I. Stangel - Academia.edu (original) (raw)
Papers by I. Stangel
Le Journal de Physique IV, 1997
4To whom correspondence and reprint requests should be addressed This investigation was supported... more 4To whom correspondence and reprint requests should be addressed This investigation was supported in part with the financial assistance of the Den-Mat Corporation and Austenal Dental.
The chemical nature of the interface between dentin and adhesive resin materials was characterize... more The chemical nature of the interface between dentin and adhesive resin materials was characterized by micro-Raman spectroscopy. The resulting chemical profiles were correlated with photomicrographs obtained by SEM after an argon-ion-beam etching treatment of the sample surface. Two commercially available dentin adhesive systems, of which one was also applied with a different conditioning agent, were investigated. Raman spectra, which were recorded along line scans across the interface with a step increment of 1 micron, revealed that resin effectively penetrated 4 to 6 microns deep into the superficially decalcified dentin zone. Across the interface, a gradual transition from resin to dentin over the interdiffusion zone with a mixed contribution of both substances was noticed. Finally, resin appeared to penetrate to the entire decalcification depth of dentin regardless of the aggressiveness of the conditioning procedure.
During the past decade, dental faculties in North America have reduced class sizes due to a perce... more During the past decade, dental faculties in North America have reduced class sizes due to a perceived oversupply of dentists. Several schools have been closed outright, and others have been threatened with closure. These actions may have a negative impact on the future supply of dentists. The current beliefs with regards to the oversupply of dentists have inadequately accounted for the dramatic demographic and epidemiologic changes that are occurring in North America. Major changes in population distribution and disease trends point to an increased need for adult dental services in the future. Therefore, models for dental manpower needs should integrate these data to avoid a potential shortage of dental health care personnel in the future.
Journal of Dental Research, 2015
Dental caries is a microbially mediated disease that can result in significant tooth structure de... more Dental caries is a microbially mediated disease that can result in significant tooth structure degradation. Although the preponderance of lesions is treated by surgical intervention, various strategies have been developed for its noninvasive management. Here, we use a novel approach for noninvasive treatment based on killing Streptococcus mutans with high-frequency microwave energy (ME). The rationale for this approach is based on modulating the pH of caries to a physiological state to enable spontaneous tooth remineralization from exogenous sources. In the present study, after demonstrating that ME kills >99% of S. mutans in planktonic cultures, 8 enamel slabs were harvested from a single tooth. Baseline mineral concentration at each of 12 points per slab was obtained using Fourier transform (FT)–Raman spectroscopy. Surface demineralization was subsequently promoted by subjecting all samples to an S. mutans acidic biofilm for 6 d. Half of the samples were then exposed to high-fr...
Science of The Total Environment, 2000
Although the use of alternatives to dental amalgam is increasing, the possible hazard associated ... more Although the use of alternatives to dental amalgam is increasing, the possible hazard associated with their occupational exposure has received inadequate attention. The purpose of this study is to use available toxicological and environmental information in a qualitative risk assessment to address potential health hazards associated with exposure to these materials by dental personnel. The members of dental profession should be aware of risk due to long-term exposure to dental materials.
Progress in Surface Science, 1995
We consider the conditions and demonstrable reactions which promote chemical bonding to human den... more We consider the conditions and demonstrable reactions which promote chemical bonding to human dentin. The desirability of developing durable adhesion to dentin is used as background for a discussion of feasible reactions to the dentin components, for possible use in new formulations. This is followed by a discussion of the demonstrable reactions found in the literature, as well as our
Journal of Oral Rehabilitation, 1990
Two composite resins were evaluated for clinical acceptability as restorative materials in Class ... more Two composite resins were evaluated for clinical acceptability as restorative materials in Class I and II cavities over a 2-year-period. In addition, dispersed phase alloy was evaluated for comparison. All restorations were assessed for anatomical form, marginal integrity and marginal leakage using modified United States Public Health Service (USPHS) criteria. At the 2-year recall, 96% of the composites and 100% of the amalgams were rated 'alpha' or 'bravo', using the parameters of assessment defined in this study. However, a significant number of shifts from the baseline, within the level of acceptability, had occurred. The two composites showed the greatest number of shifts for anatomical form and marginal leakage, while there were no differences between the composites and the amalgam for shifts in marginal integrity. Although a very high level of acceptability was determined for all of the materials, the frequency of rating change within categories for the composites was a cause of concern with regard to their long-term clinical use.
