finite Element Analysis program (FEMAP, E.S.P., Maryland Height, MO, USA). The apparent Young's modulus was measured for layers with thicknesses of 0.5 mm (C = 6.0) and 6.0 mm (C = 0.5) and compared with the results of the Finite Element Analysis (FEA) analysis. RESULTS: The apparent Young's modulus in the 0.5 mm layer was 20% higher than the apparent Young's modulus in the 6.0 mm layer. This result was confirmed by the results of the F.E. analysis. For very thin layers the stiffness will be 25% higher than the Young's modulus. SIGNIFICANCE: The hindering of the transverse contraction has to be taken into account studying the mechanical properties of dental luting cements because it influences the behavior of these luting cements in thin layers.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2004

Shear bond strength of different types of luting cements to an aluminum oxide-reinforced glass ceramic core material.

OBJECTIVE: The aim of this study was to find the optimal choice of luting cement to Synthoceram, an aluminum oxide-reinforced glass ceramic material. The bond strength of five different commercial luting cements to the ceramic material was evaluated. The effect of surface treatments, etching, sandblasting, silanizing, and combinations of these treatments was also investigated. METHODS: Shear bond strength tests were performed using the ceramic material as substrate with each of the luting cements. Cements rods were prepared on pre-treated ceramic surfaces. The shear bond strength was determined 24 h after cementation. The effect of surface treatments: etching, sandblasting, and sandblasting followed by etching, respectively, on the morphology of the material, was investigated with SEM. RESULTS: The shear bond strength increases significantly from Ketac Cem, Rely X Luting, Fuji Plus, Panavia F to Xeno Cem. The surface treatments etching and/or sandblasting followed by silanization generally provide the highest bond strength values. SIGNIFICANCE: Based on the results of this study, the use of resin composite based cements is preferred for cementation of an all-ceramic restoration with an aluminum oxide-reinforced glass ceramic base. Surface treatment of etching and/or sandblasting followed by silanization is recommended.

Aluminum Oxide↗

PubMed2004

Relation in color of three regions of vital human incisors.

OBJECTIVES: For an adequate color reproduction, it is very valuable to quantify the color distribution in human teeth accurately. The aim of this study was to determine the color relation between three tooth segments (cervical, middle and incisal) in vital upper central incisors, using digital photography. METHODS: Digital recordings of 64 upper right central incisors were made using a standardized head-camera setup. The L*a*b* values of three regions were attained from the standardized digital images using software. RESULTS: There were statistically significant linear correlations for L* and b* between the three tooth segments (all r's > or = 0.60; p < 0.001). The correlation coefficient for a* was lower compared to L* and b* values. The L* and b* values of cervical and incisal tooth segment could be calculated from L* and b* values of middle tooth segment. SIGNIFICANCE: These results show the potency for color mapping of a whole tooth surface by extrapolation of color values of only one part of the surface.

Adult↗

PubMed2004

Mechanical properties of glass ionomer cements affected by curing methods.

OBJECTIVE: The primary objective of the study was to assess the influence of externally applied 'command' set applications on the mechanical properties of several commercially available conventional glass ionomer cement (GIC). METHODS: Four different restorative GICs cements (Fuji IX FAST, Fuji IX, Ketac Molar Quick, Ketac Molar) were cured using three different methods, e.g. standard curing conditions (SC), ultrasonic excitation (UC) and by an external heat source (HC). The compressive strength of these samples was measured and the groups were compared using one-way ANOVA. A standard thermocouple (K-type) measured the temperature in GIC during curing. RESULTS: In general all experiments showed an increase in strength going from SC, UC to HC. Especially, the compressive strength of Fuji IX FAST and Ketac Molar increased by UC and HC compared to the SC values. The compressive strength of Fuji IX FAST as a function of time showed an increase in strength during 28d. There was a clear relationship between the temperature in the sample (SC<UC<HC) and the compressive strength of the GICs. SIGNIFICANCE: An increase in strength was found, especially at the early curing time. Enhanced material properties at early curing time can improve the survival rate of GICs in the clinical situation. Ultrasonic excitation can be used as a 'command' set method and improves the properties of GIC at early setting time.

Analysis of Variance↗

PubMed2004

In situ transformation of glass-ionomer into an enamel-like material.

PURPOSE: To assess the nature of clinically detectable alterations in glass-ionomer after long-term clinical service. METHODS: In addition to clinical macro pictures, SEM was carried out on replicas and on two sectioned primary molars SEM-EDAX analysis was performed to determine chemical transformation in the glass-ionomer. Also with SEM-EDAX, the composition was determined of a partially removed half-year old sealant. RESULTS: The clinically observed altered optical aspect and increased hardness could be related with surface structure changes as identified by SEM. The changed glass-ionomer showed a continuous integration with the adjacent enamel. The SEM-EDAX analysis revealed an increase of calcium and phosphorus in the surface layer, tentatively suggesting a sort of additional "mineralization" of the material. This phenomenon was only observed for restorations that had minimally 2-3 years in vivo dwell time.

Adolescent↗

PubMed2004

Effectiveness of preparation guidelines for an all-ceramic restorative system.