Journal of Dental Research, 1993
The chemical nature of the interface between dentin and adhesive resin materials was characterize... more The chemical nature of the interface between dentin and adhesive resin materials was characterized by micro-Raman spectroscopy. The resulting chemical profiles were correlated with photomicrographs obtained by SEM after an argon-ion-beam etching treatment of the sample surface. Two commercially available dentin adhesive systems, of which one was also applied with a different conditioning agent, were investigated. Raman spectra, which were recorded along line scans across the interface with a step increment of 1 μm, revealed that resin effectively penetrated 4 to 6 μm deep into the superficially decalcified dentin zone. Across the interface, a gradual transition from resin to dentin over the interdiffusion zone with a mixed contribution of both substances was noticed. Finally, resin appeared to penetrate to the entire decalcification depth of dentin regardless of the aggressiveness of the conditioning procedure.
Journal of Dental Research, 1997
Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its r... more Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its role in promoting adhesion is not completely understood. Here, we use FT-Raman spectroscopy to elucidate further the nature of the interaction of HEMA with dentin. Ground dentin was exposed to 2.5% (w/w) nitric acid, washed, dried in air, and treated with HEMA. The samples were then sequentially washed
Journal of Biomedical Materials Research, 1996
This study investigated the effect of iron-containing mordants on the discoloration of human dent... more This study investigated the effect of iron-containing mordants on the discoloration of human dentin. Dentin wafers with intact enamel borders were treated with one of several acid solutions containing iron. After exposure to aqueous sodium sulfide, color change was evaluated colorimetrically. X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectrometry (EDS) were used to probe surfaces for the presence of iron. Changes in surface morphology were evaluated by scanning electron microscopy (SEM). The results indicated that dentin treated by iron-containing solutions always discolored when the sodium-sulfide concentration exceeded 9.7 mM; variability in discoloration occurred below this level. XPS detected iron in enamel but not in dentin, while EDS detected iron in both enamel and dentin. Since XPS probes the upper atomic layers, these results indicate that acid-demineralized dentin absorbs iron; however, a water wash removes iron from the uppermost dentin surface, suggesting that the iron is physically absorbed. When exposed to sodium sulfide, at least some of the iron remaining in the bulk region is able to migrate to the surface to form iron-sulfide compounds. Based on SEM findings, discoloration is associated with the formation of a surface film on dentin.
Journal of Biomedical Materials Research, 1998
We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments... more We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments on human dentin. Two basic points were determined: the first is the ability of AFM to discriminate the effect of phosphoric acid (pH approximately equal to 1) on polished dentin, and the second is the demonstrable effect of moisture on fibrous collagen structure. AFM images confirmed that the polishing process led to the removal of both smear layer and smear plugs. Our AFM study of undried dentin, which was then acid treated and kept moist, revealed substantial morphological changes at the dentin surface. Collagen fibers, having a characteristic periodicity of 67 nm, were imaged in situ for the first time; these structures were absent in dentin treated by phosphoric acid and subsequently vacuum dried, even after prolonged reimmersion in water. The AFM technique permitted us to demonstrate the important roles that moisture and etching play in the determination of the structure of collagen fibrils. Such structure may also play an important role in the diffusibility of subsequently applied dental adhesion systems.