PURPOSE: To evaluate, in a clinical field-test, the implementation of manufacturer's preparation guidelines for the all-ceramic CICERO system. METHODS: General dental practitioners from the northwest region of The Netherlands were asked to make complete crown preparations in accordance with the specific guidelines of the CICERO system. 3,446 tooth preparations were evaluated with regard to shoulder angle, shoulder width and top angle. They were quantified using a special software program. The results were compared with criteria defined in the manufacturer's preparation guidelines. RESULTS: On a multivariate level all (main and interaction) effects were significant (P < 0.05) excluding the interaction effect of the location of measurement on the tooth by the upper or lower jaw. The value of the shoulder angle showed a strong relation with the tooth position in the mouth as well as with the location of measurement on the tooth. The shoulder width in the lower jaw was significantly smaller when compared to the width in the upper jaw. The shoulder width of the lower incisors was the smallest and also showed the largest variance per tooth. On a group level (incisor, cuspid, premolar, molar), except for the shoulder width of the lower incisors, the average values of all preparation parameters were within the borders as defined in the preparation guidelines of the manufacturer. However, on an individual tooth level nearly all preparations showed to have one or more locations with imperfections.

Bicuspid↗

PubMed2003

The influence of the veneering porcelain and different surface treatments on the biaxial flexural strength of a heat-pressed ceramic.

STATEMENT OF PROBLEM: The strength of all-ceramic restorations can be adversely affected by surface defects, leading to restoration failures. Additionally, when a 2-layer all-ceramic restoration is required for esthetic purposes, part of the stronger ceramic core material is replaced by veneering porcelain. PURPOSE: This study evaluated the effect of different surface treatments on the strength of a ceramic core material and veneering porcelain, as well as the influence of veneering porcelain on the strength of a 2-layer ceramic structure. MATERIAL AND METHODS: Fifty heat-pressed ceramic cores and 30 veneering porcelain discs (17 mm diameter x 2 mm) were made. From the ceramic core group, 20 discs were selected and reduced to a thickness of 1 mm and veneered with 1 mm of porcelain. These specimens were divided into 2 groups of 10 each. The remaining 30 ceramic core and the 30 veneering porcelain discs were divided into 2 sets of 3 equal sized groups (n=10). Ceramic core groups were prepared for testing having the following surfaces: airborne-particle abrasion, ground, and overglazed. Veneering porcelain groups were tested: as fired (no additional treatment), ground, and overglazed. Biaxial flexural strength was measured using the ball-on-ring test method. All specimens were loaded to fracture. One and 2-way analysis of variance were used to analyze the data (alpha=.05). RESULTS: The ceramic core discs were significantly (P=.001) stronger than the veneering porcelain discs for the airborne-particle abrasion, as-fired, and ground surface treatments (82 +/- 11 MPa vs 51 +/- 8 MPa and 93 +/- 14 MPa vs 60 +/- 6 MPa, respectively). For the overglazed treatment, there was not a significant difference between the core (115 +/- 1 4 MPa) and the veneer materials (107 +/- 14 MPa). The ground 1-layer core was significantly (P=.015) stronger (93 +/- 14 MPa) than the 2-layer with the core tested in tension (72 +/- 19 MPa). There was no significant difference between 1-layer veneer overglazed (107 +/- 14 MPa) and 2-layer discs when tested with the veneer in tension (105 +/- 16 MPa). CONCLUSION: The overglazed surface treatment significantly improved the strength of the materials tested, as well as the strength of 2-layer discs with the veneer in tension. The veneering porcelain influenced the strength of 2-layer specimens only when tested with the ground ceramic core surface in tension.

Analysis of Variance↗

PubMed2003

Modeling of the viscoelastic behavior of dental light-activated resin composites during curing.

OBJECTIVE: Three models consisting of springs and dashpots were investigated to describe the viscoelastic behavior of a commercial light-activated restorative composite during curing. METHODS: Stress-strain data on Z100 were recorded by means of a dynamic test method performed on a universal testing machine. The model was tested by matching its response to experimental data and the material parameters, E (Young's modulus) and eta (viscosity), associated with the model were calculated. RESULTS: The universal testing machine generated reliable stress-strain data on the fast curing, light-activated resin composite during curing. The high polymerization rate of Z100 had a negative effect on the viscous flow capability of the material. A predictive model of the viscoelastic behavior of Z100 during curing was carried out, using the Maxwell model for the initial 3 min in the curing process and the Kelvin model for the remainder of the process. SIGNIFICANCE: Dental researchers analyzing shrinkage stress problems by mathematical modeling can obtain a good quantitative estimate of the shrinkage stress development of Z100 before the restoration is actually made.

Composite Resins↗

PubMed2003

Microtensile bond strength testing of luting cements to prefabricated CAD/CAM ceramic and composite blocks.