Inorganica Chimica Acta, 2006
The effects of high external pressures on the principal IR and Raman bands of crystalline dichlor... more The effects of high external pressures on the principal IR and Raman bands of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(COD)Cl2 (COD=η4-C8H12), have been investigated for pressures up to ∼30kbar by diamond-anvil cell microspectroscopy. This square-planar Pt(II) complex does not undergo any pressure-induced structural change throughout the pressure range investigated and the pressure dependences (dν/dP) for the vibrational modes range from −0.18 to 0.79cm−1kbar−1.
Dental Materials, 2001
Tapping mode atomic force microscopy (AFM) was used to investigate the surface changes of collage... more Tapping mode atomic force microscopy (AFM) was used to investigate the surface changes of collagen exposed to phosphoric acid treatment. We focus on denaturation and collapse following demineralization and exposure to air. Unpolished dentin disks, obtained from freshly extracted human molars, were etched in 37% phosphoric acid for 15s, rinsed ultrasonically and gently blotted with soft paper; the specimens were then continuously observed using tapping mode AFM. Immediately after the removal of bulk water, the surface consisted of a porous network of banded collagen fibrils, having periodicities of 67nm. After approximately 8min of subsequent air-drying, the spacing between fibrils was lost, and the surface was observed to consist of a dense array of closely spaced fibrils. The banding periodicity was still observable. The air drying of etched dentin results in the collapse of the collagen network, but not in the denaturation of the collagen fibrils. This study indicates that collapse and denaturation are separate phenomena. It further shows that water loss occurs rapidly, and disrupts the native conformation of the collagen network. This would have adverse effects on adhesion.
Journal of Dental Research, 2005
Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a ... more Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a concern when thin layers of resin are being polymerized, or in circumstances where conventional means of eliminating inhibition are inappropriate. In this study, we tested the hypothesis that viscosity, filler content, and polymerization temperature modify oxygen diffusion in the resin or the reactivity of radical species, and affect the degree of conversion near the surface. Confocal Raman micro-spectroscopy was used to measure monomer conversion from the surface to the bulk of cured resins. Increased viscosity was shown to limit oxygen diffusion and increase conversion near the surface, without necessarily modifying the depth of inhibition. The filler material was shown to increase, simultaneously, oxygen diffusivity and the viscosity of the resin, which have opposite effects on conversion. Polymerization at a temperature above approximately 110 degrees C was shown to eliminate oxygen ...
The Journal of Adhesion, 1994
The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetr... more The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetraacetic acid (EGTA) and three proprietary agents containing ethylenediamine tetraacetic acid (EDTA), maleic acid and dipentaerythritol pentaacrylate phsophoric acid ester (PENTA). Ground dentin was treated with EGTA or one of the three proprietary agents. After adhering composite resin to treated surfaces, the shear bond strength (SBS) was determined with and without thermal stress. Scanning electron and atomic force microscopies were used to assess morphological effects of each of the agents, while low resolution X-ray photoelectron spectroscopy (XPS) was employed to evaluate elemental changes due to treatment. Mean bond strength was greatest for the PENTA-conditioned surfaces. EDTA and maleic acid demineralized the dentin surface while the agent containing PENTA produced an adherent surface film. The XPS survey showed a reduction in Ca and an increase in N for agents containing EGTA, EDTA and maleic acid, while a simultaneous reduction in both these species was observed for PENTA. EGTA did not improve adhesion for systems which were based on smear layer removal and substrate demineralization. For the PENTA-based system, which relied on the development of a molecular overlayer, EGTA degraded bond strength.
The Journal of Adhesion, 1994
The possible interaction between dentin and a proprietary dentin bonding agent (DBA), Gluma, was ... more The possible interaction between dentin and a proprietary dentin bonding agent (DBA), Gluma, was studied by Phase Photoacoustic FTIR. The determination of the existence and nature of a chemical bond between the DBA and the substrate can be of great importance in explaining the performance of these agents. Human dentin was treated by solutions of 2-hydroxyethyl methacrylate (HEMA), glutaraldehyde and
Le Journal de Physique IV, 1997
4To whom correspondence and reprint requests should be addressed This investigation was supported... more 4To whom correspondence and reprint requests should be addressed This investigation was supported in part with the financial assistance of the Den-Mat Corporation and Austenal Dental.
The chemical nature of the interface between dentin and adhesive resin materials was characterize... more The chemical nature of the interface between dentin and adhesive resin materials was characterized by micro-Raman spectroscopy. The resulting chemical profiles were correlated with photomicrographs obtained by SEM after an argon-ion-beam etching treatment of the sample surface. Two commercially available dentin adhesive systems, of which one was also applied with a different conditioning agent, were investigated. Raman spectra, which were recorded along line scans across the interface with a step increment of 1 micron, revealed that resin effectively penetrated 4 to 6 microns deep into the superficially decalcified dentin zone. Across the interface, a gradual transition from resin to dentin over the interdiffusion zone with a mixed contribution of both substances was noticed. Finally, resin appeared to penetrate to the entire decalcification depth of dentin regardless of the aggressiveness of the conditioning procedure.
During the past decade, dental faculties in North America have reduced class sizes due to a perce... more During the past decade, dental faculties in North America have reduced class sizes due to a perceived oversupply of dentists. Several schools have been closed outright, and others have been threatened with closure. These actions may have a negative impact on the future supply of dentists. The current beliefs with regards to the oversupply of dentists have inadequately accounted for the dramatic demographic and epidemiologic changes that are occurring in North America. Major changes in population distribution and disease trends point to an increased need for adult dental services in the future. Therefore, models for dental manpower needs should integrate these data to avoid a potential shortage of dental health care personnel in the future.
Journal of Dental Research, 2015
Dental caries is a microbially mediated disease that can result in significant tooth structure de... more Dental caries is a microbially mediated disease that can result in significant tooth structure degradation. Although the preponderance of lesions is treated by surgical intervention, various strategies have been developed for its noninvasive management. Here, we use a novel approach for noninvasive treatment based on killing Streptococcus mutans with high-frequency microwave energy (ME). The rationale for this approach is based on modulating the pH of caries to a physiological state to enable spontaneous tooth remineralization from exogenous sources. In the present study, after demonstrating that ME kills >99% of S. mutans in planktonic cultures, 8 enamel slabs were harvested from a single tooth. Baseline mineral concentration at each of 12 points per slab was obtained using Fourier transform (FT)–Raman spectroscopy. Surface demineralization was subsequently promoted by subjecting all samples to an S. mutans acidic biofilm for 6 d. Half of the samples were then exposed to high-fr...
Science of The Total Environment, 2000
Although the use of alternatives to dental amalgam is increasing, the possible hazard associated ... more Although the use of alternatives to dental amalgam is increasing, the possible hazard associated with their occupational exposure has received inadequate attention. The purpose of this study is to use available toxicological and environmental information in a qualitative risk assessment to address potential health hazards associated with exposure to these materials by dental personnel. The members of dental profession should be aware of risk due to long-term exposure to dental materials.
Progress in Surface Science, 1995
We consider the conditions and demonstrable reactions which promote chemical bonding to human den... more We consider the conditions and demonstrable reactions which promote chemical bonding to human dentin. The desirability of developing durable adhesion to dentin is used as background for a discussion of feasible reactions to the dentin components, for possible use in new formulations. This is followed by a discussion of the demonstrable reactions found in the literature, as well as our
Journal of Oral Rehabilitation, 1990
Two composite resins were evaluated for clinical acceptability as restorative materials in Class ... more Two composite resins were evaluated for clinical acceptability as restorative materials in Class I and II cavities over a 2-year-period. In addition, dispersed phase alloy was evaluated for comparison. All restorations were assessed for anatomical form, marginal integrity and marginal leakage using modified United States Public Health Service (USPHS) criteria. At the 2-year recall, 96% of the composites and 100% of the amalgams were rated 'alpha' or 'bravo', using the parameters of assessment defined in this study. However, a significant number of shifts from the baseline, within the level of acceptability, had occurred. The two composites showed the greatest number of shifts for anatomical form and marginal leakage, while there were no differences between the composites and the amalgam for shifts in marginal integrity. Although a very high level of acceptability was determined for all of the materials, the frequency of rating change within categories for the composites was a cause of concern with regard to their long-term clinical use.