OBJECTIVES: To investigate the Microtensile bond strength (microTBS) and failure mode of resin cements bonded to composite and ceramic CAD/CAM blocks following various surface treatments. METHODS: Paradigm composite blocks and Cerec Vitablocs received three surface treatments following the control treatment of surface grinding with 600 SiC grit. (1) Application of adhesive resin (Adh), (2) etching with hydrofluoric acid and silanization (HF+S) or (3) combination of the previous two treatments (HF+S+Adh). Three resin cements (Tetric Flow, Nexus 2, RelyX ARC) were applied to these surfaces and built-up in layers. After 24 h water storage at 37 degrees C, the non-trimming version of microTBS test was used to produce 1 mm(2) microbars. The Microbars were subjected to a tensile load using a modified testing device. The broken specimens were examined with a stereomicroscope and SEM to determine the failure mode. RESULTS: All control and adhesive treated groups of the ceramic substrate showed premature debonding during cutting. The overall mean microTBS for the three resin cements bonded to ceramic following HF+S and HF+S+Adh surface treatment, was 27 and 29.2 MPa and for the resin cements bonded to composite substrate was 42.3 and 54.2 MPa, respectively. The mode of failure was 98% adhesive with composite as a substrate and 68% mixed failures with ceramic as a substrate. CLINICAL SIGNIFICANCE: CAD/CAM restorations fabricated from processed composite blocks may have advantage over the ceramic blocks with regard to the higher bond strength with resin cements.

Adhesives↗

PubMedDate not supplied

Porcelain-veneered computer-generated partial crowns.

OBJECTIVE: It would be advantageous to be able to use computer-aided design and manufacturing to fabricate a restoration that can be layered with a conventional porcelain veneer in the occlusal region, thus optimizing esthetics, function, and strength. This case study reports the laboratory technique and the clinical performance of 38 partial crowns fabricated with computer technology and veneered with porcelain. METHOD AND MATERIALS: Twenty-one mandibular and 17 maxillary molars in 27 patients were prepared for partial crowns. The occlusal surfaces were lowered (1.5 to 2.0 mm), deep shoulders (1.5 mm) were prepared around the functional cusps, and 1.0-mm-deep shoulders were prepared in the proximal gingival regions. The nonfunctional cusps were prepared with an occlusal shoulder at approximately a right angle with the axial surfaces of the seat. In the computer-aided design procedure, the occlusal table was reduced to 1.4 mm above the preparation surface. The marginal ridge points, the marginal ridge line, the equator line, and the fissure line heights were adjusted accordingly. RESULTS: The lowest occlusal table thickness was 1.1 mm in six partial crowns, 1.2 mm in 26 partial crowns, and 1.3 mm in six partial crowns. The lowest occlusal table thickness of the porcelain veneers varied between 0.4 and 0.6 mm. The total occlusal table thickness thus was 1.5 mm or more. Clinically, no fractures occurred during an observation period varying between 1 and 4 years after placement. CONCLUSION: Computer-aided design and manufacturing technology is also convenient for partial crown preparation design with shoulder finish lines.

Cementation↗

PubMedDate not supplied

A literature review of two-unit cantilevered FPDs.

PURPOSE: This review article evaluated the clinical performance of two-unit cantilevered, single-abutment, single-pontic, resin-bonded fixed partial dentures (FPDs) by comparing them to noncantilevered resin-bonded FPDs with two abutments and a single pontic. MATERIALS AND METHODS: One publication on design principles and 11 clinical research studies were selected by searching two databases. RESULTS: Six of the studies dealt exclusively with two-unit cantilevered resin-bonded FPDs, and five studies compared fixed-fixed design resin-bonded partial dentures with cantilevered resin-bonded FPDs. Two-unit cantilevered resin-bonded FPDs for single-tooth replacement appear to be reliable and predictable restorations, provided their preparations meet the right standards. CONCLUSION: According to the studies reviewed, two-unit cantilevered FPDs show better longevity than resin-bonded fixed-fixed partial dentures in similar situations.

Adolescent↗

PubMedDate not supplied

Influence of fatigue loading on the performance of adhesive and nonadhesive luting cements for cast post-and-core buildups in maxillary premolars.

PURPOSE: This study evaluated the influence of fatigue loading on the performance of an adhesive and a nonadhesive cement for cast post-and-core restorations in maxillary premolars. MATERIALS AND METHODS: The adhesive cement used was Panavia 21, a resin-based composite cement, and the nonadhesive cement was PhosphaCem/C, a zinc-oxy-phosphate cement. The coronal sections of single-rooted human maxillary premolars were removed at the level of the proximal CEJ. After endodontic treatment, a cast post and core was prepared for each tooth and cemented into the root canal with either Panavia 21 (n = 8) or PhosphaCem/C (n = 8). Half of the specimens from each cement group were exposed to fatigue loading almost perpendicular to the axial axis; the other half were used as controls. Three parallel transverse root sections were cut from each specimen and used for evaluation of the influence of fatigue loading. For each section, cement integrity was studied by SEM, and retention strength of the cemented post section was determined with a push-out test. RESULTS: For SEM evaluation and the push-out test, Panavia 21 proved significantly better than PhosphaCem/C. However, fatigue loading did not show any effect. CONCLUSION: Under the conditions of this study, fatiguing of cemented cast post-and-core restorations was not decisive as a single test to evaluate the quality of the cement.

Adhesives↗