Journal of Dental Research, 1993
The chemical nature of the interface between dentin and adhesive resin materials was characterize... more The chemical nature of the interface between dentin and adhesive resin materials was characterized by micro-Raman spectroscopy. The resulting chemical profiles were correlated with photomicrographs obtained by SEM after an argon-ion-beam etching treatment of the sample surface. Two commercially available dentin adhesive systems, of which one was also applied with a different conditioning agent, were investigated. Raman spectra, which were recorded along line scans across the interface with a step increment of 1 μm, revealed that resin effectively penetrated 4 to 6 μm deep into the superficially decalcified dentin zone. Across the interface, a gradual transition from resin to dentin over the interdiffusion zone with a mixed contribution of both substances was noticed. Finally, resin appeared to penetrate to the entire decalcification depth of dentin regardless of the aggressiveness of the conditioning procedure.
Journal of Dental Research, 1997
Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its r... more Although 2-hydroxyethylmethacrylate (HEMA) is commonly used for adhesive bonding to dentin, its role in promoting adhesion is not completely understood. Here, we use FT-Raman spectroscopy to elucidate further the nature of the interaction of HEMA with dentin. Ground dentin was exposed to 2.5% (w/w) nitric acid, washed, dried in air, and treated with HEMA. The samples were then sequentially washed
Journal of Biomedical Materials Research, 1996
This study investigated the effect of iron-containing mordants on the discoloration of human dent... more This study investigated the effect of iron-containing mordants on the discoloration of human dentin. Dentin wafers with intact enamel borders were treated with one of several acid solutions containing iron. After exposure to aqueous sodium sulfide, color change was evaluated colorimetrically. X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray spectrometry (EDS) were used to probe surfaces for the presence of iron. Changes in surface morphology were evaluated by scanning electron microscopy (SEM). The results indicated that dentin treated by iron-containing solutions always discolored when the sodium-sulfide concentration exceeded 9.7 mM; variability in discoloration occurred below this level. XPS detected iron in enamel but not in dentin, while EDS detected iron in both enamel and dentin. Since XPS probes the upper atomic layers, these results indicate that acid-demineralized dentin absorbs iron; however, a water wash removes iron from the uppermost dentin surface, suggesting that the iron is physically absorbed. When exposed to sodium sulfide, at least some of the iron remaining in the bulk region is able to migrate to the surface to form iron-sulfide compounds. Based on SEM findings, discoloration is associated with the formation of a surface film on dentin.
Journal of Biomedical Materials Research, 1998
We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments... more We used atomic force microscopy (AFM) to investigate the effects of acidic and aqueous treatments on human dentin. Two basic points were determined: the first is the ability of AFM to discriminate the effect of phosphoric acid (pH approximately equal to 1) on polished dentin, and the second is the demonstrable effect of moisture on fibrous collagen structure. AFM images confirmed that the polishing process led to the removal of both smear layer and smear plugs. Our AFM study of undried dentin, which was then acid treated and kept moist, revealed substantial morphological changes at the dentin surface. Collagen fibers, having a characteristic periodicity of 67 nm, were imaged in situ for the first time; these structures were absent in dentin treated by phosphoric acid and subsequently vacuum dried, even after prolonged reimmersion in water. The AFM technique permitted us to demonstrate the important roles that moisture and etching play in the determination of the structure of collagen fibrils. Such structure may also play an important role in the diffusibility of subsequently applied dental adhesion systems.
Inorganica Chimica Acta, 2006
The effects of high external pressures on the principal IR and Raman bands of crystalline dichlor... more The effects of high external pressures on the principal IR and Raman bands of crystalline dichloro(1,5-cycloctadiene)platinum(II), Pt(COD)Cl2 (COD=η4-C8H12), have been investigated for pressures up to ∼30kbar by diamond-anvil cell microspectroscopy. This square-planar Pt(II) complex does not undergo any pressure-induced structural change throughout the pressure range investigated and the pressure dependences (dν/dP) for the vibrational modes range from −0.18 to 0.79cm−1kbar−1.
Dental Materials, 2001
Tapping mode atomic force microscopy (AFM) was used to investigate the surface changes of collage... more Tapping mode atomic force microscopy (AFM) was used to investigate the surface changes of collagen exposed to phosphoric acid treatment. We focus on denaturation and collapse following demineralization and exposure to air. Unpolished dentin disks, obtained from freshly extracted human molars, were etched in 37% phosphoric acid for 15s, rinsed ultrasonically and gently blotted with soft paper; the specimens were then continuously observed using tapping mode AFM. Immediately after the removal of bulk water, the surface consisted of a porous network of banded collagen fibrils, having periodicities of 67nm. After approximately 8min of subsequent air-drying, the spacing between fibrils was lost, and the surface was observed to consist of a dense array of closely spaced fibrils. The banding periodicity was still observable. The air drying of etched dentin results in the collapse of the collagen network, but not in the denaturation of the collagen fibrils. This study indicates that collapse and denaturation are separate phenomena. It further shows that water loss occurs rapidly, and disrupts the native conformation of the collagen network. This would have adverse effects on adhesion.
Journal of Dental Research, 2005
Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a ... more Oxygen inhibits free radical polymerization and yields polymers with uncured surfaces. This is a concern when thin layers of resin are being polymerized, or in circumstances where conventional means of eliminating inhibition are inappropriate. In this study, we tested the hypothesis that viscosity, filler content, and polymerization temperature modify oxygen diffusion in the resin or the reactivity of radical species, and affect the degree of conversion near the surface. Confocal Raman micro-spectroscopy was used to measure monomer conversion from the surface to the bulk of cured resins. Increased viscosity was shown to limit oxygen diffusion and increase conversion near the surface, without necessarily modifying the depth of inhibition. The filler material was shown to increase, simultaneously, oxygen diffusivity and the viscosity of the resin, which have opposite effects on conversion. Polymerization at a temperature above approximately 110 degrees C was shown to eliminate oxygen ...
The Journal of Adhesion, 1994
The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetr... more The effect of conditioning dentin was investigated using ethyleneglycol bis(aminoethylether) tetraacetic acid (EGTA) and three proprietary agents containing ethylenediamine tetraacetic acid (EDTA), maleic acid and dipentaerythritol pentaacrylate phsophoric acid ester (PENTA). Ground dentin was treated with EGTA or one of the three proprietary agents. After adhering composite resin to treated surfaces, the shear bond strength (SBS) was determined with and without thermal stress. Scanning electron and atomic force microscopies were used to assess morphological effects of each of the agents, while low resolution X-ray photoelectron spectroscopy (XPS) was employed to evaluate elemental changes due to treatment. Mean bond strength was greatest for the PENTA-conditioned surfaces. EDTA and maleic acid demineralized the dentin surface while the agent containing PENTA produced an adherent surface film. The XPS survey showed a reduction in Ca and an increase in N for agents containing EGTA, EDTA and maleic acid, while a simultaneous reduction in both these species was observed for PENTA. EGTA did not improve adhesion for systems which were based on smear layer removal and substrate demineralization. For the PENTA-based system, which relied on the development of a molecular overlayer, EGTA degraded bond strength.
The Journal of Adhesion, 1994
The possible interaction between dentin and a proprietary dentin bonding agent (DBA), Gluma, was ... more The possible interaction between dentin and a proprietary dentin bonding agent (DBA), Gluma, was studied by Phase Photoacoustic FTIR. The determination of the existence and nature of a chemical bond between the DBA and the substrate can be of great importance in explaining the performance of these agents. Human dentin was treated by solutions of 2-hydroxyethyl methacrylate (HEMA), glutaraldehyde and